EC-Earth3P-HR reproduces well the observed Boreal Summer Intraseasonal Oscillation(BSISO)and its impacts on tropical cyclone genesis(TCG)in the western North Pacific(WNP).Hence,the historical simulation(1950-1979)and ...EC-Earth3P-HR reproduces well the observed Boreal Summer Intraseasonal Oscillation(BSISO)and its impacts on tropical cyclone genesis(TCG)in the western North Pacific(WNP).Hence,the historical simulation(1950-1979)and future projection under the SSP5-8.5 scenario(2020-2049)in EC-Earth3P-HR are adopted to explore possible changes in the BSISO’s modification of WNP TCG under global warming to enhance the understanding of TC activities in the WNP.Results show that the BSISO circulation in the WNP shifts northeastward under global warming.This leads to enhanced convection in a northwest-southeast-oriented band crossing the WNP.Along the band,the BSISO-related TCG anomalies are enhanced.Analyses of genesis potential index show that changes in the BSISO-related mid-tropospheric relative humidity play the dominant role in modifying the BSISO’s impacts on WNP TCG under global warming.The enhanced BSISO convection in the band moistens the middle troposphere,which helps reduce the entrainment of generally dry mid-tropospheric air in the updrafts and the modification of the boundary layer by the downdraft of generally dry mid-tropospheric air,leading to enhanced TCG.展开更多
Based on daily precipitation data supplied by the Chinese meteorological administration,hourly reanalysis datasets provided by the ECMWF and daily outgoing long wave radiation supplied by the NOAA,the evolution regula...Based on daily precipitation data supplied by the Chinese meteorological administration,hourly reanalysis datasets provided by the ECMWF and daily outgoing long wave radiation supplied by the NOAA,the evolution regularity of continuous heavy precipitation over Southern China(SC)from April to June in 1979-2020 was systematically analyzed.The interaction between specific humidity and circulation field at the background-scale,the intra-seasonal-scale and the synoptic-scale,and its influence on persistent heavy precipitation over the SC during the April-June rainy season were quantitatively diagnosed and analyzed.The results are as follows.Persistent heavy rainfall events(PHREs)over the SC during the April-June rainy season occur frequently from mid-May to mid-and late-June,exhibiting significant intra-seasonal oscillation(10-30-day)features.Vertically integrated moisture flux convergence(VIMFC)can well represent the variation of the PHREs.A multiscale quantitative diagnosis of the VIMFC shows that the pre-summer PHREs over the SC are mainly affected by the background water vapor(greater than 30 days),intraseasonal circulation disturbance(10-30-day)and background circulation(greater than 30 days),and water vapor convergences are the main factor.The SC is under the control of a warm and humid background and a strong intraseasonal cyclonic circulation,with strong convergence and ascending movements and abundant water vapor conditions during the period of the PHREs.Meanwhile,the westward inter-seasonal oscillation of tropical atmosphere keeps the precipitation system over the SC for several consecutive days,eventually leading to the occurrence,development and persistence of heavy precipitation.展开更多
This study investigates the roles of the boreal summer intraseasonal oscillation(BSISO)in the diurnal rainfall cycle over Hainan Island during the warm season(April-September)using 20-year satellite-based precipitatio...This study investigates the roles of the boreal summer intraseasonal oscillation(BSISO)in the diurnal rainfall cycle over Hainan Island during the warm season(April-September)using 20-year satellite-based precipitation,ERA5 and the outgoing longwave radiation data with the phase composite analysis method.Results show that the spatial distributions of the hourly rainfall anomaly significantly change under the BSISO phases 1-8 while no clear variations are found on the daily and anomaly daily area-averaged rainfall over the island.During the BSISO phase 1,the rainfall anomaly distinctly increases in the morning over the southwest and late afternoon over the northeast of the island,while suppressed convection occurs in the early afternoon over the southwest area.Under this circumstance,strong low-level westerly winds bring abundant moisture into the island,which helps initiate the nocturnal-morning convection over the south coastal area,and drives the convergence region of sea breeze fronts to concentrate into the northwest.Opposite to Phase 1,an almost completely reversed diurnal cycle of rainfall anomaly is found in Phase 5,whereas a positive anomalous rainfall peak is observed in the early afternoon over the center while negative peaks are found in the morning and late afternoon over the southwest and northeast,owing to a strong low-level northeasterly anomaly flow,which causes relatively low moisture and enlarges a sea-breeze convergence area over the island.During Phase 8,strongest moisture is found over the island all through the day,which tends to produce highest rainfall in the afternoon with enhanced anomalous northerly.These results further indicate that multiscale interactions between the large-scale circulations and local land-sea breeze circulations play important roles in modulating diurnal precipitation cycles over the tropical island.展开更多
In summer 2018,a total of 18 tropical cyclones(TCs)formed in the western North Pacific(WNP)and South China Sea(SCS),among which 8 TCs landed in China,ranking respectively the second and the first highest since 1951.Mo...In summer 2018,a total of 18 tropical cyclones(TCs)formed in the western North Pacific(WNP)and South China Sea(SCS),among which 8 TCs landed in China,ranking respectively the second and the first highest since 1951.Most of these TCs travelled northwest to northward,bringing in heavy rainfall and strong winds in eastern China and Japan.The present study investigates the impacts of decaying La Nina and intraseasonal oscillation(ISO)on the extremely active TCs over the WNP and SCS in summer 2018 by use of correlation and composite analyses.It is found that the La Nina episode from October 2017 to March 2018 led to above-normal sea surface temperature(SST)over central–western Pacific,lower sea level pressure and 500-hPa geopotential height over WNP,and abnormally strong convective activities over the western Pacific in summer 2018.These preceding oceanic thermal conditions and their effects on circulation anomalies are favorable to TC genesis in summer.Detailed examination reveals that the monsoon trough was located further north and east,inducing more TCs in northern and eastern WNP;and the more eastward WNP subtropical high as well as the significant wave train with a"-+-+"height anomaly pattern over the midlatitude Eurasia–North Pacific region facilitated the northwest to northward TC tracks.Further analyses reveal that two successively active periods of Madden–Julian Oscillation(MJO)occurred in summer 2018 and the boreal summer intraseasonal oscillation(BSISO)was also active over WNP,propagating northward significantly,corresponding to the more northward TC tracks.The MJO was stagnant over the Maritime Continent to western Pacific,leading to notably enhanced convection in the lower troposphere and divergence in the upper troposphere,conducive to TC occurrences.In a word,the extremely active TC activities over the WNP and SCS in summer 2018 are closely linked with the decaying La Nina,and the MJO and BSISO;their joint effects result in increased TC occurrences and the TC tracks being shifted more northwest to northward than normal.展开更多
The boreal summer intraseasonal oscillation(BSISO) is simulated by the Climate System Model(CSM) developed at the Chinese Academy of Meteorological Sciences(CAMS), China Meteorological Administration. Firstly, the res...The boreal summer intraseasonal oscillation(BSISO) is simulated by the Climate System Model(CSM) developed at the Chinese Academy of Meteorological Sciences(CAMS), China Meteorological Administration. Firstly, the results indicate that this new model is able to reasonably simulate the annual cycle and seasonal mean of the precipitation, as well as the vertical shear of large-scale zonal wind in the tropics. The model also reproduces the eastward and northward propagating oscillation signals similar to those found in observations. The simulation of BSISO is generally in agreement with the observations in terms of variance center, periodicity, and propagation, with the exception that the magnitude of BSISO anomalous convections are underestimated during both its eastward propagation along the equator and its northward propagation over the Asian–Pacific summer monsoon region. Our preliminary evaluation of the simulated BSISO by CAMS-CSM suggests that this new model has the capability, to a certain extent, to capture the BSISO features, including its propagation zonally along the equator and meridionally over the Asian monsoon region.展开更多
基金financially supported by the National Natural Science Foundation of China[grant number 42088101]。
文摘EC-Earth3P-HR reproduces well the observed Boreal Summer Intraseasonal Oscillation(BSISO)and its impacts on tropical cyclone genesis(TCG)in the western North Pacific(WNP).Hence,the historical simulation(1950-1979)and future projection under the SSP5-8.5 scenario(2020-2049)in EC-Earth3P-HR are adopted to explore possible changes in the BSISO’s modification of WNP TCG under global warming to enhance the understanding of TC activities in the WNP.Results show that the BSISO circulation in the WNP shifts northeastward under global warming.This leads to enhanced convection in a northwest-southeast-oriented band crossing the WNP.Along the band,the BSISO-related TCG anomalies are enhanced.Analyses of genesis potential index show that changes in the BSISO-related mid-tropospheric relative humidity play the dominant role in modifying the BSISO’s impacts on WNP TCG under global warming.The enhanced BSISO convection in the band moistens the middle troposphere,which helps reduce the entrainment of generally dry mid-tropospheric air in the updrafts and the modification of the boundary layer by the downdraft of generally dry mid-tropospheric air,leading to enhanced TCG.
基金National Natural Science Foundation of China(42088101)。
文摘Based on daily precipitation data supplied by the Chinese meteorological administration,hourly reanalysis datasets provided by the ECMWF and daily outgoing long wave radiation supplied by the NOAA,the evolution regularity of continuous heavy precipitation over Southern China(SC)from April to June in 1979-2020 was systematically analyzed.The interaction between specific humidity and circulation field at the background-scale,the intra-seasonal-scale and the synoptic-scale,and its influence on persistent heavy precipitation over the SC during the April-June rainy season were quantitatively diagnosed and analyzed.The results are as follows.Persistent heavy rainfall events(PHREs)over the SC during the April-June rainy season occur frequently from mid-May to mid-and late-June,exhibiting significant intra-seasonal oscillation(10-30-day)features.Vertically integrated moisture flux convergence(VIMFC)can well represent the variation of the PHREs.A multiscale quantitative diagnosis of the VIMFC shows that the pre-summer PHREs over the SC are mainly affected by the background water vapor(greater than 30 days),intraseasonal circulation disturbance(10-30-day)and background circulation(greater than 30 days),and water vapor convergences are the main factor.The SC is under the control of a warm and humid background and a strong intraseasonal cyclonic circulation,with strong convergence and ascending movements and abundant water vapor conditions during the period of the PHREs.Meanwhile,the westward inter-seasonal oscillation of tropical atmosphere keeps the precipitation system over the SC for several consecutive days,eventually leading to the occurrence,development and persistence of heavy precipitation.
基金National Natural Science Foundation of China(41905096)Key Laboratory of South China Sea Meteorological Disaster Prevention and Mitigation of Hainan Province(SCSF202004)。
文摘This study investigates the roles of the boreal summer intraseasonal oscillation(BSISO)in the diurnal rainfall cycle over Hainan Island during the warm season(April-September)using 20-year satellite-based precipitation,ERA5 and the outgoing longwave radiation data with the phase composite analysis method.Results show that the spatial distributions of the hourly rainfall anomaly significantly change under the BSISO phases 1-8 while no clear variations are found on the daily and anomaly daily area-averaged rainfall over the island.During the BSISO phase 1,the rainfall anomaly distinctly increases in the morning over the southwest and late afternoon over the northeast of the island,while suppressed convection occurs in the early afternoon over the southwest area.Under this circumstance,strong low-level westerly winds bring abundant moisture into the island,which helps initiate the nocturnal-morning convection over the south coastal area,and drives the convergence region of sea breeze fronts to concentrate into the northwest.Opposite to Phase 1,an almost completely reversed diurnal cycle of rainfall anomaly is found in Phase 5,whereas a positive anomalous rainfall peak is observed in the early afternoon over the center while negative peaks are found in the morning and late afternoon over the southwest and northeast,owing to a strong low-level northeasterly anomaly flow,which causes relatively low moisture and enlarges a sea-breeze convergence area over the island.During Phase 8,strongest moisture is found over the island all through the day,which tends to produce highest rainfall in the afternoon with enhanced anomalous northerly.These results further indicate that multiscale interactions between the large-scale circulations and local land-sea breeze circulations play important roles in modulating diurnal precipitation cycles over the tropical island.
基金the National Key Research and Development Program of China(2018YFC1506001)National Basic Research(973)Program of China(2015CB453203)National Natural Science Foundation of China(41275073 and 41805067)
文摘In summer 2018,a total of 18 tropical cyclones(TCs)formed in the western North Pacific(WNP)and South China Sea(SCS),among which 8 TCs landed in China,ranking respectively the second and the first highest since 1951.Most of these TCs travelled northwest to northward,bringing in heavy rainfall and strong winds in eastern China and Japan.The present study investigates the impacts of decaying La Nina and intraseasonal oscillation(ISO)on the extremely active TCs over the WNP and SCS in summer 2018 by use of correlation and composite analyses.It is found that the La Nina episode from October 2017 to March 2018 led to above-normal sea surface temperature(SST)over central–western Pacific,lower sea level pressure and 500-hPa geopotential height over WNP,and abnormally strong convective activities over the western Pacific in summer 2018.These preceding oceanic thermal conditions and their effects on circulation anomalies are favorable to TC genesis in summer.Detailed examination reveals that the monsoon trough was located further north and east,inducing more TCs in northern and eastern WNP;and the more eastward WNP subtropical high as well as the significant wave train with a"-+-+"height anomaly pattern over the midlatitude Eurasia–North Pacific region facilitated the northwest to northward TC tracks.Further analyses reveal that two successively active periods of Madden–Julian Oscillation(MJO)occurred in summer 2018 and the boreal summer intraseasonal oscillation(BSISO)was also active over WNP,propagating northward significantly,corresponding to the more northward TC tracks.The MJO was stagnant over the Maritime Continent to western Pacific,leading to notably enhanced convection in the lower troposphere and divergence in the upper troposphere,conducive to TC occurrences.In a word,the extremely active TC activities over the WNP and SCS in summer 2018 are closely linked with the decaying La Nina,and the MJO and BSISO;their joint effects result in increased TC occurrences and the TC tracks being shifted more northwest to northward than normal.
基金Supported by the National Key Research and Development Program(2016YFA0601504)National Basic Research and Development(973)Program of China(2015CB453203)+1 种基金National Natural Science Foundation of China(41675068)Basic Research Funds of the Chinese Academy of Meteorological Sciences(2015Z002)
文摘The boreal summer intraseasonal oscillation(BSISO) is simulated by the Climate System Model(CSM) developed at the Chinese Academy of Meteorological Sciences(CAMS), China Meteorological Administration. Firstly, the results indicate that this new model is able to reasonably simulate the annual cycle and seasonal mean of the precipitation, as well as the vertical shear of large-scale zonal wind in the tropics. The model also reproduces the eastward and northward propagating oscillation signals similar to those found in observations. The simulation of BSISO is generally in agreement with the observations in terms of variance center, periodicity, and propagation, with the exception that the magnitude of BSISO anomalous convections are underestimated during both its eastward propagation along the equator and its northward propagation over the Asian–Pacific summer monsoon region. Our preliminary evaluation of the simulated BSISO by CAMS-CSM suggests that this new model has the capability, to a certain extent, to capture the BSISO features, including its propagation zonally along the equator and meridionally over the Asian monsoon region.
