Contrasting contributions of flows on different time scales to tropical cyclone tracks over the South China Sea

Abstract

Abstract This study investigates the relative contributions of components of flows on multiple time scales to westward and eastward-moving tropical cyclones (TCs) over the South China Sea (SCS) from a local and instantaneous perspective of TC position along the TC tracks during June to October from 1965 to 2015. The total steering flows obtained by vertical integration of winds from 850 to 300 hPa averaged along the entire TC tracks are separated into climatological mean flows, interannual, intraseasonal, and synoptic time scales. For westward-moving TCs, the zonal steering flows are contributed dominantly by climatological mean easterly, whereas the meridional steering flows are contributed dominantly by climatological mean and synoptic-scale southerly winds. In contrast, for eastward-moving TCs, the zonal steering flows are contributed equally by the intraseasonal and synoptic components, while the meridional steering flows are contributed dominantly by climatological mean southerly winds along with the secondary contribution of synoptic-scale southerly winds. This work provides a better understanding of relative contributions of different time scale components of steering flows to the TC motions over the SCS.