Experimental outputs of 11 Atmospheric Model Intercomparison Project （AMIP） models from phase 5 of the Coupled Model Intercomparison Project （CMIP5） are analyzed to assess the atmospheric circulation anomaly over ...Experimental outputs of 11 Atmospheric Model Intercomparison Project （AMIP） models from phase 5 of the Coupled Model Intercomparison Project （CMIP5） are analyzed to assess the atmospheric circulation anomaly over Northern Hemisphere induced by the anomalous rainfall over tropical Pacific and Indian Ocean during boreal winter.The analysis shows that the main features of the interannual variation of tropical rainfall anomalies,especially over the Central Pacific （CP） （5°S-5°N,175°E-135°W） and Indo-western Pacific （IWP） （20°S-20°N,110°-150°E） are well captured in all the CMIP5/AMIP models.For the IWP and western Indian Ocean （WIO） （10°S-10°N,45°-75°E）,the anomalous rainfall is weaker in the 11 CMIP5/AMIP models than in the observation.During El Ni（n）o/La Ni（n）a mature phases in boreal winter,consistent with observations,there are geopotential height anomalies known as the Pacific North American （PNA） pattern and Indo-western Pacific and East Asia （IWPEA） pattern in the upper troposphere,and the northwestern Pacific anticyclone （cyclone） （NWPA） in the lower troposphere in the models.Comparison between the models and observations shows that the ability to simulate the PNA and NWPA pattern depends on the ability to simulate the anomalous rainfall over the CP,while the ability to simulate the IWPEA pattern is related to the ability to simulate the rainfall anomaly in the IWP and WIO,as the SST anomaly is same in AMIP experiments.It is found that the tropical rainfall anomaly is important in modeling the impact of the tropical Indo-Pacific Ocean on the extratropical atmospheric circulation anomaly.展开更多
The possible mechanism behind the variability in the dipole pattern of boreal winter precipitation over East Asia is analyzed in this study. The results show that the SST anomalies（SSTAs） over the South Pacific Ocea...The possible mechanism behind the variability in the dipole pattern of boreal winter precipitation over East Asia is analyzed in this study. The results show that the SST anomalies（SSTAs） over the South Pacific Ocean（SPO） in boreal autumn are closely related to the variability in the dipole pattern of boreal winter precipitation over East Asia. The physical link between the boreal autumn SPO SSTAs and the boreal winter East Asian precipitation dipole pattern is shown to mainly be the seasonal persistence of the SPO SSTAs themselves. The seasonal persistence of the SPO SSTAs can memorize and transport the signal of the boreal autumn SSTAs to the following winter, and then stimulates a meridional teleconnection pattern from the SH to the NH, resulting in a meridional dipole pattern of atmospheric circulation over East Asia in boreal winter. As a major influencing factor, this dipole pattern of the atmospheric circulation can finally lead to the anomalous precipitation dipole pattern over East Asia in boreal winter. These observed physical processes are further confirmed in this study through numerical simulation. The evidence from this study, showing the impact of the SPO SSTAs in boreal autumn,not only deepens our understanding of the variability in East Asian boreal winter precipitation, but also provides a potentially useful predictor for precipitation in the region.展开更多
Using tropical cyclone (TC) observations over a 58-yr period (1949-2006) from the China Meteorological Administration, the 40-year ECMWF Reanalysis (ERA-40), NCEP-NCAR reanalysis, and the Hadley Centre sea ice and sea...Using tropical cyclone (TC) observations over a 58-yr period (1949-2006) from the China Meteorological Administration, the 40-year ECMWF Reanalysis (ERA-40), NCEP-NCAR reanalysis, and the Hadley Centre sea ice and sea surface temperature (HadISST) datasets, the authors have examined the behaviors of tropical cyclones (TCs) in the western north Pacific (WNP) in boreal winter (November-December-January-February). The results demonstrate that the occurrences of wintertime TCs, including super typhoons, have decreased over the 58 years. More TCs are found to move westward than northeastward, and the annual total number of parabolic-track-type TCs is found to be decreasing. It is shown that negative sea surface temperature anomalies (SSTAs) related to La Ni a events in the equatorial central Pacific facilitate more TC genesis in the WNP region. Large-scale anomalous cyclonic circulations in the tropical WNP in the lower troposphere are observed to be favorable for cyclogenesis in this area. On the contrary, the positive SSTAs and anomalous anticyclonic circulations that related to El Ni o events responsible for fewer TC genesis. Under the background of global warming, the western Pacific subtropical high tends to intensify and to expand more westward in the WNP, and the SSTAs display an increasing trend in the equatorial eastern-central Pacific. These climate trends of both atmospheric circulation and SSTAs affect wintertime TCs, inducing fewer TC occurrences and causing more TCs to move westward.展开更多
The intraseasonal oscillation (ISO) events that occurred from November 2007 to February 2008 in the tropical Indian Ocean region were investigated by analyzing observational oceanic and atmospheric datasets.The result...The intraseasonal oscillation (ISO) events that occurred from November 2007 to February 2008 in the tropical Indian Ocean region were investigated by analyzing observational oceanic and atmospheric datasets.The results reveal that two ISO events were generated and developed from November 2007 to February 2008 in the tropical area of the Indian Ocean,which both originated from the southern African continent and propagated along a northeastward direction and finally penetrated into the equatorial eastern Indian Ocean.Compared with the general winter MJO event,which tended to travel along the equator from the western Indian Ocean into the western Pacific,the ISO of winter 2007 propagated not only along the equator into the eastern part of the Indian Ocean but was also transported northward into the subtropical region in the eastern Indian Ocean,which is more similar to the behavior of traditional summer ISO events.展开更多
Using the NCEP/NCAR reanalysis and the ENSO indices from the Climate Prediction Center over the period 1978-2014,we have investigated the contemporaneous circulation variations in the Northern and Southern Hemispheres...Using the NCEP/NCAR reanalysis and the ENSO indices from the Climate Prediction Center over the period 1978-2014,we have investigated the contemporaneous circulation variations in the Northern and Southern Hemispheres by performing the singular value decomposition analysis of sea level pressure anomalies（SLPA） after the ENSO signal is regressed out.It is found that there exists a polar-tropical seesaw mode（PTSM） that characterizes with the out of phase fluctuations of SLPA between the polar and tropical regions in the Northern and Southern Hemispheres in boreal winter.This PTSM explains 47.74%of the total covariance of SLPA and is almost independent of ENSO.It demonstrates a long-term trend and oscillation cycles of 2-3 and 4-6 yr.The long-term trend in PTSM indicates that the sea level pressure gradually decreases in the tropics and increases in the polar region with time.This PTSM looks roughly symmetric about the equator besides the seesaw pattern of SLPA between the tropics and polar region in each hemisphere.The disturbances in the geopotential height field in association with the PTSM shows baroclinic features in the tropics whereas equivalent barotropic features in the mid and high latitudes in the troposphere.The anomalous thermal forcing in the tropical region is possibly one of the factors facilitating the formation of this PTSM.Significant global precipitation and temperature anomalies related to the PTSM are observed.In the positive PTSM phase,precipitation and temperature are higher than normal in southern Europe and the Mediterranean and surrounding areas,but lower than normal in northern Europe and Siberia.Precipitation is higher than normal while temperature is lower than normal in Northeast Asia.Significant temperature and precipitation anomalies possibly occur in the regions of western China,northern India,parts of North America,parts of subtropical Africa,Maritime Continent,and Antarctic.These results are helpful for better understanding of the circulation variations and the mechanisms behind the interactions between the Northern and Southern Hemispheres and the related winter climate anomalies over globe.展开更多
基金supported by the Ministry of Science and Technology of China (National Basic Research Program of China Grant No. 2012CB955602)the National Natural Science Foundation of China (Grant Nos. 41176006 and 41221063)
文摘Experimental outputs of 11 Atmospheric Model Intercomparison Project （AMIP） models from phase 5 of the Coupled Model Intercomparison Project （CMIP5） are analyzed to assess the atmospheric circulation anomaly over Northern Hemisphere induced by the anomalous rainfall over tropical Pacific and Indian Ocean during boreal winter.The analysis shows that the main features of the interannual variation of tropical rainfall anomalies,especially over the Central Pacific （CP） （5°S-5°N,175°E-135°W） and Indo-western Pacific （IWP） （20°S-20°N,110°-150°E） are well captured in all the CMIP5/AMIP models.For the IWP and western Indian Ocean （WIO） （10°S-10°N,45°-75°E）,the anomalous rainfall is weaker in the 11 CMIP5/AMIP models than in the observation.During El Ni（n）o/La Ni（n）a mature phases in boreal winter,consistent with observations,there are geopotential height anomalies known as the Pacific North American （PNA） pattern and Indo-western Pacific and East Asia （IWPEA） pattern in the upper troposphere,and the northwestern Pacific anticyclone （cyclone） （NWPA） in the lower troposphere in the models.Comparison between the models and observations shows that the ability to simulate the PNA and NWPA pattern depends on the ability to simulate the anomalous rainfall over the CP,while the ability to simulate the IWPEA pattern is related to the ability to simulate the rainfall anomaly in the IWP and WIO,as the SST anomaly is same in AMIP experiments.It is found that the tropical rainfall anomaly is important in modeling the impact of the tropical Indo-Pacific Ocean on the extratropical atmospheric circulation anomaly.
基金jointly supported by the Special Fund for Public Welfare Industry (meteorology) (Grant No. GYHY201306026)the National Natural Science Foundation of China (Grant Nos. 41421004 and 41522503)
文摘The possible mechanism behind the variability in the dipole pattern of boreal winter precipitation over East Asia is analyzed in this study. The results show that the SST anomalies（SSTAs） over the South Pacific Ocean（SPO） in boreal autumn are closely related to the variability in the dipole pattern of boreal winter precipitation over East Asia. The physical link between the boreal autumn SPO SSTAs and the boreal winter East Asian precipitation dipole pattern is shown to mainly be the seasonal persistence of the SPO SSTAs themselves. The seasonal persistence of the SPO SSTAs can memorize and transport the signal of the boreal autumn SSTAs to the following winter, and then stimulates a meridional teleconnection pattern from the SH to the NH, resulting in a meridional dipole pattern of atmospheric circulation over East Asia in boreal winter. As a major influencing factor, this dipole pattern of the atmospheric circulation can finally lead to the anomalous precipitation dipole pattern over East Asia in boreal winter. These observed physical processes are further confirmed in this study through numerical simulation. The evidence from this study, showing the impact of the SPO SSTAs in boreal autumn,not only deepens our understanding of the variability in East Asian boreal winter precipitation, but also provides a potentially useful predictor for precipitation in the region.
基金supported by the National Basic Research Program of China[grant number 2014CB953901],support from the National Basic Research Program of China[grant number 2015CB453200]the National Natural Science Foundation of China[grant numbers 41675096,41575043,41375095,and 41505067],the National Natural Science Foundation of China[grant numbers 41475084 and 41630423]
基金supported by the National Natural Science Foundation of China[grant numbers 41475081,41275081,41505048,41505061,and 41461164005]the State Key Laboratory of Severe Weather Special Fund[grant number 2015LASW-B04]
基金jointly supported by the National Basic Research Program of China (973 Program) (2009CB421505)the National Key Technology R&D Program in the 11th Five-year Plan of China (2006BAC02B01)
文摘Using tropical cyclone (TC) observations over a 58-yr period (1949-2006) from the China Meteorological Administration, the 40-year ECMWF Reanalysis (ERA-40), NCEP-NCAR reanalysis, and the Hadley Centre sea ice and sea surface temperature (HadISST) datasets, the authors have examined the behaviors of tropical cyclones (TCs) in the western north Pacific (WNP) in boreal winter (November-December-January-February). The results demonstrate that the occurrences of wintertime TCs, including super typhoons, have decreased over the 58 years. More TCs are found to move westward than northeastward, and the annual total number of parabolic-track-type TCs is found to be decreasing. It is shown that negative sea surface temperature anomalies (SSTAs) related to La Ni a events in the equatorial central Pacific facilitate more TC genesis in the WNP region. Large-scale anomalous cyclonic circulations in the tropical WNP in the lower troposphere are observed to be favorable for cyclogenesis in this area. On the contrary, the positive SSTAs and anomalous anticyclonic circulations that related to El Ni o events responsible for fewer TC genesis. Under the background of global warming, the western Pacific subtropical high tends to intensify and to expand more westward in the WNP, and the SSTAs display an increasing trend in the equatorial eastern-central Pacific. These climate trends of both atmospheric circulation and SSTAs affect wintertime TCs, inducing fewer TC occurrences and causing more TCs to move westward.
基金supported by the National Basic Research Program of China(Grant Nos.2010CB950304,2012CB955601,and 2010CB950303)the National Natural Science Foundation of China(Grant No.40706014)
文摘The intraseasonal oscillation (ISO) events that occurred from November 2007 to February 2008 in the tropical Indian Ocean region were investigated by analyzing observational oceanic and atmospheric datasets.The results reveal that two ISO events were generated and developed from November 2007 to February 2008 in the tropical area of the Indian Ocean,which both originated from the southern African continent and propagated along a northeastward direction and finally penetrated into the equatorial eastern Indian Ocean.Compared with the general winter MJO event,which tended to travel along the equator from the western Indian Ocean into the western Pacific,the ISO of winter 2007 propagated not only along the equator into the eastern part of the Indian Ocean but was also transported northward into the subtropical region in the eastern Indian Ocean,which is more similar to the behavior of traditional summer ISO events.
基金Supported by the National Natural Science Foundation of China(41175062 and 41330425)Science Innovation Program of the State Key Laboratory of Severe Weather,Chinese Academy of Meteorological Sciences(2015LASW-A03)
文摘Using the NCEP/NCAR reanalysis and the ENSO indices from the Climate Prediction Center over the period 1978-2014,we have investigated the contemporaneous circulation variations in the Northern and Southern Hemispheres by performing the singular value decomposition analysis of sea level pressure anomalies（SLPA） after the ENSO signal is regressed out.It is found that there exists a polar-tropical seesaw mode（PTSM） that characterizes with the out of phase fluctuations of SLPA between the polar and tropical regions in the Northern and Southern Hemispheres in boreal winter.This PTSM explains 47.74%of the total covariance of SLPA and is almost independent of ENSO.It demonstrates a long-term trend and oscillation cycles of 2-3 and 4-6 yr.The long-term trend in PTSM indicates that the sea level pressure gradually decreases in the tropics and increases in the polar region with time.This PTSM looks roughly symmetric about the equator besides the seesaw pattern of SLPA between the tropics and polar region in each hemisphere.The disturbances in the geopotential height field in association with the PTSM shows baroclinic features in the tropics whereas equivalent barotropic features in the mid and high latitudes in the troposphere.The anomalous thermal forcing in the tropical region is possibly one of the factors facilitating the formation of this PTSM.Significant global precipitation and temperature anomalies related to the PTSM are observed.In the positive PTSM phase,precipitation and temperature are higher than normal in southern Europe and the Mediterranean and surrounding areas,but lower than normal in northern Europe and Siberia.Precipitation is higher than normal while temperature is lower than normal in Northeast Asia.Significant temperature and precipitation anomalies possibly occur in the regions of western China,northern India,parts of North America,parts of subtropical Africa,Maritime Continent,and Antarctic.These results are helpful for better understanding of the circulation variations and the mechanisms behind the interactions between the Northern and Southern Hemispheres and the related winter climate anomalies over globe.
