Adler R.F., Coauthors, 2003: The Version-2 global precipitation climatology project (GPCP) monthly precipitation analysis (1979-Present). Journal of Hydrometeorology, 4, 1147- 1167.10.1175/1525-7541(2003)004<1147:TVGPCP>2.0.CO;2e8c3bc43-a3c3-4a4f-a879-0056190f82f453064fd724346e9bd7d78eab17550121http%3A%2F%2Fwww.researchgate.net%2Fpublication%2F23837598_The_Version_2_Global_Precipitation_Climatology_Project_%28GPCP%29_Monthly_Precipitation_Analysis_%281979-Present%29refpaperuri:(6d3afea98ce646aaa127cb18ee109d24)http://www.researchgate.net/publication/23837598_The_Version_2_Global_Precipitation_Climatology_Project_(GPCP)_Monthly_Precipitation_Analysis_(1979-Present)The Global Precipitation Climatology Project (GPCP) Version-2 Monthly Precipitation Analysis is described. This globally complete, monthly analysis of surface precipitation at 2.517 latitude 17 2.517 longitude resolution is available from January 1979 to the present. It is a merged analysis that incorporates precipitation estimates from low-orbit satellite microwave data, geosynchronous-orbit satellite infrared data, and surface rain gauge observations. The merging approach utilizes the higher accuracy of the low-orbit microwave observations to calibrate, or adjust, the more frequent geosynchronous infrared observations. The dataset is extended back into the premicrowave era (before mid-1987) by using infrared-only observations calibrated to the microwave-based analysis of the later years. The combined satellite-based product is adjusted by the rain gauge analysis. The dataset archive also contains the individual input fields, a combined satellite estimate, and error estimates for each field. This monthly analysis is the foundation for the GPCP suite of products, including those at finer temporal resolution. The 23-yr GPCP climatology is characterized, along with time and space variations of precipitation.
Ambrizzi T., B. J. Hoskins, and H. H. Hsu, 1995: Rossby wave propagation and teleconnection patterns in the austral winter. J. Atmos. Sci., 52, 3661- 3672.10.1175/1520-0469(1995)052<3661:RWPATP>2.0.CO;28d0bbbbfac87d618835b1303b1cae630http%3A%2F%2Fadsabs.harvard.edu%2Fabs%2F1995JAtS...52.3661Ahttp://adsabs.harvard.edu/abs/1995JAtS...52.3661AAbstract Observational evidence of and theoretical support for the Northern and Southern Hemisphere teleconnection patterns in the austral (Southern Hemisphere) winter are examined through an upper troposphere streamfunction teleconnectivity map and time-lag cross-correlation analysis using ECMWF initialized analysis 2OO-hPa winds for the 11 June–August periods from 1979 to 1989. As was previously found for the Northern Hemisphere winter, the regions of strong teleconnectivity, particularly in the winter hemisphere, tend to he oriented in the zonal direction and coincide with the location of the major jet streams. Although equatorward propagation from the Northern and Southern Hemispheres is observed, little evidence of cross-equatorial propagation has been found. For comparison, the response of a barotropic model, linearized about a climatological 300-hPa June–August time-mean flow to localized forcing is determined. It is found that the activity tends to be trapped inside each of the Southern Hemisphere subtropical and polar jet streams, with these acting as waveguides. In the Northern Hemisphere a weak waveguide belt is found near 40°N around the whole hemisphere. The patterns simulated by the model are generally in good agreement with the teleconnectivity study described above. Both the observations and the model support the existence of the Pacific–South American pattern.
Ao J., J. Q. Sun, 2015a: Decadal change in factors affecting winter precipitation over eastern China. Climate Dyn., doi: 10.1007/s00382-015-2572-7.10.1007/s00382-015-2572-74f8138df941f99810f510c9727a57f84http%3A%2F%2Flink.springer.com%2F10.1007%2Fs00382-015-2572-7http://link.springer.com/10.1007/s00382-015-2572-7The temporal and spatial distributions of winter precipitation variability over eastern China were analyzed on the basis of the empirical orthogonal function method. The results showed that the primary mode of winter precipitation variability over this area presented a homogeneous change during the study period, with a significant decadal change around the late 1980s. The factors that influenced winter precipitation variability over eastern China changed over different interdecadal periods. Before the late 1980s, the Eurasian (EU) mode and North Pacific Oscillation (NPO) mode were the two major atmospheric factors. After the late 1980s, the influence of the EU mode remained. However, the impact of the NPO weakened significantly, and a new Rossby Wave (RW) pattern became a key factor. Further analyses of both observations and numerical simulations indicated that the convective activity over the western tropical Pacific strengthened significantly around the late 1980s; the convection encouraged the RW mode and ultimately contributed to the anomalous winter precipitation over eastern China after the late 1980s. The results imply that the prediction of winter precipitation should consider different interdecadal backgrounds; otherwise, the changing factors could result in failure of the prediction over some decadal periods.
Ao J., J. Q. Sun, 2015b: Connection between November snow cover over Eastern Europe and winter precipitation over East Asia. Int. J. Climatol., doi: 10.1002/joc.4484.10.1002/joc.44840ac525b0244ff38e1ca9950cd4ca94cbhttp%3A%2F%2Fonlinelibrary.wiley.com%2Fdoi%2F10.1002%2Fjoc.4484%2Fabstracthttp://onlinelibrary.wiley.com/doi/10.1002/joc.4484/abstractABSTRACT In this study, the connected spatial and temporal features of winter precipitation over East Asia and November snow cover over Eurasia are analysed using the singular value decomposition (SVD) method. The results show that a strong consistent variation of winter precipitation occurs over East Asia, especially north of 35°N, closely related to the snow cover change over Eastern Europe. Mechanism analysis indicates that the processes behind the physical link between the November snow cover over Eastern Europe and East Asian winter precipitation are different in December compared to January and February. In December, the persistence of the snow cover anomaly can ‘memorize’ the signal of the November snow cover and impact December circulation and precipitation over East Asia. During January–February, the snow cover anomaly disappears, while the variability of the polar vortex resulting from the interaction of the troposphere and stratosphere serves as a bridge connecting the November snow cover over Eastern Europe and the January–February precipitation over East Asia. Revealing the role of the November snow cover is significant not only for understanding East Asian winter precipitation variability but also for its prediction.
Bueh C., L. R. Ji, 1999: Anomalous activity of East Asian winter monsoon and the tropical Pacific SSTA. Chinese Science Bulletin, 44, 890- 898.10.1007/BF02885058ee52df91ba7e77cea40988a535cc1908http%3A%2F%2Flink.springer.com%2F10.1007%2FBF02885058http://www.cnki.com.cn/Article/CJFDTotal-JXTW199910002.htmThe relationship between the anomalous East Asian winter monsoon (EAWM) activity and the tropical Pacific SST anomalies has been identified using the results of 40-year integration of the IAP CGCM1 model and 10-year observational data, In the strong EAWM year, the western and central Pacific are dominated by positive SST anomalies while the eastern Pacific is negative ones. In the weak EAWM year, the SSTA pattern is quite different and shows El Nio-like SSTanomalies. The strong EAWM activity tends to create extra easterly flow to the east and extra westerly flow to the west of the warm SSTA region over the equatorial western and central Pacific, thus leading to the enhancement of convergence and convection of the flow in this region and favorable to the maintenance and development of such an SSTA pattern. On the other hand, the warm SST anomaly over the western and central Pacific, as a forcing, may lead to a specific pattern of the northern extratropical atmosphere, which is favorable to the strong EAW
Cohen J., D. Entekhabi, 1999: Eurasian snow cover variability and northern hemisphere climate predictability. Geophys. Res. Lett., 26, 345- 348.10.1029/1998GL9003218a69195bad48f8230d2fb89b57636da7http%3A%2F%2Fonlinelibrary.wiley.com%2Fdoi%2F10.1029%2F1998GL900321%2Ffullhttp://onlinelibrary.wiley.com/doi/10.1029/1998GL900321/fullABSTRACT We present observational evidence demonstrating dynamic interactions and feedbacks between multi-seasonal snow cover and winter-time circulation anomalies over mid-high latitudes. The cooling effect of snow cover is associated with a strengthened and more expansive Siberian high with more frequent, topographically constrained intrusions west and north. Early-season snow cover variability leads to altered general circulation patterns consistent with the dominant mode of winter variability observed in the Northern Hemisphere troposphere. The implications of the surface-atmosphere coupling for seasonal to interannual predictability are also discussed.
Cohen J., D. Entekhabi, 2001: The influence of snow cover on northern hemisphere climate variability. Atmos.-Ocean, 39, 35- 53.10.1080/07055900.2001.9649665190e1075778eed480acbc9052596edf7http%3A%2F%2Fwww.tandfonline.com%2Fdoi%2Fabs%2F10.1080%2F07055900.2001.9649665http://www.tandfonline.com/doi/abs/10.1080/07055900.2001.9649665The importance of snow cover anomalies on the local energy balance is well known, however, the potential impact of snow cover anomalies on local and remote atmospheric dynamics is less understood. We present observational evidence demonstrating a statistically significant relationship between seasonal snow cover and winter‐time circulation anomalies over mid‐high latitudes. To explore snow forcing further, a General Circulation Model is used to test whether the local diabatic changes caused by snow cover can induce large‐scale dynamical responses. A six‐member ensemble, three winter month (DJF) integration is performed for a control case and a case where snow cover is increased as observed during the positive‐anomalous winter of 1977/1978. Snow cover variability results in altered general circulation patterns resembling observed anomaly patterns at mid‐high latitudes in the Northern Hemisphere winter.
Cohen J., D. Salstein, and K. Saito, 2002: A dynamical framework to understand and predict the major Northern Hemisphere mode. Geophys. Res. Lett., 29( 10), 51- 54.10.1029/2001GL01411758111a60-051f-485f-8736-a0cd1065f59641b707fc3c3f0541f20244ae39f11440http%3A%2F%2Fonlinelibrary.wiley.com%2Fdoi%2F10.1029%2F2001GL014117%2Fabstractrefpaperuri:(8fdce8c781a316de0d049bb788da2306)http://onlinelibrary.wiley.com/doi/10.1029/2001GL014117/abstract[1] The dynamics of the leading mode of boreal winter and its excitation by varying boundary conditions remain mostly unclear. A novel framework is presented to explain the evolution of this dominant winter mode. It is shown that there exists a dichotomy of pathways with the characteristics of the dominant mode dependent upon the pathway taken. All winters examined fall into one of the two different dynamic evolutions presented, the knowledge of which clarifies prior uncertainties associated with the dominant mode and provides excellent potential for the successful prediction of subsequent winter mean climate states.
Chen H. S., Z. B. Sun, 2003: The effects of Eurasian snow cover anomaly on winter atmospheric general circulation Part I. observational studies. Chinese J. Atmos. Sci., 27, 304- 316. (in Chinese)10.1007/BF0294888383e80388cfcde5abed57e74563fed1f6http%3A%2F%2Fen.cnki.com.cn%2FArticle_en%2FCJFDTotal-ZSYZ802.000.htmhttp://en.cnki.com.cn/Article_en/CJFDTotal-ZSYZ802.000.htmThe effects of Eurasian winter snow anomaly on atmospheric general circulation was investigated by using the ECMWF 2.5°×2.5° snow depth (1979～1993) and NCEP/NCAR reanalysis data. Results show: (1) the anomalous winter snow cover in the extratropical Eurasian continent bears an intimate relation to the anomaly of contemporary atmospheric general circulation, i.e., the positive anomaly of winter snow cover usually is followed positive atmospheric Eurasia-Pacific teleconnection pattern and stronger East Asian winter monsoon; or vice versa. (2) The relationship between the anomalous snow cover and atmospheric general circulation suggested the facts that the anomaly of winter snow cover have an important impacts on winter 500 hPa height and winter atmospheric general circulation, especially on Eurasia-Pacific pattern due to the cooling effect of abnormal snow cover. (3) The coupling relationship by using singular value decomposition (SVD) analysis arrives at the same conclusion.
Chen H. S., Z. B. Sun, and W. J. Zhu, 2003: The effects of Eurasian snow cover anomaly on winter atmospheric general circulation Part II. Model simulation. Chinese J. Atmos. Sci., 27, 847- 860. (in Chinese)10.1007/BF0294888360516cf076459d070adb3251fc5bc436http%3A%2F%2Fen.cnki.com.cn%2FArticle_en%2FCJFDTOTAL-DQXK200305005.htmhttp://en.cnki.com.cn/Article_en/CJFDTOTAL-DQXK200305005.htmBased on the observational studies, three numerical experiments are designed to study the impacts of anomalous snow pattern on winter atmospheric general circulation and the relevant physics by using NCAR CCM2 coupled with BATS land surface scheme Both the simulation and the observation show: due to its radiative cooling effect, the anomalous pattern of snow cover can change the surface thermal condition and the surface heating, which can modify the atmospheric temperature and the atmospheric general circulation in such a way to trigger the atmospheric Eurasia Pacific teleconnection pattern and result in the abnormal circulation of East Asian winter monsoon
Cohen J., M. Barlow, P. J. Kushner, and K. Saito, 2007: Stratosphere-troposphere coupling and links with Eurasian land surface variability. J.Climate, 20, 5335- 5343.10.1175/2007JCLI1725.1b8382f43-076a-489d-9777-bb71183ee736b0f99d39bc33e607b79154b8acbcb63chttp%3A%2F%2Fadsabs.harvard.edu%2Fabs%2F2007JCli...20.5335Crefpaperuri:(49735cd59253d9be3a31aad625a59ea7)http://adsabs.harvard.edu/abs/2007JCli...20.5335CAbstract A diagnostic of Northern Hemisphere winter extratropical stratosphere–troposphere interactions is presented to facilitate the study of stratosphere–troposphere coupling and to examine what might influence these interactions. The diagnostic is a multivariate EOF combining lower-stratospheric planetary wave activity flux in December with sea level pressure in January. This EOF analysis captures a strong linkage between the vertical component of lower-stratospheric wave activity over Eurasia and the subsequent development of hemisphere-wide surface circulation anomalies, which are strongly related to the Arctic Oscillation. Wintertime stratosphere–troposphere events picked out by this diagnostic often have a precursor in autumn: years with large October snow extent over Eurasia feature strong wintertime upward-propagating planetary wave pulses, a weaker wintertime polar vortex, and high geopotential heights in the wintertime polar troposphere. This provides further evidence for predictability of wintertime circulation based on autumnal snow extent over Eurasia. These results also raise the question of how the atmosphere will respond to a modified snow cover in a changing climate.
Cohen J., J. C. Furtado, J. Jones, M. Barlow, D. Whittleston, and D. Entekhabi, 2014: Linking Siberian snow cover to precursors of stratospheric variability. J.Climate, 27, 5422- 5432.10.1175/JCLI-D-13-00779.15e622576a6e4fe752c2981b5282bdaabhttp%3A%2F%2Fadsabs.harvard.edu%2Fabs%2F2014JCli...27.5422Chttp://adsabs.harvard.edu/abs/2014JCli...27.5422CPrevious research has linked wintertime Arctic Oscillation (AO) variability to indices of Siberian snow cover and upward wave activity flux in the preceding fall season. Here, daily data are used to examine the surface and tropospheric processes that occur as the link between snow cover and upward forcing into the stratosphere develops. October Eurasian mean snow cover is found to be significantly related to sea level pressure (SLP) and to lower-stratosphere (100 hPa) meridional heat flux. Analysis of daily SLP and 100-hPa heat flux shows that in years with high October snow, the SLP is significantly higher from approximately 1 November to 15 December, and the 100-hPa heat flux is significantly increased with a two-week lag, from approximately 15 November to 31 December. During November-揇ecember, there are periods with upward wave activity flux extending coherently from the surface to the stratosphere, and these events occur nearly twice as often in high snow years compared to low snow years. The vertical structure of these events is a westward-tilting pattern of high eddy heights, with the largest normalized anomalies near the surface in the same region as the snow and SLP changes. These results suggest that high SLP develops in response to the snow cover and this higher pressure, in turn, provides part of the structure of a surface-to-stratosphere wave activity flux event, thus making full events more likely. Implications for improved winter forecasts exist through recognition of these precursor signals.
Collins, M., Coauthors, 2013: Long-term climate change: projections, commitments and irreversibility. Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change, T. F. Stocker et al., Eds., Cambridge University Press, 1029- 1136.
Feng J., L. Wang, W. Chen, S. K. Fong, and K. C. Leong, 2010: Different impacts of two types of Pacific Ocean warming on Southeast Asian rainfall during boreal winter. J. Geophys. Res., 115, D24122.10.1029/2010JD014761c703dffd83c287877e5a06216dbc81a0http%3A%2F%2Fonlinelibrary.wiley.com%2Fdoi%2F10.1029%2F2010JD014761%2Fcitedbyhttp://onlinelibrary.wiley.com/doi/10.1029/2010JD014761/citedbyABSTRACT The impacts of conventional El Ni&ntilde;o-Southern Oscillation (ENSO) and ENSO Modoki on wintertime Southeast Asian rainfall and related mechanisms are studied using the method of partial regression and correlation and numerical simulations of a simple baroclinic model. Results show that the Southeast Asian rainfall associated with these two kinds of ENSO exhibits different spatial distributions. In the case of El Ni&ntilde;o, wet conditions are observed over south China, and dry conditions are seen over the Philippines, Borneo, Celebes, and Sulawesi. In contrast, for El Ni&ntilde;o Modoki, the negative rainfall anomalies around the Philippines are weaker and are located more northward compared to the El Ni&ntilde;o counterpart. The different Southeast Asian rainfalls that are related to ENSO and ENSO Modoki are attributed to the different anomalous Walker circulation and low-level anticyclone around the Philippines. Both the Philippine anticyclone and the descending branch center of the Walker circulation over the western North Pacific occupy a smaller domain and are located more northward during El Ni&ntilde;o Modoki than during El Ni&ntilde;o. All of these factors favor the difference in the Southeast Asian rainfall anomalies between the two events. Numerical experiments also suggest that the different low-level atmospheric responses are mainly induced by different diabatic cooling over the western North Pacific related to El Ni&ntilde;o and El Ni&ntilde;o Modoki.
Gent, P. R., Coauthors, 2011: The community climate system model Version 4. J. Climate, 24, 4973- 4991.10.1175/2011JCLI4083.129ea5917-d3e1-42e9-940c-59df742c81311262048e87cc58728918a5ed03f21f04http%3A%2F%2Fadsabs.harvard.edu%2Fabs%2F2011JCli...24.4973Grefpaperuri:(00848f71c6cb0bc7a12384180928d7e8)http://adsabs.harvard.edu/abs/2011JCli...24.4973GThe fourth version of the Community Climate System Model (CCSM4) was recently completed and released to the climate community. This paper describes developments to all the CCSM components, and documents fully coupled pre-industrial control runs compared to the previous version, CCSM3. Using the standard atmosphere and land resolution of 1{sup o} results in the sea surface temperature biases in the major upwelling regions being comparable to the 1.4{sup o} resolution CCSM3. Two changes to the deep convection scheme in the atmosphere component result in the CCSM4 producing El Nino/Southern Oscillation variability with a much more realistic frequency distribution than the CCSM3, although the amplitude is too large compared to observations. They also improve the representation of the Madden-Julian Oscillation, and the frequency distribution of tropical precipitation. A new overflow parameterization in the ocean component leads to an improved simulation of the deep ocean density structure, especially in the North Atlantic. Changes to the CCSM4 land component lead to a much improved annual cycle of water storage, especially in the tropics. The CCSM4 sea ice component uses much more realistic albedos than the CCSM3, and the Arctic sea ice concentration is improved in the CCSM4. An ensemble of 20th century simulations more&raquo; runs produce an excellent match to the observed September Arctic sea ice extent from 1979 to 2005. The CCSM4 ensemble mean increase in globally-averaged surface temperature between 1850 and 2005 is larger than the observed increase by about 0.4 C. This is consistent with the fact that the CCSM4 does not include a representation of the indirect effects of aerosols, although other factors may come into play. The CCSM4 still has significant biases, such as the mean precipitation distribution in the tropical Pacific Ocean, too much low cloud in the Arctic, and the latitudinal distributions of short-wave and long-wave cloud forcings. less
Gong G., D. Entekhabi, and J. Cohen, 2002: A large-ensemble model study of the wintertime AO-NAO and the role of interannual snow perturbations. J. Climate, 15, 3488- 3499.6ec3c38af615b5a25d7609a98430c1ffhttp%3A%2F%2Fwww.bioone.org%2Fservlet%2Flinkout%3Fsuffix%3Di0276-4741-32-4-431-Gong3%26dbid%3D16%26doi%3D10.1659%252FMRD-JOURNAL-D-12-00062.1%26key%3D10.1175%252F1520-0442%282002%290152.0.CO%253B2/s?wd=paperuri%3A%2855d88b6ae362be3ada410deba88735a5%29&filter=sc_long_sign&tn=SE_xueshusource_2kduw22v&sc_vurl=http%3A%2F%2Fwww.bioone.org%2Fservlet%2Flinkout%3Fsuffix%3Di0276-4741-32-4-431-Gong3%26dbid%3D16%26doi%3D10.1659%252FMRD-JOURNAL-D-12-00062.1%26key%3D10.1175%252F1520-0442%282002%290152.0.CO%253B2&ie=utf-8
He S. P., H. J. Wang, and J. P. Liu, 2013: Changes in the relationship between ENSO and Asia-Pacific midlatitude winter atmospheric circulation. J. Climate, 26, 3377- 3393.10.1175/JCLI-D-12-00355.181913884a4645890945aaa791d9aa55dhttp%3A%2F%2Fadsabs.harvard.edu%2Fabs%2F2013JCli...26.3377Hhttp://adsabs.harvard.edu/abs/2013JCli...26.3377HAbstract Interdecadal changes in the relationship between El Ni09o–Southern Oscillation (ENSO) and midlatitude atmospheric circulation are investigated in this study. Comparison of associations between ENSO and midlatitude atmospheric circulation anomalies between 1958–76 and 1977–2010 suggest that during 1958–76, ENSO exerted a strong impact on the East Asian winter monsoon (EAWM) and the associated atmospheric circulation pattern was similar to the positive North Pacific Oscillation (NPO). In contrast, during 1977–2010, the NPO-like atmospheric pattern disappeared. Instead, ENSO exerted a strong impact on the eastern North Pacific Ocean (NP) and North America, and the associated atmospheric circulation pattern resembled the Pacific–North America (PNA) teleconnection. Also, significant correlations between ENSO and sea surface temperature anomalies (SSTAs) over the western subtropical NP during 1958–76 became insignificant during 1977–2010, whereas negative correlations between ENSO and SSTAs in the central and northeastern subtropical NP became more significant since the mid-1970s. Further analyses suggest that the interdecadal shift of the Aleutian low, which occurred around the mid-1970s, might be responsible for the identified changes. Before the mid-1970s, warm ENSO events generated an anomalous anticyclone over the western NP, which is a key system bridging ENSO and EAWM-related atmospheric circulation. After the mid-1970s, the Aleutian low intensified and shifted eastward, leading to the impact of ENSO prevailing over the eastern NP. In addition, the weakened (strengthened) ENSO–NPO/EAWM (ENSO–PNA) relationship likely contributed to the weakened (strengthened) relationship between ENSO and SSTAs over the western (central and eastern) subtropical NP.
Huang R. H., F. Y. Sun, 1994: Impacts of the thermal state and the convective activities in the tropical western warm pool on the summer climate anomalies in East Asia. Chinese J. Atmos. Sci., 18, 141- 151. (in Chinese)10.1007/BF02658170a608af86379458f32266ec04a293bbcchttp%3A%2F%2Fwww.oalib.com%2Fpaper%2F1556175http://www.oalib.com/paper/1556175In this paper, impacts of the thermal state in the western tropical Pacific warm pool and the convective activities over the warm pool on the summer climate anonialies in East Asia ate analysed by using the observed data of the sea temperatare in surface and subsurface of the westem tropical Pacific warm pool, the high cloud amount and precipitation for 1978-1989. The analysed results show that the thermal state in the tropical western Pacific warm pool and the convective activities over the warm pool play an important role in the summer climate anomalies in East Asia. When the western tropical Pacific warm pool is warming, the convective activities are intensified from the area around the Philippines to the Indo-China Peninsula through the South China Sea, the western Pacific subtropical high may shift nortbward, the summer rainfall may be below normal in the Yangtze River valley and the Huaihe River valley. On the Contrary, the convective activities are weak around the Philippines, the western Pacific subtropical high may shift southward, the summer rainfall may be above normal and it may be below normal in the Yellow River valley, drought summer is frequently caused there.The observational facts also show that after the enhancement of the convective activities over the western tropical Pacific warm pool, there is a teleconnection pattern in the circu1ation anomalies over the regions from Southeast Asia to the western Coast of North America through East Asia, i.e., the so-called East Asia / Pacific Pattern.
Jin Z. H., S. Y. Tao, 1999: A study on the relationships between ENSO cycle and rainfalls during summer and winter in Eastern China. Chinese J. Atmos. Sci., 23, 663- 672. (in Chinese)31ec950bed3064382e36d76e6a2e55edhttp%3A%2F%2Fen.cnki.com.cn%2FArticle_en%2FCJFDTOTAL-DQXK199906003.htmhttp://en.cnki.com.cn/Article_en/CJFDTOTAL-DQXK199906003.htmRelationships between ENSO for different phase and precipitation are investigated on the basis of SST data of Ni n锝 o 3 area over the Pacific and monthly mean rainfalls for 160 stations throughout China. It has been found that rainfalls and its spatial, temporal variability in the eastern China during summer and winter are greatly effected by ENSO cycle. During the growth of ENSO deficiency summer rainfalls are over most of eastern China with the 30锝50 percentage below normal in the some areas, and abundance rainfall band located in the area of the Changjiang-Huaihe basin. In the period of ENSO cold phase, the deficiency rainfalls are in the southeastern China and the area extended from the Changjiang River to the Huanghe River, but near normal rainfalls are occurred outside above areas. During the quasi-normal phase, the rainfall distribution is characterized by the positive anomalies to the north of the Changjiang River and near normal rainfalls over large part of the south of the Changjiang River. It has been explored too that there exist obvious relationships between the rainfalls during winter and ENSO warm phase. Because of the ENSO quasi-normal phase rainfall mean values are used to instead of the general climate mean, our results obtained are obviously better than other studies earlier.
Kalnay E., Coauthors, 1996: The NCEP/NCAR 40-year reanalysis project. Bull. Amer. Meteor. Soc., 77, 437- 470.3f2f81b7-8518-4899-877c-2adbadd1a28f23d674534321ec5c56bf181fd85f5561http%3A%2F%2Fwww.bioone.org%2Fservlet%2Flinkout%3Fsuffix%3Di1536-1098-69-2-93-Kalnay1%26dbid%3D16%26doi%3D10.3959%252F1536-1098-69.2.93%26key%3D10.1175%252F1520-0477%281996%29077%3C0437%253ATNYRP%3E2.0.CO%253B2refpaperuri:(fe1c070047a030c900beb40441caee5a)/s?wd=paperuri%3A%28fe1c070047a030c900beb40441caee5a%29&filter=sc_long_sign&tn=SE_xueshusource_2kduw22v&sc_vurl=http%3A%2F%2Fwww.bioone.org%2Fservlet%2Flinkout%3Fsuffix%3Di1536-1098-69-2-93-Kalnay1%26dbid%3D16%26doi%3D10.3959%252F1536-1098-69.2.93%26key%3D10.1175%252F1520-0477%281996%29077%253C0437%253ATNYRP%253E2.0.CO%253B2&ie=utf-8
Li S. L., G. T. Bates, 2007: Influence of the Atlantic multi-decadal oscillation on the winter climate of East China. Adv. Atmos. Sci.,24, 126-135, doi: 10.1007/s00376-007-0126-6.10.1007/s00376-007-0126-6c75add71-21c0-4a8e-80cb-bc89a3da40d7bccca0cb470212275f14af8e90e8ae65http%3A%2F%2Fd.wanfangdata.com.cn%2FPeriodical_dqkxjz-e200701012.aspxrefpaperuri:(dd8192424d2c5cc836e58bc0364acd46)http://d.wanfangdata.com.cn/Periodical_dqkxjz-e200701012.aspx
Li F., H. J. Wang, 2013: Autumn Sea Ice cover, winter northern hemisphere annular mode, and winter precipitation in Eurasia. J. Climate, 26, 3968- 3981.10.1175/JCLI-D-12-00380.18657821d159d39fa593daede88847917http%3A%2F%2Fconnection.ebscohost.com%2Fc%2Farticles%2F87915654%2Fautumn-sea-ice-cover-winter-northern-hemisphere-annular-mode-winter-precipitation-eurasiahttp://connection.ebscohost.com/c/articles/87915654/autumn-sea-ice-cover-winter-northern-hemisphere-annular-mode-winter-precipitation-eurasiaAbstract This paper examines the impacts of the previous autumn sea ice cover (SIC) on the winter Northern Hemisphere annular mode (NAM) and winter precipitation in Eurasia. The coherent variations among the Kara–Laptev autumn SIC, winter NAM, and Eurasian winter precipitation appear after the year 1982, which may prove useful for seasonal prediction of winter precipitation. From a physical point of view, the Kara–Laptev SIC and sea surface temperature (SST) anomalies develop in autumn and remain in winter. Given that winter NAM is characterized by an Arctic–midlatitude seesaw centered over the Barents Sea and Kara–Laptev Seas, it is closely linked to the Arctic forcing that corresponds to the Kara–Laptev sea ice increase (reduction) and the associated surface temperature cooling (warming). Moreover, based on both model simulations and observations, the diminishing Kara–Laptev sea ice does induce positive sea level pressure (SLP) anomalies over high-latitude Eurasia in winter, which is accompanied by a significant surface warming in northern Eurasia and cooling south of the Mediterranean. This surface air temperature (SAT) anomaly pattern facilitates increases of specific humidity in northern Eurasia with a major ridge extending southward along the East Asian coast. As a result, the anomalous Eurasian winter precipitation has a more zonal band structure.
Li G., C. Y. Li, Y. K. Tan, and X. Wang, 2014: Observed relationship of boreal winter South Pacific Tripole SSTA with Eastern China rainfall during the following boreal spring. J. Climate, 27, 8094- 8106.10.1175/JCLI-D-14-00074.1e8a6fae053d6fb3f2aa2aa8a8781ecf5http%3A%2F%2Fwww.researchgate.net%2Fpublication%2F267573744_Observed_Relationship_of_Boreal_Winter_South_Pacific_Tripole_SSTA_with_Eastern_China_Rainfall_during_the_Following_Boreal_Springhttp://www.researchgate.net/publication/267573744_Observed_Relationship_of_Boreal_Winter_South_Pacific_Tripole_SSTA_with_Eastern_China_Rainfall_during_the_Following_Boreal_SpringAbstract The present study investigates the relationships between the December–February (DJF) South Pacific tripole (SPT) sea surface temperature anomaly (SSTA) pattern and the following March–May (MAM) rainfall over eastern China based on multiple datasets. It is found that the relationships between the DJF SPT and the following MAM rainfall over eastern China are modulated by the El Ni09o–Southern Oscillation (ENSO). When the ENSO signal is removed, the positive DJF SPT is significantly associated with more rainfall over eastern China during the following boreal spring. However, such significant relationships disappear if ENSO is considered. After removing ENSO impacts, the possible mechanisms through which the DJF SPT impacts the following MAM rainfall over eastern China are investigated. The positive DJF SPT is associated with the significantly positive SSTA in the tropical western Pacific, which can persist to the following MAM. In response to the positive SSTA in the tropical western Pacific, a wave-like train in the low-level troposphere extends from the tropical western Pacific (an anomalous cyclone) to the western North Pacific (an anomalous anticyclone) during the following MAM. The anomalous anticyclone over the western North Pacific enhances the anomalous southwesterly over eastern China, which can bring more moisture and favor anomalous increased rainfall. It should be pointed out that La Ni09a (El Ni09o) could induce an anomalous cyclone (anticyclone) over the western North Pacific, which offsets the MAM anomalous anticyclone (cyclone) caused by the positive (negative) SPT in the preceding DJF and thus weakens the relationship between the SPT and the rainfall over eastern China.
Liu J. P., J. A. Curry, H. J. Wang, M. R. Song, and R. M. Horton, 2012: Impact of declining Arctic sea ice on winter snowfall. Proc. Natl. Acad. Sci., 109, 4074- 4079.
Ma J. H., H. J. Wang, and Y. Zhang, 2012: Will boreal winter precipitation over China increase in the future? An AGCM simulation under summer "ice-free Arctic" conditions. Chinese Science Bulletin, 57, 921- 926.10.1007/s11434-011-4925-x48ab107fefd1685ffb19c34bdd253d77http%3A%2F%2Flink.springer.com%2F10.1007%2Fs11434-011-4925-xhttp://www.cnki.com.cn/Article/CJFDTotal-JXTW201208015.htm
Matthews A. J., G. N. Kiladis, 2000: A model of Rossby waves linked to submonthly convection over the eastern Tropical Pacific. J. Atmos. Sci., 57, 3785- 3798.10.1175/1520-0469(2000)057<3785:AMORWL>2.0.CO;25c2484539e981164e603bef55cc88c5fhttp%3A%2F%2Fadsabs.harvard.edu%2Fabs%2F2000JAtS...57.3785Mhttp://adsabs.harvard.edu/abs/2000JAtS...57.3785MABSTRACT Equatorward-propagating wave trains in the upper troposphere are observed to be associated with deep convection over the eastern tropical Pacific on the submonthly timescale during northern winter. The convection occurs in the regions of ascent and reduced static stability ahead of cyclonic anomalies in the wave train. In this study an atmospheric primitive equation model is used to examine the roles of the dry wave dynamics and the diabatic heating associated with the convection. Many features of a dry integration initialized with a localized wave train in the African-Asian jet on a three- dimensional climatological basic state quantitatively agree with the observations, including the zonal wavenumber 6-7 scale of the waves, the time period of approximately 12 days, and the cross-equatorial Rossby wave propagation over the eastern Pacific. There is ascent and reduced static stability ahead of the cyclonic anomalies, consistent with the interpretation that the waves force the convection. The spatial scale of the waves appears to be set by the basic state; baroclinic growth upstream in the Asian jet favors waves with zonal wavenumber 6. On reaching the Pacific sector, lower-wavenumber components of the wave train are not refracted so strongly equatorward, while higher-wavenumber components are advected quickly along the Pacific jet before they can propagate equatorward. Once over the Pacific, the wave train approximately obeys barotropic Rossby wave dynamics. The observed lower-tropospheric anomalies include an equatorial Rossby wave that propagates westward from the region of cross-equatorial wave propagation and tropical convection. However, this equatorial Rossby wave is not forced directly by the dry equatorward-propagating wave train but appears in a separate integration as a forced response to the observed diabatic heating associated with the tropical convection.
Nitta T., 1987: Convective activities in the tropical western Pacific and their impact on the Northern Hemisphere summer circulation. J. Meteor. Soc.Japan, 65, 373- 390.10.1175/1520-0469(1987)044<1554:TAOPVT>2.0.CO;2af5b68de-3681-4ebe-ae76-3e53b273cf8e84fda2b986d0d4e7d94b9557e8a62161http%3A%2F%2Fci.nii.ac.jp%2Fnaid%2F10013126166%2Frefpaperuri:(9b2fb89014c1d66010d07550d41568c2)http://ci.nii.ac.jp/naid/10013126166/Investigation, à l'aide de la couverture nuageuse vue par satellite, de la TSM (SST) et du géopotentiel, toutes données sur 7 ans (1978-84), des variations interannuelle et intrasaisonnière de l'activité convective en été, dans le Pacifique tropical ouest, ainsi que de l'impact sur la circulation dans l'hémisphère nord. Résultats principaux: lorsque la TSM est plus chaude de 1,0°C que la normale, les régions de convection active (typhons, dépressions tropicales) se déplacent vers le NE à partir d'une position normale près des Philippines jusqu'à 20 N, la couverture nuageuse dans les zones tempérée et équatoriale est fortement atténuée; une anomalie de haute p prédomine dans la zone tempérée (de la Chine est jusqu'au Pacifique nord); l'activité convective est très modulée par la variation intrasaisonnière; il existe des trains d'ondes de hauteur géopotentielle qui émanent de la source de chaleur qui s'étend des Philippines à l'Amérique du Nord; ils sont générés lorsque l'activité convective dans la mer des Philippines devient intense; en conclusion les ondes de Rossby sont générées par la source de chaleur associée à la variation intrasaisonnière; des anomalies de p en Asie de l'Est peuvent être considérées comme une conséquence de la génération de ces ondes
Smith T. M., R. W. Reynolds, 2003: Extended reconstruction of global Sea surface temperatures based on COADS data (1854-1997). J. Climate, 16, 1495- 1510.58f50db8-53a3-4854-8f46-535ffc02c806db94afef77913e493322a43811244df4http%3A%2F%2Fwww.bioone.org%2Fservlet%2Flinkout%3Fsuffix%3Di1551-5036-68-sp1-1-bibr057%26dbid%3D16%26doi%3D10.2112%252FSI68-001.1%26key%3D10.1175%252F1520-0442-16.10.1495refpaperuri:(5dabf7c0e12a02012ca13b5a4fa1dd26)/s?wd=paperuri%3A%285dabf7c0e12a02012ca13b5a4fa1dd26%29&filter=sc_long_sign&tn=SE_xueshusource_2kduw22v&sc_vurl=http%3A%2F%2Fwww.bioone.org%2Fservlet%2Flinkout%3Fsuffix%3Di1551-5036-68-sp1-1-bibr057%26dbid%3D16%26doi%3D10.2112%252FSI68-001.1%26key%3D10.1175%252F1520-0442-16.10.1495&ie=utf-8
Sun J. Q., J. Ao, 2013: Changes in precipitation and extreme precipitation in a warming environment in China. Chinese Science Bulletin, 58, 1395- 1401.10.1007/s11434-012-5542-z6e67410eb762707e31d8b0a3b3ed3f34http%3A%2F%2Fwww.cqvip.com%2FQK%2F86894X%2F201312%2F45349907.htmlhttp://www.cnki.com.cn/Article/CJFDTotal-JXTW201312009.htmThis study analyses the decadal changes in winter precipitation and extreme precipitation in a warming environment in China. The results show that, together with a trend of winter warming in China, winter precipitation and extreme precipitation in the region are also increasing. In addition, concurrent with the decadal warming shift that occurred in the mid-1980s, precipitation and extreme precipitation both increased significantly. Quantitative analysis shows that precipitation and extreme precipitation increased at rates of 9.7% and 22.6% per 1鈩 of surface warming in China. This rate of precipitation increase is greater than the global mean, which indicates that precipitation in China is highly sensitive to climate warming and further highlights the importance of studying regional responses to climate warming. The fact that extreme precipitation is increasing at a higher rate than precipitation implies that winter precipitation in China will increasingly be of more extreme type in the context of global warming, which could partly explain why there have recently been a number of record-breaking extreme snowfall events in China.
Sun J. Q., H. J. Wang, and W. Yuan, 2009a: A preliminary investigation on causes of the catastrophic snowstorm in March, 2007 in the northeastern parts of China. Acta Meteorologica Sinica, 67, 469- 477. (in Chinese)10.11676/qxxb2009.0474821b8fe-63bf-4164-94be-51a366fe7716558420093134fb53c721b66a8af3e195af633f8cca5http%3A%2F%2Fen.cnki.com.cn%2FArticle_en%2FCJFDTOTAL-QXXB200903015.htmrefpaperuri:(0b755d2592a72373f8a315672b5aab2d)http://en.cnki.com.cn/Article_en/CJFDTOTAL-QXXB200903015.htmA snowstorm deposited record breaking snowfall over the northeastern parts of China on March 3-5, 2007, resulting in severe disasters and heavy losses. The objective of this study is to explore the possible mechanism responsible for this extreme event by analyzing the atmospheric circulation anomalies prior to and during the event. The results show that there had been persistent strong anomalous Arctic Oscillations, Antarctic Oscillations, Eurasian teleconnection pattern, and North Pacific Oscillations in about two weeks before the event. Those anomalous atmospheric circulations stimulated the strong anomalous southerlies along the east coastal regions of China, which persistently transferred the warm and wet air to the northeastern areas of China, thus raising the moisture content and air temperature there and providing proper warm and wet conditions for the occurrence of the extreme snowstorm event. When the atmospheric general circulation changed in early March, the strong cold air from the high latitudes met the warm air over the northeastern China, resulting in a remarkably cold front and associated strong snowfall and low temperature in that region.The results of this study imply that the anomalous atmospheric circulation and the cumulative moisture condition in the forecast region in the early stage should be fully considered, which is helpful to the improvement of rainfall forecast, especially the heavy rainfall forecast.
Sun J. Q., H. J. Wang, and W. Yuan, 2009b: A possible mechanism for the co-variability of the boreal spring Antarctic Oscillation and the Yangtze River valley summer rainfall. Int. J. Climatol. ,29, 1276-1284, doi:10.1002/joc.1773.10.1002/joc.1773414820bb-17ba-4518-a3d3-c0d3965917d737f215b6b07b7cd735bf5701343842fehttp://onlinelibrary.wiley.com/doi/10.1002/joc.1773/fullhttp://onlinelibrary.wiley.com/doi/10.1002/joc.1773/fullA significant correlation between the boreal spring Antarctic Oscillation (AAO) and the Yangtze River valley summer rainfall (YRVSR) has been found in previous studies, although the mechanisms that might lead to such far-reaching teleconnection remain unresolved. In this study, one of possible mechanisms responsible for the co-variability of the boreal spring AAO and the YRVSR is proposed. It f...
Sun J. Q., H. J. Wang, W. Yuan, and H. P. Chen, 2010: Spatial-temporal features of intense snowfall events in China and their possible change. J. Geophys. Res., 115, D16110.10.1029/2009JD013541c0013f2189180fd8248fe3f84825bbb6http%3A%2F%2Fonlinelibrary.wiley.com%2Fdoi%2F10.1029%2F2009JD013541%2Ffullhttp://onlinelibrary.wiley.com/doi/10.1029/2009JD013541/fullAbstract Top of page Abstract 1.Introduction 2.Method and Data 3.Observational Analysis 4.Evaluation of the Coupled Model Simulation 5.Projection for the ISE in China 6.Conclusion and Discussion Acknowledgments References Supporting Information [1] The statistical spatial-temporal features of the intense snowfall event (ISE) in China are investigated over the period of 1962-2000. The results indicate that eastern China, northern Xinjiang, the eastern Tibetan plateau, and northeastern China are four key regions for the ISE, with more frequency and strong variability. Annual cycle analysis shows the ISE exhibits a unimodal distribution with maximum frequency at winter months for eastern China, a bimodal distribution with maximum frequency at early winter and spring months for northern Xinjiang and northeastern China, and a bimodal distribution with maximum frequency at autumn and spring months for the eastern Tibetan plateau. Linear trend analysis indicates that in the last 39 years, the ISE exhibits a decreasing trend for eastern China and an increasing trend for northern Xinjiang and the eastern Tibetan plateau. The linear trend of the ISE is weak over northeastern China. Based on the simulations of the most recent and comprehensive climate models in the 20th century run, the performance of the current climate models in simulating the Chinese ISE is investigated. The results indicate that, of the 20 models, there are four models that can reasonably reproduce the spatial-temporal features of the Chinese ISE. Based on these four models' simulation for the 21st century under A1B and A2 scenarios, the future variability of the Chinese ISE is projected. It is found that global warming will cause the ISE frequency over southern China to decrease, while the ISE over northern China will initially increase and then decrease.
Wang H. J., S. P. He, 2012: Weakening relationship between East Asian winter monsoon and ENSO after mid-1970s. Chinese Science Bulletin, 57, 3535- 3540.10.1007/s11434-012-5285-x12e2dd29149405f915759bf891a55180http%3A%2F%2Flink.springer.com%2F10.1007%2Fs11434-012-5285-xhttp://www.cnki.com.cn/Article/CJFDTotal-JXTW201227002.htmThe East Asian winter monsoon(EAWM) is characterized by the frequent cold surges and associated closely with the Siberia High,East Asian Trough,and high-level westerly jet stream.The ENSO cycle can modulate the EAWM since it has co-variability with the sea surface temperature over the Indo-Western-Pacific which can tune the land-sea thermal contrast for the EAWM.This paper,by analyzing the EAWM,ENSO,and associated atmosphere-ocean variability,documents the weakening of the EAWMENSO relationship after the 1970s.The significant out-of-phase inter-relationship is found to be diminished after the 1970s.Further study in this work suggests that the weakened co-variability of the tropical Indo-Western-Pacific climate associated with ENSO after the 1970s is partly responsible for the weakened inter-relationship.Meanwhile,the reduced EAWM interannual variability and northward retreat of the EAWM-associated climate variability are favorable to the weakened ENSO-EAWM connection.
Wang H. J., S. P. He, 2013: The increase of snowfall in Northeast China after the mid-1980s. Chinese Science Bulletin, 58, 1350- 1354.10.1007/s11434-012-5508-1fd56537b81dd6ebbc347ab7607bb60f7http%3A%2F%2Fwww.cqvip.com%2FQK%2F86894X%2F201312%2F45349902.htmlhttp://www.cnki.com.cn/Article/CJFDTotal-JXTW201312004.htm
Wang L., W. Chen, R. Q. Feng, and J. J. Liang, 2011: The seasonal march of the North Pacific Oscillation and its association with the interannual variations of China's climate in boreal winter and spring. Chinese J. Atmos. Sci., 35, 393- 402. (in Chinese)
Yang S., K.-M. Lau, and K.-M. Kim, 2002: Variations of the East Asian jet stream and Asian-Pacific-American winter climate anomalies. J. Climate, 15, 306- 325.10.1175/1520-0442(2002)015<0306:VOTEAJ>2.0.CO;2a7f71303-0872-4fe4-86f1-be42d928ad0360a4024a518ba1e3a1b378ac23df3d4ehttp%3A%2F%2Fci.nii.ac.jp%2Fnaid%2F10013127551%2Frefpaperuri:(7d1aef2fb8c22e98233a0725c604d3a4)http://ci.nii.ac.jp/naid/10013127551/Variations of the East Asian jet stream and Asian-Pacific-American winter climate anomalies YANG S. J. Climate 15, 307-325, 2002
Zhang L., X. H. Zhu, K. Fraedrich, F. Sielmann, and X. F. Zhi, 2014: Interdecadal variability of winter precipitation in Southeast China. Climate Dyn., 43, 2239- 2248.
Zhou L. T., R. G. Wu, 2010: Respective impacts of the East Asian winter monsoon and ENSO on winter rainfall in China. J. Geophys. Res., 115, D02107.10.1029/2009JD012502c1fd95c9-71dc-4520-8b18-a259299a6f9129ca76d53e0c85f307b6b925635de0b5http%3A%2F%2Fwww.researchgate.net%2Fpublication%2F248805814_Respective_impacts_of_East_Asian_winter_monsoon_and_ENSO_on_winter_rainfall_in_Chinarefpaperuri:(ed121239a8aebb26cef235231b9d501e)http://www.researchgate.net/publication/248805814_Respective_impacts_of_East_Asian_winter_monsoon_and_ENSO_on_winter_rainfall_in_ChinaABSTRACT Using station rainfall observations and the ERA-40 reanalysis, this study investigates respective impacts of the East Asian winter monsoon (EAWM) and El Ni&ntilde;o-Southern Oscillation (ENSO) on winter (November-March) rainfall in China by removing the interdependence between the EAWM and ENSO using a linear regression. It is found that circulation and temperature anomalies over the tropics and midlatitude North Pacific are mainly induced by ENSO, and those over the midlatitude Asia are closely linked to the EAWM. The warm ENSO induced lower-level southwesterly winds deflect from the southeast coast of China, and thus, the influence of ENSO on winter rainfall is mainly in southern China. The lower-level southerly winds associated with a weak EAWM penetrate northward over eastern China, and thus, the EAWM influences winter rainfall in eastern China.
Zhou L. T., C. Y. Tam, W. Zhou, and J. C. L. Chan, 2010: Influence of South China Sea SST and the ENSO on winter rainfall over South China. Adv. Atmos. Sci.,27(4), 832-844, doi: 10.1007/s00376-009-9102-7.10.1007/s00376-009-9102-7faf6500b68d145f726ed13820c0a9f70http%3A%2F%2Flink.springer.com%2F10.1007%2Fs00376-009-9102-7http://d.wanfangdata.com.cn/Periodical/dqkxjz-e201004010The present study investigates the influence of South China Sea (SCS) SST and ENSO on winter (January-February-March; JFM) rainfall over South China and its dynamic processes by using station observations for the period 1951-2003, Met Office Hadley Center SST data for the period 1900-2008, and ERA-40 reanalysis data for the period 1958-2002. It is found that JFM rainfall over South China has a sig- nificant correlation with Ni-3 and SCS SST. Analyses show that in El Ni or positive SCS SST anomaly years, southwesterly anomalies at 700 hPa dominate over the South China Sea, which in turn transports more moisture into South China and favors increased rainfall. A partial regression analysis indicates that the independent ENSO influence on winter rainfall occurs mainly over South China, whereas SCS SST has a larger independent influence on winter rainfall in northern part of South China. The temperature over South China shows an obvious decrease at 300 hPa and an increase near the surface, with the former induced by Ni-3 and the latter SCS SST anomalies. This enhances the convective instability and weakens the potential vorticity (PV), which explains the strengthening of ascending motion and the increase of JFM rainfall over South China.