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
In this study, changes in climatological conditions around the KoreanPeninsula are estimated quantitatively using various types of high order statistical analyses. Thetemperature data collected from Incheon station ha...In this study, changes in climatological conditions around the KoreanPeninsula are estimated quantitatively using various types of high order statistical analyses. Thetemperature data collected from Incheon station have been analyzed for the assessment of the climatevariation. According to our analysis, the climate changes observed over the Korean Peninsula forthe last century are similar to the global observational data in many respects. First of all, thewarming trend [+1.5℃ (100 yr)^(-1)] and the overall evolving pattern throughout the century axequite similar to each other. The temperature change in the Korean Peninsula is about two to threetimes larger than that of the global scale which may partially be ascribed to the influence ofurbanization at mid and high latitudes. In this work, a new Winter Monsoon Index (WMI) is suggestedbased on the European continental scale circulation index (EU1) pattern. Our WMI is defined as thenormalized sea level pressure (SLP) difference in the winter period between the centers of the EastSea and west of Lake Baikal in Siberia, the two eastern centers of the EU1 action patterns. A strongsimilarity is found between the time series of the WMI and surface air temperature at Incheon. TheWMI has decreased gradually since the 1920s but has shifted to a rapid increasing trend in the lasttwo decades; it was in fact accompanied by a weakening of the Siberian High and a decreasing of thenortherly during winter. Our findings of the close correlations between the surface air temperatureat Incheon and the WMI strongly indicate that our newly suggested index is unique and can be used asan efficient tool to predict climate variability in Korea.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In this study, changes in climatological conditions around the KoreanPeninsula are estimated quantitatively using various types of high order statistical analyses. Thetemperature data collected from Incheon station have been analyzed for the assessment of the climatevariation. According to our analysis, the climate changes observed over the Korean Peninsula forthe last century are similar to the global observational data in many respects. First of all, thewarming trend [+1.5℃ (100 yr)^(-1)] and the overall evolving pattern throughout the century axequite similar to each other. The temperature change in the Korean Peninsula is about two to threetimes larger than that of the global scale which may partially be ascribed to the influence ofurbanization at mid and high latitudes. In this work, a new Winter Monsoon Index (WMI) is suggestedbased on the European continental scale circulation index (EU1) pattern. Our WMI is defined as thenormalized sea level pressure (SLP) difference in the winter period between the centers of the EastSea and west of Lake Baikal in Siberia, the two eastern centers of the EU1 action patterns. A strongsimilarity is found between the time series of the WMI and surface air temperature at Incheon. TheWMI has decreased gradually since the 1920s but has shifted to a rapid increasing trend in the lasttwo decades; it was in fact accompanied by a weakening of the Siberian High and a decreasing of thenortherly during winter. Our findings of the close correlations between the surface air temperatureat Incheon and the WMI strongly indicate that our newly suggested index is unique and can be used asan efficient tool to predict climate variability in Korea.
