Journal articles on the topic 'Cyclones Tracking'
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1
Xia, Lan, and Yue Zhou. "Tracking Jianghuai Cyclones in China and Their Climate Characteristics." Atmosphere 9, no. 9 (August 30, 2018): 341. http://dx.doi.org/10.3390/atmos9090341.
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A Jianghuai cyclone is an extratropical cyclone, which influences the middle and lower reaches of the Yangtze River and Huai River basins in China. According to the definition of Jianghuai cyclones, statistics of their climate characteristics from 1979 to 2010 are obtained by an objective detection and tracking algorithm using ERA-Interim reanalysis data. The results show that the frequency of Jianghuai cyclones has a strong year-to-year variability but no obvious trend. Jianghuai cyclones are most frequent in May but fewest in December. As the cold air is active in spring, which interacts with the warm air from the southwest of the subtropical high at the Yangtze-Huai River region, it makes Jianghuai cyclones occur more frequently in this season. The main origins of Jianghuai cyclones are located in the Poyang Lake region, Dongting Lake region, and Dabie Mountain area. The maximum deepening rate of 0–2 hPa/6 h is featured in 66.4% of Jianghuai cyclones. Over 40% of Jianghuai cyclones have a mean deepening rate of 0–1 hPa/6 h. The lifetime of Jianghuai cyclones is short, mainly lasting for one to two days. In addition, background characteristics are compared between the formation, climax, and decaying periods of Jianghuai cyclones.
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Picornell, M. A., J. Campins, and A. Jansà. "Detection and thermal description of medicanes from numerical simulation." Natural Hazards and Earth System Sciences Discussions 1, no. 6 (December 12, 2013): 7417–47. http://dx.doi.org/10.5194/nhessd-1-7417-2013.
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Abstract. Tropical-like cyclones rarely affect the Mediterranean region and they can produce strong winds and heavy precipitations. These warm-core cyclones, called MEDICANES (MEDIterranean hurriCANES), are small size, develop over the sea and are infrequent. For these reasons, the detection and forecast of medicanes are a difficult task and many efforts have been devoted to identify them. The goals of this work are to contribute to a proper description of these structures and to develop some criteria to identify medicanes from numerical weather prediction (NWP) model outputs. To do that, existing methodologies for detecting, characterizating and tracking cyclones have been adapted to small-scale intense cyclonic perturbations. First, a mesocyclone detection and tracking algorithm has been modified to select intense cyclones. Next, the parameters that define the Hart's cyclone phase diagram are tuned and calculated to examine their thermal structure. Four well-known medicane events have been described from numerical simulation outputs of the ECMWF model. The predicted cyclones and their evolution have been validated against available observational data and numerical analyses from literature.
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Picornell, M. A., J. Campins, and A. Jansà. "Detection and thermal description of medicanes from numerical simulation." Natural Hazards and Earth System Sciences 14, no. 5 (May 7, 2014): 1059–70. http://dx.doi.org/10.5194/nhess-14-1059-2014.
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Abstract. Tropical-like cyclones rarely affect the Mediterranean region but they can produce strong winds and heavy precipitations. These warm-core cyclones, called MEDICANES (MEDIterranean hurriCANES), are small in size, develop over the sea and are infrequent. For these reasons, the detection and forecast of medicanes are a difficult task and many efforts have been devoted to identify them. The goals of this work are to contribute to a proper description of these structures and to develop some criteria to identify medicanes from numerical weather prediction (NWP) model outputs. To do that, existing methodologies for detecting, characterizating and tracking cyclones have been adapted to small-scale intense cyclonic perturbations. First, a mesocyclone detection and tracking algorithm has been modified to select intense cyclones. Next, the parameters that define the Hart's cyclone phase diagram are tuned and calculated to examine their thermal structure. Four well-known medicane events have been described from numerical simulation outputs of the European Centre for Medium-Range Weather Forecast (ECMWF) model. The predicted cyclones and their evolution have been validated against available observational data and numerical analyses from the literature.
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Raible, C. C., P. M. Della-Marta, C. Schwierz, H. Wernli, and R. Blender. "Northern Hemisphere Extratropical Cyclones: A Comparison of Detection and Tracking Methods and Different Reanalyses." Monthly Weather Review 136, no. 3 (March 1, 2008): 880–97. http://dx.doi.org/10.1175/2007mwr2143.1.
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Abstract The applicability of three different cyclone detection and tracking schemes is investigated with reanalysis datasets. First, cyclone climatologies and cyclone characteristics of the 40-yr ECMWF Re-Analysis (ERA-40) are compared with the NCEP–NCAR dataset using one method. ERA-40 shows systematically more cyclones, and therefore a higher cyclone center density, than the NCEP–NCAR reanalysis dataset. Geostrophically adjusted geopotential height gradients around cyclone centers, a measure of cyclone intensity, are enhanced in ERA-40 compared with the NCEP–NCAR reanalysis dataset. The variability of the number of cyclones per season is significantly correlated between the two reanalysis datasets, but time series of the extreme cyclone intensity exhibit a higher correlation. This suggests that the cyclone intensity is a more robust measure of variability than the number of cyclones. Second, three cyclone detection and tracking schemes are compared, based on the ERA-40 dataset. In general the schemes show a good correspondence. The approaches differ in technical aspects associated with the cyclone identification and the tracking procedure, leading to deviations in cyclone track length. However, it is often not clear which scheme is correct or incorrect. With the application of lifetime thresholds, some of the cyclone tracks are too short to be included in statistical measures of cyclones. Nevertheless, consequences of these differences in mean cyclone characteristics are minor, but for specific research questions—for example, what is the cyclone activity in the Mediterranean in winter—the users should be aware of these potential differences and adjust their scheme if necessary. A trend analysis of cyclone characteristics shows that results appear to be sensitive to both the choice of cyclone detection and tracking schemes and the reanalysis dataset.
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Lim, Eun-Pa, and Ian Simmonds. "Southern Hemisphere Winter Extratropical Cyclone Characteristics and Vertical Organization Observed with the ERA-40 Data in 1979–2001." Journal of Climate 20, no. 11 (June 1, 2007): 2675–90. http://dx.doi.org/10.1175/jcli4135.1.
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Abstract The mean characteristics and trends of Southern Hemisphere (SH) winter extratropical cyclones occurring at six levels of the troposphere over the period 1979–2001 have been investigated using the 40-yr ECMWF Re-Analysis (ERA-40) data. Cyclonic systems were identified with the Melbourne University cyclone finding and tracking scheme. This study shows that mean sea level pressure (MSLP) cyclones are more numerous, more intense, smaller, deeper, and slower moving than higher-level cyclones. The novel vertical tracing scheme devised for this research revealed that about 52% of SH winter MSLP cyclones have a vertically well organized structure, extending through to the 500-hPa level. About 80% of these vertically coherent SH cyclones keep their westward tilt until the surface cyclones reach their maximum depths, and the mean distance is 300 km between the surface and the 500-hPa level cyclone centers when the surface cyclones obtain their maturity. According to the authors’ definition of vertical organization, explosively developing cyclones are vertically very well organized systems, whose surface development is antecedent to their 500-hPa level counterpart. Over 1979–2001 cyclones have increased in their system density, intensity, and translational velocity but decreased in their scale at almost all levels. However, some of the trends are not statistically significant. The proportion of vertically well organized systems in the entire population of SH winter extratropical cyclones has considerably increased over the last 23 yr, and the mean distance between the surface and the 500-hPa- level cyclone centers has decreased. Such changes in vertical organization of extratropical cyclones are statistically significant at the 95% confidence level.
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Neu, Urs, Mirseid G. Akperov, Nina Bellenbaum, Rasmus Benestad, Richard Blender, Rodrigo Caballero, Angela Cocozza, et al. "IMILAST: A Community Effort to Intercompare Extratropical Cyclone Detection and Tracking Algorithms." Bulletin of the American Meteorological Society 94, no. 4 (April 1, 2013): 529–47. http://dx.doi.org/10.1175/bams-d-11-00154.1.
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The variability of results from different automated methods of detection and tracking of extratropical cyclones is assessed in order to identify uncertainties related to the choice of method. Fifteen international teams applied their own algorithms to the same dataset—the period 1989–2009 of interim European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis (ERAInterim) data. This experiment is part of the community project Intercomparison of Mid Latitude Storm Diagnostics (IMILAST; see www.proclim.ch/imilast/index.html). The spread of results for cyclone frequency, intensity, life cycle, and track location is presented to illustrate the impact of using different methods. Globally, methods agree well for geographical distribution in large oceanic regions, interannual variability of cyclone numbers, geographical patterns of strong trends, and distribution shape for many life cycle characteristics. In contrast, the largest disparities exist for the total numbers of cyclones, the detection of weak cyclones, and distribution in some densely populated regions. Consistency between methods is better for strong cyclones than for shallow ones. Two case studies of relatively large, intense cyclones reveal that the identification of the most intense part of the life cycle of these events is robust between methods, but considerable differences exist during the development and the dissolution phases.
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Muskulus, M., and D. Jacob. "Tracking cyclones in regional model data: the future of Mediterranean storms." Advances in Geosciences 2 (February 22, 2005): 13–19. http://dx.doi.org/10.5194/adgeo-2-13-2005.
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Abstract. With the advent of regional climate modelling, there are high-resolution data available for regional climatological change studies. Automatic tracking of cyclones in these datasets encounters problems with high spatial resolution due to cyclone substructure. Watershed segmentation, a technique from image analysis, has been used to obtain estimates for the spatial extent of cyclones, enabling better tracking and precipitation analysis. In this study we have used data from a 0.5° Regional Model (REMO) climatological model run for the period from 1961-2099, following the International Panel on Climate Change Special Report on Emissions Scenarios (IPCC SRES) B2 forcing. The resulting hourly mean sea level pressure (MSLP) fields have been analysed for cyclone numbers and tracks in the Mediterranean region. According to the results, the total number of cyclones in the Mediterranean seems to be increasing in the future, in spite of a general decrease of the numbers of stronger systems. In Summer, the increase in each gridbox seems to be proportional to the total number of cyclones in that box, whereas in Winter there is a slight proportional decrease. As concerns track properties and precipitation estimates along tracks, no significant change could be detected.
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Aragão, Leonardo, and Federico Porcù. "Cyclonic activity in the Mediterranean region from a high-resolution perspective using ECMWF ERA5 dataset." Climate Dynamics 58, no. 5-6 (October 15, 2021): 1293–310. http://dx.doi.org/10.1007/s00382-021-05963-x.
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AbstractThis study focuses on developing a new Cyclone Detection and Tracking Method (CDTM) to take advantage of the recent availability of a high-resolution reanalysis dataset of ECMWF ERA5. The proposed algorithm is used to perform a climatological analysis of the cyclonic activity in the Mediterranean Region (MR) into a 40-year window (1979–2018). The tuning of the new CDTM was based on the comparison with currently available CDTMs and verified through careful subjective analysis to fully exploit the finer details of MR cyclones features. The application of the new CDTM to the ERA5 high-resolution dataset resulted in an increase of 40% in the annual number of cyclones, mainly associated with subsynoptic and baroclinic driven lows. The main cyclogenetic areas and seasonal cycle were properly identified into the MR context, including areas often underestimated, such as the Aegean Sea, and emerging new ones with cyclogenetic potential such as the coast of Tunisia and Libya. The better cyclone features description defined three distinct periods of cyclonic activity in the MR with peculiar and persistent characteristics. In the first period (Apr–Jun), cyclones develop more frequently and present higher velocities and deepening rates. In the second (Jul–Sep), the cyclonic activity is governed by thermal lows spreading slowly over short tracks without reaching significant depths. In the last and longest season (Oct–Mar), cyclones become less frequent, but with the highest deepening rates and the lowest MSLP values, ranking this period as the most favourable to intense storms.
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Ragone, Francesco, Monica Mariotti, Antonio Parodi, Jost von Hardenberg, and Claudia Pasquero. "A Climatological Study of Western Mediterranean Medicanes in Numerical Simulations with Explicit and Parameterized Convection." Atmosphere 9, no. 10 (October 11, 2018): 397. http://dx.doi.org/10.3390/atmos9100397.
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The semi-enclosed Mediterranean basin, surrounded by high mountains, is placed in a favorable location for cyclonic storms development. Most of these are extratropical cyclones of baroclinic and orographic origin, but occasionally, some low pressure systems may develop to assume features characteristic of tropical cyclones. Medicanes (MEDIterranean hurriCANES) are infrequent and small-sized tropical-like cyclones. They originate and develop over sea, and are associated with strong winds and heavy precipitations. Proper definitions and classifications for Medicanes are still partially lacking, and systematic climatic studies have appeared only in recent years. In this work, we provide climatologies of Medicanes in the Western Mediterranean basin based on multidecadal runs performed with the Weather Research and Forecasting regional model with different resolutions and setups. The detection of Medicanes is based on a cyclone tracking algorithm and on the methodology of Hart cyclone phase space diagrams. We compare the statistics of Medicanes in the historical period 1979–1998 between runs at a resolution of 11 km with different convective parameterizations and microphysics schemes and one run at a resolution of 4 km with explicitly resolved convection. We show how different convective parameterization schemes lead to different statistics of Medicanes, while the use of different microphysical schemes impacts the length of the cyclone trajectories.
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Pfahl, Stephan, Paul A. O’Gorman, and Martin S. Singh. "Extratropical Cyclones in Idealized Simulations of Changed Climates." Journal of Climate 28, no. 23 (December 1, 2015): 9373–92. http://dx.doi.org/10.1175/jcli-d-14-00816.1.
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Abstract Cyclones are a key element of extratropical weather and frequently lead to extreme events like wind storms and heavy precipitation. Understanding potential changes of cyclone frequency and intensity is thus essential for a proper assessment of climate change impacts. Here the behavior of extratropical cyclones under strongly varying climate conditions is investigated using idealized climate model simulations in an aquaplanet setup. A cyclone tracking algorithm is applied to assess various statistics of cyclone properties such as intensity, size, lifetime, displacement velocity, and deepening rates. In addition, a composite analysis of intense cyclones is performed. In general, the structure of extratropical cyclones in the idealized simulations is very robust, and changes in major cyclone characteristics are relatively small. Median cyclone intensity, measured in terms of minimum sea level pressure and lower-tropospheric relative vorticity, has a maximum in simulations with global mean temperature slightly warmer than present-day Earth, broadly consistent with the behavior of the eddy kinetic energy analyzed in previous studies. Maximum deepening rates along cyclone tracks behave similarly and are in agreement with linear quasigeostrophic growth rates if the effect of latent heat release on the stratification is taken into account. In contrast to moderate cyclones, the relative vorticity of intense cyclones continues to increase with warming to substantially higher temperatures, and this is associated with enhanced lower-tropospheric potential vorticity anomalies likely caused by increased diabatic heating. Moist processes may, therefore, lead to the further strengthening of intense cyclones in warmer climates even if cyclones weaken on average.
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Gray, Suzanne L., Kevin I. Hodges, Jonathan L. Vautrey, and John Methven. "The role of tropopause polar vortices in the intensification of summer Arctic cyclones." Weather and Climate Dynamics 2, no. 4 (December 23, 2021): 1303–24. http://dx.doi.org/10.5194/wcd-2-1303-2021.
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Abstract. Human activity in the Arctic is increasing as new regions become accessible, with a consequent need for improved understanding of hazardous weather there. Arctic cyclones are the major weather systems affecting the Arctic environment during summer, including the sea ice distribution. Mesoscale to synoptic-scale tropopause polar vortices (TPVs) frequently occur in polar regions and are a proposed mechanism for Arctic cyclone genesis and intensification. However, while the importance of pre-existing tropopause-level features for cyclone development, as well as being an integral part of the three-dimensional mature cyclone structure, is well established in the mid-latitudes, evidence of the importance of pre-existing TPVs for Arctic cyclone development is mainly limited to a few case studies. Here we examine the extent to which Arctic cyclone growth is coupled to TPVs by analysing a climatology of summer Arctic cyclones and TPVs produced by tracking both features in the latest ECMWF reanalysis (ERA5). The annual counts of Arctic cyclones and TPVs are significantly correlated for features with genesis either within or outside the Arctic, implying that TPVs have a role in the development of Arctic cyclones. However, only about one-third of Arctic cyclones have their genesis or intensify while a TPV of Arctic origin is (instantaneously) within about twice the Rossby radius of the cyclone centre. Consistent with the different track densities of the full sets of Arctic cyclones and TPVs, cyclones with TPVs within range throughout their intensification phase (matched cyclones) track preferentially over the Arctic Ocean along the North American coastline and Canadian Arctic Archipelago. In contrast, cyclones intensifying distant from any TPV (unmatched cyclones) track preferentially along the northern coast of Eurasia. Composite analysis reveals the presence of a distinct relative vorticity maximum at and above the tropopause level associated with the TPV throughout the intensification period for matched cyclones and that these cyclones have a reduced upstream tilt compared to unmatched cyclones. Interaction of cyclones with TPVs has implications for the predictability of Arctic weather, given the long lifetime but relatively small spatial scale of TPVs compared with the density of the polar observation network.
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Yanase, Wataru, Hiroshi Niino, Kevin Hodges, and Naoko Kitabatake. "Parameter Spaces of Environmental Fields Responsible for Cyclone Development from Tropics to Extratropics." Journal of Climate 27, no. 2 (January 15, 2014): 652–71. http://dx.doi.org/10.1175/jcli-d-13-00153.1.
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Abstract Objective cyclone tracking applied to a 30-yr reanalysis dataset shows that cyclone development in the summer and autumn seasons is active in the tropics and extratropics and inactive in the subtropics. To understand this geographically bimodal distribution of cyclone development associated with tropical and extratropical cyclones quantitatively, the direct relationship between cyclone types and their environments are assessed by using a parameter space of environmental variables [environmental parameter space (EPS)]. The number of cyclones is analyzed in terms of two different factors: the environmental conditions favorable for cyclone development and the area size that satisfies the favorable condition. The EPS analysis is mainly conducted for two representative environmental parameters that are commonly used for cyclone analysis: potential intensity for tropical cyclones and baroclinicity for extratropical cyclones. The geographically bimodal distribution is attributed to the high sensitivity of the cyclone development to the change in the environmental fields from tropics to extratropics. In addition, the bimodal distribution is partly attributed to the rapid change in the environmental fields from tropics to extratropics. The EPS analysis also shows that other environmental parameters, including relative humidity and vertical velocity, may enhance the contrast between the tropics (extratropics) and subtropics, whereas they are not essential for determining cyclone types. The relationship between cyclones and their environments is found to be similar between the hemispheres in the EPS, although the geographical distribution, particularly the longitudinal uniformity, is markedly different between the hemispheres.
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RAGHAVAN, S. "Radar observations of tropical cyclones over the Indian Seas." MAUSAM 48, no. 2 (December 15, 2021): 169–88. http://dx.doi.org/10.54302/mausam.v48i2.3962.
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ABSTRACT. A review is presented of the radar observation of tropical cyclones in the Indian seas. The use of radar in operational cyclone tracking and forecasting as well as the knowledge gained from radar observations of the structure, wind and rainfall distribution and motion of cyclones are discussed. In the context of the expected introduction of operational Doppler ra1ars in India, the future prospects in the use of radar for operations and research are outlined. Some important areas where our understanding of cyclones can be improved by studies with radar in conjunction with other observations are listed.
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RAO, P. RAJESH, R. C. SAXENA, and S. K. BANERJEE. "Some aspects of accuracy of radar/satellite fixes of tropical cyclone over Bay of Bengal." MAUSAM 43, no. 4 (December 31, 2021): 379–84. http://dx.doi.org/10.54302/mausam.v43i4.3505.
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Consequent to installation of 10 cyclone detection radars and availability of INSAT observations availability of fixes* of cyclones by two or more radars and satellite has become a common feature during tracking of cyclones. Generally these fixes differ from each other to some extent. The paper presents a study of tracks of four cyclones in Bay of Bengal as determined by coastal radars and satellite. It is seen that satellite fix is generally closer to coast as compared to radar fix. Amongst radar fixes, the fix of radar closest to the storm may be considered as best fix of the system.
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Rae, Jamie G. L., Alexander D. Todd, Edward W. Blockley, and Jeff K. Ridley. "How much should we believe correlations between Arctic cyclones and sea ice extent?" Cryosphere 11, no. 6 (December 21, 2017): 3023–34. http://dx.doi.org/10.5194/tc-11-3023-2017.
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Abstract. This paper presents an investigation of the robustness of correlations between characteristics of Arctic summer cyclones and September Arctic sea ice extent. A cyclone identification and tracking algorithm is run for output from 100-year coupled climate model simulations at two resolutions and for 30 years of reanalysis data, using two different tracking variables (mean sea-level pressure, MSLP; and 850 hPa vorticity) for identification of the cyclones. The influence of the tracking variable, the spatial resolution of the model, and spatial and temporal sampling on the correlations is then explored. We conclude that the correlations obtained depend on all of these factors and that care should be taken when interpreting the results of such analyses. Previous studies of this type have used around 30 years of reanalysis and observational data, analysed with a single tracking variable. Our results therefore cast some doubt on the conclusions drawn in those studies.
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Makmur, E. E. S., W. Fitria, A. S. Praja, S. P. Rahayu, B. E. Pratama, R. S. S. Sudewi, H. Harsa, et al. "Strengthening the Early Detection and Tracking of Tropical Cyclones near Indonesian Waters." IOP Conference Series: Earth and Environmental Science 925, no. 1 (November 1, 2021): 012010. http://dx.doi.org/10.1088/1755-1315/925/1/012010.
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Abstract In early April 2021, the territory of Indonesia, around the province of East Nusa Tenggara in particular, was severely damaged due to being hit by tropical cyclone Seroja. The impact of tropical cyclone Seroja does not only occur in Nusa Tenggara but also in Australia. In fact, the impact that hit Australia exceeded the damage that occurred in East Nusa Tenggara. The impacts caused by tropical cyclone Seroja in East Nusa Tenggara included 181 deaths and 74,222 houses damaged. Tropical cyclones are extreme weather anomalies that hit many countries, especially in the middle latitudes associated with vast oceans, such as the area around the South China Sea, the Pacific Ocean and the Atlantic Ocean, such as the Philippines, Japan, America, Australia, Europe, etc. Early detection systems for the genesis of tropical cyclones are still being developed by international collaborations such as The Research Moored Array for African-Asian-Australian Monsoon Analysis and Prediction (RAMA) in the Indian Ocean, Tropical Atmosphere Ocean (TAO) in the Pacific Ocean, and Prediction and Research Moored, Array in the Tropical Atlantic (PIRATA). To find out the early sign of a tropical cyclone, it is characterized by sea surface temperatures > 26.5 C, the growth of very broad and thick convective clouds, and rotating wind speeds of > 63 km/hour. For this reason, continuous observations are needed in the area where the tropical cyclone first developed. Observation equipment required includes satellite observations, buoys, and weather radar. Unfortunately, in the territory of Indonesia, especially in the Indian and Pacific oceans around Indonesia, this equipment is not equipped with such equipment due to very expensive funding factors and vandalism constraints. For this reason, in the future, national and international cooperation will be needed to start building an early warning system for the emergence of tropical cyclones among research centers globally.
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Flaounas, E., V. Kotroni, K. Lagouvardos, and I. Flaounas. "Tracking winter extra-tropical cyclones based on their relative vorticity evolution and sensitivity to prior data filtering (cycloTRACK v1.0)." Geoscientific Model Development Discussions 7, no. 1 (February 3, 2014): 1245–76. http://dx.doi.org/10.5194/gmdd-7-1245-2014.
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Abstract. In this study we present a new cyclone identification and tracking algorithm. Identification is based on a recognition pattern of enclosed contours of 850 hPa filtered relative vorticity values, while tracking is based on the minimization of a cost function. In particular, for each tracked cyclone our algorithm builds all possible tracks and finally chooses the one which presents the least differences of relative vorticity between consecutive track points. In parallel, for each track point the algorithm provides a cyclone area within which different physical diagnostics are calculated (such as pressure and wind speed). The area size is a function of the cyclone relative vorticity. To validate our approach we apply the algorithm on the Northern Hemisphere for the winters of 1989–2009. Three integrations of the algorithm were performed, each by using different filtering strengths. Using the three integrations, we assess the algorithm sensitivity to prior filtering the relative vorticity field. We show that filtering the input relative vorticity fields has an impact only on the weak cyclones, while in their majority the strong cyclones are independently detected and tracked.
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Horn, Michael, Kevin Walsh, Ming Zhao, Suzana J. Camargo, Enrico Scoccimarro, Hiroyuki Murakami, Hui Wang, et al. "Tracking Scheme Dependence of Simulated Tropical Cyclone Response to Idealized Climate Simulations." Journal of Climate 27, no. 24 (December 10, 2014): 9197–213. http://dx.doi.org/10.1175/jcli-d-14-00200.1.
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Abstract Future tropical cyclone activity is a topic of great scientific and societal interest. In the absence of a climate theory of tropical cyclogenesis, general circulation models are the primary tool available for investigating the issue. However, the identification of tropical cyclones in model data at moderate resolution is complex, and numerous schemes have been developed for their detection. The influence of different tracking schemes on detected tropical cyclone activity and responses in the Hurricane Working Group experiments is examined herein. These are idealized atmospheric general circulation model experiments aimed at determining and distinguishing the effects of increased sea surface temperature and other increased CO2 effects on tropical cyclone activity. Two tracking schemes are applied to these data and the tracks provided by each modeling group are analyzed. The results herein indicate moderate agreement between the different tracking methods, with some models and experiments showing better agreement across schemes than others. When comparing responses between experiments, it is found that much of the disagreement between schemes is due to differences in duration, wind speed, and formation-latitude thresholds. After homogenization in these thresholds, agreement between different tracking methods is improved. However, much disagreement remains, accountable for by more fundamental differences between the tracking schemes. The results indicate that sensitivity testing and selection of objective thresholds are the key factors in obtaining meaningful, reproducible results when tracking tropical cyclones in climate model data at these resolutions, but that more fundamental differences between tracking methods can also have a significant impact on the responses in activity detected.
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KELKAR, R. R. "Satellite-based monitoring and prediction of tropical cyclone intensity and movement." MAUSAM 48, no. 2 (December 15, 2021): 157–68. http://dx.doi.org/10.54302/mausam.v48i2.3965.
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ABSTRACT. Capabilities of meteorological satellites have gone a long way in meeting requirements of synoptic analysis and forecasting of tropical cyclones. This paper shows the impact made by the satellite data in the intensity estimation and track prediction of tropical cyclones in the Indian Seas and also reviews the universally applied Dvorak algorithm for performing tropical cyclone intensity analysis.
Extensive use of Dvorak's intensity estimation scheme has revealed many of its limitations and elements of subjectivity in the analysis of tropical cyclones over the Arabian Sea and the Bay of Bengal, which, like cyclones in other ocean basins, also exhibit wide structural variability as seen in the satellite imagery.
Satellite-based cyclone tracking techniques include: (i) use of satellite-derived mean wind flow, (ii) animation of sequence of satellite images and extrapolation of the apparent motion of the cloud system and (iii) monitoring changes in the upper level moisture patterns in the water vapour absorption channel imagery.
Satellite-based techniques on tropical cyclone intensity estimation and track prediction have led to very significant improvement in disaster warning and consequent saving of life and property.
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Koyama, Tomoko, Julienne Stroeve, John Cassano, and Alex Crawford. "Sea Ice Loss and Arctic Cyclone Activity from 1979 to 2014." Journal of Climate 30, no. 12 (June 2017): 4735–54. http://dx.doi.org/10.1175/jcli-d-16-0542.1.
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Extensive summer sea ice loss has occurred within the Beaufort, Chukchi, East Siberian, and Laptev Seas over the last decade. Associated anomalies in sensible and latent heat fluxes in autumn have increased Arctic atmospheric precipitable water and air temperatures, with the potential to impact autumn and winter cyclone activity. To examine if a connection exists between recent Arctic sea ice loss and cyclone activity, several cyclone metrics from 60° to 90°N are analyzed. Results show that following years with less September sea ice, there is a subsequent increase in moisture availability, regional baroclinicity, and changes in vertical stability that favor cyclogenesis. However, tracking of individual cyclones indicates no coherent increase in cyclone frequency or intensity associated with sea ice loss. Furthermore, no robust northward progression of extreme cyclones is observed.
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Bell, Ray, Jane Strachan, Pier Luigi Vidale, Kevin Hodges, and Malcolm Roberts. "Response of Tropical Cyclones to Idealized Climate Change Experiments in a Global High-Resolution Coupled General Circulation Model." Journal of Climate 26, no. 20 (October 4, 2013): 7966–80. http://dx.doi.org/10.1175/jcli-d-12-00749.1.
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Abstract The authors present an assessment of how tropical cyclone activity might change owing to the influence of increased atmospheric carbon dioxide concentrations, using the U.K. High-Resolution Global Environment Model (HiGEM) with N144 resolution (~90 km in the atmosphere and ~40 km in the ocean). Tropical cyclones are identified using a feature-tracking algorithm applied to model output. Tropical cyclones from idealized 30-yr 2×CO2 (2CO2) and 4×CO2 (4CO2) simulations are compared to those identified in a 150-yr present-day simulation that is separated into a five-member ensemble of 30-yr integrations. Tropical cyclones are shown to decrease in frequency globally by 9% in the 2CO2 and 26% in the 4CO2. Tropical cyclones only become more intense in the 4CO2; however, uncoupled time slice experiments reveal an increase in intensity in the 2CO2. An investigation into the large-scale environmental conditions, known to influence tropical cyclone activity in the main development regions, is used to determine the response of tropical cyclone activity to increased atmospheric CO2. A weaker Walker circulation and a reduction in zonally averaged regions of updrafts lead to a shift in the location of tropical cyclones in the Northern Hemisphere. A decrease in mean ascent at 500 hPa contributes to the reduction of tropical cyclones in the 2CO2 in most basins. The larger reduction of tropical cyclones in the 4CO2 arises from further reduction of the mean ascent at 500 hPa and a large enhancement of vertical wind shear, especially in the Southern Hemisphere, North Atlantic, and northeast Pacific.
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Tilinina, Natalia, Sergey K. Gulev, Irina Rudeva, and Peter Koltermann. "Comparing Cyclone Life Cycle Characteristics and Their Interannual Variability in Different Reanalyses." Journal of Climate 26, no. 17 (August 23, 2013): 6419–38. http://dx.doi.org/10.1175/jcli-d-12-00777.1.
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Abstract Characteristics of Northern Hemisphere extratropical cyclone activity were compared for five concurrent reanalyses: the NCEP–U.S. Department of Energy (DOE) reanalysis (herein NCEP–DOE), the Japanese 25-year Reanalysis Project (JRA-25), the ECMWF Interim Re-Analysis (ERA-Interim), the National Aeronautics and Space Administration's Modern-Era Retrospective Analysis for Research and Applications (NASA-MERRA), and the NCEP Climate Forecast System Reanalysis (NCEP-CFSR), for the period 1979–2010 using a single cyclone tracking algorithm. The total number of cyclones, ranging from 1400 to more than 1800 yr−1, was found to depend strongly on the spatial resolution of the respective reanalysis. The largest cyclone population was identified using NASA-MERRA data, which also showed the highest occurrence of very deep cyclones. Of the reanalyses, two (NCEP–DOE and ERA-Interim) are associated with statistically significant positive trends in the total number of cyclones from 1% to 2% decade−1. These trends result from moderate and shallow cyclones contributing to approximately 90% of the total cyclone count on average. The number of very deep cyclones (<960 hPa) in the North Atlantic increased in most reanalyses until 1990 and then declined during the last decade. In the North Pacific, the number of these events reached a peak in 2000 and then decreased during the last decade. The winter pattern is characterized by robust trends in cyclone numbers, with an enhancement of the North Atlantic storm track and a weakening of the North Pacific subtropical storm track. In the summer, there is a robust intensification of the Mediterranean storm track and a decrease in counts over the North Atlantic. Interannual variability and decadal-scale variations of the cyclone counts are highly correlated among the reanalyses, with the greatest agreement in moderate and deep cyclones.
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Dacre, Helen F., Simon A. Josey, and Alan L. M. Grant. "Extratropical-cyclone-induced sea surface temperature anomalies in the 2013–2014 winter." Weather and Climate Dynamics 1, no. 1 (February 4, 2020): 27–44. http://dx.doi.org/10.5194/wcd-1-27-2020.
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Abstract. The 2013–2014 winter averaged sea surface temperature (SST) was anomalously cool in the mid-North Atlantic region. This season was also unusually stormy, with extratropical cyclones passing over the mid-North Atlantic every 3 d. However, the processes by which cyclones contribute towards seasonal SST anomalies are not fully quantified. In this paper a cyclone identification and tracking method is combined with European Centre for Medium-Range Weather Forecasts (ECMWF) atmosphere and ocean reanalysis fields to calculate cyclone-relative net surface heat flux anomalies and resulting SST changes. Anomalously large negative heat flux is located behind the cyclones' cold front, resulting in anomalous cooling up to 0.2 K d−1 when the cyclones are at maximum intensity. This extratropical-cyclone-induced “cold wake” extends along the cyclones' cold front but is small compared to climatological variability in the SSTs. To investigate the potential cumulative effect of the passage of multiple cyclone-induced SST cooling in the same location, we calculate Earth-relative net surface heat flux anomalies and resulting SST changes for the 2013–2014 winter period. Anomalously large winter averaged negative heat flux occurs in a zonally orientated band extending across the North Atlantic between 40 and 60∘ N. The 2013–2014 winter SST cooling anomaly associated with air–sea interactions (ASIs; anomalous heat flux, mixed layer depth and entrainment at the base of the ocean mixed layer) is estimated to be −0.67 K in the mid-North Atlantic (68 % of the total cooling anomaly). The role of cyclones is estimated using a cyclone-masking technique which encompasses each cyclone centre and its cold wake. The environmental flow anomaly in 2013–2014 sets the overall tripole pattern of heat flux anomalies over the North Atlantic. However, the presence of cyclones doubles the magnitude of the negative heat flux anomaly in the mid-North Atlantic. Similarly, the environmental flow anomaly determines the location of the SST cooling anomaly, but the presence of cyclones enhances the SST cooling anomaly. Thus air–sea interactions play a major part in determining the extreme 2013–2014 winter season SST cooling anomaly. The environmental flow anomaly determines where anomalous heat flux and associated SST changes occur, and the presence of cyclones influences the magnitude of those anomalies.
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Hu, Ye, Chuhan Lu, Yujing Qin, and Jiaxi Cai. "Comparison of Two Automatic Identification Algorithms for Cyclones Affecting the Changjiang River–Huaihe River Valleys." Atmosphere 10, no. 3 (March 3, 2019): 115. http://dx.doi.org/10.3390/atmos10030115.
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In this study, two commonly used automated methods of detecting cyclones in the lower troposphere were compared with respect to various features of cyclone activity. The first method is based on the neighbor cyclone center point (NCP), while the second method is the cyclone area algorithm (CAA), which relies on the detection of the outermost enclosed contour to identify the horizontal structure of a cyclone. We obtained climatologies of cyclones that affected the Changjiang River–Huaihe River Valleys (CHV) of China (derived from ERA-Interim data for 1979–2015) and compared their structures. We found that the distribution of the track and the cyclogenesis locations of influential cyclones (ICs) showed a consistent spatial pattern between the NCP and CAA. However, there were still notable differences between the statistical features of cyclone activity derived by the NCP and CAA: (1) Only <46% of cyclones shared the same cyclone center between these two schemes. (2) ICs derived from the CAA typically had longer lifetimes and travel distances, with stronger central intensities than those from the NCP. (3) The track of ICs by the CAA with high resolution was consistent with that of ICs by the low-resolution CAA as well as the low-resolution NCP. However, compared to other methods, the high-resolution NCP presented large deviations during the early cyclone stage. The involvement of open systems in the NCP resulted in weaker cyclone intensities and increased uncertainty in cyclone tracking. On the other hand, more cyclones with stronger intensities and longer lifetimes coming from the midlatitudes were detected using the CAA. In addition, the short-lifetime ICs (<18 h) found using the CAA were active (39%) in the CHV, and were typically excluded by the NCP. These ICs had comparable center intensity and showed a good correlation with the occurrence of simultaneous rainfall events.
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Čampa, Jana, and Heini Wernli. "A PV Perspective on the Vertical Structure of Mature Midlatitude Cyclones in the Northern Hemisphere." Journal of the Atmospheric Sciences 69, no. 2 (February 1, 2012): 725–40. http://dx.doi.org/10.1175/jas-d-11-050.1.
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Abstract Development of extratropical cyclones can be seen as an interplay of three positive potential vorticity anomalies: an upper-level stratospheric intrusion, low-tropospheric diabatically produced potential vorticity (PV), and a warm anomaly at the surface acting as a surrogate PV anomaly. This study, based on the interim ECMWF Re-Analysis (ERA-Interim) dataset, quantifies the amplitude of the PV anomalies of mature extratropical cyclones in different regions in the Northern Hemisphere on a climatological basis. A tracking algorithm is applied to sea level pressure (SLP) fields to identify cyclone tracks. Surface potential temperature anomalies Δθ and vertical profiles of PV anomalies ΔPV are calculated at the time of the cyclones’ minimum SLP in a vertical cylinder around the surface cyclone center. To compare the cyclones’ characteristics they are grouped according to their location and intensity. Composite ΔPV profiles are calculated for each region and intensity class at the time of minimum SLP and during the cyclone intensification phase. In the mature stage all three anomalies are on average larger for intense than for weak winter cyclones [e.g., 0.6 versus 0.2 potential vorticity units (PVU; 1 PVU = 10−6 K kg−1 m2 s−1) at lower levels, and 1.5 versus 0.5 PVU at upper levels]. The regional variability of the cyclones’ vertical structure and the profile evolution is prominent (cyclones in some regions are more sensitive to the amplitude of a particular anomaly than in other regions). Values of Δθ and low-level ΔPV are on average larger in the western parts of the oceans than in the eastern parts. Results for summer are qualitatively similar, except for distinctively weaker surface Δθ values.
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Wernli, Heini, and Cornelia Schwierz. "Surface Cyclones in the ERA-40 Dataset (1958–2001). Part I: Novel Identification Method and Global Climatology." Journal of the Atmospheric Sciences 63, no. 10 (October 1, 2006): 2486–507. http://dx.doi.org/10.1175/jas3766.1.
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Abstract A novel method is introduced to generate climatological frequency distributions of meteorological features from gridded datasets. The method is used here to derive a climatology of extratropical cyclones from sea level pressure (SLP) fields. A simple and classical conception of cyclones is adopted where a cyclone is identified as the finite area that surrounds a local SLP minimum and is enclosed by the outermost closed SLP contour. This cyclone identification procedure can be applied to individual time instants, and climatologies of cyclone frequency, fc, are obtained by simple time averaging. Therefore, unlike most other climatologies, the method is not based on the application of a tracking algorithm and considers the size of cyclones. In combination with a conventional cyclone center tracking algorithm that allows the determination of cyclone life times and the location of cyclogenesis and cyclolysis, additional frequency fields can be obtained for special categories of cyclones that are generated in, move through, or decay in a specified geographical area. The method is applied to the global SLP dataset for the time period 1958–2001 from the latest 40-yr European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis (ERA-40). In the Northern Hemisphere and during winter, the cyclone frequency field has three maxima in the Pacific storm track (with fc up to 35%), the Atlantic storm track (with fc up to 32%), and the Mediterranean (with fc up to 15%). During the other seasons the fc values are generally reduced in midlatitudes and the subtropical monsoon areas appear as regions with enhanced fc. In the Southern Hemisphere, the seasonal variations are smaller with year-round maxima of fc in the belt from 50° to 70°S (along the coast of Antarctica, with maximum values of almost 40%) and to the east of the Andes (with fc up to 35% during summer). Application of a lifetime threshold value significantly reduces fc, in particular over and close to the continents. Subsets of cyclone frequency fields are calculated for several subjectively chosen regions of cyclone genesis, passage, and lysis. They show some interesting aspects of the behavior of extratropical cyclones; cyclones that decay along the U.S. West Coast, for instance, have a short lifetime and originate almost exclusively from the eastern North Pacific, whereas long-lived and long-distance Pacific cyclones terminate farther north in the Gulf of Alaska. The approach to calculate frequency distributions of atmospheric flow structures as introduced in this study can be easily applied to gridded data from global atmospheric models and assimilation systems. It combines the counts of atmospheric features with their area of influence, and hence provides a robust and easily interpretable measure of key meteorological structures when comparing and evaluating different analysis datasets and climate model integrations. Further work is required to comprehensively exploit the presented global ERA-40 cyclone climatology, in particular, aspects of its interannual variability.
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Colle, Brian A., Zhenhai Zhang, Kelly A. Lombardo, Edmund Chang, Ping Liu, and Minghua Zhang. "Historical Evaluation and Future Prediction of Eastern North American and Western Atlantic Extratropical Cyclones in the CMIP5 Models during the Cool Season." Journal of Climate 26, no. 18 (September 9, 2013): 6882–903. http://dx.doi.org/10.1175/jcli-d-12-00498.1.
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Abstract Extratropical cyclone track density, genesis frequency, deepening rate, and maximum intensity distributions over eastern North America and the western North Atlantic were analyzed for 15 models from phase 5 of the Coupled Model Intercomparison Project (CMIP5) for the historical period (1979–2004) and three future periods (2009–38, 2039–68, and 2069–98). The cyclones were identified using an automated tracking algorithm applied to sea level pressure every 6 h. The CMIP5 results for the historical period were evaluated using the Climate Forecast System Reanalysis (CFSR). The CMIP5 models were ranked given their track density, intensity, and overall performance for the historical period. It was found that six of the top seven CMIP5 models with the highest spatial resolution were ranked the best overall. These models had less underprediction of cyclone track density, more realistic distribution of intense cyclones along the U.S. East Coast, and more realistic cyclogenesis and deepening rates. The best seven models were used to determine projected future changes in cyclones, which included a 10%–30% decrease in cyclone track density and weakening of cyclones over the western Atlantic storm track, while in contrast there is a 10%–20% increase in cyclone track density over the eastern United States, including 10%–40% more intense (<980 hPa) cyclones and 20%–40% more rapid deepening rates just inland of the U.S. East Coast. Some of the reasons for these CMIP5 model differences were explored for the selected models based on model generated Eady growth rate, upper-level jet, surface baroclinicity, and precipitation.
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Grise, Kevin M., Seok-Woo Son, and John R. Gyakum. "Intraseasonal and Interannual Variability in North American Storm Tracks and Its Relationship to Equatorial Pacific Variability." Monthly Weather Review 141, no. 10 (September 25, 2013): 3610–25. http://dx.doi.org/10.1175/mwr-d-12-00322.1.
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Abstract Extratropical cyclones play a principal role in wintertime precipitation and severe weather over North America. On average, the greatest number of cyclones track 1) from the lee of the Rocky Mountains eastward across the Great Lakes and 2) over the Gulf Stream along the eastern coastline of North America. However, the cyclone tracks are highly variable within individual winters and between winter seasons. In this study, the authors apply a Lagrangian tracking algorithm to examine variability in extratropical cyclone tracks over North America during winter. A series of methodological criteria is used to isolate cyclone development and decay regions and to account for the elevated topography over western North America. The results confirm the signatures of four climate phenomena in the intraseasonal and interannual variability in North American cyclone tracks: the North Atlantic Oscillation (NAO), the El Niño–Southern Oscillation (ENSO), the Pacific–North American pattern (PNA), and the Madden–Julian oscillation (MJO). Similar signatures are found using Eulerian bandpass-filtered eddy variances. Variability in the number of extratropical cyclones at most locations in North America is linked to fluctuations in Rossby wave trains extending from the central tropical Pacific Ocean. Only over the far northeastern United States and northeastern Canada is cyclone variability strongly linked to the NAO. The results suggest that Pacific sector variability (ENSO, PNA, and MJO) is a key contributor to intraseasonal and interannual variability in the frequency of extratropical cyclones at most locations across North America.
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Pravia-Sarabia, Enrique, Juan José Gómez-Navarro, Pedro Jiménez-Guerrero, and Juan Pedro Montávez. "TITAM (v1.0): the Time-Independent Tracking Algorithm for Medicanes." Geoscientific Model Development 13, no. 12 (December 2, 2020): 6051–75. http://dx.doi.org/10.5194/gmd-13-6051-2020.
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Abstract. This work aims at presenting TITAM, a time-independent tracking algorithm specifically suited for medicanes. In the last decades, the study of medicanes has been repeatedly addressed given their potential to damage coastal zones. Their hazardous associated meteorological conditions have converted them to a major threat. Even though medicane similarities to tropical cyclones have been widely studied in terms of genesis mechanisms and structure, the fact that the former appear in baroclinic environments, as well as the limited extension of the Mediterranean basin, makes them prone to maintaining their warm-cored and symmetric structure for short time periods. Thus, the usage of a measure for the warm-core nature of the cyclone, namely the Hart conditions, is a key factor for successful identification of a medicane. Furthermore, given their relatively small spatial extent, medicanes tend to appear embedded in or to coexist with larger lows. Hence, the implementation of a time-independent methodology, avoiding the search for a medicane based on its location at previous time steps, seems to be fundamental when facing situations of cyclone coexistence. The examples selected showcase how the algorithm presented throughout this paper is useful and robust for the tracking of medicanes. This methodology satisfies the requirements expected for a tracking method of this nature, namely the capacity to track multiple simultaneous cyclones, the ability to track a medicane in the presence of an intense trough inside the domain, the potential to separate the medicane from other similar structures by handling the intermittent loss of structure, and the capability to isolate and follow the medicane center regardless of other cyclones that could be present in the domain. The complete TITAM package, including preprocessing and post-processing tools, is available as free software extensively documented and prepared for its deployment. As a final remark, this algorithm sheds some light on medicane understanding regarding medicane structure, warm-core nature, and the existence of tilting.
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Froude, Lizzie S. R., Lennart Bengtsson, and Kevin I. Hodges. "The Prediction of Extratropical Storm Tracks by the ECMWF and NCEP Ensemble Prediction Systems." Monthly Weather Review 135, no. 7 (July 1, 2007): 2545–67. http://dx.doi.org/10.1175/mwr3422.1.
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Abstract The prediction of extratropical cyclones by the European Centre for Medium-Range Weather Forecasts (ECMWF) and the National Centers for Environmental Prediction (NCEP) ensemble prediction systems (EPSs) has been investigated using an objective feature tracking methodology to identify and track the cyclones along the forecast trajectories. Overall the results show that the ECMWF EPS has a slightly higher level of skill than the NCEP EPS in the Northern Hemisphere (NH). However in the Southern Hemisphere (SH), NCEP has higher predictive skill than ECMWF for the intensity of the cyclones. The results from both EPSs indicate a higher level of predictive skill for the position of extratropical cyclones than their intensity and show that there is a larger spread in intensity than position. Further analysis shows that the predicted propagation speed of cyclones is generally too slow for the ECMWF EPS and shows a slight bias for the intensity of the cyclones to be overpredicted. This is also true for the NCEP EPS in the SH. For the NCEP EPS in the NH the intensity of the cyclones is underpredicted. There is small bias in both the EPS for the cyclones to be displaced toward the poles. For each ensemble forecast of each cyclone, the predictive skill of the ensemble member that best predicts the cyclone’s position and intensity was computed. The results are very encouraging showing that the predictive skill of the best ensemble member is significantly higher than that of the control forecast in terms of both the position and intensity of the cyclones. The prediction of cyclones before they are identified as 850-hPa vorticity centers in the analysis cycle was also considered. It is shown that an indication of extratropical cyclones can be given by at least 1 ensemble member 7 days before they are identified in the analysis. Further analysis of the ECMWF EPS shows that the ensemble mean has a higher level of skill than the control forecast, particularly for the intensity of the cyclones, from day 3 of the forecast. There is a higher level of skill in the NH than the SH and the spread in the SH is correspondingly larger. The difference between the ensemble mean error and spread is very small for the position of the cyclones, but the spread of the ensemble is smaller than the ensemble mean error for the intensity of the cyclones in both hemispheres. Results also show that the ECMWF control forecast has ½ to 1 day more skill than the perturbed members, for both the position and intensity of the cyclones, throughout the forecast.
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Flaounas, E., V. Kotroni, K. Lagouvardos, and I. Flaounas. "CycloTRACK (v1.0) – tracking winter extratropical cyclones based on relative vorticity: sensitivity to data filtering and other relevant parameters." Geoscientific Model Development 7, no. 4 (August 29, 2014): 1841–53. http://dx.doi.org/10.5194/gmd-7-1841-2014.
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Abstract. In this study we present a new cyclone identification and tracking algorithm, cycloTRACK. The algorithm describes an iterative process. At each time step it identifies all potential cyclone centers, defined as relative vorticity maxima embedded in smoothed enclosed contours of at least 3 × 10−5 s−1 at the atmospheric level of 850 hPa. Next, the algorithm finds all the potential cyclone paths by linking the cyclone centers at consecutive time steps and selects the most probable track based on the minimization of a cost function. The cost function is based on the average differences of relative vorticity between consecutive track points, weighted by their distance. Last, for each cyclone, the algorithm identifies "an effective area" for which different physical diagnostics are measured, such as the minimum sea level pressure and the maximum wind speed. The algorithm was applied to the ERA-Interim reanalyses for tracking the Northern Hemisphere extratropical cyclones of winters from 1989 until 2009, and we assessed its sensitivity for the several free parameters used to perform the tracking.
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Garde, L. A., A. B. Pezza, I. Simmonds, and N. E. Davidson. "A methodology of tracking transitioning Cyclones." IOP Conference Series: Earth and Environmental Science 11 (August 1, 2010): 012007. http://dx.doi.org/10.1088/1755-1315/11/1/012007.
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Colle, Brian A., and Michael E. Charles. "Spatial Distribution and Evolution of Extratropical Cyclone Errors over North America and its Adjacent Oceans in the NCEP Global Forecast System Model." Weather and Forecasting 26, no. 2 (April 1, 2011): 129–49. http://dx.doi.org/10.1175/2010waf2222422.1.
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Abstract Short- to medium-range (1–5 day) forecasts of extratropical cyclones around North America and its adjacent oceans are verified within the Global Forecast System (GFS) model at the National Centers for Environmental Prediction (NCEP) during the 2002–07 cool seasons (October–March). Cyclones in the immediate lee of the Rockies and U.S. Great Plains have 25%–50% smaller pressure errors than other regions after hour 36. The central pressure and displacement errors are largest over the central and eastern Pacific for the 42–72-h forecast, while the western and central Atlantic pressure errors for 96–120 h are similar to the central and eastern Pacific. For relatively strong cyclones, the western Atlantic and central/eastern Canada pressure errors are larger than those for the Pacific by 108–120 h. There are large spatial variations in the central pressure biases at 72–120 h, with overdeepened GFS cyclones (negative errors) extending from the northern Pacific and Bering Strait eastward to western Canada, while underdeepened GFS cyclones (positive errors) occur across northeast Canada and just east of the U.S. east coast. GFS cyclone tracks and spatial composites using the daily NCEP reanalysis are used to illustrate flow patterns and source regions for some of the large GFS cyclone errors and biases. Relatively large central pressure errors over the central Pacific early in the forecast (30 h) spread eastward over Canada by 66 h and the eastern United States by 84 h. The underdeepened GFS cyclone errors (>1.5 standard deviations) at day 4 over the western Atlantic are associated with an anomalous ridge over the western United States and trough over the eastern United States, and most of the underdeepening occurs with cyclones tracking east-northeastward across the Gulf Stream. Many of the overdeepened cyclones have tracks more parallel to the U.S. east coast. The underdeepened cyclones over the central and eastern Pacific tend to occur farther south (35°–45°N) than the overdeepened events.
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Simmonds, Ian, Craig Burke, and Kevin Keay. "Arctic Climate Change as Manifest in Cyclone Behavior." Journal of Climate 21, no. 22 (November 15, 2008): 5777–96. http://dx.doi.org/10.1175/2008jcli2366.1.
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Abstract The Arctic region has exhibited dramatic changes in recent times. Many of these are intimately tied up with synoptic activity, but little research has been undertaken on how the characteristics of Arctic cyclones have changed. This paper presents a comprehensive analysis of Arctic (here defined as the domain north of 70°N) cyclones diagnosed with the Melbourne University cyclone tracking scheme applied to the 40-yr ECMWF Re-Analysis (ERA-40) and the NCEP–NCAR (NCEP1) and NCEP–Department of Energy (DOE) Atmospheric Model Intercomparison Project (AMIP)-II (NCEP2) reanalysis sets (the last two extending to the end of 2006). A wide variety of cyclone characteristics is presented as befits these complex features. In winter the highest density of cyclones is found between Norway and Svalbard and to the east to the Barents and Kara Seas, and significant numbers are found in the central Arctic. In summer the greatest frequencies are found in the central Arctic. The total number of cyclones identified in the ERA-40 record exceeds those in the two NCEP compilations. The mean size of cyclones shows similar maxima in the central Arctic in both winter and summer. By contrast, the greatest mean system depth in winter (in excess of 8 hPa) is found to the southeast of Greenland, although average depths exceed 6 hPa over a considerable portion of the basin. In summer the deepest cyclones are found in the central portion of the Arctic. The analysis shows that the total number of cyclones in winter exceeds that in summer, a result in contrast to earlier studies. This difference comes about primarily due to the greater numbers of “open strong” systems in winter in all reanalyses. Cyclones in this category are associated with very active synoptic situations; it is of importance that they be included in cyclone counts but would not be considered in many cyclone identification schemes. Since 1979 neither the ERA-40 nor the NCEP2 sets show significant trends in any of the cyclone variables considered. However, over the entire record starting in 1958 the NCEP1 reanalysis exhibits a significant increase in summer cyclone frequency (due mainly to the increase in closed strong systems). Both NCEP1 and ERA-40 also reveal significant increases in the number of summer closed strong cyclones, as well as in their mean depth and intensity in that season. Interannual variations in Arctic cyclone numbers are closely related to the Arctic Oscillation (AO) index in the full reanalyses records. An even stronger relationship is found between the AO and the number of deep cyclones. These relationships have still held in the last decade when the AO has returned to more normal values but the summer and fall sea ice extent has continued to decrease.
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Pinto, Joaquim G., and Patrick Ludwig. "Extratropical cyclones over the North Atlantic and western Europe during the Last Glacial Maximum and implications for proxy interpretation." Climate of the Past 16, no. 2 (April 1, 2020): 611–26. http://dx.doi.org/10.5194/cp-16-611-2020.
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Abstract. Extratropical cyclones are a dominant feature of the midlatitudes, as their passage is associated with strong winds, precipitation and temperature changes. The statistics and characteristics of extratropical cyclones over the North Atlantic region exhibit some fundamental differences between pre-industrial (PI) and Last Glacial Maximum (LGM) climate conditions. Here, the statistics are analysed based on results of a tracking algorithm applied to global PI and LGM climate simulations. During the LGM, both the number and the intensity of detected cyclones were higher compared to PI. In particular, increased cyclone track activity is detected close to the Laurentide ice sheet and over central Europe. To determine changes in cyclone characteristics, the top 30 extreme storm events for PI and LGM have been simulated with a regional climate model and high resolution (12.5 km grid spacing) over the eastern North Atlantic and western Europe. Results show that LGM extreme cyclones were characterised by weaker precipitation, enhanced frontal temperature gradients and stronger wind speeds than PI analogues. These results are in line with the view of a colder and drier Europe, characterised by little vegetation and affected by frequent dust storms, leading to reallocation and build-up of thick loess deposits in Europe.
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Ullrich, Paul A., Colin M. Zarzycki, Elizabeth E. McClenny, Marielle C. Pinheiro, Alyssa M. Stansfield, and Kevin A. Reed. "TempestExtremes v2.1: a community framework for feature detection, tracking, and analysis in large datasets." Geoscientific Model Development 14, no. 8 (August 13, 2021): 5023–48. http://dx.doi.org/10.5194/gmd-14-5023-2021.
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Abstract. TempestExtremes (TE) is a multifaceted framework for feature detection, tracking, and scientific analysis of regional or global Earth system datasets on either rectilinear or unstructured/native grids. Version 2.1 of the TE framework now provides extensive support for examining both nodal (i.e., pointwise) and areal features, including tropical and extratropical cyclones, monsoonal lows and depressions, atmospheric rivers, atmospheric blocking, precipitation clusters, and heat waves. Available operations include nodal and areal thresholding, calculations of quantities related to nodal features such as accumulated cyclone energy and azimuthal wind profiles, filtering data based on the characteristics of nodal features, and stereographic compositing. This paper describes the core algorithms (kernels) that have been added to the TE framework since version 1.0, including algorithms for editing pointwise trajectory files, composition of fields around nodal features, generation of areal masks via thresholding and nodal features, and tracking of areal features in time. Several examples are provided of how these kernels can be combined to produce composite algorithms for evaluating and understanding common atmospheric features and their underlying processes. These examples include analyzing the fraction of precipitation from tropical cyclones, compositing meteorological fields around extratropical cyclones, calculating fractional contribution to poleward vapor transport from atmospheric rivers, and building a climatology of atmospheric blocks.
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Tilinina, Natalia, Alexander Gavrikov, and Sergey K. Gulev. "Association of the North Atlantic Surface Turbulent Heat Fluxes with Midlatitude Cyclones." Monthly Weather Review 146, no. 11 (October 24, 2018): 3691–715. http://dx.doi.org/10.1175/mwr-d-17-0291.1.
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Abstract Atmospheric mechanisms leading to the formation of very strong turbulent air–sea heat fluxes in the North Atlantic are analyzed using the National Centers for Environmental Prediction (NCEP) Climate Forecast System Reanalysis (CFSR) for the winter periods from 1979 to 2010. Surface turbulent flux extremes were quantified by considering both absolute and relative extremeness of these fluxes. For all cases of very strong surface turbulent fluxes, regional composites of the associated atmospheric conditions were built using reanalysis output. These composites clearly demonstrate a critical role of the cyclone–anticyclone interaction zone in forming very strong surface fluxes. The implied importance of cyclones followed by anticyclones in generation of surface air–sea heat flux extremes was demonstrated by the analysis of case studies. We further used the results of numerical cyclone tracking to identify extratropical cyclones associated with air–sea flux events of different intensities and to quantify the life cycle characteristics of these cyclones. Analysis of frequency distribution of surface heat fluxes has shown that extreme fluxes over the North Atlantic are associated with less than 30% of winter cyclones and that this association occurs mostly during the initial stage of their life cycle. Analysis of life cycle characteristics of these cyclones shows, in turn, that they are considerably more intense than most North Atlantic cyclones and are characterized by rapid deepening and slower propagation. We argue that variability of the North American high is a key factor controlling atmospheric conditions favorable for the occurrence of high turbulent air–sea heat fluxes in the North Atlantic mid- and subpolar latitudes.
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Kravtsov, Sergey, I. Rudeva, and Sergey K. Gulev. "Reconstructing Sea Level Pressure Variability via a Feature Tracking Approach." Journal of the Atmospheric Sciences 72, no. 1 (January 1, 2015): 487–506. http://dx.doi.org/10.1175/jas-d-14-0169.1.
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Abstract The aim of this paper is to quantify the contribution of synoptic transients to the full spectrum of space–time variability of sea level pressure (SLP) in middle latitudes. In previous work by the authors it was shown that tracking cyclones and anticyclones in an idealized atmospheric model allows one to reconstruct a surprisingly large fraction of the model’s variability, including not only synoptic components, but also its large-scale low-frequency component. Motivated by this result, the authors performed tracking of cyclones and anticyclones and estimated cyclone and anticyclone size and geometry characteristics in the observed SLP field using the 1948–2008 NCEP–NCAR reanalysis dataset. The reconstructed synoptic field was then produced via superimposing radially symmetrized eddies moving along their actual observed trajectories. It was found that, similar to earlier results for an idealized model, the synoptic reconstruction so obtained accounts for a major fraction of the full observed SLP variability across a wide range of time scales, from synoptic to those associated with the low-frequency variability (LFV). The synoptic reconstruction technique developed in this study helps elucidate connections between the synoptic eddies and LFV defined via more traditional spatiotemporal filtering. In particular, we found that the dominant variations in the position of the zonal-mean midlatitude jet are synonymous with random ultralow-frequency redistributions of cyclone and anticyclone trajectories and, hence, is inseparable of that in the storm-track statistics.
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Graff, L. S., and J. H. LaCasce. "Changes in Cyclone Characteristics in Response to Modified SSTs." Journal of Climate 27, no. 11 (May 29, 2014): 4273–95. http://dx.doi.org/10.1175/jcli-d-13-00353.1.
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Abstract The impact of changes in sea surface temperature (SST) on the statistics of extratropical cyclones is investigated. The cyclones were identified in an atmospheric general circulation model (AGCM) using an objective Lagrangian tracking algorithm, applied to the 850-hPa relative vorticity. The statistics were generated for several 20-yr simulations, in which the SSTs were warmed or cooled by 2 K in latitudinal bands. The response was studied in both hemispheres, during summer and winter. Changes in the position of the storm tracks are largely consistent with those seen in previous studies. Increasing SSTs uniformly or increasing the midlatitude SST gradient results in a poleward shift in the storm tracks, with the clearest trends seen in the Southern Hemisphere (SH). Here it is demonstrated that the SST modifications alter the cyclone characteristics as well. When the warming includes the low latitudes and/or the midlatitude gradient is increased, there are more short-lived cyclones. These are also on average more intense and translate faster, both poleward and eastward. The poleward displacement is correlated with cyclone intensity, so that stronger cyclones translate to higher latitudes. This is suggestive of vortex self-advection in the presence of a mean potential vorticity (PV) gradient. The increased eastward translation is correlated with the depth-averaged zonal velocity, and so is likely related to an increase in the steering-level velocity. These changes in cyclone translation probably contribute to the changes in the storm tracks seen previously.
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Polly, James B., and William B. Rossow. "Cloud Radiative Effects and Precipitation in Extratropical Cyclones." Journal of Climate 29, no. 18 (August 26, 2016): 6483–507. http://dx.doi.org/10.1175/jcli-d-15-0857.1.
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Abstract Clouds associated with extratropical cyclones complicate the well-developed theory of dry baroclinic waves through feedback on their dynamics by precipitation and cloud-altered radiative heating. The relationships between cyclone characteristics and the diabatic heating associated with cloud radiative effects (CREs) and latent heat release remain unclear. A cyclone tracking algorithm [NASA’s Modeling, Analysis, and Prediction (MAP) Climatology of Midlatitude Storminess (MCMS)] is used to identify over 106 cyclones in 33 years of the ERA-Interim and collect the properties of each disturbance. Considering storm intensity as related to wind speeds, which depend on the pressure gradient, the distribution of cyclone properties is investigated using groups defined by their depth (local pressure anomaly) and the radius of the region within closed pressure contours to investigate variations with longitude (especially ocean and land), hemisphere, and season. Using global data products of cloud radiative effects on in-atmosphere net radiation [the ISCCP radiative flux profile dataset (ISCCP-FD)] and precipitation (GPCP), composites are assembled for each cyclone group and for “nonstormy” locations. On average, the precipitation rate and the CRE are approximately the same among all cyclone groups and do not strongly differ from nonstormy conditions. The variance of both precipitation and CRE increases with cyclone size and depth. In larger, deeper storms, maximum precipitation and CRE increase, but so do the amounts of nonprecipitating and clear-sky conditions.
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Schemm, Sebastian, Lukas Papritz, and Gwendal Rivière. "Storm track response to uniform global warming downstream of an idealized sea surface temperature front." Weather and Climate Dynamics 3, no. 2 (May 19, 2022): 601–23. http://dx.doi.org/10.5194/wcd-3-601-2022.
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Abstract. The future evolution of storm tracks, their intensity, shape, and location, is an important driver of regional precipitation changes, cyclone-associated weather extremes, and regional climate patterns. For the North Atlantic storm track, Coupled Model Intercomparison Project (CMIP) data indicate a tripole pattern of change under the RCP8.5 scenario. In this study, the tripole pattern is qualitatively reproduced by simulating the change of a storm track generated downstream of an idealized sea surface temperature (SST) front under uniform warming on an aquaplanet. The simulated tripole pattern consists of reduced eddy kinetic energy (EKE) upstream and equatorward of the SST front, extended and poleward shifted enhanced EKE downstream of the SST front, and a regionally reduced EKE increase at polar latitudes. In the absence of the idealized SST front, in contrast, the storm track exhibits a poleward shift but no tripole pattern. A detailed analysis of the EKE and eddy available potential energy (EAPE) sources and sinks reveals that the changes are locally driven by changes in baroclinic conversion rather than diabatic processes. However, globally the change in baroclinic conversion averages to zero; thus the observed global EAPE increase results from diabatic generation. In particular, resolved-scale condensation plus parameterized cloud physics dominate the global EAPE increase followed by longwave radiation. Amplified stationary waves affect EKE and EAPE advection, which contributes to the local EKE and EAPE minimum at polar latitudes. Feature-based tracking provides further insight into cyclone life cycle changes downstream of the SST front. Moderately deepening cyclones deepen less in a warmer climate, while strongly deepening cyclones deepen more. Similarly, the average cyclone becomes less intense in a warmer climate, while the extremely intense cyclones become more intense. Both results hold true for cyclones with genesis in the vicinity of the SST front and elsewhere. The mean cyclone lifetime decreases, while it increases for those cyclones downstream of the SST front. The mean poleward displacement between genesis and maximum intensity increases for the most intense cyclones, while averaged over all cyclones there is a mild reduction and the result depends on the definition of the displacement. Finally, the number of cyclones decreases by approximately 15 %. Aquaplanet simulations with a localized SST front thus provide an enriched picture of storm track dynamics and associated changes with warming.
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Cao, Zuohao, and Da-Lin Zhang. "Tracking surface cyclones with moist potential vorticity." Advances in Atmospheric Sciences 21, no. 5 (October 2004): 830–35. http://dx.doi.org/10.1007/bf02916379.
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Strachan, Jane, Pier Luigi Vidale, Kevin Hodges, Malcolm Roberts, and Marie-Estelle Demory. "Investigating Global Tropical Cyclone Activity with a Hierarchy of AGCMs: The Role of Model Resolution." Journal of Climate 26, no. 1 (January 1, 2013): 133–52. http://dx.doi.org/10.1175/jcli-d-12-00012.1.
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Abstract The ability to run general circulation models (GCMs) at ever-higher horizontal resolutions has meant that tropical cyclone simulations are increasingly credible. A hierarchy of atmosphere-only GCMs, based on the Hadley Centre Global Environmental Model version 1 (HadGEM1) with horizontal resolution increasing from approximately 270 to 60 km at 50°N, is used to systematically investigate the impact of spatial resolution on the simulation of global tropical cyclone activity, independent of model formulation. Tropical cyclones are extracted from ensemble simulations and reanalyses of comparable resolutions using a feature-tracking algorithm. Resolution is critical for simulating storm intensity and convergence to observed storm intensities is not achieved with the model hierarchy. Resolution is less critical for simulating the annual number of tropical cyclones and their geographical distribution, which are well captured at resolutions of 135 km or higher, particularly for Northern Hemisphere basins. Simulating the interannual variability of storm occurrence requires resolutions of 100 km or higher; however, the level of skill is basin dependent. Higher resolution GCMs are increasingly able to capture the interannual variability of the large-scale environmental conditions that contribute to tropical cyclogenesis. Different environmental factors contribute to the interannual variability of tropical cyclones in the different basins: in the North Atlantic basin the vertical wind shear, potential intensity, and low-level absolute vorticity are dominant, whereas in the North Pacific basins midlevel relative humidity and low-level absolute vorticity are dominant. Model resolution is crucial for a realistic simulation of tropical cyclone behavior, and high-resolution GCMs are found to be valuable tools for investigating the global location and frequency of tropical cyclones.
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Ullrich, Paul A., and Colin M. Zarzycki. "TempestExtremes: a framework for scale-insensitive pointwise feature tracking on unstructured grids." Geoscientific Model Development 10, no. 3 (March 7, 2017): 1069–90. http://dx.doi.org/10.5194/gmd-10-1069-2017.
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Abstract. This paper describes a new open-source software framework for automated pointwise feature tracking that is applicable to a wide array of climate datasets using either structured or unstructured grids. Common climatological pointwise features include tropical cyclones, extratropical cyclones and tropical easterly waves. To enable support for a wide array of detection schemes, a suite of algorithmic kernels have been developed that capture the core functionality of algorithmic tracking routines throughout the literature. A review of efforts related to pointwise feature tracking from the past 3 decades is included. Selected results using both reanalysis datasets and unstructured grid simulations are provided.
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Leibensperger, E. M., L. J. Mickley, and D. J. Jacob. "Sensitivity of US air quality to mid-latitude cyclone frequency and implications of 1980–2006 climate change." Atmospheric Chemistry and Physics Discussions 8, no. 3 (June 24, 2008): 12253–82. http://dx.doi.org/10.5194/acpd-8-12253-2008.
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Abstract. We show that the frequency of summertime mid-latitude cyclones tracking across eastern North America at 40°–50° N (the southern climatological storm track) is a strong predictor of stagnation and ozone pollution episodes in the eastern United States. The NCEP/NCAR Reanalysis, going back to 1948, shows a significant long-term decline in the number of summertime mid-latitude cyclones in that track starting in 1980 (−0.15 a-1). The more recent but shorter NCEP/DOE Reanalysis (1979–2006) shows similar interannual variability in cyclone frequency but no significant long-term trend. A GISS general circulation model (GCM) simulation including historical forcing by greenhouse gases reproduces the cyclone trend seen in the NCEP/NCAR data. Such a long-term decrease in mid-latitude cyclone frequency over the 1980–2006 period would have offset by about a factor of 2 the ozone air quality gains from reductions in anthropogenic emissions in the northeastern United States. We find that if mid-latitude cyclone frequency had not declined, the northeastern US would have been largely compliant with the ozone air quality standard by 2001. Mid-latitude cyclone frequency is expected to decrease further over the coming decades in response to greenhouse warming and this trend needs to be considered in air quality management.
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Korfe, Nathan G., and Brian A. Colle. "Evaluation of Cool-Season Extratropical Cyclones in a Multimodel Ensemble for Eastern North America and the Western Atlantic Ocean." Weather and Forecasting 33, no. 1 (January 10, 2018): 109–27. http://dx.doi.org/10.1175/waf-d-17-0036.1.
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Abstract This paper evaluates the extratropical cyclones within three operational global ensembles [the 20-member Canadian Meteorological Centre (CMC), 20-member National Centers for Environmental Prediction (NCEP), and 50-member European Centre for Medium-Range Weather Forecasts (ECMWF)]. The day-0–6 forecasts were evaluated over the eastern United States and western Atlantic for the 2007–15 cool seasons (October–March) using the ECMWF’s ERA-Interim dataset as the verifying analysis. The Hodges cyclone-tracking scheme was used to track cyclones using 6-h mean sea level pressure (MSLP) data. For lead times less than 72 h, the NCEP and ECMWF ensembles have comparable mean absolute errors in cyclone intensity and track, while the CMC errors are larger. For days 4–6 ECMWF has 12–18 and 24–30 h more accuracy for cyclone intensity than NCEP and CMC, respectively. All ensembles underpredict relatively deep cyclones in the medium range, with one area near the Gulf Stream. CMC, NCEP, and ECMWF all have a slow along-track bias that is significant from 24 to 90 h, and they have a left-of-track bias from 120 to 144 h. ECMWF has greater probabilistic skill for intensity and track than CMC and NCEP, while the 90-member multimodel ensemble (NCEP + CMC + ECMWF) has more probabilistic skill than any single ensemble. During the medium range, the ECMWF + NCEP + CMC multimodel ensemble has the fewest cases (1.9%, 1.8%, and 1.0%) outside the envelope compared to ECMWF (5.6%, 5.2%, and 4.1%) and NCEP (13.7%, 10.6%, and 11.0%) for cyclone intensity and along- and cross-track positions.
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Froude, Lizzie S. R. "TIGGE: Comparison of the Prediction of Northern Hemisphere Extratropical Cyclones by Different Ensemble Prediction Systems." Weather and Forecasting 25, no. 3 (June 1, 2010): 819–36. http://dx.doi.org/10.1175/2010waf2222326.1.
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Abstract The Observing System Research and Predictability Experiment (THORPEX) Interactive Grand Global Ensemble (TIGGE) is a World Weather Research Programme project. One of its main objectives is to enhance collaboration on the development of ensemble prediction between operational centers and universities by increasing the availability of ensemble prediction system (EPS) data for research. This study analyzes the prediction of Northern Hemisphere extratropical cyclones by nine different EPSs archived as part of the TIGGE project for the 6-month time period of 1 February 2008–31 July 2008, which included a sample of 774 cyclones. An objective feature tracking method has been used to identify and track the cyclones along the forecast trajectories. Forecast verification statistics have then been produced [using the European Centre for Medium-Range Weather Forecasts (ECMWF) operational analysis as the truth] for cyclone position, intensity, and propagation speed, showing large differences between the different EPSs. The results show that the ECMWF ensemble mean and control have the highest level of skill for all cyclone properties. The Japanese Meteorological Administration (JMA), the National Centers for Environmental Prediction (NCEP), the Met Office (UKMO), and the Canadian Meteorological Centre (CMC) have 1 day less skill for the position of cyclones throughout the forecast range. The relative performance of the different EPSs remains the same for cyclone intensity except for NCEP, which has larger errors than for position. NCEP, the Centro de Previsão de Tempo e Estudos Climáticos (CPTEC), and the Australian Bureau of Meteorology (BoM) all have faster intensity error growth in the earlier part of the forecast. They are also very underdispersive and significantly underpredict intensities, perhaps due to the comparatively low spatial resolutions of these EPSs not being able to accurately model the tilted structure essential to cyclone growth and decay. There is very little difference between the levels of skill of the ensemble mean and control for cyclone position, but the ensemble mean provides an advantage over the control for all EPSs except CPTEC in cyclone intensity and there is an advantage for propagation speed for all EPSs. ECMWF and JMA have an excellent spread–skill relationship for cyclone position. The EPSs are all much more underdispersive for cyclone intensity and propagation speed than for position, with ECMWF and CMC performing best for intensity and CMC performing best for propagation speed. ECMWF is the only EPS to consistently overpredict cyclone intensity, although the bias is small. BoM, NCEP, UKMO, and CPTEC significantly underpredict intensity and, interestingly, all the EPSs underpredict the propagation speed, that is, the cyclones move too slowly on average in all EPSs.
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Crawford, Alex D., and Mark C. Serreze. "Does the Summer Arctic Frontal Zone Influence Arctic Ocean Cyclone Activity?" Journal of Climate 29, no. 13 (June 27, 2016): 4977–93. http://dx.doi.org/10.1175/jcli-d-15-0755.1.
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Abstract Extratropical cyclone activity over the central Arctic Ocean reaches its peak in summer. Previous research has argued for the existence of two external source regions for cyclones contributing to this summer maximum: the Eurasian continent interior and a narrow band of strong horizontal temperature gradients along the Arctic coastline known as the Arctic frontal zone (AFZ). This study incorporates data from an atmospheric reanalysis and an advanced cyclone detection and tracking algorithm to critically evaluate the relationship between the summer AFZ and cyclone activity in the central Arctic Ocean. Analysis of both individual cyclone tracks and seasonal fields of cyclone characteristics shows that the Arctic coast (and therefore the AFZ) is not a region of cyclogenesis. Rather, the AFZ acts as an intensification area for systems forming over Eurasia. As these systems migrate toward the Arctic Ocean, they experience greater deepening in situations when the AFZ is strong at midtropospheric levels. On a broader scale, intensity of the summer AFZ at midtropospheric levels has a positive correlation with cyclone intensity in the Arctic Ocean during summer, even when controlling for variability in the northern annular mode. Taken as a whole, these findings suggest that the summer AFZ can intensify cyclones that cross the coast into the Arctic Ocean, but focused modeling studies are needed to disentangle the relative importance of the AFZ, large-scale circulation patterns, and topographic controls.
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Maslova, V. N., E. N. Voskresenskaya, A. V. Yurovsky, V. Yu Zhuravsky, V. P. Evstigneev, and V. A. Naumova. "Methodological approaches to the study of cyclonic systems related to different types of intense storms in the North Black Sea region." Monitoring systems of environment, no. 3 (September 24, 2020): 05–14. http://dx.doi.org/10.33075/2220-5861-2020-3-5-14.
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The aim of the paper is to study the surface and mid – tropospheric synoptic fields, the location of trajectories and of the deep cyclones centers for different selected types of storm for the cases if the wave heights are of at least 5 m. The sets of cyclone parameters in the Black Sea region were analysef within the 37°-50° N, 27°-45° E. Cyclones and their main parameters were determined using 4-term NCEP / NCAR reanalysis data sets on the 1000 and 500 hPa geopotential height (GPH) in 1951-2017. Bardin’s methodology was used for calculation. Deep cyclones were identified by the criterion of exceeding the upper 75% quartile threshold of the depth (≥40 gpm) and intensity (≥16.8 gpm) of cyclones. It was done by analogy with the method used earlier by the authors to calculate extreme precipitation and statistical characteristics of storms. In addition, we used the author’s method of objective tracking using spline interpolation on the bases of sea surface pressure from the same NCEP / NCAR reanalysis. The reason to apply an additional method was the result obtained during the work realisation: about 30% of extreme storms in the region are caused by small local cyclones that occur over the Black sea. however, some of them cannot be determined using method 1 due to the coarser step of isogyps. As a result, the distribution of deep cyclone centers and their trajectories of different storm types at the Northern Black Sea coast for the cases if the wave height of at least 5 m is shown. It is found that storm types depend of synoptic field features. The centers of deep cyclones are concentrated to the North from the Black Sea coast (for Western type 1B), to the Northwest (for mixed type 2A), to the North-East (for mixed type 2B), and to the South-Eeast (for Central type 3).
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Bauer, Mike, and Anthony D. Del Genio. "Composite Analysis of Winter Cyclones in a GCM: Influence on Climatological Humidity." Journal of Climate 19, no. 9 (May 1, 2006): 1652–72. http://dx.doi.org/10.1175/jcli3690.1.
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Abstract The role of midlatitude baroclinic cyclones in maintaining the extratropical winter distribution of water vapor in an operational global climate model is investigated. A cyclone identification and tracking algorithm is used to compare the frequency of occurrence, propagation characteristics, and composite structure of 10 winters of storms in the Goddard Institute for Space Studies general circulation model (GCM) and in two reanalysis products. Cyclones are the major dynamical source of water vapor over the extratropical oceans in the reanalyses. The GCM produces fewer, generally weaker, and slower-moving cyclones than the reanalyses and is especially deficient in storms associated with secondary cyclogenesis. Composite fields show that GCM cyclones are shallower and drier aloft than those in the reanalyses and that their vertical structure is less tilted in the frontal region because of the GCM’s weaker ageostrophic circulation. This is consistent with the GCM’s underprediction of midlatitude cirrus. The GCM deficiencies do not appear to be primarily due to parameterization errors; the model is too dry despite producing less storm precipitation than is present in the reanalyses and in an experimental satellite precipitation dataset, and the weakness and shallow structure of GCM cyclones is already present at storm onset. These shortcomings may be common to most climate GCMs that do not resolve the mesoscale structure of frontal zones, and this may account for some universal problems in climate GCM midlatitude cloud properties.