In recent years, the socio-economic impacts of winter extreme climate events have underscored the importance of winter climate anomalies in Southwest China （SWC）. The spatio-temporal variability of surface air tempe...In recent years, the socio-economic impacts of winter extreme climate events have underscored the importance of winter climate anomalies in Southwest China （SWC）. The spatio-temporal variability of surface air temperature （SAT） and precipitation in SWC and their possible causes have been investigated in this paper based on observational data from 1961 to 2010. The results indicate that SAT anomalies in SWC have two dominate modes, one is homogenous, and the other a zonal dipole. The former is caused by the anomalies of East Asian winter monsoon; the latter arises from the anomalies of both subtropical west Pacific high and regional cold air in lower troposphere. The most dominant mode of precipitation anomalies in SWC is homogenous and it has a high correlation with northern hemisphere annular mode （NAM, AO）. Neither NAM nor ENSO has significant impacts on SAT in SWC. The anomalies of NAM are associated with the anomalies of tropical circulations, and therefore precipitation over the SWC. When NAM is in positive （negative） phase, the winter precipitation is more （less） than normal in SWC. Winter precipitation increase over the whole SWC is associated with the El Nino. However, during La Nina winter, the pattern is not uniform. There is an increase in precipitation over the central parts and a decrease in western and eastern parts of SWC. The severe drought in SWC in winter 2010 is more likely caused by anomalies of NAM, not El Nino.展开更多
The Northern-Hemisphere high-latitude continents experienced extremely cold weathers in winter 2009 2010. In the present paper, we show that the cold winter was associated with the activity of tile Arctic oscillation ...The Northern-Hemisphere high-latitude continents experienced extremely cold weathers in winter 2009 2010. In the present paper, we show that the cold winter was associated with the activity of tile Arctic oscillation （AO）, which demonstrated the strongest negative polarity over the past six decades and persisted from December, 2009 to March, 2010. It is found that variations of the surface AO was closely linked to stratospheric polar vortex anomalies, and that the surface AO phases followed downward propagation of stratospheric Northern-Hemisphere Annular mode （NAM） anomalies during the winter. The case of 2009-2010 winter provides us with a typical example that anomalous stratospheric signals can be used to improve skills of long-range weather forecast and intra-seasonal climate prediction in winter time. We also show that the E1 Nifio event, which started developing from May 2009, might contribute the formation of exceptionally negative and persistent AO and stratospheric NAM, particularly over North Pacific and North America.展开更多
基金National Natural Science Foundation of China, No.40875060 No.60832012 Basic Research and Operation Program of institute of Plateau Meteorology, China Meteorological Administration, No.BROP201017 Acknowledgements We thank Hyacinth Cyprain Nnamchi for his kind help in improving our English writing.
文摘In recent years, the socio-economic impacts of winter extreme climate events have underscored the importance of winter climate anomalies in Southwest China （SWC）. The spatio-temporal variability of surface air temperature （SAT） and precipitation in SWC and their possible causes have been investigated in this paper based on observational data from 1961 to 2010. The results indicate that SAT anomalies in SWC have two dominate modes, one is homogenous, and the other a zonal dipole. The former is caused by the anomalies of East Asian winter monsoon; the latter arises from the anomalies of both subtropical west Pacific high and regional cold air in lower troposphere. The most dominant mode of precipitation anomalies in SWC is homogenous and it has a high correlation with northern hemisphere annular mode （NAM, AO）. Neither NAM nor ENSO has significant impacts on SAT in SWC. The anomalies of NAM are associated with the anomalies of tropical circulations, and therefore precipitation over the SWC. When NAM is in positive （negative） phase, the winter precipitation is more （less） than normal in SWC. Winter precipitation increase over the whole SWC is associated with the El Nino. However, during La Nina winter, the pattern is not uniform. There is an increase in precipitation over the central parts and a decrease in western and eastern parts of SWC. The severe drought in SWC in winter 2010 is more likely caused by anomalies of NAM, not El Nino.
文摘The Northern-Hemisphere high-latitude continents experienced extremely cold weathers in winter 2009 2010. In the present paper, we show that the cold winter was associated with the activity of tile Arctic oscillation （AO）, which demonstrated the strongest negative polarity over the past six decades and persisted from December, 2009 to March, 2010. It is found that variations of the surface AO was closely linked to stratospheric polar vortex anomalies, and that the surface AO phases followed downward propagation of stratospheric Northern-Hemisphere Annular mode （NAM） anomalies during the winter. The case of 2009-2010 winter provides us with a typical example that anomalous stratospheric signals can be used to improve skills of long-range weather forecast and intra-seasonal climate prediction in winter time. We also show that the E1 Nifio event, which started developing from May 2009, might contribute the formation of exceptionally negative and persistent AO and stratospheric NAM, particularly over North Pacific and North America.
