The latest dataset from the SCS(South China Sea)Monsoon Experiment is used to investigate the features of abrupt change in some meteorological elements before,during and after the summer monsoon's establishment in...The latest dataset from the SCS(South China Sea)Monsoon Experiment is used to investigate the features of abrupt change in some meteorological elements before,during and after the summer monsoon's establishment in 1998 and explore its onset characteristic process.We have arrived at a preliminary conclusion that the 1998 Asian summer monsoon is established first in the SCS as early as May 23,which is representative of the earliest indicator of the conversion from a winter into a summer monsoon situation in Asia;the continued retreat eastward of the western Pacific subtropical high from the SCS region has direct effect on the SCS summer monsoon establishment because the withdrawal favors the release of unstable energy,responsible for the sudden onset of the monsoon.Our tentative investigation indicates that the eastward extension of the westerly and rainfall band from the equatorial Indian Ocean into the Indo-China Peninsula and the southward spreading of an active South-China stationary front,acting as the interaction between mid and low latitude systems,are likely to be the characteristic events contributing to the subtropical high's eastward retreating and the summer monsoon's onset over the SCS.展开更多
The onset dates and intensities for the South China Sea (SCS) summer monsoon over the past 51 years are established using the reanalyzed gridpoint data of NCEP and SST data from 1950 to 2000.As is shown in the t test,...The onset dates and intensities for the South China Sea (SCS) summer monsoon over the past 51 years are established using the reanalyzed gridpoint data of NCEP and SST data from 1950 to 2000.As is shown in the t test,the activities of the SCS monsoon (including the dates of onset and intensities) experienced a significant interdecadal change in the mid-1970s.The monsoon activity is closely related with the anomalies of the general circulation in the mid- and higher-latitudes but it is not related with those of the SST in tropical oceans before 1975.After 1975,the onset is earlier and the intensity is weaker and the SST anomalies in the tropical Indian Ocean and the Pacific Ocean have significant impacts on the activity of the SCS summer monsoon.These significant changes are thought to be associated with the interdecadal variation of SST over the oceans.展开更多
By using the NCEP reanalysis data set in 1979-1995, the fluxes of the latent heat, the sensible heat and the net long-wave radiation in the South China Sea (SCS) are expanded by means of EOF in order to discuss the ba...By using the NCEP reanalysis data set in 1979-1995, the fluxes of the latent heat, the sensible heat and the net long-wave radiation in the South China Sea (SCS) are expanded by means of EOF in order to discuss the basic climatological features in the SCS. The detailed analysis shows that the air-sea heat exchanges in different SCS regions have different seasonal variations. The middle and the north of the SCS are the high value regions of the air-sea heat exchanges during the winter and the summer monsoon periods, respectively, the seasonal variations of air-sea heat exchanges in the south of the SCS are small. In addition, the proportions of different components in the total air-sea heat exchanges have different seasonal variations in different regions. The results show that the SCS monsoon and the air-sea heat exchanges in the SCS region are the accompaniments of each other, the great difference of the sensible heat flux between the Indochina Peninsula and the SCS before the SCS summer monsoon onset may be one of the triggers of the latter. There maintains a high value center of the sensible heat flux before the 13th dekad, its disappearing time consists with that of the summer monsoon onset. It means that as far as the SCS local conditions are concerned, the northwest of the Indochina Peninsula is probably a sensitive region to the SCS summer monsoon onset and the land may play a leading role in the SCS summer monsoon onset.展开更多
In this paper,some data observed during the Intensive Observation Period of the South China Sea Monsoon Experiment (IOP-SCSMEX) were analyzed.Based on the meteorological observation data,the sea surface heat flux is c...In this paper,some data observed during the Intensive Observation Period of the South China Sea Monsoon Experiment (IOP-SCSMEX) were analyzed.Based on the meteorological observation data,the sea surface heat flux is calculated by the iterative flux-profile method.Based on the CTD (conductivity-temperature-depth) data the thermal and dynamical features of the mixed layer and its relation with the onset of the SCS summer monsoon were also analyzed.There are the thin barrier layers in the SCS in May and June,During the onset of summer monsoon in 1998,the barrier layer became thicker (about 28 m) than before monsoon onset (its thickness is 2-5 m) in north of the SCS.During May and June 1998,the variations of the upper mixed layer temperature and depth could be divided into three stages:before the summer monsoon onset,the onset period and after onset.There is not only difference of the thermal and dynamical features in the three stages,but also difference in the north and south observation points.The numerical simulation and experiment results to use the turbulence kinetic Energy (TKE) model are introduced in the two observation points.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
基金-Research on the Formation Mechanism and Prediction Theory of Severe Climate Disasters in China(G1998040900-Part 1)and China Scaling Project A"SCSMEX".
文摘The latest dataset from the SCS(South China Sea)Monsoon Experiment is used to investigate the features of abrupt change in some meteorological elements before,during and after the summer monsoon's establishment in 1998 and explore its onset characteristic process.We have arrived at a preliminary conclusion that the 1998 Asian summer monsoon is established first in the SCS as early as May 23,which is representative of the earliest indicator of the conversion from a winter into a summer monsoon situation in Asia;the continued retreat eastward of the western Pacific subtropical high from the SCS region has direct effect on the SCS summer monsoon establishment because the withdrawal favors the release of unstable energy,responsible for the sudden onset of the monsoon.Our tentative investigation indicates that the eastward extension of the westerly and rainfall band from the equatorial Indian Ocean into the Indo-China Peninsula and the southward spreading of an active South-China stationary front,acting as the interaction between mid and low latitude systems,are likely to be the characteristic events contributing to the subtropical high's eastward retreating and the summer monsoon's onset over the SCS.
基金National Climbing Project A-South China Sea Monsoon ExperimentNational Key Program for Developing Basic Sciences (G1998040900)
文摘The onset dates and intensities for the South China Sea (SCS) summer monsoon over the past 51 years are established using the reanalyzed gridpoint data of NCEP and SST data from 1950 to 2000.As is shown in the t test,the activities of the SCS monsoon (including the dates of onset and intensities) experienced a significant interdecadal change in the mid-1970s.The monsoon activity is closely related with the anomalies of the general circulation in the mid- and higher-latitudes but it is not related with those of the SST in tropical oceans before 1975.After 1975,the onset is earlier and the intensity is weaker and the SST anomalies in the tropical Indian Ocean and the Pacific Ocean have significant impacts on the activity of the SCS summer monsoon.These significant changes are thought to be associated with the interdecadal variation of SST over the oceans.
文摘By using the NCEP reanalysis data set in 1979-1995, the fluxes of the latent heat, the sensible heat and the net long-wave radiation in the South China Sea (SCS) are expanded by means of EOF in order to discuss the basic climatological features in the SCS. The detailed analysis shows that the air-sea heat exchanges in different SCS regions have different seasonal variations. The middle and the north of the SCS are the high value regions of the air-sea heat exchanges during the winter and the summer monsoon periods, respectively, the seasonal variations of air-sea heat exchanges in the south of the SCS are small. In addition, the proportions of different components in the total air-sea heat exchanges have different seasonal variations in different regions. The results show that the SCS monsoon and the air-sea heat exchanges in the SCS region are the accompaniments of each other, the great difference of the sensible heat flux between the Indochina Peninsula and the SCS before the SCS summer monsoon onset may be one of the triggers of the latter. There maintains a high value center of the sensible heat flux before the 13th dekad, its disappearing time consists with that of the summer monsoon onset. It means that as far as the SCS local conditions are concerned, the northwest of the Indochina Peninsula is probably a sensitive region to the SCS summer monsoon onset and the land may play a leading role in the SCS summer monsoon onset.
基金the SCSMEX of the Climbing Program Athe National Key Program for Developing Basic Science (G19992043807) under the Ministry of Science and Technology
文摘In this paper,some data observed during the Intensive Observation Period of the South China Sea Monsoon Experiment (IOP-SCSMEX) were analyzed.Based on the meteorological observation data,the sea surface heat flux is calculated by the iterative flux-profile method.Based on the CTD (conductivity-temperature-depth) data the thermal and dynamical features of the mixed layer and its relation with the onset of the SCS summer monsoon were also analyzed.There are the thin barrier layers in the SCS in May and June,During the onset of summer monsoon in 1998,the barrier layer became thicker (about 28 m) than before monsoon onset (its thickness is 2-5 m) in north of the SCS.During May and June 1998,the variations of the upper mixed layer temperature and depth could be divided into three stages:before the summer monsoon onset,the onset period and after onset.There is not only difference of the thermal and dynamical features in the three stages,but also difference in the north and south observation points.The numerical simulation and experiment results to use the turbulence kinetic Energy (TKE) model are introduced in the two observation points.
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.
