The 1979-2001 ERA-40 monthly mean meridional winds are used to calculate the mass streamfunctions in the monsoon region (60-140° E) and Nio zone (160° E-120° W),with which the climate characteristics ...The 1979-2001 ERA-40 monthly mean meridional winds are used to calculate the mass streamfunctions in the monsoon region (60-140° E) and Nio zone (160° E-120° W),with which the climate characteristics and intensity variation of the localized Hadley circulation (LHC) are analyzed over the two regions and the linkage of this LHC to Pacific SST is explored.Evidence suggests as follows.1) The climatological LHC is stronger in the monsoon than in the Nio zone,with its position in the former northward of the latter,especially in the summer half-year.The resulting difference is due mainly to the land-sea heterogeneous distribution and the existence of a cold pool in the equatorial eastern Pacific.2) The LHC experiences a distinct interannual variability in intensity and during 1979-2001 the LHC strength of the two regions changes broadly in an anti-phase manner.3) The LHC has its intensity associated closely with Pacific SST in such a way that its strength anomaly in the monsoon (Nio) band in January is correlated negatively (positively) with the SSTA over the all-Nio (1-4) zone (ANZ) in the equatorial middle and eastern Pacific but positively (negatively) correlated to SSTA in the C-shaped area that surrounds the ANZ.The pattern of July is in rough agreement with that of January,except for more feeble correlativity in July,especially over the monsoon region;4) The ENSO episode has different impacts on the LHC vigor in the two regions.With the occurrence of an El Nio,the LHC is weakened (strengthened) in the monsoon (Nio) region,and the reversal takes place during the La Nia year,with greater anomaly in the Nio area.展开更多
The characteristics of atmospheric heat source associated with the summer monsoon onset in the South China Sea (SCS) are studied using ECMWF reanalysis data from 1979 to 1993. A criterion of the SCS summer monsoon ons...The characteristics of atmospheric heat source associated with the summer monsoon onset in the South China Sea (SCS) are studied using ECMWF reanalysis data from 1979 to 1993. A criterion of the SCS summer monsoon onset is defined by the atmospheric heat source. Applying this criterion to the 15-year (1979 – 1993) mean field, the onset of the SCS summer monsoon is found to occur in the fourth pentad of May. And this criterion can also give reasonable results for the onset time of the SCS summer monsoon on a year-to-year basis. In addition, pretty high correlation has been found between the onset time of the SCS summer monsoon and the zonal mean vertically integrated heat source <Q1> at 40°S in April. The causes for the late or early onset of the SCS summer monsoon and the close relationship between the onset time and the zonal mean vertically integrated heat source <Q1> at 40 °S in April might be explained by the variations in intensity of the Hadley circulation.展开更多
The linkage between Hadley circulation(HC)and sea ice extent in the Bering Sea during March-April is investigated through an analysis of observed data in this research.It is found that HC is negatively correlated to t...The linkage between Hadley circulation(HC)and sea ice extent in the Bering Sea during March-April is investigated through an analysis of observed data in this research.It is found that HC is negatively correlated to the sea ice extent in the Bering Sea,namely,strong(weak)HC is corresponding to less(more)sea ice in the Bering Sea.The present study also addresses the large-scale atmospheric general circulation changes underlying the relationship between HC and sea ice in the Bering Sea.It follows that a positive phase of HC corresponds to westward located Aleutian low,anomalous southerlies over the eastern North Pacific and higher temperature in the Bering Sea,providing unfavorable atmospheric and thermal conditions for the sea ice forming,and thus sea ice extent in the Bering Sea is decreased,and vice versa.In addition,it is further identified that East Asian-North Pacific-North America telecon-nection may play an important role in linking HC and changes of atmospheric circulations as well as sea ice in the Bering Sea.展开更多
The mass stream function of mean me-ridional circulation is calculated from the ECMWF andNCEP/NCAR reanalysis data sets using a superposi-tion computation scheme. The comparison of resultsshows that the common ascendi...The mass stream function of mean me-ridional circulation is calculated from the ECMWF andNCEP/NCAR reanalysis data sets using a superposi-tion computation scheme. The comparison of resultsshows that the common ascending leg of the Hadleycell calculated from the ECMWF data is strong andnarrow, and averagely lies more north of the equatorin comparison with its counterpart from the NCEP/ NCAR data, and furthermore the Hadley cell from theECMWF data shows an obvious double-layer struc-ture. Therefore, there are obvious differences be-tween Hadley cells displayed by the two objectiveanalysis data sets.展开更多
基金Natural Science Foundation of China (NSFC,40975057)The Structure of Tibetan Heat Sources and Oscillation Properties in Conjunction with the Mechanism for the Heat Propagating and Influencing as a key project of the NSFC (40633018)Hadley Circulation Anomaly with Its relation to the Anomaly of Summer Climate in China (E3000008098005)
文摘The 1979-2001 ERA-40 monthly mean meridional winds are used to calculate the mass streamfunctions in the monsoon region (60-140° E) and Nio zone (160° E-120° W),with which the climate characteristics and intensity variation of the localized Hadley circulation (LHC) are analyzed over the two regions and the linkage of this LHC to Pacific SST is explored.Evidence suggests as follows.1) The climatological LHC is stronger in the monsoon than in the Nio zone,with its position in the former northward of the latter,especially in the summer half-year.The resulting difference is due mainly to the land-sea heterogeneous distribution and the existence of a cold pool in the equatorial eastern Pacific.2) The LHC experiences a distinct interannual variability in intensity and during 1979-2001 the LHC strength of the two regions changes broadly in an anti-phase manner.3) The LHC has its intensity associated closely with Pacific SST in such a way that its strength anomaly in the monsoon (Nio) band in January is correlated negatively (positively) with the SSTA over the all-Nio (1-4) zone (ANZ) in the equatorial middle and eastern Pacific but positively (negatively) correlated to SSTA in the C-shaped area that surrounds the ANZ.The pattern of July is in rough agreement with that of January,except for more feeble correlativity in July,especially over the monsoon region;4) The ENSO episode has different impacts on the LHC vigor in the two regions.With the occurrence of an El Nio,the LHC is weakened (strengthened) in the monsoon (Nio) region,and the reversal takes place during the La Nia year,with greater anomaly in the Nio area.
基金National Natural Science Foundation of China (40275026) Part One of National KeyFundamental Research and Development Planning Project (G1998040900)
文摘The characteristics of atmospheric heat source associated with the summer monsoon onset in the South China Sea (SCS) are studied using ECMWF reanalysis data from 1979 to 1993. A criterion of the SCS summer monsoon onset is defined by the atmospheric heat source. Applying this criterion to the 15-year (1979 – 1993) mean field, the onset of the SCS summer monsoon is found to occur in the fourth pentad of May. And this criterion can also give reasonable results for the onset time of the SCS summer monsoon on a year-to-year basis. In addition, pretty high correlation has been found between the onset time of the SCS summer monsoon and the zonal mean vertically integrated heat source <Q1> at 40°S in April. The causes for the late or early onset of the SCS summer monsoon and the close relationship between the onset time and the zonal mean vertically integrated heat source <Q1> at 40 °S in April might be explained by the variations in intensity of the Hadley circulation.
基金the National Natural Science Foundation of China(Grant Nos.40631005,40620130113and40523001)
文摘The linkage between Hadley circulation(HC)and sea ice extent in the Bering Sea during March-April is investigated through an analysis of observed data in this research.It is found that HC is negatively correlated to the sea ice extent in the Bering Sea,namely,strong(weak)HC is corresponding to less(more)sea ice in the Bering Sea.The present study also addresses the large-scale atmospheric general circulation changes underlying the relationship between HC and sea ice in the Bering Sea.It follows that a positive phase of HC corresponds to westward located Aleutian low,anomalous southerlies over the eastern North Pacific and higher temperature in the Bering Sea,providing unfavorable atmospheric and thermal conditions for the sea ice forming,and thus sea ice extent in the Bering Sea is decreased,and vice versa.In addition,it is further identified that East Asian-North Pacific-North America telecon-nection may play an important role in linking HC and changes of atmospheric circulations as well as sea ice in the Bering Sea.
基金supported by the National Natural Science Foundation of China(Grant No.40475028)"The Six Talent Peaks Project of Jiangsu Province".
文摘The mass stream function of mean me-ridional circulation is calculated from the ECMWF andNCEP/NCAR reanalysis data sets using a superposi-tion computation scheme. The comparison of resultsshows that the common ascending leg of the Hadleycell calculated from the ECMWF data is strong andnarrow, and averagely lies more north of the equatorin comparison with its counterpart from the NCEP/ NCAR data, and furthermore the Hadley cell from theECMWF data shows an obvious double-layer struc-ture. Therefore, there are obvious differences be-tween Hadley cells displayed by the two objectiveanalysis data sets.
