Baldwin M. P., T. J. Dunkerton, 1999: Propagation of the Arctic Oscillation from the stratosphere to the troposphere. J. Geophys. Res., 104, 30 937- 30 946.10.1029/1999JD9004455cb2458d112b564926ed45f3ba29c8fchttp%3A%2F%2Fonlinelibrary.wiley.com%2Fdoi%2F10.1029%2F1999JD900445%2Ffullhttp://onlinelibrary.wiley.com/doi/10.1029/1999JD900445/fullGeopotential anomalies ranging from the Earth's surface to the middle stratosphere in the northern hemisphere are dominated by a mode of variability known as the Arctic Oscillation (AO). The AO is represented herein by the leading mode (the first empirical orthogonal function) of low-frequency variability of wintertime geopotential between 1000 and 10 hPa. In the middle stratosphere the signature of the AO is a nearly zonally symmetric pattern representing a strong or weak polar vortex. At 1000 hPa the AO is similar to the North Atlantic Oscillation, but with more zonal symmetry, especially at high latitudes. In zonal-mean zonal wind the AO is seen as a north-south dipole centered on 40°–45°N; in zonal-mean temperature it is seen as a deep warm or cold polar anomaly from the upper troposphere to 6510 hPa. The association of the AO pattern in the troposphere with modulation of the strength of the stratospheric polar vortex provides perhaps the best measure of coupling between the stratosphere and the troposphere. By examining separately time series of AO signatures at tropospheric and stratospheric levels, it is shown that AO anomalies typically appear first in the stratosphere and propagate downward. The midwinter correlation between the 90-day low-pass-filtered 10-hPa anomaly and the 1000-hPa anomaly exceeds 0.65 when the surface anomaly time series is lagged by about three weeks. The tropospheric signature of the AO anomaly is characterized by substantial changes to the storm tracks and strength of the midtropospheric flow, especially over the North Atlantic and Europe. The implications of large stratospheric anomalies as precursors to changes in tropospheric weather patterns are discussed.
Baldwin M. P., T. J. Dunkerton, 2001: Stratospheric harbingers of anomalous weather regimes. Science, 294, 581- 584.10.1126/science.106331511641495eef35230b9a42dc2ec1960dde3dbee70http%3A%2F%2Fmed.wanfangdata.com.cn%2FPaper%2FDetail%2FPeriodicalPaper_PM11641495http://med.wanfangdata.com.cn/Paper/Detail/PeriodicalPaper_PM11641495Observations show that large variations in the strength of the stratospheric circulation, appearing first above approximately 50 kilometers, descend to the lowermost stratosphere and are followed by anomalous tropospheric weather regimes. During the 60 days after the onset of these events, average surface pressure maps resemble closely the Arctic Oscillation pattern. These stratospheric events also precede shifts in the probability distributions of extreme values of the Arctic and North Atlantic Oscillations, the location of storm tracks, and the local likelihood of mid-latitude storms. Our observations suggest that these stratospheric harbingers may be used as a predictor of tropospheric weather regimes.
Barriopedro D., R. Garcia-Herrera, A. R. Lupo, and E. Hernãndez, 2006: A climatology of Northern Hemisphere Blocking. J.Climate, 19, 1042- 1063.10.1175/JCLI3678.10c4a80e05bcaa37ed0edbcc505a41ecbhttp%3A%2F%2Fwww.researchgate.net%2Fpublication%2F233729991_A_Climatology_of_Northern_Hemisphere_Blockinghttp://www.researchgate.net/publication/233729991_A_Climatology_of_Northern_Hemisphere_BlockingAbstract In this paper a 55-yr (1948-2002) Northern Hemisphere blocking climatology is presented. Traditional blocking indices and methodologies are revised and a new blocking detection method is designed. This algorithm detects blocked flows and provides for a better characterization of blocking events with additional information on blocking parameters such as the location of the blocking center, the intensity, and extension. Additionally, a new tracking procedure has been incorporated following simultaneously the individual evolution of blocked flows and identifying coherently persistent blocked patterns. Using this method, the longest known Northern Hemisphere blocking climatology is obtained and compared with previous studies. A new regional classification into four independent blocking sectors has been obtained based on the seasonally preferred regions of blocking formation: Atlantic (ATL), European (EUR), West Pacific (WPA), and East Pacific (EPA). Global and regional blocking characteristics have been described, examining their variability from the seasonal to interdecadal scales. The global long-term blocking series in the North Hemisphere showed a significant trend toward weaker and less persistent events, as well as regional increases (decreases) in blocking frequency over the WPA (ATL and EUR) sector. The influence of teleconnection patterns (TCPs) on blocking parameters is also explored, being confined essentially to wintertime, except in the WPA sector. Additionally, regional blocking parameters, especially frequency and duration, are sensitive to regional TCPs, supporting the regional classification obtained in this paper. The ENSO-related blocking variability is evident in blocking intensities and preferred locations but not in frequency. Finally, the dynamical connection between blocking occurrence and regional TCPs is examined through the conceptual model proposed by Charney and DeVore. Observational evidence of a dynamical link between the asymmetrical temperature distributions induced by TCPs and blocking variability is provided with a distinctive contrast arm ocean/cold land pattern favoring the blocking occurrence in winter. However, the conceptual model is not coherent in the WPA sector, suggesting different blocking mechanisms operating in this sector.
Christiansen B., 2000: A model study of the dynamical connection between the Arctic Oscillation and stratospheric vacillations. J. Geophys. Res., 105, 29 461- 29 474.10.1029/2000JD900542a266ee064c7a9c278356786877c92afchttp%3A%2F%2Fonlinelibrary.wiley.com%2Fdoi%2F10.1029%2F2000JD900542%2Fcitedbyhttp://onlinelibrary.wiley.com/doi/10.1029/2000JD900542/citedbyABSTRACT The dynamical connection between the stratosphere and the troposphere in the Northern Hemisphere winter is investigated with general circulation model (GCM) simulations under perpetual January conditions. The variability in the stratosphere is strongly dominated by vacillations on a timescale of 100 days. One-point correlation maps of the zonal mean zonal wind reveal the characteristic downward propagation of the stratospheric disturbances. The meridional structure of the stratospheric vacillations is well described by a few empirical orthogonal functions (EOFs) of geopotential height. The leading EOF describes a standing oscillation of the stratosphere, while the two next describe the vertical and horizontal propagation. In the troposphere the leading EOF of the surface pressure shows the characteristic circumpolar structure of the Arctic Oscillation. The covariance between the leading EOF of the surface pressure and the zonal mean zonal wind reveals a vertical structure similar to the observed below 10 hPa, while the sign of the covariance changes above 10 hPa where observations are scarce. The downward propagating stratospheric modes play a prominent role in the vertical coupling. Singular value decomposition of the cross-covariance matrix between the stratospheric zonal mean zonal wind and the surface pressure shows that a significant part of the tropospheric variability can be related to the downward propagating anomalies. The leading pattern of surface pressure anomalies found in this way closely resembles the pattern of the Arctic Oscillation and describes 20-30% of the total variance. This result is confirmed by studying the covariance between the geopotential height fields and the stratospheric principal components.
Christiansen B., 2001: Downward propagation of zonal mean zonal wind anomalies from the stratosphere to the troposphere: Model and reanalysis. J. Geophys. Res., 106, 27 307- 27 322.10.1029/2000JD000214c783b03c5a5d38dcc5b8b3f21c12683dhttp%3A%2F%2Fonlinelibrary.wiley.com%2Fdoi%2F10.1029%2F2000JD000214%2Fcitedbyhttp://onlinelibrary.wiley.com/doi/10.1029/2000JD000214/citedbyABSTRACT The connection between the Arctic Oscillation and the stratosphere is investigated on intra-annual timescales. Both the National Centers for Environmental Prediction reanalysis data and a general circulation model simulation are used. In the winter half year November-April the dominant variability in the stratosphere in middle and high latitudes has the form of downward propagation of zonal mean zonal wind anomalies. The strength of the anomalies decays below 10 hPa, but often the anomalies reach the surface. The time for the propagation from 10 hPa to the surface is ~15 days. When positive anomalies reach the surface, the phase of the Arctic Oscillation tends to be positive. The stratospheric variability and the downward propagation is found to be driven by the vertical component of the Eliassen-Palm flux. This flux propagates from the lower troposphere to the tropopause on a time scale of 5 days. Model and reanalysis compare well in the structure of the stratospheric variability and the connection between the stratosphere and troposphere. However, the strength of the stratospheric variability is ~25% weaker in the model.
Coughlin K., K. K. Tung, 2005: Tropospheric wave response to decelerated stratosphere seen as downward propagation in northern annular mode. J. Geophys. Res. , 110,D01103, doi:10.1029/2004JD004661.10.1029/2004JD0046618254fe9f7e63cfde9374eb20aabdd141http%3A%2F%2Fonlinelibrary.wiley.com%2Fdoi%2F10.1029%2F2004JD004661%2Fcitedbyhttp://onlinelibrary.wiley.com/doi/10.1029/2004JD004661/citedby[1] Baldwin and Dunkerton [1999] found that negative northern annular mode (NAM) anomalies sometimes descend all the way from the stratosphere into the lower troposphere. However, no viable mechanism has been proposed so far to account for the magnitude of the anomalies in the denser troposphere. Further, analysis shows that the character of the anomaly changes across the tropopause. Above the tropopause the NAM pattern is approximately zonal, and its descent represents the descent of decelerated zonal mean winds. This stratospheric change is explainable using theories similar to those for the descent of the zero-wind line associated with a major stratospheric sudden warming. However, such a reversal in the zonal mean wind rarely reaches the denser troposphere. The descent of the NAM anomalies into the troposphere may be implying a different relationship between the stratosphere and the troposphere. We note that in the troposphere the structure of the NAM has a large wave component. In some cases, this wave component appears to react to the decelerated wind configuration aloft. Here we show observations of the wave component and the zonal mean component in comparison to corresponding NAM events to show that the wave response is a sizable component of the NAM anomaly in the troposphere. We will also present a simple model calculation to show that tropospheric waves forced by topography can react to changing stratospheric winds. These tropospheric waves can project directly onto the tropospheric NAM patterns and produce anomalies in the index which appear to be connected to the negative NAM anomalies in the stratosphere.
Dee, D. P., Coauthors, 2011: The ERA-Interim reanalysis: configuration and performance of the data assimilation system. Quart. J. Roy. Meteor. Soc., 137, 553- 597.10.1002/qj.828b8698c40-b145-4364-9b39-4e603f942b9ff1b44af3b88d0a7be27ce2739fe46ee7http://onlinelibrary.wiley.com/doi/10.1002/qj.828/pdfhttp://onlinelibrary.wiley.com/doi/10.1002/qj.828/pdfABSTRACT ERA-Interim is the latest global atmospheric reanalysis produced by the European Centre for Medium-Range Weather Forecasts (ECMWF). The ERA-Interim project was conducted in part to prepare for a new atmospheric reanalysis to replace ERA-40, which will extend back to the early part of the twentieth century. This article describes the forecast model, data assimilation method, and input datasets used to produce ERA-Interim, and discusses the performance of the system. Special emphasis is placed on various difficulties encountered in the production of ERA-40, including the representation of the hydrological cycle, the quality of the stratospheric circulation, and the consistency in time of the reanalysed fields. We provide evidence for substantial improvements in each of these aspects. We also identify areas where further work is needed and describe opportunities and objectives for future reanalysis projects at ECMWF. Copyright 2011 Royal Meteorological Society
Dunn-Sigouin E., T. A. Shaw, 2015: Comparing and contrasting extreme stratospheric events,including their coupling to the tropospheric circulation. J. Geophys. Res.: Atmos., 120, 1374-1390, doi: 10.1002/2014JD022116.7b2c6d11-941e-489e-8b90-a2d2af18105acf40198a3edd6cbc185083d691bc1bf5http%3A%2F%2Fonlinelibrary.wiley.com%2Fdoi%2F10.1002%2F2014JD022116%2Fabstractrefpaperuri:(a1b4f5b49fa5229cfbf539ee309cf851)/s?wd=paperuri%3A%28a1b4f5b49fa5229cfbf539ee309cf851%29&filter=sc_long_sign&tn=SE_xueshusource_2kduw22v&sc_vurl=http%3A%2F%2Fonlinelibrary.wiley.com%2Fdoi%2F10.1002%2F2014jd022116%2Fabstract&ie=utf-8
Geller M. A., J. C. Alpert, 1980: Planetary wave coupling between the troposphere and the middle atmosphere as a possible sun-weather mechanism. J. Atmos. Sci., 37, 1197- 1214.10.1175/1520-0469(1980)0372.0.CO;2294a4933d4f935efaa6a1261dcf55debhttp%3A%2F%2Fwww.researchgate.net%2Fpublication%2F4691689_Planetary_wave_coupling_between_the_troposphere_and_the_middle_atmosphere_as_a_possible_sun-weather_mechanism%3Fev%3Dprf_cithttp://www.researchgate.net/publication/4691689_Planetary_wave_coupling_between_the_troposphere_and_the_middle_atmosphere_as_a_possible_sun-weather_mechanism?ev=prf_citAbstract The possibility of planetary wave coupling between the troposphere and solar-induced alterations in the upper atmosphere providing a viable mechanism for giving rise to sun-weather relationships is investigated. Some of the observational evidence for solar-activity-induced effects on levels of the upper atmosphere ranging from the thermosphere down to the lower stratosphere are reviewed. It is concluded that there is evidence for such effects extending down to the middle stratosphere and below. Evidence is also reviewed that these effects are due to changes in solar ultraviolet emission during disturbed solar conditions. A theoretical planetary wave model is then used to see at what levels in the upper atmosphere moderate changes in the mean zonal wind state would result in tropospheric changes. It is concluded that changes in the mean zonal flow of 20% at levels in the vicinity of 35 km or below would give rise to changes in the tropospheric planetary wave pattern that are less than but on the same order as the observed interannual variability in the tropospheric wave pattern at middle and high latitudes. Thus, planetary wave coupling between the troposphere and the upper atmosphere appears to be a plausible mechanism to give a tropospheric response to solar activity. This mechanism is not viable, however, to provide for short-period changes such as the suggested solar sector boundary vorticity index relation, but rather is applicable to changes of longer period such as the 11- or 22-year solar cycles.
Hines C. O., 1974: A possible mechanism for the production of sun-weather correlations. J. Atmos. Sci., 31, 589- 591.10.1175/1520-0469(1974)031<0589:APMFTP>2.0.CO;240c5d4fa9e2f32af47fc41ecc2b7718ehttp%3A%2F%2Fwww.researchgate.net%2Fpublication%2F234226259_A_Possible_Mechanism_for_the_Production_of_Sun-Weather_Correlationshttp://www.researchgate.net/publication/234226259_A_Possible_Mechanism_for_the_Production_of_Sun-Weather_CorrelationsAbstract If, as has been alleged, variations in the outflow of solar plasma have some effect on our weather, then the relevant coupling mechanism must be sought. It is suggested here that planetary waves, which may be subjected to variable reflection in the upper atmosphere and so may induce variable interference patterns in the lower atmosphere, constitute a potential candidate.
Hui G., 2009: China's snow disaster in 2008,who is the principal player? International Journal of Climatology, 29, 2191-2196, doi: 10.1002/joc.1859.10.1002/joc.1859b41dfdf0-aa39-4af8-bfea-e3e68fd96cfa8da3b8274a768873f8d09a392c161cdchttp%3A%2F%2Fonlinelibrary.wiley.com%2Fdoi%2F10.1002%2Fjoc.1859%2Fabstractrefpaperuri:(f1c9a07f0a6ab8b238e8904e10e9d44c)http://onlinelibrary.wiley.com/doi/10.1002/joc.1859/abstractAbstract The unprecedented snow disaster in January 2008 brought serious human and economic losses to China. It has been suggested that the La Nina event is the principal cause. But analysis indicates that in December 2007, the circulation patterns in the tropical regions are quite similar with those in January 2008. In contrast large differences existed at high latitudes, especially the Siberia high (SH) and the north polar vortex (NPV). The differences can also be found between other extreme heavy and light snow years. In the extreme heavy (light) snow years, the SH is stronger (weaker) and the NPV is deeper (shallower). But these extreme snow events don't correspond to ENSO events well. Statistical results also indicate that both the SH and the NPV are independent of ENSO. So, rather than the La Nina event, the abnormal circulations at the high latitudes may play a more crucial role in making this snow disaster. Copyright 2009 Royal Meteorological Society
Kodera K., M. Chiba, 1995: Tropospheric circulation changes associated with stratospheric sudden warmings: A case study. J. Geophys. Res., 100, 11 055- 11 068.10.1029/95JD007716888aa20213f26675fb2659b37fd4557http%3A%2F%2Fonlinelibrary.wiley.com%2Fdoi%2F10.1029%2F95JD00771%2Fcitedbyhttp://onlinelibrary.wiley.com/doi/10.1029/95JD00771/citedbyIt was theoretically demonstrated by Matsuno that stratospheric warmings are caused by an intensified vertical propagation of tropospheric planetary waves. However, the question of how the resultant changes in the stratospheric circulation affect the troposphere in return is left unanswered. In the present study, a case study on the 1984&ndash;1985 stratospheric warming event is conducted to clarify the changes in the tropospheric circulation associated with stratospheric sudden warmings. The results of the present study indicate that during stratospheric warmings, not only the intensification of the upward propagation of planetary waves is found in the stratosphere, but also changes in the direction of the meridional propagation of waves occur in the troposphere as well as in the stratosphere. Changes in the meridional phase structure of tropospheric planetary waves produce enhanced cold surges over the oceans, which in turn generate intense synoptic eddies. Further disturbances, such as blockings, can be produced through interactions between the planetary waves and synoptic eddies, but this may be only indirectly related with the stratospheric warmings. Comparisons between the observed changes in circulation and results of numerical model experiments suggest a potential role of the stratosphere in the tropospheric circulation through changes in meridional propagation of planetary waves.
Kuroda Y., K. Kodera, 1999: Role of planetary waves in the stratosphere-troposphere coupled variability in the Northern Hemisphere winter. Geophys. Res. Lett., 26, 2375- 2378.10.1029/1999GL900507189dbecbff624196e9207f6ed8a34dd2http%3A%2F%2Fonlinelibrary.wiley.com%2Fdoi%2F10.1029%2F1999GL900507%2Ffullhttp://onlinelibrary.wiley.com/doi/10.1029/1999GL900507/fullABSTRACT The role of planetary waves in stratosphere-troposphere coupled variability is investigated using an extended singular value decomposition analysis of zonal-mean zonal wind and the vertical component of the Eliassen-Palm (E-P) flux for the winters from 1979/80 to 1995/96. The results suggest a close relationship between anomalies of zonal-mean zonal wind and the convergence zone of E-P flux, which together shift poleward and downward from the stratosphere to the troposphere as time advances. Following enhanced vertical propagation of waves into the stratosphere, the Arctic Oscillation (AO) pattern is seen in the 500 hPa geopotential height field in association with an increased poleward propagation of tropospheric waves.
Kodera K., H. Mukougawa, and S. Itoh, 2008: Tropospheric impact of reflected planetary waves from the stratosphere. Geophys. Res. Lett., 35,L16806, doi: 10.1029/2008GL034575.10.1029/2008GL034575017099393141c4ed78e8fbe946b898cfhttp%3A%2F%2Fonlinelibrary.wiley.com%2Fdoi%2F10.1029%2F2008GL034575%2Fabstracthttp://onlinelibrary.wiley.com/doi/10.1029/2008GL034575/abstract[1] A reflection of stratospheric planetary waves and its impact on the troposphere during a stratospheric sudden warming of March 2007 are investigated. Zonal propagation and reflection of the planetary waves is clearly seen in the longitude-height sections of the eddy geopotential height and the vertical and zonal component of the three-dimensional wave activity flux. A wave packet propagating upward and eastward from Eurasian continent was reflected by a negative wind shear in the upper stratospheric westerly jet caused by stratospheric warming. Waves then propagated downward to the American-Atlantic sector of the troposphere, which led to the formation of a deep trough over the Atlantic and brought cold weather to the northeastern part of the American continent.
Kodera K., H. Mukougawa, and A. Fujji, 2013: Influence of the vertical and zonal propagation of stratospheric planetary waves on tropospheric blockings. J. Geophys. Res.: Atmos., 118, 8333- 8345.10.1002/jgrd.50650d46d36cc71e50f55d3171ea554040193http%3A%2F%2Fonlinelibrary.wiley.com%2Fdoi%2F10.1002%2Fjgrd.50650%2Fabstracthttp://onlinelibrary.wiley.com/doi/10.1002/jgrd.50650/abstractAbstract [1] Case studies are used to elucidate the relationship between stratospheric planetary wave reflection and blocking formation in the troposphere. The enhanced upward propagation of a planetary-scale wave packet from the Eurasian sector, involving a Euro-Atlantic blocking, leads to a stratospheric sudden warming (SSW). Following the weakening of the stratospheric westerly jet due to polar warming, the stratospheric planetary wave packet then propagates downward over the American sector, inducing a ridge over the North Pacific as well as a trough over eastern Canada in the upper troposphere. The ridge promotes the formation of a Pacific blocking. This result explains why Pacific blockings tend to form after SSW, and why they are associated with suppressed upward propagation of planetary waves.
Kodera K., K. Yamazaki, M. Chiba, and K. Shibata, 1990: Downward propagation of upper stratospheric mean zonal wind perturbation to the troposphere. Geophys. Res. Lett., 17, 1263- 1266.10.1029/GL017i009p01263f77afeadf155e25a75b56d17b4ef1152http%3A%2F%2Fonlinelibrary.wiley.com%2Fdoi%2F10.1029%2FGL017i009p01263%2Ffullhttp://onlinelibrary.wiley.com/doi/10.1029/GL017i009p01263/fullAn investigation is conducted to determine the influence of changes in the upper stratospheric mean zonal wind on the circulation of the lower atmosphere. In addition to observed data, results of numerical experiments with a general circulation model are used, in which the solar ultraviolet heating rate is varied to force changes in the mean zonal wind in the upper stratosphere. It is found that when the upper stratospheric mid-latitude westerlies are strong during December, lower stratospheric polar night jet is persistent and the westerlies in the polar region of the troposphere become stronger in the following February. These results are common to both the observations and the numerical experiments.
Martius O., L. M. Polvani, and H. C. Davies, 2009: Blocking precursors to stratospheric sudden warming events.Geophys. Res. Lett., 36, L14806, doi: 10.1029/2009GL038776.10.1029/2009GL038776a3fde84e6085c650d1b511727425e3a3http%3A%2F%2Fonlinelibrary.wiley.com%2Fdoi%2F10.1029%2F2009GL038776%2Ffullhttp://onlinelibrary.wiley.com/doi/10.1029/2009GL038776/fullAbstract Top of page Abstract 1.Introduction 2.Data and Methodology 3.Results 4.Discussion Acknowledgments References Supporting Information [1] The primary causes for the onset of major, midwinter, stratospheric sudden warming events remain unclear. In this paper, we report that 25 of the 27 events objectively identified in the ERA-40 dataset for the period 1957-2001 are preceded by blocking patterns in the troposphere. The spatial characteristics of tropospheric blocks prior to sudden warming events are strongly correlated with the type of sudden warming event that follows. Vortex displacement events are nearly always preceded by blocking over the Atlantic basin only, whereas vortex splitting events are preceded by blocking events occurring in the Pacific basin or in both basins contemporaneously. The differences in the geographical blocking distribution prior to sudden warming events are mirrored in the patterns of planetary waves that are responsible for producing events of either type. The evidence presented here, suggests that tropospheric blocking plays an important role in determining the onset and the type of warmings.
Namias J., P. F. Clapp, 1951: Observational studies of general circulation patterns. Compendium of Meteorology, T. F. Malone, Ed., Amer. Meteor. Soc., 551- 568.f85021c9-5d91-4aa8-99b3-8131aeccf733b900702203b369f2f7c3f1844d987f24http%3A%2F%2Fagris.fao.org%2Fagris-search%2Fsearch.do%3FrecordID%3DUS201300397210refpaperuri:(1dabc331e261075c6f6f8204f54e532a)/s?wd=paperuri%3A%281dabc331e261075c6f6f8204f54e532a%29&filter=sc_long_sign&tn=SE_xueshusource_2kduw22v&sc_vurl=http%3A%2F%2Fagris.fao.org%2Fagris-search%2Fsearch.do%3FrecordID%3DUS201300397210&ie=utf-8
Nath D., S. Sridharan, S. Sathishkumar, S. Gurubaran, and W. Chen, 2013: Lower stratospheric gravity wave activity over Gadanki (13.5\circN, 79.2\circE) during the stratospheric sudden warming of 2009: Link with potential vorticity intrusion near Indian sector. Journal of Atmospheric and Solar-Terrestrial Physics, 94, 54- 64.
Nath D., W. Chen, L. Wang, and Y. Ma, 2014: Planetary wave reflection and its impact on tropospheric cold weather over Asia during January 2008. Adv. Atmos. Sci.,31, 851-862, doi: 10.1007/s00376-013-3195-8.10.1007/s00376-013-3195-877d600a26aed8ba054051d3b5e8bd7ebhttp%3A%2F%2Fd.wanfangdata.com.cn%2FPeriodical_dqkxjz-e201404011.aspxhttp://d.wanfangdata.com.cn/Periodical_dqkxjz-e201404011.aspxReflection of stratospheric planetary waves and its impact on tropospheric cold weather over Asia during January 2008 were investigated by applying two dimensional Eliassen–Palm(EP) flux and three-dimensional Plumb wave activity fluxes. The planetary wave propagation can clearly be seen in the longitude–height and latitude–height sections of the Plumb wave activity flux and EP flux, respectively, when the stratospheric basic state is partially reflective. Primarily, a wave packet emanating from Baffin Island/coast of Labrador propagated eastward, equatorward and was reflected over Central Eurasia and parts of China, which in turn triggered the advection of cold wind from the northern part of the boreal forest regions and Siberia to the subtropics. The wide region of Central Eurasia and China experienced extreme cold weather during the second ten days of January 2008, whereas the extraordinary persistence of the event might have occurred due to an anomalous blocking high in the Urals–Siberia region.
Perlwitz J., H. F. Graf, 2001: Troposphere-stratosphere dynamic coupling under strong and weak polar vortex conditions. Geophys. Res. Lett., 28, 271- 274.10.1029/2000GL012405fbf1bb5f7675a213caa08ea80261ec48http%3A%2F%2Fonlinelibrary.wiley.com%2Fdoi%2F10.1029%2F2000GL012405%2Ffullhttp://onlinelibrary.wiley.com/doi/10.1029/2000GL012405/fullThe relationship between Northern Hemisphere (NH) tropospheric and stratospheric wave-like anomalies of spherical zonal wave number (ZWN) 1 is studied by applying Canonical Correlation Analysis (CCA). A lag-correlation technique is used with 10-day lowpass filtered daily time series of 50- and 500-hPa geopotential heights. Generally stratospheric circulation is determined by ultralong tropospheric planetary waves. During winter seasons characterized either by an anomalously strong or weak polar winter vortex different propagation characteristics for waves of ZWN 1 are observed. The non-linear perspective of the results have implications for medium range weather forecast and climate sensitivity experiments.
Perlwitz J., N. Harnik, 2003: Observational evidence of a stratospheric influence on the troposphere by planetary wave reflection. J.Climate, 16, 3011- 3026.10.1175/1520-0442(2003)016<3011:OEOASI>2.0.CO;2e8127032de2e1ad42d5481b2a6f2307dhttp%3A%2F%2Fwww.researchgate.net%2Fpublication%2F253549403_Observational_Evidence_of_a_Stratospheric_Influence_on_the_Troposphere_by_Planetary_Wave_Reflectionhttp://www.researchgate.net/publication/253549403_Observational_Evidence_of_a_Stratospheric_Influence_on_the_Troposphere_by_Planetary_Wave_ReflectionRecent studies have pointed out the impact of the stratosphere on the troposphere by dynamic coupling. In the present paper, observational evidence for an effect of downward planetary wave reflection in the stratosphere on Northern Hemisphere tropospheric waves is given by combining statistical and dynamical diagnostics. A time-lagged singular value decomposition analysis is applied to daily tropospheric and stratospheric height fields recomposed for a single zonal wavenumber. A wave geometry diagnostic for wave propagation characteristics that separates the index of refraction into vertical and meridional components is used to diagnose the occurrence of reflecting surfaces. For zonal wavenumber 1, this study suggests that there is one characteristic configuration of the stratospheric jet that reflects waves back into the troposphere when the polar night jet peaks in the high-latitude midstratosphere. This configuration is related to the formation of a reflecting surface for vertical propagation at around 5 hPa as a result of the vertical curvature of the zonal-mean wind and a clear meridional waveguide in the lower to middle stratosphere that channels the reflected wave activity to the high-latitude troposphere.
Perlwitz J., N. Harnik, 2004: Downward coupling between the stratosphere and troposphere: The relative roles of wave and zonal mean processes. J.Climate, 17, 4902- 4909.10.1175/JCLI-3247.15e6f2f86b13c81466b2db91845ac28dbhttp%3A%2F%2Fwww.researchgate.net%2Fpublication%2F228421473_Downward_coupling_between_the_stratosphere_and_troposphere_The_relative_roles_of_wave_and_zonal_mean_processeshttp://www.researchgate.net/publication/228421473_Downward_coupling_between_the_stratosphere_and_troposphere_The_relative_roles_of_wave_and_zonal_mean_processesWave and zonal mean features of the downward dynamic coupling between the stratosphere and troposphere are compared by applying a time-lagged singular value decomposition analysis to Northern Hemisphere height fields decomposed into zonal mean and its deviations. It is found that both zonal and wave components contribute to the downward interaction, with zonal wave 1 (due to reflection) dominating on the short time scale (up to 12 days) and the zonal mean (due to waveean-flow interaction) dominating on the longer time scale. It is further shown that the two processes dominate during different years, depending on the state of the stratosphere. Winters characterized by a basic state that is reflective for wave 1 show a strong relationship between stratospheric and tropospheric wave-1 fields when the stratosphere is leading and show no significant correlations in the zonal mean fields. On the other hand, winters characterized by a stratospheric state that does not reflect waves show a strong relationship only between stratospheric and tropospheric zonal mean fields. This study suggests that there are two types of stratospheric winter states, characterized by different downward dynamic interaction. In one state, most of the wave activity gets deposited in the stratosphere, resulting in strong wave ean-flow interaction, while in the other state, wave activity is reflected back down to the troposphere, primarily affecting the structure of tropospheric planetary waves.
Plumb R. A., 1985: On the three-dimensional propagation of stationary waves. J. Atmos. Sci., 42, 217- 229.10.1175/1520-0469(1985)042<0217:OTTDPO>2.0.CO;2ccdb9bc2c2853e3ba3d7632e5f9db2c5http%3A%2F%2Fci.nii.ac.jp%2Fnaid%2F10013124971%2Fhttp://ci.nii.ac.jp/naid/10013124971/On the three-dimensional propagation of stationary waves. PLUMB R. A. J. Atmos. Sci. 42, 217-229, 1985
Shaw T. A., J. Perlwitz, 2013: The life cycle of Northern Hemisphere downward wave coupling between the stratosphere and troposphere, J.Climate, 26, 1745- 1763.10.1175/JCLI-D-12-00251.1cf850a90-39ec-4ae6-9f45-4a58b998f54fe75651b021f3b8a0dba77c52c8ea1a84http%3A%2F%2Fwww.researchgate.net%2Fpublication%2F258795490_The_Life_Cycle_of_Northern_Hemisphere_Downward_Wave_Coupling_between_the_Stratosphere_and_Troposphererefpaperuri:(428500ae0defc9db71b5836752217110)http://www.researchgate.net/publication/258795490_The_Life_Cycle_of_Northern_Hemisphere_Downward_Wave_Coupling_between_the_Stratosphere_and_TroposphereAbstract The life cycle of Northern Hemisphere downward wave coupling between the stratosphere and troposphere via wave reflection is analyzed. Downward wave coupling events are defined by extreme negative values of a wave coupling index based on the leading principal component of the daily wave-1 heat flux at 30 hPa. The life cycle occurs over a 28-day period. In the stratosphere there is a transition from positive to negative total wave-1 heat flux and westward to eastward phase tilt with height of the wave-1 geopotential height field. In addition, the zonal-mean zonal wind in the upper stratosphere weakens leading to negative vertical shear. Following the evolution in the stratosphere there is a shift toward the positive phase of the North Atlantic Oscillation (NAO) in the troposphere. The pattern develops from a large westward-propagating wave-1 anomaly in the high-latitude North Atlantic sector. The subsequent equatorward propagation leads to a positive anomaly in midlatitudes. The near-surface temperature and circulation anomalies are consistent with a positive NAO phase. The results suggest that wave reflection events can directly influence tropospheric weather. Finally, winter seasons dominated by extreme wave coupling and stratospheric vortex events are compared. The largest impacts in the troposphere occur during the extreme negative seasons for both indices, namely seasons with multiple wave reflection events leading to a positive NAO phase or seasons with major sudden stratospheric warmings (weak vortex) leading to a negative NAO phase. The results reveal that the dynamical coupling between the stratosphere and NAO involves distinct dynamical mechanisms that can only be characterized by separate wave coupling and vortex indices.
Shaw T. A., J. Perlwitz, and N. Harnik, 2010: Downward wave coupling between the stratosphere and troposphere: The importance of meridional wave guiding and comparison with zonal-mean coupling. J.Climate, 23, 6365- 6381.10.1175/2010JCLI3804.1c1f7d0f81188ad452187f66a14aa400dhttp%3A%2F%2Fonlinelibrary.wiley.com%2Fresolve%2Freference%2FADS%3Fid%3D2010JCli...23.6365Shttp://onlinelibrary.wiley.com/resolve/reference/ADS?id=2010JCli...23.6365SAbstract The nature of downward wave coupling between the stratosphere and troposphere in both hemispheres is analyzed using the 40-yr European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis (ERA-40) dataset. Downward wave coupling occurs when planetary waves reflected in the stratosphere impact the troposphere, and it is distinct from zonal-mean coupling, which results from wave dissipation and its subsequent impact on the zonal-mean flow. Cross-spectral correlation analysis and wave geometry diagnostics reveal that downward wave-1 coupling occurs in the presence of both a vertical reflecting surface in the mid-to-upper stratosphere and a high-latitude meridional waveguide in the lower stratosphere. In the Southern Hemisphere, downward wave coupling occurs from September to December, whereas in the Northern Hemisphere it occurs from January to March. A vertical reflecting surface is also present in the stratosphere during early winter in both hemispheres; however, it forms at the poleward edge of the meridional waveguide, which is not confined to high latitudes. The absence of a high-latitude waveguide allows meridional wave propagation into the subtropics and decreases the likelihood of downward wave coupling. The results highlight the importance of distinguishing between wave reflection in general, which requires a vertical reflecting surface, and downward wave coupling between the stratosphere and troposphere, which requires both a vertical reflecting surface and a high-latitude meridional waveguide. The relative roles of downward wave and zonal-mean coupling in the Southern and Northern Hemispheres are subsequently compared. In the Southern Hemisphere, downward wave-1 coupling dominates, whereas in the Northern Hemisphere downward wave-1 coupling and zonal-mean coupling are found to be equally important from winter to early spring. The results suggest that an accurate representation of the seasonal cycle of the wave geometry is necessary for the proper representation of downward wave coupling between the stratosphere and troposphere.
Shaw T. A., J. Perlwitz, and O. Weiner, 2014: Troposphere-stratosphere coupling: Links to North Atlantic weather and climate, including their representation in CMIP5 models. J. Geophys. Res.:Atmos., 119, 5864- 5880.10.1002/2013JD02119171133adda40a21b33a3c996ae215d54fhttp%3A%2F%2Fonlinelibrary.wiley.com%2Fdoi%2F10.1002%2F2013JD021191%2Fpdfhttp://onlinelibrary.wiley.com/doi/10.1002/2013JD021191/pdfAbstract A new dynamical metric of troposphere-stratosphere coupling is established based on extreme stratospheric planetary-scale wave heat flux events, defined as the 10th and 90th percentile of the daily high-latitude averaged heat flux distribution at 50 Pa using ERA-Interim reanalysis data. The stratospheric heat flux extremes are linked instantaneously to high-latitude planetary-scale wave patterns in the troposphere and zonal wind, temperature and mean sea level pressure anomalies in the Atlantic basin. The impacts are reminiscent of different phases of the North Atlantic Oscillation. In particular extreme positive (negative) heat flux events in the stratosphere are associated with an equatorward (poleward) jet shift in the North Atlantic basin. The metric is used to evaluate troposphere-stratosphere coupling in models participating in the Coupled Model Intercomparison Project Phase 5. The results show that models with a degraded representation of stratospheric extremes exhibit robust biases in the troposphere relative to ERA-Interim. In particular, models with biased stratospheric extremes exhibit a biased climatological stationary wave pattern and Atlantic jet stream position in the troposphere. In addition these models exhibit biases in geopotential height and zonal wind extremes in the North Atlantic region. The stratospheric biases are connected to model lid height but it is not sufficient for assessing the tropospheric impacts. Our analysis reveals that the mean bias of the stratospheric heat flux is also not sufficient for assessing the representation of troposphere-stratosphere coupling. Overall the results suggest that a metric based on stratospheric heat flux extremes should be used in conjunction with metrics based on extreme polar vortex events in multi-model assessments of troposphere-stratosphere coupling.
Tibaldi S., F. Molteni, 1990: On the operational predictability of blocking. Tellus A, 42, 343- 365.10.1034/j.1600-0870.1990.t01-2-00003.x14e00c4593f3fca22fd1d7852e693d15http%3A%2F%2Fonlinelibrary.wiley.com%2Fdoi%2F10.1034%2Fj.1600-0870.1990.t01-2-00003.x%2Fpdfhttp://onlinelibrary.wiley.com/doi/10.1034/j.1600-0870.1990.t01-2-00003.x/pdfABSTRACT The entire 7-year archive of ECMWF operational analysis and forecast data is used to assess the skill of the Centre's model in short- and medium-range forecasting of atmospheric blocking. The assessment covers 7100-day periods, from 1 December to 10 March of all winters from 1980-81 to 1986-87, inclusive. A slightly modified version of the Legen&auml;s and &Oslash;kland objective zonal index is used to quantify both observed and forecast occurrence of blocking. The study is performed on 500 hPa geopotential height and on Euro-Atlantic and Pacific blocking separately. It is found that blocking frequency is severely underestimated in medium-range forecasts; the model is, on average, reasonably skilful if the initial conditions are blocked, but blocking onset is poorly represented if it occurs more than a few days into the forecast. This inability in entering the blocking regime has a substantial impact on the systematic error of the model.
Treidl R. A., E. C. Birch, and P. Sajecki, 1981: Blocking action in the Northern Hemisphere: A climatological study. Atmos.-Ocean, 19, 1- 23.10.1080/07055900.1981.96490964f2e4ec18742f6d6f3cb735abff60925http%3A%2F%2Fwww.tandfonline.com%2Fdoi%2Fabs%2F10.1080%2F07055900.1981.9649096http://www.tandfonline.com/doi/abs/10.1080/07055900.1981.9649096Using criteria developed from scientific studies, the blocking situations observed in the Northern Hemisphere during the period 1945–1977 are subjectively assessed and statistically analysed. Earlier findings are largely confirmed while new results are presented on seasonal and secular blocking trends, and the probability of multiple blocking. A catalogue of'664 blocking cases was prepared but is not included here because of its size; however, copies of the catalogue may be obtained from the authors.
Uppala S. M., D. Dee, S. Kobayashi, P. Berrisford, and A. Simmons, 2008: Towards a climate data assimilation system: Status update of ERA-Interim. ECMWF Newsletter, 115, 12- 18.b049b4451ca6109dc3d45d5791497345http%3A%2F%2Fwww.researchgate.net%2Fpublication%2F284038917_Towards_a_climate_data_assimilation_system_Status_update_of_ERA-Interim%3Fev%3Dauth_pubhttp://www.researchgate.net/publication/284038917_Towards_a_climate_data_assimilation_system_Status_update_of_ERA-Interim?ev=auth_pub
Zhou W., J. C. L. Chan, W. Chen, J. Ling, J. G. Pinto, and Y. Shao, 2009: Synoptic-scale controls of persistent low temperature and icy weather over Southern China in January 2008. Mon. Wea. Rev., 137, 3978- 3991.10.1175/2009MWR2952.1d9b407fb4b1b62b6ff39473041586094http%3A%2F%2Fwww.researchgate.net%2Fpublication%2F249621701_Synoptic-Scale_Controls_of_Persistent_Low_Temperature_and_Icy_Weather_over_Southern_China_in_January_2008http://www.researchgate.net/publication/249621701_Synoptic-Scale_Controls_of_Persistent_Low_Temperature_and_Icy_Weather_over_Southern_China_in_January_2008In January 2008, central and southern China experienced persistent low temperatures, freezing rain, and snow. The large-scale conditions associated with the occurrence and development of these snowstorms are examined in order to identify the key synoptic controls leading to this event. Three main factors are identified: 1) the persistent blocking high over Siberia, which remained quasi-stationary around 65E for 3 weeks, led to advection of dry and cold Siberian air down to central and southern China; 2) a strong persistent southwesterly flow associated with the western Pacific subtropical high led to enhanced moisture advection from the Bay of Bengal into central and southern China; and 3) the deep inversion layer in the lower troposphere associated with the extended snow cover over most of central and southern China. The combination of these three factors is likely responsible for the unusual severity of the event, and hence a long return period.