Defining the intensity of the East Asian winter monsoon （EAWM） with a simple index has been a difficult task. This paper elaborates on the meanings of 18 existing EAWM strength indices and classifies them into four ...Defining the intensity of the East Asian winter monsoon （EAWM） with a simple index has been a difficult task. This paper elaborates on the meanings of 18 existing EAWM strength indices and classifies them into four categories： low level wind indices, upper zonal wind shear indices, east-west pressure contrast indices, and East Asian trough indices. The temporal/spatial performance and prediction potential of these indices are then analyzed for the 1957-2001 period. It reveals that on the decadal timescale, most indices except the east-west pressure contrast indices can well capture the continuous weakening of the EAWM around 1986. On the interannual timescale, the low level wind indices and East Asian trough indices have the best predictability based on knowledge of the El Nio-Southern Oscillation and Arctic Oscillation, respectively. All the 18 existing indices can well describe the EAWM-related circulation, precipitation, and lower tropospheric air temperature anomalies. However, the variations of surface air temperature over large areas of central China cannot be well captured by most indices, which is possibly related to topographic effects. The results of this study may provide a possible reference for future studies of the EAWM.展开更多
The seasonal predictability of various East Asian winter monsoon （EAWM） indices was investigated in this study based on the retrospective forecasts of the five state-of-the-art coupled models from ENSEMBLES for a 46...The seasonal predictability of various East Asian winter monsoon （EAWM） indices was investigated in this study based on the retrospective forecasts of the five state-of-the-art coupled models from ENSEMBLES for a 46-year period of 19612006.It was found that the ENSEMBLES models predict five out of the 21 EAWM indices well,with temporal correlation coefficients ranging from 0.54 to 0.61.These five indices are defined by the averaged lower-tropospheric winds over the low latitudes （south of 30°N）.Further analyses indicated that the predictability of these five indices originates from their intimate relationship with ENSO.A cross-validated prediction,which took the preceding （November） observed Nifo3.4 index as a predictor,gives a prediction skill almost identical to that shown by the model.On the other hand,the models present rather low predictability for the other indices and for surface air temperature in East Asia.In addition,the models fail to reproduce the relationship between the indices of different categories,implying that they cannot capture the tropicalextratropical interaction related to EAWM variability.Together,these results suggest that reliable prediction of the EAWM indices and East Asian air temperature remains a challenge.展开更多
Using the NCEP/NCAR reanalysis data （Version 1.0） and the observation data of China from January 1951 to February 2007, a new index of East Asian winter monsoon circulation （I EAWM） was defined based on the compar...Using the NCEP/NCAR reanalysis data （Version 1.0） and the observation data of China from January 1951 to February 2007, a new index of East Asian winter monsoon circulation （I EAWM） was defined based on the comparison of previous different winter monsoon indices and circulation factors influencing the winter climate over China. Its relationships with winter temperature over China and large-scale circulation were analyzed. Results show that IEAWM can successfully describe the variation of China＇s mainland winter temperature and the East Asian winter monsoon （EAWM） system. This index reflects the integrated effect of the circulations over high and low latitudes and the thermal difference between the continent and the ocean. While in the previous studies, most monsoon indices only describe the single monsoon member. The IEAWM is a good indicator of the intensity of the EAWM. Positive values of/EAWM correspond to the strong EAWM, the stronger Siberian high and East Asian trough than normal , and the strengthening of the meridional shear of 500-hPa zonal wind between high and low latitudes over East Asia, and therefore, the southward cold advection becomes stronger and leads to the decrease in surface temperature over China; and vice versa. The IEAWM inter decadal change is obviously positive before the mid-1980s, but negative since the mid-1980s, in good agreement with the fact of the winter warming in China after 1985.展开更多
利用1961—2016年宁夏20个气象站冬季逐月气温资料,英国气象局哈德莱Hadley中心秋季逐月海冰密集度资料,美国国家环境预报中心/国家大气研究中心(NCEP/NCAR)冬季逐月大气再分析资料,分析2016年宁夏冬季气温异常特征及其成因。结果表明:2...利用1961—2016年宁夏20个气象站冬季逐月气温资料,英国气象局哈德莱Hadley中心秋季逐月海冰密集度资料,美国国家环境预报中心/国家大气研究中心(NCEP/NCAR)冬季逐月大气再分析资料,分析2016年宁夏冬季气温异常特征及其成因。结果表明:2016年冬季,宁夏气温创1961年以来同期最高。2016年500 hPa欧亚中高纬地区纬向环流明显,乌拉尔山阻塞高压异常偏弱,中国大陆上空位势高度场异常偏强,极涡偏向大西洋欧洲区和北美大陆;东亚冬季风指数为-1. 29 m·s^(-1),为1961年以来第5低值;西伯利亚高压强度距平为-1. 5 h Pa,为2000年以来第2低值。秋季格陵兰海冰密集度偏低,导致东亚冬季风偏弱;500 h Pa位势高度场上北极、欧亚大陆和阿留申地区呈现"-+-"的波列形态,使得北极与欧亚大陆中高纬地区的位势高度差增强,中高纬西风气流偏强,纬向活动加强;海平面气压场上西伯利亚高压偏弱,不利于北极冷空气向低纬地区侵袭,使得2016年冬季宁夏气温异常偏高。展开更多
基金supported jointly by the National Basic Research Program of China(2009CB421405)the National Key Technology R&D Program of China (2008BAK50B02)+1 种基金the National Natural Science Foundation of China (40905026 and 40775035)Key Laboratory of Global Change and Marine-Atmospheric Chemistry, SOA (GCMAC0901)
文摘Defining the intensity of the East Asian winter monsoon （EAWM） with a simple index has been a difficult task. This paper elaborates on the meanings of 18 existing EAWM strength indices and classifies them into four categories： low level wind indices, upper zonal wind shear indices, east-west pressure contrast indices, and East Asian trough indices. The temporal/spatial performance and prediction potential of these indices are then analyzed for the 1957-2001 period. It reveals that on the decadal timescale, most indices except the east-west pressure contrast indices can well capture the continuous weakening of the EAWM around 1986. On the interannual timescale, the low level wind indices and East Asian trough indices have the best predictability based on knowledge of the El Nio-Southern Oscillation and Arctic Oscillation, respectively. All the 18 existing indices can well describe the EAWM-related circulation, precipitation, and lower tropospheric air temperature anomalies. However, the variations of surface air temperature over large areas of central China cannot be well captured by most indices, which is possibly related to topographic effects. The results of this study may provide a possible reference for future studies of the EAWM.
基金supported by the National Natural Science Foundation of China(Grant No.41320104007)
文摘The seasonal predictability of various East Asian winter monsoon （EAWM） indices was investigated in this study based on the retrospective forecasts of the five state-of-the-art coupled models from ENSEMBLES for a 46-year period of 19612006.It was found that the ENSEMBLES models predict five out of the 21 EAWM indices well,with temporal correlation coefficients ranging from 0.54 to 0.61.These five indices are defined by the averaged lower-tropospheric winds over the low latitudes （south of 30°N）.Further analyses indicated that the predictability of these five indices originates from their intimate relationship with ENSO.A cross-validated prediction,which took the preceding （November） observed Nifo3.4 index as a predictor,gives a prediction skill almost identical to that shown by the model.On the other hand,the models present rather low predictability for the other indices and for surface air temperature in East Asia.In addition,the models fail to reproduce the relationship between the indices of different categories,implying that they cannot capture the tropicalextratropical interaction related to EAWM variability.Together,these results suggest that reliable prediction of the EAWM indices and East Asian air temperature remains a challenge.
基金Supported jointly by the National Natural Science Foundation of China (40505014)China Meteorological Administration (CMATG2005M04) and GYHY 200706010.
文摘Using the NCEP/NCAR reanalysis data （Version 1.0） and the observation data of China from January 1951 to February 2007, a new index of East Asian winter monsoon circulation （I EAWM） was defined based on the comparison of previous different winter monsoon indices and circulation factors influencing the winter climate over China. Its relationships with winter temperature over China and large-scale circulation were analyzed. Results show that IEAWM can successfully describe the variation of China＇s mainland winter temperature and the East Asian winter monsoon （EAWM） system. This index reflects the integrated effect of the circulations over high and low latitudes and the thermal difference between the continent and the ocean. While in the previous studies, most monsoon indices only describe the single monsoon member. The IEAWM is a good indicator of the intensity of the EAWM. Positive values of/EAWM correspond to the strong EAWM, the stronger Siberian high and East Asian trough than normal , and the strengthening of the meridional shear of 500-hPa zonal wind between high and low latitudes over East Asia, and therefore, the southward cold advection becomes stronger and leads to the decrease in surface temperature over China; and vice versa. The IEAWM inter decadal change is obviously positive before the mid-1980s, but negative since the mid-1980s, in good agreement with the fact of the winter warming in China after 1985.
文摘利用1961—2016年宁夏20个气象站冬季逐月气温资料,英国气象局哈德莱Hadley中心秋季逐月海冰密集度资料,美国国家环境预报中心/国家大气研究中心(NCEP/NCAR)冬季逐月大气再分析资料,分析2016年宁夏冬季气温异常特征及其成因。结果表明:2016年冬季,宁夏气温创1961年以来同期最高。2016年500 hPa欧亚中高纬地区纬向环流明显,乌拉尔山阻塞高压异常偏弱,中国大陆上空位势高度场异常偏强,极涡偏向大西洋欧洲区和北美大陆;东亚冬季风指数为-1. 29 m·s^(-1),为1961年以来第5低值;西伯利亚高压强度距平为-1. 5 h Pa,为2000年以来第2低值。秋季格陵兰海冰密集度偏低,导致东亚冬季风偏弱;500 h Pa位势高度场上北极、欧亚大陆和阿留申地区呈现"-+-"的波列形态,使得北极与欧亚大陆中高纬地区的位势高度差增强,中高纬西风气流偏强,纬向活动加强;海平面气压场上西伯利亚高压偏弱,不利于北极冷空气向低纬地区侵袭,使得2016年冬季宁夏气温异常偏高。
