By Using the P-σ five-layer primitive equation model,three sets of numerical experiments are performed with normal zonal mean SST(the control case),the positive SST anomalies in the Kuroshio current and east-of-Japan...By Using the P-σ five-layer primitive equation model,three sets of numerical experiments are performed with normal zonal mean SST(the control case),the positive SST anomalies in the Kuroshio current and east-of-Japan Ocean(the midlatitude western Pacific),and positive SST anomalies over both the midlatitude and the equatorial western Pacific.The experimental results show that the positive SST anomalies over the midlatitude western Pacific have great influence on the Asian summer monsoon:the Indian monsoon is weak- ened and the East Asian monsoon is intensified.This happens just reverse to the effects of positive SST anomalies over the equatorial westero Pacific on the Asian summer monsoon.Further,the influence mechanism of the SST anomalies over the midlatitude westcrn Pacific on the Asian summer monsoon is discussed.展开更多
The relationship between the variation of precipitation in Guangdong Province is investigated using the correlation analysis and composite comparison methods in conjunction with precipitation data from 36 surface weat...The relationship between the variation of precipitation in Guangdong Province is investigated using the correlation analysis and composite comparison methods in conjunction with precipitation data from 36 surface weather stations in the province and reanalyzed 850 hPa data from NCEP, U.S.A. A significant positive correlation is found between the variation of precipitation in summer there and the intensity of the southwesterly over the South China Sea though without being so inconclusive that a strong southwesterly over the sea is accompanied by more rain in Guangdong. For the front-associated flood season in April - June, the former is a carrier of rainwater for Guangdong but with insignificant linkage with the intensity of the southwest monsoon. There is even such a situation in which the precipitation gets stronger though with a weakened southwest monsoon from the tropics in May - June, which is mainly attributable to the increase of monsoon from the subtropics. For the typhoon-associated flood season in July - September, the Guangdong precipitation increases as the southwest monsoon strengthens over the central and northern South China Sea and the subtropical monsoon reduces its effects on the province.展开更多
Numerical experiments with a low resolution atmospheric general circulation model (AGCM) were conducted to investigate the influences of SST anomalies (SSTA) over the South China Sea- tropical eastern indian Ocean (SC...Numerical experiments with a low resolution atmospheric general circulation model (AGCM) were conducted to investigate the influences of SST anomalies (SSTA) over the South China Sea- tropical eastern indian Ocean (SCS-TEIO) on the onset of the South China Sea summer Monsoon (SCSM).With positive SSTA over the SCS-TEIO,the anomalous cyclones appear over both sides of the equator at low layer,which weakens the Somali and Australian cross-equatorial SW flow. The anomalous anticyclone in the east of Phillips strengthens the subtropical high with its ridge southwestward shifted.The anomalous anticyclones over both sides of equator at high layer strengthen the South Asia high,thus weaken the SCSM and delay its onset.With negative SSTA over the SCS-ETIO,the anomalous anticyclones appear over both sides of the equator at low layer,which strengthen the Australian but weaken the Somali cross-equatorial SW flow.The anomalous cyclone in northeast of Phillips will weaken the subtropical high.The stronger monsoon meridional circulation over the tropical western Pacific will strengthen the cross-equatorial southerly flow,and the anomalous cyclones over both sides of equator at high layer will weaken the South Asia high,hence strengthen the SCSM and advance its onset.展开更多
The SST variation in the equatorial Indian Ocean is studied with special interest in analyzing its dipole oscillation feature. The dipole oscillation appears to be stronger in September-November and weaker in January-...The SST variation in the equatorial Indian Ocean is studied with special interest in analyzing its dipole oscillation feature. The dipole oscillation appears to be stronger in September-November and weaker in January-April with higher SST in the west region and lower SST in the east region as the positive phase and higher SST in the east region and lower SST in the west region as the negative phase. Generally, the amplitude of the positive phase is larger than the negative phase. The interannual variation (4-5 year period) and the interdecadal variation (25-30 year period) also exist in the dipole. The analyses also showed the significant impact of the Indian Ocean dipole on the Asian monsoon activity, because the lower tropospheric wind fields over the Southern Asia, the Tibetan high in the upper troposphere and the subtropical high over the northwestern Pacific are all related to the Indian Ocean dipole. On the other, the Indian Ocean dipole still has significant impact on atmospheric circulation and climate in North America and the southern Indian Ocean region (including Australia and South Africa).展开更多
Several sensitivity experiments are done by using the T42L9 global spectral model developed by IAP for investigating the influence of sea surface temperature anomaly (SSTA) in different regions on the South China Sea ...Several sensitivity experiments are done by using the T42L9 global spectral model developed by IAP for investigating the influence of sea surface temperature anomaly (SSTA) in different regions on the South China Sea Summer Monsoon (SCSM).It shows that when SSTA presents a La Nina pattern,the onset date of SCSM will be earlier and the convection in the South China Sea region will be consistently stronger,and vice versa.Specially,SSTA in the central and eastern Pacific plays a main role in the variation of the onset and the strength of SCSM.When SSTA of this area is lower,the onset of SCSM comes earlier,the strength of SCSM becomes stronger, otherwise,the conclusion is contrary.The influence of SSTA in the tropical West Pacific on the onset date of SCSM is not clear,but it strongly affects the strength of the monsoon.The warmer SST in this region will bring about a stronger SCSM,and vice versa.The relationship between SSTA in the tropical western Indian Ocean and SCSM has been investigated.It is found that the SSTA in this region can influence the onset of SCSM,and plays a role similar to the one in the eastern Pacific.The above results also reflect that the activity of SCSM has a close relationship with the El Nino or La Nina events.The onset and the strength change of the SCSM are obviously influenced by the heating status anomaly on the tropic Pacific through the Walker circulation.展开更多
文摘By Using the P-σ five-layer primitive equation model,three sets of numerical experiments are performed with normal zonal mean SST(the control case),the positive SST anomalies in the Kuroshio current and east-of-Japan Ocean(the midlatitude western Pacific),and positive SST anomalies over both the midlatitude and the equatorial western Pacific.The experimental results show that the positive SST anomalies over the midlatitude western Pacific have great influence on the Asian summer monsoon:the Indian monsoon is weak- ened and the East Asian monsoon is intensified.This happens just reverse to the effects of positive SST anomalies over the equatorial westero Pacific on the Asian summer monsoon.Further,the influence mechanism of the SST anomalies over the midlatitude westcrn Pacific on the Asian summer monsoon is discussed.
文摘The relationship between the variation of precipitation in Guangdong Province is investigated using the correlation analysis and composite comparison methods in conjunction with precipitation data from 36 surface weather stations in the province and reanalyzed 850 hPa data from NCEP, U.S.A. A significant positive correlation is found between the variation of precipitation in summer there and the intensity of the southwesterly over the South China Sea though without being so inconclusive that a strong southwesterly over the sea is accompanied by more rain in Guangdong. For the front-associated flood season in April - June, the former is a carrier of rainwater for Guangdong but with insignificant linkage with the intensity of the southwest monsoon. There is even such a situation in which the precipitation gets stronger though with a weakened southwest monsoon from the tropics in May - June, which is mainly attributable to the increase of monsoon from the subtropics. For the typhoon-associated flood season in July - September, the Guangdong precipitation increases as the southwest monsoon strengthens over the central and northern South China Sea and the subtropical monsoon reduces its effects on the province.
基金National Climbing Programme"South China Sea Monsoon Experiment"National Key Programme for Developing Basic Sciences G1998040900
文摘Numerical experiments with a low resolution atmospheric general circulation model (AGCM) were conducted to investigate the influences of SST anomalies (SSTA) over the South China Sea- tropical eastern indian Ocean (SCS-TEIO) on the onset of the South China Sea summer Monsoon (SCSM).With positive SSTA over the SCS-TEIO,the anomalous cyclones appear over both sides of the equator at low layer,which weakens the Somali and Australian cross-equatorial SW flow. The anomalous anticyclone in the east of Phillips strengthens the subtropical high with its ridge southwestward shifted.The anomalous anticyclones over both sides of equator at high layer strengthen the South Asia high,thus weaken the SCSM and delay its onset.With negative SSTA over the SCS-ETIO,the anomalous anticyclones appear over both sides of the equator at low layer,which strengthen the Australian but weaken the Somali cross-equatorial SW flow.The anomalous cyclone in northeast of Phillips will weaken the subtropical high.The stronger monsoon meridional circulation over the tropical western Pacific will strengthen the cross-equatorial southerly flow,and the anomalous cyclones over both sides of equator at high layer will weaken the South Asia high,hence strengthen the SCSM and advance its onset.
基金This work was supported by the National Key Basic Science Program in China (Grant No.1998040903) and Chinese NSF (Grant No 498
文摘The SST variation in the equatorial Indian Ocean is studied with special interest in analyzing its dipole oscillation feature. The dipole oscillation appears to be stronger in September-November and weaker in January-April with higher SST in the west region and lower SST in the east region as the positive phase and higher SST in the east region and lower SST in the west region as the negative phase. Generally, the amplitude of the positive phase is larger than the negative phase. The interannual variation (4-5 year period) and the interdecadal variation (25-30 year period) also exist in the dipole. The analyses also showed the significant impact of the Indian Ocean dipole on the Asian monsoon activity, because the lower tropospheric wind fields over the Southern Asia, the Tibetan high in the upper troposphere and the subtropical high over the northwestern Pacific are all related to the Indian Ocean dipole. On the other, the Indian Ocean dipole still has significant impact on atmospheric circulation and climate in North America and the southern Indian Ocean region (including Australia and South Africa).
基金the Climbing Programme"A"of SCSMEX under the Ministry of Science and Technology of Chinathe project ZKCX2-SW-210 under the Chinese Academy of Sciencesthe key project 40135020 of NSFC
文摘Several sensitivity experiments are done by using the T42L9 global spectral model developed by IAP for investigating the influence of sea surface temperature anomaly (SSTA) in different regions on the South China Sea Summer Monsoon (SCSM).It shows that when SSTA presents a La Nina pattern,the onset date of SCSM will be earlier and the convection in the South China Sea region will be consistently stronger,and vice versa.Specially,SSTA in the central and eastern Pacific plays a main role in the variation of the onset and the strength of SCSM.When SSTA of this area is lower,the onset of SCSM comes earlier,the strength of SCSM becomes stronger, otherwise,the conclusion is contrary.The influence of SSTA in the tropical West Pacific on the onset date of SCSM is not clear,but it strongly affects the strength of the monsoon.The warmer SST in this region will bring about a stronger SCSM,and vice versa.The relationship between SSTA in the tropical western Indian Ocean and SCSM has been investigated.It is found that the SSTA in this region can influence the onset of SCSM,and plays a role similar to the one in the eastern Pacific.The above results also reflect that the activity of SCSM has a close relationship with the El Nino or La Nina events.The onset and the strength change of the SCSM are obviously influenced by the heating status anomaly on the tropic Pacific through the Walker circulation.
