Bibliografie tematiche / Atmospheric reanalyses

Letteratura scientifica selezionata sul tema "Atmospheric reanalyses"

Autore: Grafiati

Pubblicato: 25 maggio 2024

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Articoli di riviste sul tema "Atmospheric reanalyses":

Kumar, Arun, Li Zhang e Wanqiu Wang. "Sea Surface Temperature–Precipitation Relationship in Different Reanalyses". Monthly Weather Review 141, n. 3 (1 marzo 2013): 1118–23. http://dx.doi.org/10.1175/mwr-d-12-00214.1.

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Abstract The focus of this investigation is how the relationship at intraseasonal time scales between sea surface temperature and precipitation (SST–P) varies among different reanalyses. The motivation for this work was spurred by a recent report that documented that the SST–P relationship in Climate Forecast System Reanalysis (CFSR) was much closer to that in the observation than it was for the older generation of reanalyses [i.e., NCEP–NCAR reanalysis (R1) and NCEP–Department of Energy (DOE) reanalysis (R2)]. Further, the reason was attributed either to the fact that the CFSR is a partially coupled reanalysis, while R1 and R2 are atmospheric-alone reanalyses, or that R1 and R2 use the observed weekly-averaged SST. The authors repeated the comparison of the SST–P relationship among R1, R2, and CFSR, as well as two recent generations of atmosphere-alone reanalyses, the Modern-Era Retrospective Analysis for Research and Applications (MERRA) and the ECMWF Re-Analysis Interim (ERA-Interim). The results clearly demonstrate that the differences in the SST–P relationship at intraseasonal time scales across different reanalyses are not due to whether the reanalysis system is coupled or atmosphere alone, but are due to the specification of different SSTs. The SST–P relationship in different reanalyses, when computed against a single SST for the benchmark, demonstrates a relationship that is common across all of the reanalyses and observations.

Zib, Behnjamin J., Xiquan Dong, Baike Xi e Aaron Kennedy. "Evaluation and Intercomparison of Cloud Fraction and Radiative Fluxes in Recent Reanalyses over the Arctic Using BSRN Surface Observations". Journal of Climate 25, n. 7 (28 marzo 2012): 2291–305. http://dx.doi.org/10.1175/jcli-d-11-00147.1.

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Abstract With continual advancements in data assimilation systems, new observing systems, and improvements in model parameterizations, several new atmospheric reanalysis datasets have recently become available. Before using these new reanalyses it is important to assess the strengths and underlying biases contained in each dataset. A study has been performed to evaluate and compare cloud fractions (CFs) and surface radiative fluxes in several of these latest reanalyses over the Arctic using 15 years (1994–2008) of high-quality Baseline Surface Radiation Network (BSRN) observations from Barrow (BAR) and Ny-Alesund (NYA) surface stations. The five reanalyses being evaluated in this study are (i) NASA's Modern-Era Retrospective analysis for Research and Applications (MERRA), (ii) NCEP's Climate Forecast System Reanalysis (CFSR), (iii) NOAA's Twentieth Century Reanalysis Project (20CR), (iv) ECMWF's Interim Reanalysis (ERA-I), and (v) NCEP–Department of Energy (DOE)'s Reanalysis II (R2). All of the reanalyses show considerable bias in reanalyzed CF during the year, especially in winter. The large CF biases have been reflected in the surface radiation fields, as monthly biases in shortwave (SW) and longwave (LW) fluxes are more than 90 (June) and 60 W m−2 (March), respectively, in some reanalyses. ERA-I and CFSR performed the best in reanalyzing surface downwelling fluxes with annual mean biases less than 4.7 (SW) and 3.4 W m−2 (LW) over both Arctic sites. Even when producing the observed CF, radiation flux errors were found to exist in the reanalyses suggesting that they may not always be dependent on CF errors but rather on variations of more complex cloud properties, water vapor content, or aerosol loading within the reanalyses.

Hertzog, Albert, Claude Basdevant e François Vial. "An Assessment of ECMWF and NCEP–NCAR Reanalyses in the Southern Hemisphere at the End of the Presatellite Era: Results from the EOLE Experiment (1971–72)". Monthly Weather Review 134, n. 11 (1 novembre 2006): 3367–83. http://dx.doi.org/10.1175/mwr3256.1.

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Abstract This article estimates the biases and standard deviations of the 40-yr European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis (ERA-40) and the 50-yr National Centers for Environmental Prediction–National Center for Atmospheric Research (NCEP–NCAR) Reanalysis (NN50) in the upper troposphere and lower stratosphere in 1971–72. These estimates are obtained by comparing the reanalyzed temperatures and winds with EOLE observations, a dataset collected during 480 superpressure-ballon flights in the Southern Hemisphere (SH). Dedicated algorithms have been developped to control the quality of this dataset and a stringent selection has been performed on the observations. None of the atmospheric centers has assimilated the EOLE dataset, which is therefore fully independent from the reanalyses. It is furthermore argued that the statistics obtained in this study at the end of the presatellite era may be representative of the reanalysis accuracy since 1957. The results of these comparisons indicate that NN50 tends to be a few degrees colder than the observations in the SH subpolar latitudes, while ERA-40 is less hit by this cold-pole issue. Both reanalyses, on the other hand, are found to be warmer than the observations by about 1 K in the subtropics. In contrast, the wind comparisons only exhibit nonsignificant or small reanalysis biases, even though the reanalyzed subtropical jet is slightly displaced equatorward with respect to the observations. The ability of reanalyses to capture the atmospheric synoptic-scale variability in the upper troposphere is assessed by computing the standard deviations of the reanalysis minus observation differences. The ERA-40 and NN50 standard deviations show a maximum (i.e., a poorer reanalysis accuracy) in the SH storm track. However, ERA-40 standard deviations are found to be much larger than NN50 standard deviations. The standard deviations also exhibit a marked decrease above the continents, stressing the heterogeneity of the atmospheric observation network during the presatellite era. Finally, in contrast with previous studies, the reanalysis accuracy does not appear to be better during summer than during winter.

Fujiwara, Masatomo, Jonathon S. Wright, Gloria L. Manney, Lesley J. Gray, James Anstey, Thomas Birner, Sean Davis et al. "Introduction to the SPARC Reanalysis Intercomparison Project (S-RIP) and overview of the reanalysis systems". Atmospheric Chemistry and Physics 17, n. 2 (31 gennaio 2017): 1417–52. http://dx.doi.org/10.5194/acp-17-1417-2017.

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Abstract. The climate research community uses atmospheric reanalysis data sets to understand a wide range of processes and variability in the atmosphere, yet different reanalyses may give very different results for the same diagnostics. The Stratosphere–troposphere Processes And their Role in Climate (SPARC) Reanalysis Intercomparison Project (S-RIP) is a coordinated activity to compare reanalysis data sets using a variety of key diagnostics. The objectives of this project are to identify differences among reanalyses and understand their underlying causes, to provide guidance on appropriate usage of various reanalysis products in scientific studies, particularly those of relevance to SPARC, and to contribute to future improvements in the reanalysis products by establishing collaborative links between reanalysis centres and data users. The project focuses predominantly on differences among reanalyses, although studies that include operational analyses and studies comparing reanalyses with observations are also included when appropriate. The emphasis is on diagnostics of the upper troposphere, stratosphere, and lower mesosphere. This paper summarizes the motivation and goals of the S-RIP activity and extensively reviews key technical aspects of the reanalysis data sets that are the focus of this activity. The special issue The SPARC Reanalysis Intercomparison Project (S-RIP) in this journal serves to collect research with relevance to the S-RIP in preparation for the publication of the planned two (interim and full) S-RIP reports.

Song, Hua, e Minghua Zhang. "Changes of the Boreal Winter Hadley Circulation in the NCEP–NCAR and ECMWF Reanalyses: A Comparative Study". Journal of Climate 20, n. 20 (15 ottobre 2007): 5191–200. http://dx.doi.org/10.1175/jcli4260.1.

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Abstract Both the ECMWF and the NCEP–NCAR reanalyses show a strengthening of the atmospheric Hadley circulation in boreal winter over the last 50 years, but the intensification is much stronger in the ECMWF than in the NCEP–NCAR reanalysis. This study focuses on the difference of these trends in the two reanalyses. It is shown that trends in the Hadley circulation in the two reanalyses differ mainly over the tropical western Pacific. This difference is found to be consistent with respective trends of the atmospheric transport of moist static energy, longwave cloud radiative forcing, and upper-level clouds in the two reanalyses. Two independent datasets of upper-level cloud cover and sea level pressure from ship-based measurements are then used to evaluate the reanalyses over the tropical western Pacific. They are found to be more consistent with the trends in the NCEP–NCAR reanalysis than those in the ECMWF reanalysis. The results suggest a weakening of the vertical motion associated with the Hadley circulation in the tropical western Pacific.

King, Austin T., e Aaron D. Kennedy. "North American Supercell Environments in Atmospheric Reanalyses and RUC-2". Journal of Applied Meteorology and Climatology 58, n. 1 (gennaio 2019): 71–92. http://dx.doi.org/10.1175/jamc-d-18-0015.1.

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AbstractA suite of modern atmospheric reanalyses is analyzed to determine how they represent North American supercell environments. This analysis is performed by comparing a database of Rapid Update Cycle (RUC-2) proximity soundings with profiles derived from the nearest grid point in each reanalysis. Parameters are calculated using the Sounding and Hodograph Analysis and Research Program in Python (SHARPpy), an open-source Python sounding-analysis package. Representation of supercell environments varies across the reanalyses, and the results have ramifications for climatological studies that use these datasets. In particular, thermodynamic parameters such as the convective available potential energy (CAPE) show the widest range in biases, with reanalyses falling into two camps. The North American Regional Reanalysis (NARR) and the Japanese 55-year Reanalysis (JRA-55) are similar to RUC-2, but other reanalyses have a substantial negative bias. The reasons for these biases vary and range from thermodynamic biases at the surface to evidence of convective contamination. Overall, it is found that thermodynamic biases feed back to other convective parameters that incorporate CAPE directly or indirectly via the effective layer. As a result, significant negative biases are found for indices such as the supercell composite parameter. These biases are smallest for NARR and JRA-55. Kinematic parameters are more consistent across the reanalyses. Given the issues with thermodynamic properties, better segregation of soundings by storm type is found for fixed-layer parameters than for effective-layer shear parameters. Although no reanalysis can exactly reproduce the results of earlier RUC-2 studies, many of the reanalyses can broadly distinguish between environments that are significantly tornadic versus nontornadic.

Lader, Rick, Uma S. Bhatt, John E. Walsh, T. Scott Rupp e Peter A. Bieniek. "Two-Meter Temperature and Precipitation from Atmospheric Reanalysis Evaluated for Alaska". Journal of Applied Meteorology and Climatology 55, n. 4 (aprile 2016): 901–22. http://dx.doi.org/10.1175/jamc-d-15-0162.1.

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AbstractAlaska is experiencing effects of global climate change that are due, in large part, to the positive feedback mechanisms associated with polar amplification. The major risk factors include loss of sea ice and glaciers, thawing permafrost, increased wildfires, and ocean acidification. Reanalyses, integral to understanding mechanisms of Alaska’s past climate and to helping to calibrate modeling efforts, are based on the output of weather forecast models that assimilate observations. This study evaluates temperature and precipitation from five reanalyses at monthly and daily time scales for the period 1979–2009. Monthly data are evaluated spatially at grid points and for six climate zones in Alaska. In addition, daily maximum temperature, minimum temperature, and precipitation from reanalyses are compared with meteorological-station data at six locations. The reanalyses evaluated in this study include the NCEP–NCAR reanalysis (R1), North American Regional Reanalysis (NARR), Climate Forecast System Reanalysis (CFSR), ERA-Interim, and the Modern-Era Retrospective Analysis for Research and Applications (MERRA). Maps of seasonal bias and standard deviation, constructed from monthly data, show how the reanalyses agree with observations spatially. Cross correlations between the monthly gridded and daily station time series are computed to provide a measure of confidence that data users can assume when selecting reanalysis data in a region without many surface observations. A review of natural hazards in Alaska indicates that MERRA is the top reanalysis for wildfire and interior-flooding applications. CFSR is the recommended reanalysis for North Slope coastal erosion issues and, along with ERA-Interim, for heavy precipitation in southeastern Alaska.

Sang, Xiaozhuo, Xiu-Qun Yang, Lingfeng Tao, Jiabei Fang e Xuguang Sun. "Evaluation of synoptic eddy activities and their feedback onto the midlatitude jet in five atmospheric reanalyses with coarse versus fine model resolutions". Climate Dynamics 58, n. 5-6 (27 settembre 2021): 1363–81. http://dx.doi.org/10.1007/s00382-021-05965-9.

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AbstractInteraction between synoptic eddy and mean flow plays a crucial role in maintaining midlatitude westerly jet. In this study, climatologies of synoptic eddy activities and their feedback onto midlatitude jet for 1980–2016 are evaluated and compared through analyzing daily data from five atmospheric reanalyses with different resolutions including one coarse-resolution reanalysis (NCEP2) and four fine-resolution reanalyses (ERA-Interim, JRA-55, MERRA-2, and CFSR). Horizontal resolutions of the atmospheric models generating those reanalyses are approximately equivalent to 210, 79, 60, 50, and 38 km, respectively. Results show that the eddy activities and their feedback onto the midlatitude jet in those fine-resolution reanalyses are consistently and significantly stronger than those in the coarse-resolution reanalysis (NCEP2). The maximal relative increases that are found to occur primarily in the midlatitudes of the Southern Hemisphere are estimated to be up to 55% for the baroclinicity, 53% for the eddy energetics, 59% for the eddy forcing, and even 85% for the eddy feedback onto the mean flow. Those increases are reasonably conjectured to be related to increased model resolutions, since the synoptic eddy genesis is proportional to the low-level atmospheric meridional temperature gradient which is sensitive to the meridional resolution of atmospheric models. Although the coarse-resolution reanalysis resolves synoptic eddies insufficiently and thus underestimates their feedback onto the mean flow, the magnitudes of eddy-driven jets are almost the same among five reanalyses, implying a mismatch between the eddy feedback and the eddy-driven jet in the coarse-resolution reanalysis. Therefore, the results of this study imply the importance of using fine-resolution reanalyses in accurately understanding the midlatitude synoptic eddy–mean flow interaction.

Hynčica, Martin, e Radan Huth. "Modes of Atmospheric Circulation Variability in the Northern Extratropics: A Comparison of Five Reanalyses". Journal of Climate 33, n. 24 (15 dicembre 2020): 10707–26. http://dx.doi.org/10.1175/jcli-d-19-0904.1.

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AbstractModes of low-frequency circulation variability in the Northern Hemisphere extratropics are compared between five reanalyses. Circulation modes are detected by rotated principal component analysis (PCA) of monthly mean 500-hPa geopotential heights between 1957 and 2002, separately for individual seasons. The quantification of differences between reanalyses is based on the percentage of grid points (approximately corresponding to the percentage of area) where the spatial representations of a mode (loadings) significantly differ between reanalyses. The differences between surface-input reanalyses (20CRv2c, ERA-20C) and full-input reanalyses (NCEP-1, ERA-40, JRA-55) are larger than differences within the reanalysis groups in all seasons except for autumn. The causes of the differences are of two kinds. First, the differences may be inherent to PCA: namely, the spatial structure of the modes may be sensitive to the number of components rotated. This concerns only a few modes. Second, the differences may reflect real correlation structures in reanalysis data. We demonstrate that the differences concentrate in three or fewer modes in each season. The reanalysis most different from the rest is 20CRv2c, with the differences concentrating over the southern half of Asia and in the subtropical belt over the Pacific and adjacent southwestern North America. The 20CRv2c reanalysis disagrees from other reanalyses there predominantly before the 1980s, which points to the impact of insufficient amount of assimilated observations. On the contrary, ERA-20C exhibits a higher agreement with full-input reanalyses, which is why we recommend it for studies of atmospheric circulation over the entire twentieth century.

Millán, Luis F., Gloria L. Manney e Zachary D. Lawrence. "Reanalysis intercomparison of potential vorticity and potential-vorticity-based diagnostics". Atmospheric Chemistry and Physics 21, n. 7 (7 aprile 2021): 5355–76. http://dx.doi.org/10.5194/acp-21-5355-2021.

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Abstract. Global reanalyses from data assimilation systems are among the most widely used datasets in weather and climate studies, and potential vorticity (PV) from reanalyses is invaluable for many studies of dynamical and transport processes. We assess how consistently modern reanalyses represent potential vorticity (PV) among each other, focusing not only on PV but also on process-oriented dynamical diagnostics including equivalent latitude calculated from PV and PV-based tropopause and stratospheric polar vortex characterization. In particular we assess the National Centers for Environmental Prediction Climate Forecast System Reanalysis/Climate Forecast System, version 2 (CFSR/CFSv2) reanalysis, the European Centre for Medium-Range Weather Forecasts Interim (ERA-Interim) reanalysis, the Japanese Meteorological Agency's 55-year (JRA-55) reanalysis, and the NASA Modern-Era Retrospective analysis for Research and Applications, version 2 (MERRA-2). Overall, PV from all reanalyses agrees well with the reanalysis ensemble mean, providing some confidence that all of these recent reanalyses are suitable for most studies using PV-based diagnostics. Specific diagnostics where some larger differences are seen include PV-based tropopause locations in regions that have strong tropopause gradients (such as around the subtropical jets) or are sparse in high-resolution data (such as over Antarctica), and the stratospheric polar vortices during fall vortex formation and (especially) spring vortex breakup; studies of sensitive situations or regions such as these should examine PV from multiple reanalyses.

Più fonti

Tesi sul tema "Atmospheric reanalyses":

Huynh, Jonathan. "Heat Stress in a Climate Setting| A Framework for Reanalyses". Thesis, University of California, Davis, 2017. http://pqdtopen.proquest.com/#viewpdf?dispub=10619617.

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The proliferation of reanalysis models for the atmosphere in recent decades has allowed researchers to study Earth’s past climate in great detail. While much work has gone into understanding key climate indicators such as surface temperature and precipitation trends, there have been few studies dealing with heat stress. As climate change grows increasingly exigent, it is becoming vitally important to understand the thermal impacts on biological systems.

This study analyzed data from five reanalysis models (20CRv2, NARR, NNRA 1, NCEP DOE 2, and ERA-I) and found agreement in average surface temperature increases of 0.2–0.6°C per decade across the U.S. west coast and east coast since 1979. These trends were consistent with previous studies. Less agreement was found for the central U.S. The Temperature Humidity Index and the Heat Index were found to generally follow the temperature trends. An analysis of the role of moisture indicated that the effect of specific humidity on heat stress is dependent on climatology. Trends of heat stress over arid regions such as the desert southwest were found to be much more influenced by temperature trends than by moisture trends. In contrast, moisture seemed to play a stronger role in the more humid southeast. There appeared to be a more equal effect of temperature and moisture on heat stress in the northeast and Great Lake states.

Perhaps equally as important, the study provides a framework to reduce computational time but allows for more rigorous statistical methods that are not available in the typical suite of software and programming languages to analyze climate data. Functionality was developed to infer daily extrema from six-hourly reanalysis data. A shapefile was used to aggregate the data according to prescribed geographic boundaries and reduce the load of data for statistical analysis. Time series decomposition was performed on the aggregated daily data to determine linear trends which were then mapped out to visualize their spatial features.

Stuckman, Scott Seele. "Global Three-Dimensional Atmospheric Structure of the Atlantic Multidecadal Oscillation as Revealed by Two Reanalyses". The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1476105315092858.

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Connolly, Charlotte J. "Causes of Southern Hemisphere climate variability in the early 20th century". Ohio University Honors Tutorial College / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=ouhonors1587217042363834.

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Lytle, William. "Coupled Evaluation of Below- and Above-Ground Energy and Water Cycle Variables from Reanalysis Products Over Five Flux Tower Sites in the U.S". Thesis, The University of Arizona, 2015. http://hdl.handle.net/10150/595636.

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Reanalysis products are widely used to study the land-atmosphere exchanges of energy, water, and carbon fluxes, and have been evaluated using in situ data above or below ground. Here measurements for several years at five flux tower sites in the U.S. (with a total of 315,576 hours of data) are used for the coupled evaluation of both below- and above-ground processes from three global reanalysis products and six global land data assimilation products. All products show systematic errors in precipitation, snow depth, and the timing of the melting and onset of snow. Despite the biases in soil moisture, all products show significant correlations with observed daily soil moisture for the periods with unfrozen soil. While errors in 2 meter air temperature are highly correlated with errors in skin temperature for all sites, the correlations between skin and soil temperature errors are weaker, particularly over the sites with seasonal snow. While net shortwave and longwave radiation flux errors have opposite signs across all products, the net radiation and ground heat flux errors are usually smaller in magnitude than turbulent flux errors. On the other hand, the all-product averages usually agree well with the observations on the evaporative fraction, defined as the ratio of latent heat over the sum of latent and sensible heat fluxes. This study identifies the strengths and weaknesses of these widely-used products, and helps understand the connection of their errors in above- versus below-ground quantities.

Weese, Scott R. "A reanalysis of hurricane Hazel (1954) /". Thesis, McGill University, 2003. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=80894.

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Hurricane Hazel struck North America on 15-16 October 1954, leaving a pattern of heavy rainfall and flooding in its wake. A complete analysis of the synoptic-scale conditions associated with the transformation of Hazel from its tropical phase into an extratropical cyclone was first undertaken to discern the dynamic and thermodynamic elements crucial to the intensification of this storm.
An analogue search was then conducted for Hazel using linear correlations of anomaly sea level pressure and 1000-500 hPa thickness. Three cases were found in 1985, 1995 and 1999. A comparison of these analogues to Hazel yielded the conclusion that Hazel is a unique event in recent meteorological history, as none of the analogues produces the extreme precipitation values in Hazel. The lack of significant hurricane circulations in all of the analogues is the important difference, as Hazel provides important moisture and latent heating that are absent in the analogues.
Finally a mesoscale modeling study was carried out to test the sensitivity of Hazel to improved surface vortex structure and increased horizontal resolution. Specification of the vortex led to a dramatic improvement in the simulation results, as precipitation and track closely mimicked the observed values. Enhancing the horizontal resolution to 12 km did not improve upon the 36 km specified vortex simulation. The movement of the storm slowed considerably as the development of an upper tropospheric cutoff circulation was diminished in the 12 km run. The parameterizations governing the interaction between the diabatic outflow from Hazel and dynamics of the midlatitude trough are poorly modeled in this situation, and lead to the severe time lag in the path of Hazel.

Moraes, Ayrton Zadra. "Empirical normal mode diagnosis of reanalysis data and dynamical-core experiments". Thesis, McGill University, 2000. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=37785.

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Global data and numerical models are used to investigate the climatology and variability in the upper-troposphere and lower-stratosphere where large-scale low-frequency vorticity modes dominate over high-frequency inertia-gravity waves. An algorithm based on the Empirical Normal Mode decomposition technique is proposed as a diagnostic tool. This technique combines dynamics (a wave-activity of linear dynamics defines the orthogonality between modes) with statistics (the wave-activity amplitude of each mode provides a measure of its statistical significance) and has the unbiased ability to capture neutral normal modes as well as singular modes.
First, the algorithm is applied to winter data provided by the National Centers for Environmental Prediction (NCEP) reanalyses and results indicate that most wave-activity is carried by large-scale, eastward-propagating modes centered at mid- and high-latitudes. The phase-speeds of some leading modes are in good agreement with theoretical predictions of linear dynamics. Some mid-latitude modes exhibit properties that can be explained by the theory of quasi-modes---for example, the leading wavenumber-5 mode with a dipolar pressure field near the tropopause, a propagation speed of 12 m s-1 and a decay rate of 3 days.
In a model study, we use data from two dynamical-core experiments of the Global Environmental Multiscale model: one with the forcing proposed by Held and Suarez, later modified by Williamson et al. (called HSW experiment); the other with the forcing by Boer and Denis (BD). Modes and spectra are similar to those found in the NCEP data study, although details depend on the forcing. For instance, wave-energy amplitudes are higher with the BD forcing and an approximate energy equipartition is observed in the spectrum of wavenumber-1 modes in the studies of NCEP data and BD experiment, but not in the HSW experiment.
The HSW forcing has a relatively strong relaxation acting on the complete temperature field, whereas the BD forcing only acts on the zonal-mean temperature letting the internal dynamics alone drive the wave-activity cascade through the rest of the spectrum. This difference seems to explain why the BD forcing is more successful in reproducing the observed atmospheric wave-activity.

Wilson, Aaron Benjamin. "Enhancement of Polar WRF atmospheric and surface processes: An annual simulation". The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1268066611.

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Tastula, Esa-Matti. "Insights into the Challenges of Modeling the Atmospheric Boundary Layer". Scholar Commons, 2015. http://scholarcommons.usf.edu/etd/5782.

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This work approaches the topic of modeling the atmospheric boundary layer in four research projects, which are summarized below. i) The diurnal cycles of near-surface meteorological parameters over Antarctic sea ice in six widely used atmospheric reanalyses were validated against observations from Ice Station Weddell. The station drifted from February through May 1992 and provided the most extensive set of meteorological observations ever collected in the Antarctic sea ice zone. For the radiative and turbulent surface fluxes, both the amplitude and shape of the diurnal cycles varied considerably among different reanalyses. Near-surface temperature, specific humidity, and wind speed in the reanalyses all featured small diurnal ranges, which, in most cases, fell within the uncertainties of the observed cycle. A skill score approach revealed the superiority of the ERA-Interim reanalysis in reproducing the observed diurnal cycles. An explanation for the shortcomings in the reanalyses is their failure to capture the diurnal cycle in cloud cover fraction, which leads to errors in other quantities as well. Apart from the diurnal cycles, NCEP-CFSR gave the best error statistics. ii) The accuracy of prediction of stable atmospheric boundary layers depends on the parameterization of the surface layer which is usually derived from the Monin-Obukhov similarity theory. In this study, several surface-layer models in the format of velocity and potential temperature Deacon numbers were compared to observations from CASES-99, Cardington, and Halley datasets. The comparisons were hindered by a large amount of scatter within and among datasets. Tests utilizing R2 demonstrated that the Quasi-Normal Scale Elimination (QNSE) theory exhibits the best overall performance. Further proof of this was provided by 1D simulations with the Weather Research and Forecasting (WRF) model. iii) The increasing number of physics parameterization schemes adopted in numerical weather forecasting models has resulted in a proliferation of inter-comparison studies in recent years. Many of these studies concentrated on determining which parameterization yields results closest to observations rather than analyzing the reasons underlying the differences. In this work, the performance of two 1.5-order boundary layer parameterizations was studied, the QNSE and Mellor-Yamada-Janjić (MYJ) schemes, in the Weather Research and Forecasting (WRF) model. The objectives were to isolate the effect of stability functions on the near-surface values and vertical profiles of virtual temperature, mixing ratio and wind speed. The results demonstrate that the QNSE stability functions yield better error statistics for 2-m virtual temperature but higher up the errors related to QNSE are slightly larger for virtual temperature and mixing ratio. A surprising finding is the sensitivity of the model results to the choice of the turbulent Prandtl number for neutral stratification (Prt0): in the Monin-Obukhov similarity function for heat, the choice of Prt0 is sometimes more important than the functional form of the similarity function itself. There is a stability-related dependence to this sensitivity: with increasing near-surface stability, the relative importance of the functional form increases. In near-neutral conditions, QNSE exhibits too strong vertical mixing attributed to the applied turbulent kinetic energy subroutine and the stability functions including the effect of Prt0. iv) In recent years, many eddy-diffusivity mass flux (EDMF) planetary boundary layer (PBL) parameterizations have been introduced. Yet, most validations are based on idealized setups and/or single column models. To address this gap, this study focused on the effect the mass flux part has on the performance in the QNSE-EDMF PBL scheme in the WRF model by comparing the results to observations from the CASES-97 field campaign. In addition, two refined versions, one introducing the parameterized clouds to the WRF radiation scheme, and the second adding a different entrainment formulation, were evaluated. The introduction of mass flux reduced errors in the average moisture profile but virtual temperature and wind speed profiles did not change as much. The turbulent flux profiles for modeled virtual potential temperature were little affected, with consistent reasonable agreement with observations, if one allows for biases in the observed data and modeled surface fluxes. However, the water vapor flux divergences from QNSE tend to be more negative than observed, while including the mass flux part tends to make the divergences more positive, the latter at least partially due to deeper model PBLs resulting from excessive model surface virtual temperature fluxes. Further, both virtual potential temperature and water vapor flux profiles display spurious spikes attributed to the way the non-local and local terms interact in the model. The influence of the mass flux schemes extends to 60 – 100-km scale circulation features, which were greatly modified by both the inclusion of mass flux and the new entrainment formulation. Adding mass flux based clouds to the radiation calculation improved the time and space averaged modeled incoming shortwave flux. The choice of the representation for entrainment/detrainment often affected the results to the same extent as adding mass flux did.

Quarello, Annarosa. "Développement de nouvelles méthodes d’homogénéisation des données atmosphériques GNSS. Application à l’étude de la variabilité climatique". Electronic Thesis or Diss., Sorbonne université, 2020. http://www.theses.fr/2020SORUS457.

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L'homogénéisation est une étape importante et cruciale pour améliorer l'utilisation des données d'observation pour l'analyse du climat. Ce travail est motivé par l'analyse de les données journalières de Contenu Intégré en Vapeur d’Eau (CIVE) mesurées par GNSS (Global Navigation Satellite Systems), appelées GNSS CIVE (IWV Integrated Water Vapor en anglais) qui n'ont pas encore été utilisées dans ce contexte. Ces séries sont affectées par des inhomogénéités liées à des changements dans l'instrumentation, dans l'environnement et dans la procédure de traitement des données. En raison de la variabilité naturelle de la série, nous travaillons en fait sur la série chronologique des différences, en utilisant la réanalyse ERA-Interim comme référence pour le signal climatique. Une hypothèse de base est que les différences contiennent seulement la signature des changements brusques de la série GNSS qui peuvent être détectés au moyen d'un algorithme de segmentation. Une analyse minutieuse des résultats de la segmentation permet de trier les cas où cette hypothèse n'est en fait pas vraie. La principale contribution de cette thèse a été le développement d'une nouvelle méthode de segmentation dédiée à la détection des changements dans la moyenne de la série de différences GNSS-ERA-Interim CIVE. Ce modèle de segmentation intègre un biais périodique et une variance hétérogène, variable mensuellement, pour s'adapter correctement aux caractéristiques de la série. La méthode consiste à estimer d'abord la variance à l'aide d'un estimateur robuste puis à estimer les paramètres de segmentation (les positions des points de changement, les moyennes des segments) et le modèle de biais périodique de manière séquentielle. Les paramètres de segmentation et le modèle de biais périodique sont estimés de manière itérative pour un nombre fixe de points de changement. L'inférence est obtenue par la procédure classique du maximum de vraisemblance en utilisant l'algorithme de programmation dynamique pour l'estimation des paramètres de segmentation qui fournit la solution exacte dans un laps de temps raisonnable. La procédure est répétée pour tous les nombres de points de changement testés entre 0 et un maximum (environ 30). Enfin, le nombre optimal de points de changement est choisi en utilisant une stratégie de sélection de modèle pénalisée. Plusieurs critères sont testés. La méthode est implémentée dans le package R GNSSseg disponible sur CRAN. Les performances de la méthode proposée ont été évaluées par des simulations numériques. Une application pour un ensemble de données réel de 120 stations GNSS mondiales dans le réseau mondial IGS est présentée pour la période de janvier 1995 à décembre 2010. L'inspection des résultats révèle que les points de changement détectés contiennent une fraction (~20%) de valeurs aberrantes qui se caractérisent par des détections doubles avec deux grands décalages, généralement de signes opposés, rapprochés, p.ex. à quelques dizaines de jours d'intervalle. Afin de détecter et d'éliminer les valeurs aberrantes, une méthode de dépistage a été développée. L'ensemble final de points de changement est validé par rapport aux métadonnées GNSS qui contiennent des informations sur les changements d'équipement survenus dans les stations. Le pourcentage de validation reste modéré au niveau de 20% malgré tous les changements sont statistiquement significatifs. Certains des points de changement peuvent en fait être dus à la série de référence (ERA-Interim). Enfin, les informations de segmentation (dates des points de changement) sont incluses dans un algorithme de régression linéaire qui est utilisé pour estimer les tendances GNSS CIVE. Les tendances estimées sont testées pour leur signification et comparées aux tendances ERA-Interim. Une plus grande cohérence spatiale dans les tendances GNSS et une meilleure cohérence sont trouvées après l'homogénéisation avec ERA-Interim dans les régions où la réanalyse est connue pour ses performances
Homogenization is an important and crucial step to improve the use of observational data for climate analysis. This work is motivated by the analysis of long GNSS Integrated Water Vapor (IWV) data which have not yet been used in this context. These series are affected by inhomogeneities linked to changes in the instrumentation, in the environment, and in the data processing procedure. Due to the natural variability of the series we actually work on the time series of differences, using ERA-Interim reanalysis as reference for the climate signal. A base assumption is that the differences contain only the signature of the abrupt changes from the GNSS series which can be detected by means of a segmentation algorithm. Careful analysis of the segmentation results allows to sort the cases when this assumption is actually not true. The main contribution of this thesis was the development a novel segmentation method dedicated to detecting changes in the mean of the GNSS-ERA-Interim IWV difference series. This segmentation model integrates a periodic bias and a heterogeneous, monthly varying, variance to properly fit the characteristics of the series. The method consists of first estimating the variance using a robust estimator and then estimating the segmentation parameters (the positions of the change-points, the means of the segments) and the periodic bias model in a sequential way. The segmentation parameters and the periodic bias model are estimated iteratively for a fixed number of change-points. The inference is achieved by the classical maximum likelihood procedure using the dynamic programming algorithm for the estimation of the segmentation parameters which provides the exact solution in a reasonable amount of time. The procedure is repeated for all the numbers of change-points tested between 0 and a maximum (about 30). Finally, the optimal number of change-points is chosen using a penalized model selection strategy. Several criteria are tested. The method is implemented in the R GNSSseg package available on CRAN. The performance of the proposed method was evaluated by numerical simulations. An application for a real dataset of 120 global GNSS stations in the global IGS network is presented for the period from January 1995 to December 2010. Inspection of the results reveals that the detected change-points contain a fraction (~ 20 %) of outliers which are characterized by double detections with two large offsets, generally of opposite signs, close together, e.g. a few tens of days apart. In order to detect and eliminate the outliers a screening method was developed. The final set of change-points is validated with respect to GNSS metadata which contain information on equipment changes that occurred at the stations. The percentage of validation remains moderate at the level of 20 % despite all the changes are statistically significant. Some of the change-points may actually be due to the reference series (ERA-Interim). Finally, the segmentation information (dates of the change-points) is included in a linear regression algorithm which is used to estimate the GNSS IWV trends. The estimated trends are tested for significance and compared to the ERA-Interim trends. Higher spatial consistency in the GNSS trends and improved consistency is found after homogenisation with ERA-Interim in regions where the reanalysis is known to perform well. [...]

Friedman, Karen S. (Karen Samard). "Global atmospheric water vapor flux climatology in the NCEP/NCAR reanalysis and the Oort data set". Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/10371.

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Libri sul tema "Atmospheric reanalyses":

Wayne, Higgins R., e United States. National Weather Service, a cura di. Intercomparison of the NCEP/NCAR and NASA/DAO reanalyses (1985-1993). [Silver Springs, Md.?]: U.S. Dept. of Commerce, National Oceanic and Atmospheric Administration, National Weather Service, 1997.

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Review of the U.S. Climate Change Science Program's Synthesis and Assessment Product 1.3: Reanalyses of Historical Climate Data for Key Atmospheric Features. Washington, D.C.: National Academies Press, 2008. http://dx.doi.org/10.17226/12135.

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Gao, Yanhong, e Deliang Chen. Modeling of Regional Climate over the Tibetan Plateau. Oxford University Press, 2017. http://dx.doi.org/10.1093/acrefore/9780190228620.013.591.

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The modeling of climate over the Tibetan Plateau (TP) started with the introduction of Global Climate Models (GCMs) in the 1950s. Since then, GCMs have been developed to simulate atmospheric dynamics and eventually the climate system. As the highest and widest international plateau, the strong orographic forcing caused by the TP and its impact on general circulation rather than regional climate was initially the focus. Later, with growing awareness of the incapability of GCMs to depict regional or local-scale atmospheric processes over the heterogeneous ground, coupled with the importance of this information for local decision-making, regional climate models (RCMs) were established in the 1970s. Dynamic and thermodynamic influences of the TP on the East and South Asia summer monsoon have since been widely investigated by model. Besides the heterogeneity in topography, impacts of land cover heterogeneity and change on regional climate were widely modeled through sensitivity experiments.In recent decades, the TP has experienced a greater warming than the global average and those for similar latitudes. GCMs project a global pattern where the wet gets wetter and the dry gets drier. The climate regime over the TP covers the extreme arid regions from the northwest to the semi-humid region in the southeast. The increased warming over the TP compared to the global average raises a number of questions. What are the regional dryness/wetness changes over the TP? What is the mechanism of the responses of regional changes to global warming? To answer these questions, several dynamical downscaling models (DDMs) using RCMs focusing on the TP have recently been conducted and high-resolution data sets generated. All DDM studies demonstrated that this process-based approach, despite its limitations, can improve understandings of the processes that lead to precipitation on the TP. Observation and global land data assimilation systems both present more wetting in the northwestern arid/semi-arid regions than the southeastern humid/semi-humid regions. The DDM was found to better capture the observed elevation dependent warming over the TP. In addition, the long-term high-resolution climate simulation was found to better capture the spatial pattern of precipitation and P-E (precipitation minus evapotranspiration) changes than the best available global reanalysis. This facilitates new and substantial findings regarding the role of dynamical, thermodynamics, and transient eddies in P-E changes reflected in observed changes in major river basins fed by runoff from the TP. The DDM was found to add value regarding snowfall retrieval, precipitation frequency, and orographic precipitation.Although these advantages in the DDM over the TP are evidenced, there are unavoidable facts to be aware of. Firstly, there are still many discrepancies that exist in the up-to-date models. Any uncertainty in the model’s physics or in the land information from remote sensing and the forcing could result in uncertainties in simulation results. Secondly, the question remains of what is the appropriate resolution for resolving the TP’s heterogeneity. Thirdly, it is a challenge to include human activities in the climate models, although this is deemed necessary for future earth science. All-embracing further efforts are expected to improve regional climate models over the TP.

Capitoli di libri sul tema "Atmospheric reanalyses":

Uppala, S., A. Simmons, D. Dee, P. Kållberg e J. N. Thépaut. "Atmospheric Reanalyses and Climate Variations". In Climate Variability and Extremes during the Past 100 Years, 103–17. Dordrecht: Springer Netherlands, 2008. http://dx.doi.org/10.1007/978-1-4020-6766-2_6.

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Bromwich, D. H., R. I. Cullather e M. C. Serreze. "Reanalyses Depictions of the Arctic Atmospheric Moisture Budget". In The Freshwater Budget of the Arctic Ocean, 163–96. Dordrecht: Springer Netherlands, 2000. http://dx.doi.org/10.1007/978-94-011-4132-1_8.

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Chai, Tianfeng, Pius Lee, Li Pan, Hyuncheol Kim e Daniel Tong. "Building and Testing Atmospheric Chemistry Reanalysis Modeling System". In Air Pollution Modeling and its Application XXIII, 581–85. Cham: Springer International Publishing, 2014. http://dx.doi.org/10.1007/978-3-319-04379-1_96.

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Rousi, E., U. Ulbrich, H. W. Rust e C. Anagnostolpoulou. "An NAO Climatology in Reanalysis Data with the Use of Self-organizing Maps". In Perspectives on Atmospheric Sciences, 719–24. Cham: Springer International Publishing, 2016. http://dx.doi.org/10.1007/978-3-319-35095-0_103.

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Stathi, E., T. Mavromatis, G. Koufos, G. Lazoglou, D. Stathis e S. Koundouras. "Comparison of ERA-Interim Reanalysis Data with Observed Surface Meteorological Data Over Greece". In Perspectives on Atmospheric Sciences, 551–57. Cham: Springer International Publishing, 2016. http://dx.doi.org/10.1007/978-3-319-35095-0_79.

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Zanis, P., D. Akritidis, A. Tsikerdekis, J. Kapsomenakis, S. Kontos, D. Melas, C. S. Zerefos, J. Flemming e E. Katragkou. "An Assessment of Near Surface Ozone Over Europe from the Global CAMS Interim Reanalysis". In Perspectives on Atmospheric Sciences, 969–74. Cham: Springer International Publishing, 2016. http://dx.doi.org/10.1007/978-3-319-35095-0_138.

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Georgoulias, A. K., A. Tsikerdekis, V. Amiridis, E. Marinou, A. Benedetti, P. Zanis e K. Kourtidis. "A 3-D Evaluation of the MACC Reanalysis Dust Product Over Europe Using CALIOP/CALIPSO Satellite Observations". In Perspectives on Atmospheric Sciences, 795–800. Cham: Springer International Publishing, 2016. http://dx.doi.org/10.1007/978-3-319-35095-0_114.

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Michailoudi, G., e P. Zanis. "An Analysis of Identification of Stratospheric Intrusions and Their Influence on Ozone Distribution Over Eastern Mediterranean Using MACC Reanalysis". In Perspectives on Atmospheric Sciences, 963–68. Cham: Springer International Publishing, 2016. http://dx.doi.org/10.1007/978-3-319-35095-0_137.

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Brzeziński, Aleksander, Christian Bizouard e Sergei Petrov. "Excitation of Nutation as Deduced from Results of the Recent Atmospheric Reanalysis Project". In Geodesy on the Move, 332. Berlin, Heidelberg: Springer Berlin Heidelberg, 1998. http://dx.doi.org/10.1007/978-3-642-72245-5_50.

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Purnama, Dendi Rona, I. Nyoman Agus Astina Putra, Dewangga Palguna e Gandhi Mahendra. "Utilization of ECMWF ERA-Interim Reanalysis Data for Analysis of Atmospheric Conditions During Tropical Cyclone Dahlia". In Springer Proceedings in Physics, 793–808. Singapore: Springer Nature Singapore, 2023. http://dx.doi.org/10.1007/978-981-19-9768-6_73.

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Atti di convegni sul tema "Atmospheric reanalyses":

Bližňák, Vojtěch, e Petr Zacharov. "Evaluation of precipitation totals simulated by the ALADIN/PERUN atmospheric reanalysis at high spatial resolution". In První konference PERUN. Český hydrometeorologický ústav, 2023. http://dx.doi.org/10.59984/978-80-7653-063-8.02.

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Atmospheric reanalyses represent powerful tools for obtaining information about the state of the atmosphere in history, which is obtained by numerical weather prediction (NWP) models whose predictions may (but may not) be improved through the assimilation of measured data. Significant developments in computer technology have recently enabled to increase their spatial resolution so that even meteorological phenomena of a local nature can be better captured. However, most NWP models compensate this capability by reducing the computational domain, which largely limits the use of these forecasts for the following meteorological, climatological and/or hydrological applications. The newly developed ALADIN/PERUN atmospheric reanalysis provides simulations of various meteorological variables at high spatial (2.3 km) and temporal (1 h) resolution over most of Europe between 1989 and 2020. Due to the high resolution of the reanalysed data, it can be expected that precipitation fields will capture local-scale processes well, and thus reproduce more faithfully, for example, heavy convective precipitation. The presented paper aims to evaluate this capability based on gauge-adjusted radar estimates of precipitation totals during warm parts of the year when strong convective but also stratiform precipitation occurs in Central Europe. The accuracy of the localization and precipitation sums will be evaluated for two different runs of the NWP model. The first one (ALADIN/Reanalysis) involves a complete assimilation of the observed data every 6 hours using a 4D-VAR assimilation scheme. The second (ALADIN/Evaluation Run) uses only the boundary conditions from the ERA-5 global reanalysis and the calculation of the forecasts is not further modified based on measured data. Comparing the two runs will provide us with information about the level of physical description in the NWP model as well as the effect of assimilation on the resulting precipitation fields. In addition, the paper is unique in that it will use detailed fields of "observed" precipitation totals at high spatial resolution, which conventional rain gauge data cannot offer.

Bokuchava, Daria, e Vladimir Semenov. "Surface air temperature and pressure anomalies in the Northern Hemisphere during the 20th century: observations and reanalyses". In XXIV International Symposium, Atmospheric and Ocean Optics, Atmospheric Physics, a cura di Oleg A. Romanovskii e Gennadii G. Matvienko. SPIE, 2018. http://dx.doi.org/10.1117/12.2504509.

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Bokuchava, Daria D., Vladimir Semenov e Valeria Popova. "Features of the winter atmospheric circulation structure in the Northern Hemisphere from observations and 20th century reanalyses data". In XXV International Symposium, Atmospheric and Ocean Optics, Atmospheric Physics, a cura di Gennadii G. Matvienko e Oleg A. Romanovskii. SPIE, 2019. http://dx.doi.org/10.1117/12.2540947.

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Trenberth, Kevin E., Kevin E. Trenberth, Kevin E. Trenberth, Kevin E. Trenberth, Kevin E. Trenberth, Kevin E. Trenberth, Kevin E. Trenberth, Kevin E. Trenberth e Kevin E. Trenberth. "Atmospheric Reanalyses: A Major Resource for Ocean Product Development and Modeling". In OceanObs'09: Sustained Ocean Observations and Information for Society. European Space Agency, 2010. http://dx.doi.org/10.5270/oceanobs09.cwp.90.

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Eliseev, Alexey V., e Igor I. Mokhov. "Amplitude-phase characteristics of SAT annual cycle in Asia: tendencies of change derived from observations and reanalyses and from numerical experiments with IAP RAS CM". In Eighth Joint International Symposium on Atmospheric and Ocean Optics: Atmospheric Physics, a cura di Gelii A. Zherebtsov, Gennadii G. Matvienko, Viktor A. Banakh e Vladimir V. Koshelev. SPIE, 2002. http://dx.doi.org/10.1117/12.458513.

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Quadro, Mario F. L., Ernesto H. Berbery, Maria A. F. Silva Dias, Dirceu L. Herdies e Luis G. G. Gonçalves. "The atmospheric water cycle over South America as seen in the new generation of global reanalyses". In RADIATION PROCESSES IN THE ATMOSPHERE AND OCEAN (IRS2012): Proceedings of the International Radiation Symposium (IRC/IAMAS). AIP, 2013. http://dx.doi.org/10.1063/1.4804874.

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Ponomarev, Vladimir, Vladimir Ponomarev, Elena Dmitrieva, Elena Dmitrieva, Svetlana Shkorba, Svetlana Shkorba, Irina Mashkina, Irina Mashkina, Alexander Karnaukhov e Alexander Karnaukhov. "CLIMATIC REGIME CHANGE IN THE ASIAN PACIFIC REGION, INDIAN AND SOUTHERN OCEANS AT THE END OF THE 20TH CENTURY". In Managing risks to coastal regions and communities in a changing world. Academus Publishing, 2017. http://dx.doi.org/10.31519/conferencearticle_5b1b9475504153.46587602.

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Multiple scale climate variability in Asia of temperate and high latitudes, Pacific, Indian and South Oceans, their features and linkages are studied by using statistical analyses of monthly mean time series of Hadley, Reynolds SST, surface net heat flux (Q), atmospheric pressure (SLP), air temperature (SAT) from NCEP NCAR reanalyses (1948-2015). Three multidecadal climatic regimes were revealed for the whole area studied by using cluster analyses via Principal Components of differences between values of Q, SLP, SAT in tropical and extratropical regions of the Asian Pacific, Indian and Southern Oceans. The climate regime change in 70s of the 20th century in this area is confirmed by this method. It is also found that the climate regime is significantly changed at the end of the 20th century in both same area and World Ocean. The characteristic features of recent climate regime after 1996-1998 are SLP increase in the central extratropic area of Indian Ocean, North and South Pacific being prevailing in boreal winter. It is accompanying SLP increase and precipitation decrease in South Siberia and Mongolia prevailing in boreal summer. Inversed SLP and precipitation anomaly associated with increase of cyclone activity and extreme events in the land-ocean marginal zones including Southern Ocean, eastern Arctic, eastern Indian, western and eastern Pacific margins. It is known that low frequency PDO phase is also changed at the same time.

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Gramcianinov, C. B., R. M. Campos, C. Guedes Soares e R. de Camargo. "Comparison Between ERA5 and CFS Datasets of Extratropical Cyclones Associated With Extreme Wave Events in the Atlantic Ocean". In ASME 2020 39th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/omae2020-18488.

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Abstract Atmospheric and ocean datasets using numerical modeling allied to data assimilation are valuable tools for planning and maintaining marine activities, particularly due to their spatial coverage and resolution. However, even modern analyses and reanalyses present critical errors where cyclonic winds are often underestimated in some locations, leading to issues in wind-wave climate hindcasts and forecasts. This work aims to evaluate two of the newest datasets available regarding their ability to reproduce extratropical cyclone tracks associated with extreme waves in the Atlantic Ocean. The analysis is focused on the storm track position and cyclone intensity, two important features that control the wave climate. The datasets used are the ECMWF’s ERA5 and NCEP’s CFSv2. The cyclones are identified and compared between 2011 and 2018 using the relative vorticity at 850hPa and the intensity is measured through the 10-meters wind speed. The results show that the differences in track density exist mainly in coastal areas and they can be related to the coarser resolution of CFSv2 compared to ERA5. CFSv2 presents a higher number of cyclones associated with extreme wave events in the South and North Atlantic, corresponding to 87.1% and 89.2% of the cyclones identified, while ERA5 presents 66.6% and 59.5% respectively. The maximum intensity distribution shows that CFSv2 tends to produce more intense cyclones than ERA5, even for identical storms in the datasets. The distances of matching cyclones in the two datasets are around 0.5°.

Zacharov, Petr, Radmila Brožková e Daniela Řezáčová. "Precipitation by PERUN". In První konference PERUN. Český hydrometeorologický ústav, 2023. http://dx.doi.org/10.59984/978-80-7653-063-8.10.

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Weather reanalyses are a powerful tool for studying historical weather both at individual points and especially over an area. The detailed reanalysis produced by the PERUN project thus makes it possible to reveal various aspects of the atmosphere to a degree that we are unable to achieve with measurements. Since it is still a model approximation, it is of course necessary to detect systematic biases by verification before its use. Climate model runs, on the other hand, can uncover the future evolution of the atmosphere. Since these calculations cannot yet be verified, it is necessary to validate a historical run of the same model and subtract the revealed systematic errors from the future projections. In the PERUN project, both the historical run and two climate runs up to 2100 have been calculated. In this work, we present a basic verification and validation of the precipitation forecasts and an evaluation of the separation of precipitation into stratiform and convective precipitation and, in addition, into liquid and solid precipitation.

Rapporti di organizzazioni sul tema "Atmospheric reanalyses":

Wilson, D., Michael Shaw, Vladimir Ostashev, Michael Muhlestein, Ross Alter, Michelle Swearingen e Sarah McComas. Numerical modeling of mesoscale infrasound propagation in the Arctic. Engineer Research and Development Center (U.S.), ottobre 2022. http://dx.doi.org/10.21079/11681/45788.

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The impacts of characteristic weather events and seasonal patterns on infrasound propagation in the Arctic region are simulated numerically. The methodology utilizes wide-angle parabolic equation methods for a windy atmosphere with inputs provided by radiosonde observations and a high-resolution reanalysis of Arctic weather. The calculations involve horizontal distances up to 200 km for which interactions with the troposphere and lower stratosphere dominate. Among the events examined are two sudden stratospheric warmings, which are found to weaken upward refraction by temperature gradients while creating strongly asymmetric refraction from disturbances to the circumpolar winds. Also examined are polar low events, which are found to enhance negative temperature gradients in the troposphere and thus lead to strong upward refraction. Smaller-scale and topographically driven phenomena, such as low-level jets, katabatic winds, and surface-based temperature inversions, are found to create frequent surface-based ducting out to 100 km. The simulations suggest that horizontal variations in the atmospheric profiles, in response to changing topography and surface property transitions, such as ice boundaries, play an important role in the propagation.

Li, Tim, e Xin Zhang. Western Pacific Tropical Cyclone Reanalysis With the NRL Atmospheric Variational Data Assimilation System. Fort Belvoir, VA: Defense Technical Information Center, settembre 2009. http://dx.doi.org/10.21236/ada531971.

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Li, Tim, e Xin Zhang. Western Pacific Tropical Cyclone Reanalysis with the NRL Atmospheric Variational Data Assimilation System (NAVDAS). Fort Belvoir, VA: Defense Technical Information Center, settembre 2008. http://dx.doi.org/10.21236/ada532954.

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Compo, Gilbert P., e Prashant D. Sardeshmukh. Final Technical Report for Collaborative Research: Developing and Implementing Ocean-Atmosphere Reanalyses for Climate Applications (OARCA). Office of Scientific and Technical Information (OSTI), aprile 2018. http://dx.doi.org/10.2172/1433384.

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