The persistence barrier refers to the lag correlation of sea surface temperature anomalies （SSTA） showing a rapid and significant decline in a specific season, regardless of the starting month. This implies that the...The persistence barrier refers to the lag correlation of sea surface temperature anomalies （SSTA） showing a rapid and significant decline in a specific season, regardless of the starting month. This implies that there is a decrease in forecast skill for SSTA in this specific season. This paper investigates the possible causes for the persistence barrier of SSTA in the South China Sea （SCS） and its adjacent regions from the perspective of interannuallinterdecadal time scales. The results show that the persistence barrier of SSTA exists not only in the SCS, but also in the vicinity of Indonesia south of the equator. The SCS barrier occurs around October-November, while the occurrence of the barrier in the Indonesia region is around November-December. For these two regions, the occurrence of the persistence barrier is closely associated with the interdecadal variability of SSTA, as well as the interannual variability. The persistence barriers in the SCS and the Indonesia region do not exist alone if the interdecadal variability is not considered, because SSTA have a short memory of less than 4 months, regardless of the starting month. Moreover, the influence of the interdecadal variability of SSTA on the persistence barrier of SSTA in the SCS and the Indonesia region may be associated with SSTA in the Indian Ocean and the western Pacific, but is not closely associated with the Pacific Decadal Oscillation. However, compared with the spring persistence barrier （SPB） of ENSO, the close relationship between the persistence barriers in the SCS and the Indonesia region and the interdecadal variability is unique, since the ENSO SPB is not significantly affected by such variability. In addition, although the persistence barriers in both the SCS and the Indonesia region are quite obvious in strong ENSO cases, the interdecadal variability of SSTA also plays a non-negligible role in this relationship.展开更多
The linear regression and horizontally stepwise correction are conducted on the observational data from AMSU-A L1 B of NOAA polar orbit satellite to invert a 40-layers(from 1,000 h Pa to 0.1 h Pa) dataset of atmospher...The linear regression and horizontally stepwise correction are conducted on the observational data from AMSU-A L1 B of NOAA polar orbit satellite to invert a 40-layers(from 1,000 h Pa to 0.1 h Pa) dataset of atmospheric temperature with a horizontal resolution of 0.5°×0.5° after the correction of satellite antenna pattern and limb adjustment. Case study shows that the inversion data of temperature can reveal the detail structure of warm core in tropical cyclone. We choose two categories of tropical depressions(TDs) over the South China Sea, including the non-developing TDs and developing TDs. Both of them are developed downward from the middle and upper level to the lower level. Comparison between the evolutions of warm core in the two categories of TDs indicates that the warm core is developed downward from the middle and upper troposphere to the sea surface in all the downward-developing TDs. The difference is that in the group of further developing TDs, the warm core in the upper troposphere is intensified suddenly when it is extending to the sea surface. The warm core in the upper and lower troposphere is strengthened in a meantime. But the similar feature is not observed in the non-developing TDs. Then it may be helpful to judge the TD development by monitoring the change in its warm-core structure.展开更多
In early 2008, a persistent cold and snowy weather process occurred in South China. Severe freezing rain （FR） and blizzards hit the region, which was not seen in the past 50 years. This work studied the disaster at ...In early 2008, a persistent cold and snowy weather process occurred in South China. Severe freezing rain （FR） and blizzards hit the region, which was not seen in the past 50 years. This work studied the disaster at its most severe stage （25 January 2 February 2008） and addressed the reason for the occurrence of three rainfall types and particularly the FR that resulted from the temperature inversion and low sur- face temperature. Evidence suggests that the south-to-north distribution of rainfall, FR, and snowfall was determined by the surface temperature conditions and the stratification features of the northward-tilting front in the mid-lower troposphere over different parts of South China. Under the above frontal conditions, the temperature inversion in the mid-lower troposphere and the cold ground temperature took place and the FR formed. The temperature layer （〉 0℃） inside the inversion in this region depended on necessary intensity, depth, and height of the inversion, i.e., the depth of the inversion can be neither too thick or low nor too thin or high. For those too thick and low （too thin and high） inversions, the precipitation fell as rain （snow and ice pellets）. In the early 2008 case, the 0 6℃ layer occupied 650-850 hPa, below which was the sub-freezing level with temperature 〈 0℃. With the presence of the low sub-freezing level, FR or ice damage could occur even at the 0-1℃ surface temperature condition. Besides, even in the absence of a suitable inversion, a low ground temperature might have made ice-covered water and supercooled drops or water from melted ice freeze rapidly into ice at the surface, and the ground ice maintained and accumulated, which resulted in the severe disaster.展开更多
This study investigates the relationship between subseasonal variations of the circulation and sea surface temperature（SST） over the South China–East Asian coastal region（EACR） in association with the persistent ...This study investigates the relationship between subseasonal variations of the circulation and sea surface temperature（SST） over the South China–East Asian coastal region（EACR） in association with the persistent heavy rainfall（PHR） events over South China during May–August through statistical analysis. Based on the intensity threshold and duration criterion of the daily rainfall, a total of 63 May–June（MJ） and 59July–August（JA） PHR events are selected over South China from 1979 to 2011. The lower-level circulation anomalies on subseasonal timescale exhibit an anomalous cyclone over South China and an anomalous anticyclone shaped like a tongue over the South China Sea（SCS） during the PHR events for MJ group.The anomalous cyclone over South China in MJ originates from low-value systems in the mid-high latitudes before the rainfall. The anomalous anticyclone over the SCS is due to the westward extension of the western Pacific subtropical high（WPSH） and the southeastward propagation of the anomalous anticyclone from South China before the rainfall. For JA group, the lower-level anomalous circulation pattern is similar to that for MJ over the South China–EACR, but with di？erent features of propagation. The subseasonal anomalous anticyclone is also related to the westward stretch of the WPSH, while the anomalous cyclone is traced back to the weak anomalous cyclone over the Philippine Sea several days before the rainfall events.Positive SST anomaly（SSTA） is observed over the SCS and the Philippine Sea during the MJ PHR events on the subseasonal timescale. It is closely linked with the variation of local anomalous anticyclone. In contrast, negative SSTA occupies the South China coastal region for the JA PHR events, and it is driven by the anomalous cyclone which propagates northwestward from the Philippine Sea. The subseasonal positive（negative） SSTAs are generated via the local processes of above（below）-normal incident solar radiation and below（above）-normal latent heat fluxes. The possible role of the subseasonal SSTA in the local convective instability is also analyzed in this study.展开更多
The comparison analyses between two tropical depressions in the South China Sea are completed by numerical ex- periments with a limited area model developed in Guangzhou Institute of Tropical and Oceanic Meteorology. ...The comparison analyses between two tropical depressions in the South China Sea are completed by numerical ex- periments with a limited area model developed in Guangzhou Institute of Tropical and Oceanic Meteorology. One of the depressions develops and finally becomes a typhoon within 24 hours of the analyzing period (defined as DVD hereafter), and the other not (defined as UNDVD) The analyses show that their initial structures of temperature, humidity, pres- sure. wind and stability are obviously different from each other. There are a very deep wet layer and a clear warm-cored structure in the mid-lower troposphere in the depression area in the DVD case, but with the warm core in the upper rather than lower troposphere arid a very shallow wet layer in the lower troposphere in the depression area in the UNDVD case. The developing and non-developing processes are successfully simulated by the model, showing that the CISK mechanism plays the most important role in the development of SCSDs (Tropical Depressions in the South China Sea). Several numerical experiments show that the structures of humidity and temperature in the depression area have important effect on the development of SCSDs. It is favourable to the development of SCSDs when a very deep wet layer exists in the mid-lower troposphere or a warm-cored structure exists in the mid-lower troposphere instead of in upper troposphere, and conversely, it is unfavourable to the development of SCSDs when the wet layer is very shallow in the lower troposphere or the warm-cored structure is in the upper troposphere rather than in mid-lower troposphere. The structures of stability for each case are also analysed, which shows evident differences between the two cases, with a deeper instability layer in the DVD case and a shallower one in the UNDVD case. Finally, the sensitivity of the devel- opment of the SCSDs to the vertical structures of humidity and temperature in the depression area is discussed.展开更多
The planktonic foraminiferal faunal census of core MD 05-2894 (7°2.25′N, 111°33.11′E, water depth 1982 m), retrieved from the southern South China Sea (SCS) during the "Marco Polo" cruise in 2005...The planktonic foraminiferal faunal census of core MD 05-2894 (7°2.25′N, 111°33.11′E, water depth 1982 m), retrieved from the southern South China Sea (SCS) during the "Marco Polo" cruise in 2005, was performed to investigate the abundance changes of a subsurface dweller, Pulleniatina obliquiloculata. The results display that the abundance of P. obliquiloculata nearly declines to zero during 16.0―14.9 ka, corresponding to the Heinrich 1 (H1) cold interval. The unexpected decrease of P. obliquiloculata occurs in the adjacent cores, roughly between 17 and 14.8 ka based on the previous studies. Accordingly, the Pulleniatina Minimum Event in the last deglaciation can serve as a good stratigraphical indicator, at least in the southern SCS. To further explore the changes of sea surface temperature (SST) and subsurface seawater temperature (SSST), we made parallel Mg/Ca measurements on surface dweller Globigerinoides ruber and subsurface dweller P. obliquiloculata tests. Since the last deglaciation, the SSTs show a continuous increasing trend towards the late Holocene, while the warming of the subsurface water is punctuated by a 2℃-cooling interval across the deglacial Pulleniatina Minimum Event. Both increased δ18O differences between G. ruber and P. obliquiloculata, and increased temperature differences between surface and subsurface water suggest a shoaling of the mixed layer during the deglacial Pulleniatina Minimum Event. Therefore, we consider that the significant changes in the upper ocean structure are responsible for the Pulleniatina Minimum Event during the last deglaciation in the southern SCS.展开更多
基金supported by the 973program(2006CB403600)the National Natural Science Foundation of China(Grant No.40821092)the Project under Grant GYHY200706005
文摘The persistence barrier refers to the lag correlation of sea surface temperature anomalies （SSTA） showing a rapid and significant decline in a specific season, regardless of the starting month. This implies that there is a decrease in forecast skill for SSTA in this specific season. This paper investigates the possible causes for the persistence barrier of SSTA in the South China Sea （SCS） and its adjacent regions from the perspective of interannuallinterdecadal time scales. The results show that the persistence barrier of SSTA exists not only in the SCS, but also in the vicinity of Indonesia south of the equator. The SCS barrier occurs around October-November, while the occurrence of the barrier in the Indonesia region is around November-December. For these two regions, the occurrence of the persistence barrier is closely associated with the interdecadal variability of SSTA, as well as the interannual variability. The persistence barriers in the SCS and the Indonesia region do not exist alone if the interdecadal variability is not considered, because SSTA have a short memory of less than 4 months, regardless of the starting month. Moreover, the influence of the interdecadal variability of SSTA on the persistence barrier of SSTA in the SCS and the Indonesia region may be associated with SSTA in the Indian Ocean and the western Pacific, but is not closely associated with the Pacific Decadal Oscillation. However, compared with the spring persistence barrier （SPB） of ENSO, the close relationship between the persistence barriers in the SCS and the Indonesia region and the interdecadal variability is unique, since the ENSO SPB is not significantly affected by such variability. In addition, although the persistence barriers in both the SCS and the Indonesia region are quite obvious in strong ENSO cases, the interdecadal variability of SSTA also plays a non-negligible role in this relationship.
基金National Natural Science Foundation of China(40875026,91015011)Project for Natural Science Foundation Teams of Guangdong Province(8351030101000002)Specialized Program for Social Welfare Industries(Meteorological Sector)(GYHY201106036)
文摘The linear regression and horizontally stepwise correction are conducted on the observational data from AMSU-A L1 B of NOAA polar orbit satellite to invert a 40-layers(from 1,000 h Pa to 0.1 h Pa) dataset of atmospheric temperature with a horizontal resolution of 0.5°×0.5° after the correction of satellite antenna pattern and limb adjustment. Case study shows that the inversion data of temperature can reveal the detail structure of warm core in tropical cyclone. We choose two categories of tropical depressions(TDs) over the South China Sea, including the non-developing TDs and developing TDs. Both of them are developed downward from the middle and upper level to the lower level. Comparison between the evolutions of warm core in the two categories of TDs indicates that the warm core is developed downward from the middle and upper troposphere to the sea surface in all the downward-developing TDs. The difference is that in the group of further developing TDs, the warm core in the upper troposphere is intensified suddenly when it is extending to the sea surface. The warm core in the upper and lower troposphere is strengthened in a meantime. But the similar feature is not observed in the non-developing TDs. Then it may be helpful to judge the TD development by monitoring the change in its warm-core structure.
基金the Open Fund of Jiangsu Provincial Meteorological Bureau under Grant No.200702.
文摘In early 2008, a persistent cold and snowy weather process occurred in South China. Severe freezing rain （FR） and blizzards hit the region, which was not seen in the past 50 years. This work studied the disaster at its most severe stage （25 January 2 February 2008） and addressed the reason for the occurrence of three rainfall types and particularly the FR that resulted from the temperature inversion and low sur- face temperature. Evidence suggests that the south-to-north distribution of rainfall, FR, and snowfall was determined by the surface temperature conditions and the stratification features of the northward-tilting front in the mid-lower troposphere over different parts of South China. Under the above frontal conditions, the temperature inversion in the mid-lower troposphere and the cold ground temperature took place and the FR formed. The temperature layer （〉 0℃） inside the inversion in this region depended on necessary intensity, depth, and height of the inversion, i.e., the depth of the inversion can be neither too thick or low nor too thin or high. For those too thick and low （too thin and high） inversions, the precipitation fell as rain （snow and ice pellets）. In the early 2008 case, the 0 6℃ layer occupied 650-850 hPa, below which was the sub-freezing level with temperature 〈 0℃. With the presence of the low sub-freezing level, FR or ice damage could occur even at the 0-1℃ surface temperature condition. Besides, even in the absence of a suitable inversion, a low ground temperature might have made ice-covered water and supercooled drops or water from melted ice freeze rapidly into ice at the surface, and the ground ice maintained and accumulated, which resulted in the severe disaster.
基金Supported by the National (Key) Basic Research and Development (973) Program of China (2012CB417203)China Meteorological Administration Special Public Welfare Research Fund (GYHY201106017)
文摘This study investigates the relationship between subseasonal variations of the circulation and sea surface temperature（SST） over the South China–East Asian coastal region（EACR） in association with the persistent heavy rainfall（PHR） events over South China during May–August through statistical analysis. Based on the intensity threshold and duration criterion of the daily rainfall, a total of 63 May–June（MJ） and 59July–August（JA） PHR events are selected over South China from 1979 to 2011. The lower-level circulation anomalies on subseasonal timescale exhibit an anomalous cyclone over South China and an anomalous anticyclone shaped like a tongue over the South China Sea（SCS） during the PHR events for MJ group.The anomalous cyclone over South China in MJ originates from low-value systems in the mid-high latitudes before the rainfall. The anomalous anticyclone over the SCS is due to the westward extension of the western Pacific subtropical high（WPSH） and the southeastward propagation of the anomalous anticyclone from South China before the rainfall. For JA group, the lower-level anomalous circulation pattern is similar to that for MJ over the South China–EACR, but with di？erent features of propagation. The subseasonal anomalous anticyclone is also related to the westward stretch of the WPSH, while the anomalous cyclone is traced back to the weak anomalous cyclone over the Philippine Sea several days before the rainfall events.Positive SST anomaly（SSTA） is observed over the SCS and the Philippine Sea during the MJ PHR events on the subseasonal timescale. It is closely linked with the variation of local anomalous anticyclone. In contrast, negative SSTA occupies the South China coastal region for the JA PHR events, and it is driven by the anomalous cyclone which propagates northwestward from the Philippine Sea. The subseasonal positive（negative） SSTAs are generated via the local processes of above（below）-normal incident solar radiation and below（above）-normal latent heat fluxes. The possible role of the subseasonal SSTA in the local convective instability is also analyzed in this study.
文摘The comparison analyses between two tropical depressions in the South China Sea are completed by numerical ex- periments with a limited area model developed in Guangzhou Institute of Tropical and Oceanic Meteorology. One of the depressions develops and finally becomes a typhoon within 24 hours of the analyzing period (defined as DVD hereafter), and the other not (defined as UNDVD) The analyses show that their initial structures of temperature, humidity, pres- sure. wind and stability are obviously different from each other. There are a very deep wet layer and a clear warm-cored structure in the mid-lower troposphere in the depression area in the DVD case, but with the warm core in the upper rather than lower troposphere arid a very shallow wet layer in the lower troposphere in the depression area in the UNDVD case. The developing and non-developing processes are successfully simulated by the model, showing that the CISK mechanism plays the most important role in the development of SCSDs (Tropical Depressions in the South China Sea). Several numerical experiments show that the structures of humidity and temperature in the depression area have important effect on the development of SCSDs. It is favourable to the development of SCSDs when a very deep wet layer exists in the mid-lower troposphere or a warm-cored structure exists in the mid-lower troposphere instead of in upper troposphere, and conversely, it is unfavourable to the development of SCSDs when the wet layer is very shallow in the lower troposphere or the warm-cored structure is in the upper troposphere rather than in mid-lower troposphere. The structures of stability for each case are also analysed, which shows evident differences between the two cases, with a deeper instability layer in the DVD case and a shallower one in the UNDVD case. Finally, the sensitivity of the devel- opment of the SCSDs to the vertical structures of humidity and temperature in the depression area is discussed.
基金Supported by National Basic Research Program of China (Grant No.2007CB815900)National Natural Science Foundation of China (Grant No. 40621063)China Ocean Mineral Resources Research and Development Association (Grant No. DY 115-01-2-3)
文摘The planktonic foraminiferal faunal census of core MD 05-2894 (7°2.25′N, 111°33.11′E, water depth 1982 m), retrieved from the southern South China Sea (SCS) during the "Marco Polo" cruise in 2005, was performed to investigate the abundance changes of a subsurface dweller, Pulleniatina obliquiloculata. The results display that the abundance of P. obliquiloculata nearly declines to zero during 16.0―14.9 ka, corresponding to the Heinrich 1 (H1) cold interval. The unexpected decrease of P. obliquiloculata occurs in the adjacent cores, roughly between 17 and 14.8 ka based on the previous studies. Accordingly, the Pulleniatina Minimum Event in the last deglaciation can serve as a good stratigraphical indicator, at least in the southern SCS. To further explore the changes of sea surface temperature (SST) and subsurface seawater temperature (SSST), we made parallel Mg/Ca measurements on surface dweller Globigerinoides ruber and subsurface dweller P. obliquiloculata tests. Since the last deglaciation, the SSTs show a continuous increasing trend towards the late Holocene, while the warming of the subsurface water is punctuated by a 2℃-cooling interval across the deglacial Pulleniatina Minimum Event. Both increased δ18O differences between G. ruber and P. obliquiloculata, and increased temperature differences between surface and subsurface water suggest a shoaling of the mixed layer during the deglacial Pulleniatina Minimum Event. Therefore, we consider that the significant changes in the upper ocean structure are responsible for the Pulleniatina Minimum Event during the last deglaciation in the southern SCS.
