Datasets of equivalent temperature of black body (TBB) and sea surface temperature (SST)ranging from 1980 to 1997 are used to diagnose and analyze the characteristics of frequency spectrum andstrength of intraseasonal...Datasets of equivalent temperature of black body (TBB) and sea surface temperature (SST)ranging from 1980 to 1997 are used to diagnose and analyze the characteristics of frequency spectrum andstrength of intraseasonal variation of convection. The relationship between the strength of intraseasonaloscillation of convection, strength of convection itself and SST in the South China Sea (SCS) is studied. It isshown that, there are distinguishable annual, interannual and interdecadal variations in both strength andfrequency spectrum of intraseasonal variation of convection in SCS. There are connections between strength ofconvection, strength of ISO1 in the summer half (s.h.) year and SST in ensuing winter half (w.h.) year in SCS.The strong (weak) convection and strong (weak) ISO1 are associated with negative (positive) bias of SST inensuing w.h. year in SCS.展开更多
This study utilizes daily Asian Precipitation–Highly-Resolved Observational Data Integration Towards Evaluation（APHRODITE）gridded rainfall and the U.S.National Centers for Environmental PredictionDepartment of Ener...This study utilizes daily Asian Precipitation–Highly-Resolved Observational Data Integration Towards Evaluation（APHRODITE）gridded rainfall and the U.S.National Centers for Environmental PredictionDepartment of Energy reanalysis II products to examine the intraseasonal oscillations（ISOs）of rainfall over Eastern China during each summer of 1996,2002,and 2006.These three cases represent three typical spatial patterns of intraseasonal rainfall anomalies over Eastern China,with the strongest intraseasonal rainfall occurring over the middle and lower Yangtze Basin,southern Yangtze Basin,and Southeast China,respectively.The intraseasonal rainfall anomalies over Eastern China are dominated by both 30–60-and 10–20-day ISOs in each summer and are further modulated by the boreal summer ISOs（BSISOs）over the entire Asian summer monsoon region.The objective of this study is thus to apply the Bayesian wavelet-banding（WB）scheme to predicting intraseasonal rainfall over Eastern China.Several key factors associated with BSISOs are selected as predictors to experimentally develop a 15-day-lead statistical forecast.The forecast results show promise for the intraseasonal rainfall anomalies over Eastern China.Correlations generally greater than or equal to 0.6 are noted between the observed and predicted ISOs of rainfall over the major intraseasonal activity centers during each of the three summers.Such a high forecasting skill on intraseasonal timescales over various areas in Eastern China demonstrates the general usefulness of the WB scheme.展开更多
During the boreal winter,abundant persistent heavy rainfall(PHR)amount and significant rainfall variability at subseasonal timescale are generally observed over the southern sector of East China,where the large-scale ...During the boreal winter,abundant persistent heavy rainfall(PHR)amount and significant rainfall variability at subseasonal timescale are generally observed over the southern sector of East China,where the large-scale circulation and moisture transport are tightly connected with the equatorial Madden-Julian Oscillation(MJO).As the MJO convections occur over the equatorial Indian Ocean(MJO phases 1-4),the low-level moisture convergence is enhanced over southern China(SC,108°-120°E,21°-26°N)with the divergence to the north.Thus,a positive anomaly of PHR amount appears in SC but a negative anomaly of PHR amount is seen in the Yangtze River valley(YR,113°-122°E,28°-30°N).In contrast,the divergence(convergence)of moisture flux anomalies in the SC(YR)associated with the western equatorial Pacific MJO convections(phases 5-8)limits(benefits)the occurrence of PHR in the SC(YR).The wintertime PHR over southern China is found to undergo a long-term change over the past three decades(1979-2011)with a decreasing(an increasing)trend of PHR amount in the SC(YR).The change in PHR amount occurs consistently with the decadal change in MJO activity.In the earlier decade(1979-1994,E1),the active Indian Ocean(western Pacific)MJO events appeared more frequently while they became less frequent in the recent decade(1995-2011,E2).Accordingly,the Indian Ocean(western Pacific)MJO-related moisture convergence(divergence)anomalies in the SC tend to be weakened(enhanced),contributing to the decrease in PHR amount over the SC in the recent decade.展开更多
The authors investigate the dominant mode of climatological intraseasonal oscillation(CISO) of surface air temperature(SAT) and rainfall in China, and discuss the linkage of cold and wet climate in South China(SC) wit...The authors investigate the dominant mode of climatological intraseasonal oscillation(CISO) of surface air temperature(SAT) and rainfall in China, and discuss the linkage of cold and wet climate in South China(SC) with the Arctic circulation regime during the cold season(from November to March). Results show that a positive CISO displays a cold-dry climate in North China,whereas a cold-wet pattern prevails in SC with a quasi-30-day oscillation during the peak winter season. In SC, the intraseasonal variability of SAT plays a leading role, altering the cold-wet climate by the southward shift of a cold front. Evidence shows that the circulation regime related to the cold and wet climate in SC is mainly regulated by a pair of propagating ISO modes at the500-hPa geopotential height in the negative phase of Arctic Oscillation. It is demonstrated that the local cyclonic wave activity enhances the southward movement of the Siberian high, favoring an unstable atmosphere and resulting in the cold-wet climate over SC. Therefore, the cold-air activity acts as a precursor for subseasonal rainfall forecasting in SC.展开更多
Precipitation events spanning multiple days may have consequences different from those limited to a single day.In the present paper,the authors analyze circulation anomalies and precursory signals associated with long...Precipitation events spanning multiple days may have consequences different from those limited to a single day.In the present paper,the authors analyze circulation anomalies and precursory signals associated with long-duration（over 14 days） summer precipitation events over southern China.The results show that the over-14-day precipitation events are induced by an anomalous lowertropospheric（850-hPa） cyclone over the South China Sea（SCS） and southern China.The anomalous westerly winds to the south of the anomalous cyclone can be traced to north of New Guinea 30 days before.To the north of anomalous westerly winds,anomalous easterly winds appear later.The anomalous westerly and easterly winds form a cyclonic anomaly,moving northward and slightly westward during the following days and eventually controlling the SCS and southern China.The northward movement of anomalous westerly and easterly winds can also be found in the 30-60-day filtered wind field.This implies that the northward propagating 30-60-day intraseasonal oscillation from the equatorial western Pacific has an important contribution to over-14-day precipitation events over southern China.展开更多
This study investigates whether and how the Madden-Julian Oscillation(MJO)influences persistent extreme cold events(PECEs),a major type of natural disaster in boreal winter,over Northeast China.Significantly increased...This study investigates whether and how the Madden-Julian Oscillation(MJO)influences persistent extreme cold events(PECEs),a major type of natural disaster in boreal winter,over Northeast China.Significantly increased occurrence probabilities of PECEs over Northeast China are observed in phases 3 and 5 of the MJO,when MJOrelated convection is located over the eastern Indian Ocean and the western Pacific,respectively.Using the temperature tendency equation,it is found that the physical processes resulting in the cooling effects required for the occurrence of PECEs are distinct in the two phases of the MJO when MJO-related convection is consistently located over the warm pool area.The PECEs in phase 3 of the MJO mainly occur as a result of adiabatic cooling associated with ascending motion of the low-pressure anomaly over Northeast Asia.The cooling effect associated with phase 5 is stronger and longer than that in phase 3.The PECEs associated with phase 5 of the MJO are linked with the northwesterly cold advection of a cyclonic anomaly,which is part of the subtropical Rossby wave train induced by MJO-related convection in the tropical western Pacific.展开更多
基金"Research on the monitoring and service of South China Sea monsoons", a public welfareproject from the Ministry of Science and Technology (2002RKT01)"Response of interdecadal changes of SouthChina Sea summer monsoon to global change", a project from the Natural Science Foundation of China(902110110)
文摘Datasets of equivalent temperature of black body (TBB) and sea surface temperature (SST)ranging from 1980 to 1997 are used to diagnose and analyze the characteristics of frequency spectrum andstrength of intraseasonal variation of convection. The relationship between the strength of intraseasonaloscillation of convection, strength of convection itself and SST in the South China Sea (SCS) is studied. It isshown that, there are distinguishable annual, interannual and interdecadal variations in both strength andfrequency spectrum of intraseasonal variation of convection in SCS. There are connections between strength ofconvection, strength of ISO1 in the summer half (s.h.) year and SST in ensuing winter half (w.h.) year in SCS.The strong (weak) convection and strong (weak) ISO1 are associated with negative (positive) bias of SST inensuing w.h. year in SCS.
基金jointly supported by the National Basic Research Program of China[grant numbers 2014CB953902,2012CB417203,and 2012CB955202]the Priority Research Program of the Chinese Academy of Sciences[grant number XDA11010402]+2 种基金the National Natural Science Foundation of China[grant numbers 4117505941375087and 91537103]
文摘This study utilizes daily Asian Precipitation–Highly-Resolved Observational Data Integration Towards Evaluation（APHRODITE）gridded rainfall and the U.S.National Centers for Environmental PredictionDepartment of Energy reanalysis II products to examine the intraseasonal oscillations（ISOs）of rainfall over Eastern China during each summer of 1996,2002,and 2006.These three cases represent three typical spatial patterns of intraseasonal rainfall anomalies over Eastern China,with the strongest intraseasonal rainfall occurring over the middle and lower Yangtze Basin,southern Yangtze Basin,and Southeast China,respectively.The intraseasonal rainfall anomalies over Eastern China are dominated by both 30–60-and 10–20-day ISOs in each summer and are further modulated by the boreal summer ISOs（BSISOs）over the entire Asian summer monsoon region.The objective of this study is thus to apply the Bayesian wavelet-banding（WB）scheme to predicting intraseasonal rainfall over Eastern China.Several key factors associated with BSISOs are selected as predictors to experimentally develop a 15-day-lead statistical forecast.The forecast results show promise for the intraseasonal rainfall anomalies over Eastern China.Correlations generally greater than or equal to 0.6 are noted between the observed and predicted ISOs of rainfall over the major intraseasonal activity centers during each of the three summers.Such a high forecasting skill on intraseasonal timescales over various areas in Eastern China demonstrates the general usefulness of the WB scheme.
基金supported by the National Key R&D Program of China [grant number 2018YFC1505804]
文摘During the boreal winter,abundant persistent heavy rainfall(PHR)amount and significant rainfall variability at subseasonal timescale are generally observed over the southern sector of East China,where the large-scale circulation and moisture transport are tightly connected with the equatorial Madden-Julian Oscillation(MJO).As the MJO convections occur over the equatorial Indian Ocean(MJO phases 1-4),the low-level moisture convergence is enhanced over southern China(SC,108°-120°E,21°-26°N)with the divergence to the north.Thus,a positive anomaly of PHR amount appears in SC but a negative anomaly of PHR amount is seen in the Yangtze River valley(YR,113°-122°E,28°-30°N).In contrast,the divergence(convergence)of moisture flux anomalies in the SC(YR)associated with the western equatorial Pacific MJO convections(phases 5-8)limits(benefits)the occurrence of PHR in the SC(YR).The wintertime PHR over southern China is found to undergo a long-term change over the past three decades(1979-2011)with a decreasing(an increasing)trend of PHR amount in the SC(YR).The change in PHR amount occurs consistently with the decadal change in MJO activity.In the earlier decade(1979-1994,E1),the active Indian Ocean(western Pacific)MJO events appeared more frequently while they became less frequent in the recent decade(1995-2011,E2).Accordingly,the Indian Ocean(western Pacific)MJO-related moisture convergence(divergence)anomalies in the SC tend to be weakened(enhanced),contributing to the decrease in PHR amount over the SC in the recent decade.
基金jointly supported by the National Natural Science Foundation of China [grant numbers 41475057,41775052,and41505049]the Special Fund for Public Welfare Industry [grant number GYHY20140619]+1 种基金the Basic Scientific Research and Operation Foundation of CAMS [grant numbers 2018Z006 and2017R001]the Jiangsu Collaborative Innovation Center for Climate Change
文摘The authors investigate the dominant mode of climatological intraseasonal oscillation(CISO) of surface air temperature(SAT) and rainfall in China, and discuss the linkage of cold and wet climate in South China(SC) with the Arctic circulation regime during the cold season(from November to March). Results show that a positive CISO displays a cold-dry climate in North China,whereas a cold-wet pattern prevails in SC with a quasi-30-day oscillation during the peak winter season. In SC, the intraseasonal variability of SAT plays a leading role, altering the cold-wet climate by the southward shift of a cold front. Evidence shows that the circulation regime related to the cold and wet climate in SC is mainly regulated by a pair of propagating ISO modes at the500-hPa geopotential height in the negative phase of Arctic Oscillation. It is demonstrated that the local cyclonic wave activity enhances the southward movement of the Siberian high, favoring an unstable atmosphere and resulting in the cold-wet climate over SC. Therefore, the cold-air activity acts as a precursor for subseasonal rainfall forecasting in SC.
基金supported by the National Natural Science Foundation of China[grant numbers 41375090 and 41530425]the Basic Research Fund of the Chinese Academy of Meteorological Sciences[grant number 2015Z001]
文摘Precipitation events spanning multiple days may have consequences different from those limited to a single day.In the present paper,the authors analyze circulation anomalies and precursory signals associated with long-duration（over 14 days） summer precipitation events over southern China.The results show that the over-14-day precipitation events are induced by an anomalous lowertropospheric（850-hPa） cyclone over the South China Sea（SCS） and southern China.The anomalous westerly winds to the south of the anomalous cyclone can be traced to north of New Guinea 30 days before.To the north of anomalous westerly winds,anomalous easterly winds appear later.The anomalous westerly and easterly winds form a cyclonic anomaly,moving northward and slightly westward during the following days and eventually controlling the SCS and southern China.The northward movement of anomalous westerly and easterly winds can also be found in the 30-60-day filtered wind field.This implies that the northward propagating 30-60-day intraseasonal oscillation from the equatorial western Pacific has an important contribution to over-14-day precipitation events over southern China.
基金supported by the National Natural Science Foundation of China[grant number 42088101]the National Postdoctoral Program for Innovative Talent of China[grant number BX2021133]the China Postdoctoral Science Foundation of No.70 General Fund[grant number 2021M701753]。
文摘This study investigates whether and how the Madden-Julian Oscillation(MJO)influences persistent extreme cold events(PECEs),a major type of natural disaster in boreal winter,over Northeast China.Significantly increased occurrence probabilities of PECEs over Northeast China are observed in phases 3 and 5 of the MJO,when MJOrelated convection is located over the eastern Indian Ocean and the western Pacific,respectively.Using the temperature tendency equation,it is found that the physical processes resulting in the cooling effects required for the occurrence of PECEs are distinct in the two phases of the MJO when MJO-related convection is consistently located over the warm pool area.The PECEs in phase 3 of the MJO mainly occur as a result of adiabatic cooling associated with ascending motion of the low-pressure anomaly over Northeast Asia.The cooling effect associated with phase 5 is stronger and longer than that in phase 3.The PECEs associated with phase 5 of the MJO are linked with the northwesterly cold advection of a cyclonic anomaly,which is part of the subtropical Rossby wave train induced by MJO-related convection in the tropical western Pacific.
