Journal articles: 'Sudden warming'

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Chen, Tsing-Chang, Shih-Yu Wang, Ming-Cheng Yen, Adam J. Clark, and Jenq-Dar Tsay. "Sudden Surface Warming–Drying Events Caused by Typhoon Passages across Taiwan*." Journal of Applied Meteorology and Climatology 49, no. 2 (February 1, 2010): 234–52. http://dx.doi.org/10.1175/2009jamc2070.1.

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Abstract Typhoon passages across Taiwan can generate sudden surface warming in downslope regions. Special characteristics and mechanisms for 54 such warming events that were identified during the 1961–2007 period are examined. Preferred warming regions were identified in northwest Taiwan, where warming is generated by downslope flow from east or northeast winds in westward-moving typhoons, and in southeast Taiwan, where it is generated by downslope flow from west or northwest winds in northwestward-moving typhoons. In addition to the orographic effect, warmings occurred exclusively within nonprecipitation zones of typhoons. Most northwest (southeast) warmings occur during the day (night) with an average lifetime of 4 (5) h, which roughly corresponds to the average time a nonprecipitation zone remains over a station. During the period examined, three typhoons generated warming events in both northwest and southeast Taiwan, and only Typhoon Haitang (2005) generated warmings with comparable magnitudes (∼12-K increase) in both regions. For Typhoon Haitang as an example, diagnostic analyses with two different approaches reveal that the majority of the warming is contributed by downslope adiabatic warming, but the warming associated with the passage of a nonprecipitation zone is not negligible. Similar results were found when these two diagnostic approaches were applied to the other warming events. The diurnal mode of the atmospheric divergent circulation over East Asia–western North Pacific undergoes a clockwise rotation. The vorticity tendency generated by this diurnal divergent circulation through vortex stretching may modulate the arrival time of typhoons to cause daily (nighttime) warming in the northwest (southeast).

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Hong, Hao-Jhe, and Thomas Reichler. "Local and remote response of ozone to Arctic stratospheric circulation extremes." Atmospheric Chemistry and Physics 21, no. 2 (January 28, 2021): 1159–71. http://dx.doi.org/10.5194/acp-21-1159-2021.

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Abstract. Intense natural circulation variability associated with stratospheric sudden warmings, vortex intensifications, and final warmings is a typical feature of the winter Arctic stratosphere. The attendant changes in transport, mixing, and temperature create pronounced perturbations in stratospheric ozone. Understanding these perturbations is important because of their potential feedbacks with the circulation and because ozone is a key trace gas of the stratosphere. Here, we use Modern-Era Retrospective analysis for Research and Applications, version 2 (MERRA-2), reanalysis to contrast the typical spatiotemporal structure of ozone during sudden warming and vortex intensification events. We examine the changes of ozone in both the Arctic and the tropics, document the underlying dynamical mechanisms for the observed changes, and analyze the entire life cycle of the stratospheric events – from the event onset in midwinter to the final warming in early spring. Over the Arctic and during sudden warmings, ozone undergoes a rapid and long-lasting increase of up to ∼ 50 DU, which only gradually decays to climatology before the final warming. In contrast, vortex intensifications are passive events, associated with gradual decreases in Arctic ozone that reach ∼ 40 DU during late winter and decay thereafter. The persistent loss in Arctic ozone during vortex intensifications is dramatically compensated by sudden warming-like increases after the final warming. In the tropics, the changes in ozone from Arctic circulation events are obscured by the influences from the quasi-biennial oscillation. After controlling for this effect, small but coherent reductions in tropical ozone can be seen during the onset of sudden warmings (∼ 2.5 DU) and also during the final warmings that follow vortex intensifications (∼ 2 DU). Our results demonstrate that Arctic circulation extremes have significant local and remote influences on the distribution of stratospheric ozone.

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Charlton, Andrew J., and Lorenzo M. Polvani. "A New Look at Stratospheric Sudden Warmings. Part I: Climatology and Modeling Benchmarks." Journal of Climate 20, no. 3 (February 1, 2007): 449–69. http://dx.doi.org/10.1175/jcli3996.1.

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Abstract Stratospheric sudden warmings are the clearest and strongest manifestation of dynamical coupling in the stratosphere–troposphere system. While many sudden warmings have been individually documented in the literature, this study aims at constructing a comprehensive climatology: all major midwinter warming events are identified and classified, in both the NCEP–NCAR and 40-yr ECMWF Re-Analysis (ERA-40) datasets. To accomplish this a new, objective identification algorithm is developed. This algorithm identifies sudden warmings based on the zonal mean zonal wind at 60°N and 10 hPa, and classifies them into events that do and do not split the stratospheric polar vortex. Major midwinter stratospheric sudden warmings are found to occur with a frequency of approximately six events per decade, and 46% of warming events lead to a splitting of the stratospheric polar vortex. The dynamics of vortex splitting events is contrasted to that of events where the vortex is merely displaced off the pole. In the stratosphere, the two types of events are found to be dynamically distinct: vortex splitting events occur after a clear preconditioning of the polar vortex, and their influence on middle-stratospheric temperatures lasts for up to 20 days longer than vortex displacement events. In contrast, the influence of sudden warmings on the tropospheric state is found to be largely insensitive to the event type. Finally, a table of dynamical benchmarks for major stratospheric sudden warming events is compiled. These benchmarks are used in a companion study to evaluate current numerical model simulations of the stratosphere.

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Butler, Amy H., Jeremiah P. Sjoberg, Dian J. Seidel, and Karen H. Rosenlof. "A sudden stratospheric warming compendium." Earth System Science Data 9, no. 1 (February 9, 2017): 63–76. http://dx.doi.org/10.5194/essd-9-63-2017.

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Abstract. Major, sudden midwinter stratospheric warmings (SSWs) are large and rapid temperature increases in the winter polar stratosphere are associated with a complete reversal of the climatological westerly winds (i.e., the polar vortex). These extreme events can have substantial impacts on winter surface climate, including increased frequency of cold air outbreaks over North America and Eurasia and anomalous warming over Greenland and eastern Canada. Here we present a SSW Compendium (SSWC), a new database that documents the evolution of the stratosphere, troposphere, and surface conditions 60 days prior to and after SSWs for the period 1958–2014. The SSWC comprises data from six different reanalysis products: MERRA2 (1980–2014), JRA-55 (1958–2014), ERA-interim (1979–2014), ERA-40 (1958–2002), NOAA20CRv2c (1958–2011), and NCEP-NCAR I (1958–2014). Global gridded daily anomaly fields, full fields, and derived products are provided for each SSW event. The compendium will allow users to examine the structure and evolution of individual SSWs, and the variability among events and among reanalysis products. The SSWC is archived and maintained by NOAA's National Centers for Environmental Information (NCEI, doi:10.7289/V5NS0RWP).

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Blume, Christian, Katja Matthes, and Illia Horenko. "Supervised Learning Approaches to Classify Sudden Stratospheric Warming Events." Journal of the Atmospheric Sciences 69, no. 6 (June 1, 2012): 1824–40. http://dx.doi.org/10.1175/jas-d-11-0194.1.

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Abstract Sudden stratospheric warmings are prominent examples of dynamical wave–mean flow interactions in the Arctic stratosphere during Northern Hemisphere winter. They are characterized by a strong temperature increase on time scales of a few days and a strongly disturbed stratospheric vortex. This work investigates a wide class of supervised learning methods with respect to their ability to classify stratospheric warmings, using temperature anomalies from the Arctic stratosphere and atmospheric forcings such as ENSO, the quasi-biennial oscillation (QBO), and the solar cycle. It is demonstrated that one representative of the supervised learning methods family, namely nonlinear neural networks, is able to reliably classify stratospheric warmings. Within this framework, one can estimate temporal onset, duration, and intensity of stratospheric warming events independently of a particular pressure level. In contrast to classification methods based on the zonal-mean zonal wind, the approach herein distinguishes major, minor, and final warmings. Instead of a binary measure, it provides continuous conditional probabilities for each warming event representing the amount of deviation from an undisturbed polar vortex. Additionally, the statistical importance of the atmospheric factors is estimated. It is shown how marginalized probability distributions can give insights into the interrelationships between external factors. This approach is applied to 40-yr and interim ECMWF (ERA-40/ERA-Interim) and NCEP–NCAR reanalysis data for the period from 1958 through 2010.

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Coughlin, K., and L. J. Gray. "A Continuum of Sudden Stratospheric Warmings." Journal of the Atmospheric Sciences 66, no. 2 (February 1, 2009): 531–40. http://dx.doi.org/10.1175/2008jas2792.1.

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Abstract The k-means cluster technique is used to examine 43 yr of daily winter Northern Hemisphere (NH) polar stratospheric data from the 40-yr ECMWF Re-Analysis (ERA-40). The results show that the NH winter stratosphere exists in two natural well-separated states. In total, 10% of the analyzed days exhibit a warm disturbed state that is typical of sudden stratospheric warming events. The remaining 90% of the days are in a state typical of a colder undisturbed vortex. These states are determined objectively, with no preconceived notion of the groups. The two stratospheric states are described and compared with alternative indicators of the polar winter flow, such as the northern annular mode. It is shown that the zonally averaged zonal winds in the polar upper stratosphere at ∼7 hPa can best distinguish between the two states, using a threshold value of ∼4 m s−1, which is remarkably close to the standard WMO criterion for major warming events. The analysis also determines that there are no further divisions within the warm state, indicating that there is no well-designated threshold between major and minor warmings, nor between split and displaced vortex events. These different manifestations are simply members of a continuum of warming events.

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Erlebach, P., U. Langematz, and S. Pawson. "Simulations of stratospheric sudden warmings in the Berlin troposphere-stratosphere-mesosphere GCM." Annales Geophysicae 14, no. 4 (April 30, 1996): 443–63. http://dx.doi.org/10.1007/s00585-996-0443-6.

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Abstract. Stratospheric sudden warming events in the Northern Hemisphere of the Berlin TSM GCM are investigated. In about 50% of the simulated years (13 out of 28), major midwinter warmings occur. This agrees well with observations but, whereas real events tend to occur approximately every second season, those in the model are clustered, most of them occur in the period between years 15/16 and years 24/25. In most other years, minor warming events take place. The warming events are found earlier in the winter than in reality. Many of the observed characteristics of warming events are well captured by the model: pulses of wave activity propagate out of the troposphere; these transient events force the zonal-mean zonal wind in the stratosphere and coincide with increases of the temperature at the North Pole and cooling at low levels in the tropics; temperature changes of opposite sign are modelled at higher levels. Synoptically, the modelled stratosphere evolves quite realistically before the warmings: the cyclonic vortex is displaced from the Pole by an amplifying anticyclone. After minor warmings, the stratosphere remains too disturbed as the cyclonic centre does not return to the North Pole as quickly as in reality. In the aftermath of major warmings the cyclonic vortex is not fully eroded and the anticyclonic circulation does not develop properly over the Pole; furthermore, the wintertime circulation is not properly restored after the event.

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8

White, Loren D. "Sudden Nocturnal Warming Events in Mississippi." Journal of Applied Meteorology and Climatology 48, no. 4 (April 1, 2009): 758–75. http://dx.doi.org/10.1175/2008jamc1971.1.

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Abstract Significant episodes of sudden nocturnal warming have been observed by the Mississippi Mesonet. The probable relation of these nocturnal warming events to surface layer regime transitions between a decoupled quiescent surface layer and a more turbulent, less thermodynamically stable surface layer is discussed within the context of four examples with different temporal signatures. In general, the changes in wind speed and inversion strength are consistent with expectations for such regime changes. However, details of individual events indicate a wider variety of event characteristics than has been documented previously. The cases examined are proposed as prototypes for four different types of warming event, based on the evolution of temperature and dewpoint as well as on whether clear forcing from a mesoscale or synoptic frontal passage can be identified. Using this classification system and a subjective evaluation of event magnitude, the frequency of nocturnal warming events is analyzed for four mesonet stations at varying distance inland over the period of record.

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9

Blackshear, W. T., W. L. Grose, and R. E. Turner. "Simulated Sudden Stratospheric Warming; Synoptic Evolution." Quarterly Journal of the Royal Meteorological Society 113, no. 477 (July 1987): 815–46. http://dx.doi.org/10.1002/qj.49711347707.

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Sehra, Parmjit Singh, Taher Ahmed Sharif, and Abubaker Y. Nashnosh. "Sudden mesospheric warming over equatorial region." Archives for Meteorology, Geophysics, and Bioclimatology Series A 33, no. 4 (December 1985): 289–96. http://dx.doi.org/10.1007/bf02258480.

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11

Lee, Simon H. "The January 2021 sudden stratospheric warming." Weather 76, no. 4 (April 2021): 135–36. http://dx.doi.org/10.1002/wea.3966.

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Полех, Неля, Nelya Polekh, Марина Черниговская, Marina Chernigovskaya, Ольга Яковлева, and Olga Yakovleva. "On the formation of the F1 layer during sudden stratospheric warming events." Solar-Terrestrial Physics 5, no. 3 (September 30, 2019): 117–27. http://dx.doi.org/10.12737/stp-53201914.

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Using vertical sounding data obtained by the Irkutsk digisonde DPS-4 from 2003 to 2016, we have studied the frequency of occurrence of the F1 layer in winter conditions. The frequency of occurrence of the F1 layer in December–January is shown to be more than twice lower than that in February at any level of magnetic activity. At moderate and low solar activity under quiet geomagnetic conditions, the appearance of F1 layer in midlatitudes of the Northern Hemisphere may be caused by active thermodynamic processes, which lead to transformation or destruction of the circumpolar vortex at heights of the middle atmosphere. Such global dynamic changes occurring in the winter strato-mesosphere are often associated with sudden stratospheric warming events, which are accompanied by increased generation of atmospheric waves of various scales. These wave disturbances can propagate upward to the heights of the lower thermosphere and ionosphere, carrying a significant vertical flow of energy and causing variations in the composition, thermodynamic parameters of the neutral atmosphere and ionosphere.

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Arrak, Arno. "Arctic Warming is Not Greenhouse Warming." Energy & Environment 22, no. 8 (December 2011): 1069–83. http://dx.doi.org/10.1260/0958-305x.22.8.1069.

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After two thousand years of slow cooling Arctic, warming suddenly began more than a century ago. It has continued, with a break in the middle, until this day. The rapid start of this warming rules out the greenhouse effect as its cause. Apparently the time scale of the accumulation of CO2 in the air and the Arctic warming does not match. It is likely that the cause of this warming was a relatively sudden rearrangement of the North Atlantic current system at the turn of the century that directed warm currents into the Arctic Ocean. All observations of Arctic warming can be accounted for as consequences of these flows of warm water to the Arctic. This explains why all attempts to model Arctic warming have failed: Models set up for greenhouse warming are the wrong models for non-greenhouse warming. It turns out that satellites which have been measuring global temperature for the last 31 years cannot see any sign of current warming that supposedly started in the late seventies. This absence of warming in the satellite record is in accord with the observations of Ferenc Miskolczi on IR absorption by the atmosphere. What warming satellites do see is only a short spurt that began with the super El Nino of 1998, raised global temperature by a third of a degree in four years, and then stopped. It was of oceanic origin.

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Laskar, Fazlul I., John P. McCormack, Jorge L. Chau, Duggirala Pallamraju, Peter Hoffmann, and Ravindra P. Singh. "Interhemispheric Meridional Circulation During Sudden Stratospheric Warming." Journal of Geophysical Research: Space Physics 124, no. 8 (August 2019): 7112–22. http://dx.doi.org/10.1029/2018ja026424.

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McGuirk, James P., and Donald A. Douglas. "Sudden Stratospheric Warming and Anomalous U.S. Weather." Monthly Weather Review 116, no. 1 (January 1988): 162–74. http://dx.doi.org/10.1175/1520-0493(1988)116<0162:sswaau>2.0.co;2.

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Lu, Qian, Jian Rao, Zhuoqi Liang, Dong Guo, Jingjia Luo, Siming Liu, Chun Wang, and Tian Wang. "The sudden stratospheric warming in January 2021." Environmental Research Letters 16, no. 8 (July 28, 2021): 084029. http://dx.doi.org/10.1088/1748-9326/ac12f4.

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17

Gray, Lesley, Warwick Norton, Charlotte Pascoe, and Andrew Charlton. "A Possible Influence of Equatorial Winds on the September 2002 Southern Hemisphere Sudden Warming Event." Journal of the Atmospheric Sciences 62, no. 3 (March 1, 2005): 651–67. http://dx.doi.org/10.1175/jas-3339.1.

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Abstract The stratospheric sudden warming in the Southern Hemisphere (SH) in September 2002 was unexpected for two reasons. First, planetary wave activity in the Southern Hemisphere is very weak, and midwinter warmings have never been observed, at least not since observations of the upper stratosphere became regularly available. Second, the warming occurred in a west phase of the quasi-biennial oscillation (QBO) in the lower stratosphere. This is unexpected because warmings are usually considered to be more likely in the east phase of the QBO, when a zero wind line is present in the winter subtropics and hence confines planetary wave propagation to higher latitudes closer to the polar vortex. At first, this evidence suggests that the sudden warming must therefore be simply a result of anomalously strong planetary wave forcing from the troposphere. However, recent model studies have suggested that the midwinter polar vortex may also be sensitive to the equatorial winds in the upper stratosphere, the region dominated by the semiannual oscillation. In this paper, the time series of equatorial zonal winds from two different data sources, the 40-yr ECMWF Re-Analysis (ERA) and the Met Office assimilated dataset, are reviewed. Both suggest that the equatorial winds in the upper stratosphere above 10 hPa were anomalously easterly in 2002. Idealized model experiments are described in which the modeled equatorial winds were relaxed toward these observations for various years to examine whether the anomalous easterlies in 2002 could influence the timing of a warming event. It is found that the 2002 equatorial winds speed up the evolution of a warming event in the model. Therefore, this study suggests that the anomalous easterlies in the 1–10-hPa region may have been a contributory factor in the development of the observed SH warming. However, it is concluded that it is unlikely that the anomalous equatorial winds alone can explain the 2002 warming event.

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Inatsu, Masaru, Masahide Kimoto, and Akimasa Sumi. "Stratospheric Sudden Warming with Projected Global Warming and Related Tropospheric Wave Activity." SOLA 3 (2007): 105–8. http://dx.doi.org/10.2151/sola.2007-027.

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Nakamura, Noboru, Jonathan Falk, and Sandro W. Lubis. "Why Are Stratospheric Sudden Warmings Sudden (and Intermittent)?" Journal of the Atmospheric Sciences 77, no. 3 (February 25, 2020): 943–64. http://dx.doi.org/10.1175/jas-d-19-0249.1.

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Abstract This paper examines the role of wave–mean flow interaction in the onset and suddenness of stratospheric sudden warmings (SSWs). Evidence is presented that SSWs are, on average, a threshold behavior of finite-amplitude Rossby waves arising from the competition between an increasing wave activity A and a decreasing zonal-mean zonal wind u¯. The competition puts a limit to the wave activity flux that a stationary Rossby wave can transmit upward. A rapid, spontaneous vortex breakdown occurs once the upwelling wave activity flux reaches the limit, or equivalently, once u¯ drops below a certain fraction of uREF, a wave-free, reference-state wind inverted from the zonalized quasigeostrophic potential vorticity. This fraction is 0.5 in theory and about 0.3 in reanalyses. We propose r≡u¯/uREF as a local, instantaneous measure of the proximity to vortex breakdown (i.e., preconditioning). The ratio r generally stays above the threshold during strong-vortex winters until a pronounced final warming, whereas during weak-vortex winters it approaches the threshold early in the season, culminating in a precipitous drop in midwinter as SSWs form. The essence of the threshold behavior is captured by a semiempirical 1D model of SSWs, similar to the “traffic jam” model of Nakamura and Huang for atmospheric blocking. This model predicts salient features of SSWs including rapid vortex breakdown and downward migration of the wave activity/zonal wind anomalies, with analytical expressions for the respective time scales. The model’s response to a variety of transient wave forcing and damping is discussed.

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Balcerak, Ernie. "Sudden stratospheric warming did not cool the thermosphere." Eos, Transactions American Geophysical Union 92, no. 50 (December 13, 2011): 476. http://dx.doi.org/10.1029/2011eo500020.

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21

Yamazaki, Y., K. Yumoto, D. McNamara, T. Hirooka, T. Uozumi, K. Kitamura, S. Abe, and A. Ikeda. "Ionospheric current system during sudden stratospheric warming events." Journal of Geophysical Research: Space Physics 117, A3 (March 2012): n/a. http://dx.doi.org/10.1029/2011ja017453.

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22

Butler, Amy H., and Edwin P. Gerber. "Optimizing the Definition of a Sudden Stratospheric Warming." Journal of Climate 31, no. 6 (March 2018): 2337–44. http://dx.doi.org/10.1175/jcli-d-17-0648.1.

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Various criteria exist for determining the occurrence of a major sudden stratospheric warming (SSW), but the most common is based on the reversal of the climatological westerly zonal-mean zonal winds at 60° latitude and 10 hPa in the winter stratosphere. This definition was established at a time when observations of the stratosphere were sparse. Given greater access to data in the satellite era, a systematic analysis of the optimal parameters of latitude, altitude, and threshold for the wind reversal is now possible. Here, the frequency of SSWs, the strength of the wave forcing associated with the events, changes in stratospheric temperature and zonal winds, and surface impacts are examined as a function of the stratospheric wind reversal parameters. The results provide a methodical assessment of how to best define a standard metric for major SSWs. While the continuum nature of stratospheric variability makes it difficult to identify a decisively optimal threshold, there is a relatively narrow envelope of thresholds that work well—and the original focus at 60° latitude and 10 hPa lies within this window.

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Palmeiro, Froila M., David Barriopedro, Ricardo García-Herrera, and Natalia Calvo. "Comparing Sudden Stratospheric Warming Definitions in Reanalysis Data*." Journal of Climate 28, no. 17 (September 1, 2015): 6823–40. http://dx.doi.org/10.1175/jcli-d-15-0004.1.

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Abstract Sudden stratospheric warmings (SSWs) are characterized by a pronounced increase of the stratospheric polar temperature during the winter season. Different definitions have been used in the literature to diagnose the occurrence of SSWs, yielding discrepancies in the detected events. The aim of this paper is to compare the SSW climatologies obtained by different methods using reanalysis data. The occurrences of Northern Hemisphere SSWs during the extended-winter season and the 1958–2014 period have been identified for a suite of eight representative definitions and three different reanalyses. Overall, and despite the differences in the number and exact dates of occurrence of SSWs, the main climatological signatures of SSWs are not sensitive to the considered reanalysis. The mean frequency of SSWs is 6.7 events decade−1, but it ranges from 4 to 10 events, depending on the method. The seasonal cycle of events is statistically indistinguishable across definitions, with a common peak in January. However, the multidecadal variability is method dependent, with only two definitions displaying minimum frequencies in the 1990s. An analysis of the mean signatures of SSWs in the stratosphere revealed negligible differences among methods compared to the large case-to-case variability within a given definition. The stronger and more coherent tropospheric signals before and after SSWs are associated with major events, which are detected by most methods. The tropospheric signals of minor SSWs are less robust, representing the largest source of discrepancy across definitions. Therefore, to obtain robust results, future studies on stratosphere–troposphere coupling should aim to minimize the detection of minor warmings.

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Hocke, K., M. Lainer, and A. Schanz. "Composite analysis of a major sudden stratospheric warming." Annales Geophysicae 33, no. 6 (June 25, 2015): 783–88. http://dx.doi.org/10.5194/angeo-33-783-2015.

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Abstract. We present the characteristics of a major sudden stratospheric warming (SSW) by using the composite analysis method and ERA Interim reanalysis data from 1979 to 2014. The anomalies of the parameters total ozone column density (TOC), temperature (T), potential vorticity (PV), eastward wind (u), northward wind (v), vertical wind (w), and geopotential height (z) are derived with respect to the ERA Interim climatology (mean seasonal behaviour 1979 to 2014). The composites are calculated by using the time series of the anomalies and the central dates of 20 major SSWs. Increases of up to 90 Dobson units are found for polar TOC after the SSW. Polar TOC remains enhanced until the summer after the major SSW. Precursors of the SSW are a negative TOC anomaly 3 months before the SSW and enhanced temperature at 10 hPa at mid-latitudes about 1 month before the SSW. Eastward wind at 1 hPa is decreased at mid-latitudes about 1 month before the SSW. The 1 hPa geopotential height level is increased by about 500 m during the month before the SSW. These features are significant at the 2σ level for the mean behaviour of the ensemble of the major SSWs. However, knowledge of these precursors may not lead to a reliable prediction of an individual SSW since the variability of the individual SSWs and the polar winter stratosphere is large.

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Chandran, A., R. L. Collins, and V. L. Harvey. "Stratosphere-mesosphere coupling during stratospheric sudden warming events." Advances in Space Research 53, no. 9 (May 2014): 1265–89. http://dx.doi.org/10.1016/j.asr.2014.02.005.

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Sun, Lantao, Gang Chen, and Jian Lu. "Sensitivities and Mechanisms of the Zonal Mean Atmospheric Circulation Response to Tropical Warming." Journal of the Atmospheric Sciences 70, no. 8 (August 1, 2013): 2487–504. http://dx.doi.org/10.1175/jas-d-12-0298.1.

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Abstract Although El Niño and global warming are both characterized by warming in the tropical upper troposphere, the latitudinal changes of the Hadley cell edge and midlatitude eddy-driven jet are opposite in sign. Using an idealized dry atmospheric model, the zonal mean circulation changes are investigated with respect to different patterns of tropical warming. Generally speaking, an equatorward shift in circulation takes place in the presence of enhanced tropical temperature gradient or narrow tropical warming, similar to the changes associated with El Niño events. In contrast, the zonal mean atmospheric circulations expand or shift poleward in response to upper-tropospheric warming or broad tropical warming, resembling the changes under future global warming. The mechanisms underlying these opposite changes in circulation are investigated by comparing the dry dynamical responses to a narrow tropical warming and a broad warming as analogs for El Niño and global warming. When running the idealized model in a zonally symmetric configuration in which the eddy feedback is disabled, both the narrow and broad warmings give rise to an equatorward shift of the subtropical jet. The eddy adjustment is further examined using large ensembles of transient response to a sudden switch-on of the forcing. For both narrow and broad tropical warmings, the jets move equatorward initially. In the subsequent adjustment, the initial equatorward shift is further enhanced and sustained by the low-level baroclinicity under the narrow tropical warming, whereas the initial equatorward shift transitions to a poleward shift associated with altered irreversible mixing of potential vorticity in the upper troposphere in the case of broad warming.

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Ясюкевич, Анна, Anna Yasyukevich, Максим Клименко, Maksim Klimenko, Юрий Куликов, Yury Kulikov, Владимир Клименко, et al. "Changes in the middle and upper atmosphere parameters during the January 2013 sudden stratospheric warming." Solar-Terrestrial Physics 4, no. 4 (December 21, 2018): 48–58. http://dx.doi.org/10.12737/stp-44201807.

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We present the results of complex obser-vations of various parameters of the middle and upper atmosphere over Siberia in December 2012 – January 2013, during a major sudden stratospheric warming (SSW) event. We analyze variations in ozone concentration from microwave measurements, in stratosphere and lower mesosphere temperatures from lidar and satellite measurements, in the F2-layer critical frequency (foF2), in the total electron content (TEC), as well as in the ratio of concentrations of atomic oxygen to molecular nitrogen (O/N2) in the thermosphere. To interpret the observed disturbances in the upper atmosphere, the experimental measurements are compared with the results of model calculations obtained with the Global Self-consistent Model of Thermosphere—Ionosphere—Protonosphere (GSM TIP). The response of the upper atmosphere to the SSW event is shown to be a decrease in foF2 and TEC during the evolution of the warming event and a prolonged increase in O/N2, foF2, and TEC after the SSW maximum. For the first time, we observe the relation between the increase in stratospheric ozone, thermospheric O/N2, and ionospheric electron density for a fairly long time (up to 20 days) after the SSW maximum at midlatitudes.

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Dörnbrack, Andreas, Sonja Gisinger, Natalie Kaifler, Tanja Christina Portele, Martina Bramberger, Markus Rapp, Michael Gerding, Jens Söder, Nedjeljka Žagar, and Damjan Jelić. "Gravity waves excited during a minor sudden stratospheric warming." Atmospheric Chemistry and Physics 18, no. 17 (September 7, 2018): 12915–31. http://dx.doi.org/10.5194/acp-18-12915-2018.

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Abstract. An exceptionally deep upper-air sounding launched from Kiruna airport (67.82∘ N, 20.33∘ E) on 30 January 2016 stimulated the current investigation of internal gravity waves excited during a minor sudden stratospheric warming (SSW) in the Arctic winter 2015/16. The analysis of the radiosonde profile revealed large kinetic and potential energies in the upper stratosphere without any simultaneous enhancement of upper tropospheric and lower stratospheric values. Upward-propagating inertia-gravity waves in the upper stratosphere and downward-propagating modes in the lower stratosphere indicated a region of gravity wave generation in the stratosphere. Two-dimensional wavelet analysis was applied to vertical time series of temperature fluctuations in order to determine the vertical propagation direction of the stratospheric gravity waves in 1-hourly high-resolution meteorological analyses and short-term forecasts. The separation of upward- and downward-propagating waves provided further evidence for a stratospheric source of gravity waves. The scale-dependent decomposition of the flow into a balanced component and inertia-gravity waves showed that coherent wave packets preferentially occurred at the inner edge of the Arctic polar vortex where a sub-vortex formed during the minor SSW.

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Gavrilov, N. M., A. V. Koval, A. I. Pogoreltsev, and E. N. Savenkova. "Numerical simulation of wave interactions during sudden stratospheric warming." Izvestiya, Atmospheric and Oceanic Physics 53, no. 6 (November 2017): 592–602. http://dx.doi.org/10.1134/s0001433817060044.

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Shen, Xiaocen, Lin Wang, and Scott Osprey. "The Southern Hemisphere sudden stratospheric warming of September 2019." Science Bulletin 65, no. 21 (November 2020): 1800–1802. http://dx.doi.org/10.1016/j.scib.2020.06.028.

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Jiang, Xun, Jingqian Wang, Edward T. Olsen, Thomas Pagano, Luke L. Chen, and Yuk L. Yung. "Influence of Stratospheric Sudden Warming on AIRS Midtropospheric CO2." Journal of the Atmospheric Sciences 70, no. 8 (August 1, 2013): 2566–73. http://dx.doi.org/10.1175/jas-d-13-064.1.

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Abstract Midtropospheric CO2 retrievals from the Atmospheric Infrared Sounder (AIRS) were used to explore the influence of stratospheric sudden warming (SSW) on CO2 in the middle to upper troposphere. To choose the SSW events that had strong coupling between the stratosphere and troposphere, the authors applied a principal component analysis to the NCEP/Department of Energy Global Reanalysis 2 (NCEP-2) geopotential height data at 17 pressure levels. Two events (April 2003 and March 2005) that have strong couplings between the stratosphere and troposphere were chosen to investigate the influence of SSW on AIRS midtropospheric CO2. The authors investigated the temporal and spatial variations of AIRS midtropospheric CO2 before and after the SSW events and found that the midtropospheric CO2 concentrations increased by 2–3 ppm within a few days after the SSW events. These results can be used to better understand how the chemical tracers respond to the large-scale dynamics in the high latitudes.

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Schultz, Colin. "Sudden geoengineering termination could cause a huge warming spike." Eos, Transactions American Geophysical Union 94, no. 52 (December 24, 2013): 512. http://dx.doi.org/10.1002/2013eo520009.

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Assink, J. D., R. Waxler, P. Smets, and L. G. Evers. "Bidirectional infrasonic ducts associated with sudden stratospheric warming events." Journal of Geophysical Research: Atmospheres 119, no. 3 (February 5, 2014): 1140–53. http://dx.doi.org/10.1002/2013jd021062.

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de Paula, E. R., O. F. Jonah, A. O. Moraes, E. A. Kherani, B. G. Fejer, M. A. Abdu, M. T. A. H. Muella, I. S. Batista, S. L. G. Dutra, and R. R. Paes. "Low-latitude scintillation weakening during sudden stratospheric warming events." Journal of Geophysical Research: Space Physics 120, no. 3 (March 2015): 2212–21. http://dx.doi.org/10.1002/2014ja020731.

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Harada, Yayoi, Atsushi Goto, Hiroshi Hasegawa, Norihisa Fujikawa, Hiroaki Naoe, and Toshihiko Hirooka. "A Major Stratospheric Sudden Warming Event in January 2009." Journal of the Atmospheric Sciences 67, no. 6 (June 1, 2010): 2052–69. http://dx.doi.org/10.1175/2009jas3320.1.

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Abstract The major stratospheric sudden warming (SSW) event of January 2009 is analyzed using the Japan Meteorological Agency (JMA) Climate Data Assimilation System (JCDAS). This SSW event is characterized by the extraordinary predominance of the planetary-scale wave of zonal wavenumber 2 (wave 2). The total amount of the upward Eliassen–Palm (EP) flux for wave 2 was the strongest since the winter of 1978/79. It is found that the remarkable development of the upper troposphere ridge over Alaska played important roles in the SSW in January 2009. During the first development stage, the ridge excited wave packets upward as well as eastward over around Alaska. The eastward-propagating packets intensified a trough over eastern Siberia, which led to the development of the planetary wave over eastern Siberia during the second development stage. The results of this study indicate that the pronounced wave-2 pattern observed in the stratosphere was brought about by accumulative effects of rather localized propagation of wave packets from the troposphere during the course of this SSW event rather than by the ubiquitous propagation of planetary-scale disturbances in the troposphere. The features of the SSW in January 2009 are quite similar to those during the major stratospheric warming event in February 1989: both SSWs are characterized by the predominance of wave 2, the remarkable development of the upper troposphere ridge over around Alaska, and positive SSTs in the eastern part of the North Pacific corresponding to a La Niña condition.

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Hitchcock, Peter, Theodore G. Shepherd, and Gloria L. Manney. "Statistical Characterization of Arctic Polar-Night Jet Oscillation Events." Journal of Climate 26, no. 6 (March 15, 2013): 2096–116. http://dx.doi.org/10.1175/jcli-d-12-00202.1.

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Abstract A novel diagnostic tool is presented, based on polar-cap temperature anomalies, for visualizing daily variability of the Arctic stratospheric polar vortex over multiple decades. This visualization illustrates the ubiquity of extended-time-scale recoveries from stratospheric sudden warmings, termed here polar-night jet oscillation (PJO) events. These are characterized by an anomalously warm polar lower stratosphere that persists for several months. Following the initial warming, a cold anomaly forms in the middle stratosphere, as does an anomalously high stratopause, both of which descend while the lower-stratospheric anomaly persists. These events are characterized in four datasets: Microwave Limb Sounder (MLS) temperature observations; the 40-yr ECMWF Re-Analysis (ERA-40) and Modern Era Retrospective Analysis for Research and Applications (MERRA) reanalyses; and an ensemble of three 150-yr simulations from the Canadian Middle Atmosphere Model. The statistics of PJO events in the model are found to agree very closely with those of the observations and reanalyses. The time scale for the recovery of the polar vortex following sudden warmings correlates strongly with the depth to which the warming initially descends. PJO events occur following roughly half of all major sudden warmings and are associated with an extended period of suppressed wave-activity fluxes entering the polar vortex. They follow vortex splits more frequently than they do vortex displacements. They are also related to weak vortex events as identified by the northern annular mode; in particular, those weak vortex events followed by a PJO event show a stronger tropospheric response. The long time scales, predominantly radiative dynamics, and tropospheric influence of PJO events suggest that they represent an important source of conditional skill in seasonal forecasting.

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Flury, T., K. Hocke, N. Kämpfer, and D. L. Wu. "Enhancements of gravity wave amplitudes at midlatitudes during sudden stratospheric warmings in 2008." Atmospheric Chemistry and Physics Discussions 10, no. 12 (December 9, 2010): 29971–95. http://dx.doi.org/10.5194/acpd-10-29971-2010.

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Abstract. Two minor and one major stratospheric warming happened in January and February 2008 when the polar vortex was shifted toward midlatitudes. The analysis of temperature profiles from radiosondes in Payerne (Switzerland) during this period reveals an enhancement of gravity wave amplitudes between 25 and 30 km altitude especially during the two minor warmings around 20 January and 1 February. Increases of gravity wave amplitudes in the mid-stratosphere are associated with a strong tropopause jet and the presence of the polar vortex edge over Switzerland.

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Lindgren, Erik A., and Aditi Sheshadri. "The role of wave–wave interactions in sudden stratospheric warming formation." Weather and Climate Dynamics 1, no. 1 (March 10, 2020): 93–109. http://dx.doi.org/10.5194/wcd-1-93-2020.

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Abstract. The effects of wave–wave interactions on sudden stratospheric warming formation are investigated using an idealized atmospheric general circulation model, in which tropospheric heating perturbations of zonal wave numbers 1 and 2 are used to produce planetary-scale wave activity. Zonal wave–wave interactions are removed at different vertical extents of the atmosphere in order to examine the sensitivity of stratospheric circulation to local changes in wave–wave interactions. We show that the effects of wave–wave interactions on sudden warming formation, including sudden warming frequencies, are strongly dependent on the wave number of the tropospheric forcing and the vertical levels where wave–wave interactions are removed. Significant changes in sudden warming frequencies are evident when wave–wave interactions are removed even when the lower-stratospheric wave forcing does not change, highlighting the fact that the upper stratosphere is not a passive recipient of wave forcing from below. We find that while wave–wave interactions are required in the troposphere and lower stratosphere to produce displacements when wave number 2 heating is used, both splits and displacements can be produced without wave–wave interactions in the troposphere and lower stratosphere when the model is forced by wave number 1 heating. We suggest that the relative strengths of wave number 1 and 2 vertical wave flux entering the stratosphere largely determine the split and displacement ratios when wave number 2 forcing is used but not wave number 1.

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Xu, Fen, and X. San Liang. "On the Generation and Maintenance of the 2012/13 Sudden Stratospheric Warming." Journal of the Atmospheric Sciences 74, no. 10 (September 15, 2017): 3209–28. http://dx.doi.org/10.1175/jas-d-17-0002.1.

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Abstract Using a newly developed analysis tool, multiscale window transform (MWT), and the MWT-based localized multiscale energetics analysis, the 2012/13 sudden stratospheric warming (SSW) is diagnosed for an understanding of the underlying dynamics. The fields are first reconstructed onto three scale windows: that is, mean window, sudden warming window or SSW window, and synoptic window. According to the reconstructions, the major warming period may be divided into three stages: namely, the stages of rapid warming, maintenance, and decay, each with different mechanisms. It is found that the explosive growth of temperature in the rapid warming stage (28 December–10 January) results from the collaboration of a strong poleward heat flux and canonical transfers through baroclinic instabilities in the polar region, which extract available potential energy (APE) from the mean-scale reservoir. In the course, a portion of the acquired APE is converted to and stored in the SSW-scale kinetic energy (KE), leading to a reversal of the polar night jet. In the stage of maintenance (11–25 January), the mechanism is completely different: First the previously converted energy stored in the SSW-scale KE is converted back, and, most importantly, in this time a strong barotropic instability happens over Alaska–Canada, which extracts the mean-scale KE to maintain the high temperature, while the mean-scale KE is mostly from the lower atmosphere, in conformity with the classical paradigm of mean flow–wave interaction with the upward-propagating planetary waves. This study provides an example that a warming may be generated in different stages through distinctly different mechanisms.

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Васильев, Павел, Pavel Vasilyev, Иван Карпов, Ivan Karpov, Сергей Кшевецкий, and Sergey Kshevetskii. "Modeling of the effect of internal gravity waves on upper atmospheric conditions during sudden stratospheric warming." Solar-Terrestrial Physics 2, no. 3 (October 27, 2016): 99–105. http://dx.doi.org/10.12737/22288.

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We present results of modeling of the effect of internal gravity waves (IGW), excited in the region of development of a sudden stratospheric warming (SSW), on upper atmospheric conditions. In the numerical experiment, we use a two-dimensional model of propagation of atmospheric waves, taking into account dissipative and nonlinear processes accompanying wave propagation. As a source of disturbances we consider temperature and density disturbances in the stratosphere during SSWs. Amplitude and frequency characteristics of the source of disturbances are estimated from observations and IGW theory. Numerical calculations showed that waves generated at stratospheric heights during SSW can cause temperature changes in the upper atmosphere. Maximum relative disturbances, caused by such waves, with respect to quiet conditions are observed at 100–200 km. Disturbances of the upper atmosphere in turn have an effect on the dynamics of charged component in the ionosphere and can contribute to observable ionospheric effects of SSW.

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Shi, Chunhua, Ting Xu, Dong Guo, and Zaitao Pan. "Modulating Effects of Planetary Wave 3 on a Stratospheric Sudden Warming Event in 2005." Journal of the Atmospheric Sciences 74, no. 5 (April 26, 2017): 1549–59. http://dx.doi.org/10.1175/jas-d-16-0065.1.

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Abstract The Eliassen–Palm flux (EPF) and Plumb’s wave activity flux (WAF) were computed, using ERA-Interim data, to analyze the influence of planetary wave 3 on a stratospheric sudden warming event from 17 February to 15 March 2005 (SSW05). It was found that 1) SSW05 consisted of three stages: a prior minor warming (MnW05), a late final warming (FW05), and a warming stagnation between MnW05 and FW05; 2) the wave 3 first decreased total upward EPFs by more than 30% at 100 hPa, resulting in the warming stagnation, and then increased upward EPFs by greater than 50%, leading to FW05; and 3) the anomalies of wave-3 activity fluxes were associated with the pattern of Atlantic blocking high in the latter two stages. The interactions between the wave 3 and wave 1 partitioned the zonal upward channel of total wave activity fluxes from one longitudinal region into two longitudinal regions and affected SSW05.

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Statnaia, Irina A., Alexey Y. Karpechko, and Heikki J. Järvinen. "Mechanisms and predictability of sudden stratospheric warming in winter 2018." Weather and Climate Dynamics 1, no. 2 (October 27, 2020): 657–74. http://dx.doi.org/10.5194/wcd-1-657-2020.

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Abstract. In the beginning of February 2018 a rapid deceleration of the westerly circulation in the polar Northern Hemisphere stratosphere took place, and on 12 February the zonal-mean zonal wind at 60∘ N and 10 hPa reversed to easterly in a sudden stratospheric warming (SSW) event. We investigate the role of the tropospheric forcing in the occurrence of the SSW, its predictability and teleconnection with the Madden–Julian oscillation (MJO) by analysing the European Centre for Medium-Range Weather Forecasts (ECMWF) ensemble forecast. The SSW was preceded by significant synoptic wave activity over the Pacific and Atlantic basins, which led to the upward propagation of wave packets and resulted in the amplification of a stratospheric wavenumber 2 planetary wave. The dynamical and statistical analyses indicate that the main tropospheric forcing resulted from an anticyclonic Rossby wave breaking, subsequent blocking and upward wave propagation in the Ural Mountains region, in agreement with some previous studies. The ensemble members which predicted the wind reversal also reasonably reproduced this chain of events, from the horizontal propagation of individual wave packets to upward wave-activity fluxes and the amplification of wavenumber 2. On the other hand, the ensemble members which failed to predict the wind reversal also failed to properly capture the blocking event in the key region of the Urals and the associated intensification of upward-propagating wave activity. Finally, a composite analysis suggests that teleconnections associated with the record-breaking MJO phase 6 observed in late January 2018 likely played a role in triggering this SSW event.

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Chen, Quanliang, Luyang Xu, and Hongke Cai. "Impact of Stratospheric Sudden Warming on East Asian Winter Monsoons." Advances in Meteorology 2015 (2015): 1–10. http://dx.doi.org/10.1155/2015/640912.

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Fifty-two Stratospheric sudden warming (SSW) events that occurred from 1957 to 2002 were analyzed based on the 40-year European Centre for Medium-Range Weather Forecasts Reanalysis dataset. Those that could descent to the troposphere were composited to investigate their impacts on the East Asian winter monsoon (EAWM). It reveals that when the SSW occurs, the Arctic Oscillation (AO) and the North Pacific Oscillation (NPO) are both in the negative phase and that the tropospheric circulation is quite wave-like. The Siberian high and the Aleutian low are both strengthened, leading to an increased gradient between the Asian continent and the North Pacific. Hence, a strong EAWM is observed with widespread cooling over inland and coastal East Asia. After the peak of the SSW, in contrast, the tropospheric circulation is quite zonally symmetric with negative phases of AO and NPO. The mid-tropospheric East Asian trough deepens and shifts eastward. This configuration facilitates warming over the East Asian inland and cooling over the coastal East Asia centered over Japan. The activities of planetary waves during the lifecycle of the SSW were analyzed. The anomalous propagation and the attendant altered amplitude of the planetary waves can well explain the observed circulation and the EAWM.

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Wang, Feiyang, Yuanyuan Han, Shiyan Zhang, and Ruhua Zhang. "Influence of stratospheric sudden warming on the tropical intraseasonal convection." Environmental Research Letters 15, no. 8 (August 5, 2020): 084027. http://dx.doi.org/10.1088/1748-9326/ab98b5.

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Wu, Zheng, and Thomas Reichler. "Surface Control of the Frequency of Stratospheric Sudden Warming Events." Journal of Climate 32, no. 15 (July 3, 2019): 4753–66. http://dx.doi.org/10.1175/jcli-d-18-0801.1.

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AbstractThe frequency of stratospheric sudden warming events (SSWs) is an important characteristic of the coupled stratosphere–troposphere system. However, many modern climate models are unable to reproduce the observed SSW frequency. A previous study suggested that one of the reasons could be the momentum damping at the surface. The goal of the present study is to understand what determines the climatological SSW frequency and how the surface damping comes into play. To this end, we conduct a parameter sweep with an idealized model, using a wide range of values for the surface damping. It is found that the SSW frequency is a strong and nonlinear function of the surface damping. Various tropospheric and stratospheric factors are identified to link the surface damping to the SSW frequency. The factors include the magnitude of the surface winds, the meridional and vertical wind shear, the synoptic eddy activity in the troposphere, the transient wave activity flux at the lower stratosphere, and the strength of the stratospheric polar vortex. Mathematical–statistical modeling, informed by the parameter sweep, is used to quantify how the different factors relate to each other. This successfully reproduces the complex variations of the SSW frequency with the surface damping seen in the parameter sweep. The results may help in explaining some of the difficulties that climate models have in simulating the observed SSW frequency.

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Yiğit, Erdal, and Alexander S. Medvedev. "Gravity waves in the thermosphere during a sudden stratospheric warming." Geophysical Research Letters 39, no. 21 (November 2012): n/a. http://dx.doi.org/10.1029/2012gl053812.

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Deng, Shumei, Yuejuan Chen, Yong Huang, Tao Luo, and Yun Bi. "Transient characteristics of residual meridional circulation during stratospheric sudden warming." Advances in Atmospheric Sciences 28, no. 3 (May 2011): 551–63. http://dx.doi.org/10.1007/s00376-010-0010-7.

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Hu, Jinggao, Rongcai Ren, and Haiming Xu. "Occurrence of Winter Stratospheric Sudden Warming Events and the Seasonal Timing of Spring Stratospheric Final Warming." Journal of the Atmospheric Sciences 71, no. 7 (June 20, 2014): 2319–34. http://dx.doi.org/10.1175/jas-d-13-0349.1.

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Abstract Based on the NCEP–NCAR reanalysis dataset covering 1958–2012, this paper demonstrates a statistically significant relationship between the occurrence of major stratospheric sudden warming events (SSWs) in midwinter and the seasonal timing of stratospheric final warming events (SFWs) in spring. Specifically, early spring SFWs that on average occur in early March tend to be preceded by non-SSW winters, while late spring SFWs that on average take place up until early May are mostly preceded by SSW events in midwinter. Though the occurrence (absence) of SSW events in midwinter may not always be followed by late (early) SFWs in spring, there is a much higher (lower) probability of late SFWs than early SFWs in spring after SSW (non-SSW) winters, particularly when the winter SSWs occur no earlier than early January or in the period from late January to early February. Diagnosis shows that, corresponding to an SSW (non-SSW) winter and the following late (early)-SFW spring, intensity of planetary wave activity in the stratosphere tends to evolve out of phase from midwinter to the following spring, being anomalously stronger (weaker) in winter and anomalously weaker (stronger) in spring. Furthermore, the strengthening of the western Eurasian high, which appears during early to mid-January in late-SFW years but does not appear until late February to mid-March in early-SFW years, always precedes the strengthening of planetary wave activity in the stratosphere and thus acts as a tropospheric precursor to the seasonal timing of SFWs.

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Frelich, Lee E., Rebecca A. Montgomery, and Peter B. Reich. "Seven Ways a Warming Climate Can Kill the Southern Boreal Forest." Forests 12, no. 5 (April 29, 2021): 560. http://dx.doi.org/10.3390/f12050560.

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The southern boreal forests of North America are susceptible to large changes in composition as temperate forests or grasslands may replace them as the climate warms. A number of mechanisms for this have been shown to occur in recent years: (1) Gradual replacement of boreal trees by temperate trees through gap dynamics; (2) Sudden replacement of boreal overstory trees after gradual understory invasion by temperate tree species; (3) Trophic cascades causing delayed invasion by temperate species, followed by moderately sudden change from boreal to temperate forest; (4) Wind and/or hail storms removing large swaths of boreal forest and suddenly releasing temperate understory trees; (4) Compound disturbances: wind and fire combination; (5) Long, warm summers and increased drought stress; (6) Insect infestation due to lack of extreme winter cold; (7) Phenological disturbance, due to early springs, that has the potential to kill enormous swaths of coniferous boreal forest within a few years. Although most models project gradual change from boreal forest to temperate forest or savanna, most of these mechanisms have the capability to transform large swaths (size range tens to millions of square kilometers) of boreal forest to other vegetation types during the 21st century. Therefore, many surprises are likely to occur in the southern boreal forest over the next century, with major impacts on forest productivity, ecosystem services, and wildlife habitat.

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Котова, Дарья, Daria Kotova, Максим Клименко, Maksim Klimenko, Владимир Клименко, Vladimir Klimenko, Вениамин Захаров, et al. "Influence of January 2009 stratospheric warming on HF radio wave propagation in the low-latitude ionosphere." Solar-Terrestrial Physics 2, no. 4 (February 2, 2017): 81–93. http://dx.doi.org/10.12737/24275.

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We have considered the influence of the January 23–27, 2009 sudden stratospheric warming (SSW) event on HF radio wave propagation in the equatorial ionosphere. This event took place during extremely low solar and geomagnetic activity. We use the simulation results obtained with the Global Self-consistent Model of the Thermosphere, Ionosphere and Protonosphere (GSM TIP) for simulating environmental changes during the SSW event. We both qualitatively and quantitatively reproduced total electron content disturbances obtained from global ground network receiver observations of GPS navigation satellite signals, by setting an additional electric potential and TIME-GCM model output at a height of 80 km. In order to study the influence of this SSW event on HF radio wave propagation and attenuation, we used the numerical model of radio wave propagation based on geometrical optics approximation. It is shown that the sudden stratospheric warming leads to radio signal attenuation and deterioration of radio communication in the daytime equatorial ionosphere.

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Journal articles on the topic 'Sudden warming'

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