The impacts of multi-time-scale flows on northward and north-eastward moving tropical cyclones(TCs)near the east coast of China in August and September are investigated using reanalysis data from 1982 to 2012.TCs of i...The impacts of multi-time-scale flows on northward and north-eastward moving tropical cyclones(TCs)near the east coast of China in August and September are investigated using reanalysis data from 1982 to 2012.TCs of interest are under the influence of the subtropical high-pressure system in the western North Pacific(WNP).In August when the subtropical highpressure system is strong and close to the coast line,most TCs in the region move northward,while more TCs move north-eastward in September when the subtropical highpressure system retreats to the east.To investigate the influence from different time-scales,the environmental flow is divided intofour components,the synoptic flow,the intraseasonal flow,the interannual flow and the climatological background field.Analysis of steering flows between 25°N and 30°N indicates that the meridional steering vectors from all time-scales point to the north,dominated by the intraseasonal component.The deciding factor on whether a TC moves to the north or north-east between 25°N and 30°N is the zonal steering vector.For the northward moving group,the sum of the zonal steering from all time-scales is very small.On the other hand,the north-east moving group has a net eastward zonal component mainly contributed by the climatological mean flow.Several individual cases that stood out from the majority of the group are analyzed.For those cases,the intraseasonal flow plays an important role in affecting the movement of the TCs mainly through the wave train,in which a cyclonic circulation is located to the north-west(north)and an anticyclonic circulation to the south-east(east)of TCs.The analysis of the steering vectors indicates the importance of all components with different timescales to the movement of TCs.展开更多
基金This work was jointly supported by National Key R&D Program of China(Grant N os.2018YFC1505800 and 2015CB453200)NOAA(No.NA180AR4310298)+3 种基金National Science Foundation(No.AGS-1643297)National Natural Science Foundation of China(Nos.41630423 and 41875069)NRL(Grant No.N00173-16-1-G906)China Scholarship Council(Grant No.N201908320496).This is SOEST contribution number 10834,IPRC contribution number 1409 and ESMC number 285.
文摘The impacts of multi-time-scale flows on northward and north-eastward moving tropical cyclones(TCs)near the east coast of China in August and September are investigated using reanalysis data from 1982 to 2012.TCs of interest are under the influence of the subtropical high-pressure system in the western North Pacific(WNP).In August when the subtropical highpressure system is strong and close to the coast line,most TCs in the region move northward,while more TCs move north-eastward in September when the subtropical highpressure system retreats to the east.To investigate the influence from different time-scales,the environmental flow is divided intofour components,the synoptic flow,the intraseasonal flow,the interannual flow and the climatological background field.Analysis of steering flows between 25°N and 30°N indicates that the meridional steering vectors from all time-scales point to the north,dominated by the intraseasonal component.The deciding factor on whether a TC moves to the north or north-east between 25°N and 30°N is the zonal steering vector.For the northward moving group,the sum of the zonal steering from all time-scales is very small.On the other hand,the north-east moving group has a net eastward zonal component mainly contributed by the climatological mean flow.Several individual cases that stood out from the majority of the group are analyzed.For those cases,the intraseasonal flow plays an important role in affecting the movement of the TCs mainly through the wave train,in which a cyclonic circulation is located to the north-west(north)and an anticyclonic circulation to the south-east(east)of TCs.The analysis of the steering vectors indicates the importance of all components with different timescales to the movement of TCs.
