An energy analysis of midwinter suppression of the North Pacific storm track
Based on the daily reanalysis data of European Center for Medium Weather Forecast (ERA-40) ,by using local energy change equations to calculate the seasonal variation of the local energy in different tropospheric layers over the North Pacific storm track, the role of internal dynamic mechanism in the maintainance of the track is discussed in detail. Results show that the seasonal variation of eddy kinetic energy can well reflect the phenomenon of midwinter suppression of the North Pacific storm track,which, with an occurrence probability of nearly 80% ,is most prominent on the upper levels of the troposphere and was the strongest through the mid and late 1970s to the early 1980s. As viewed from the simultaneous variation of each energy terms averaged over the track,by adding up the stronger loss resulted from the larger decrease of the baroclinic energy conversion and eddy ageostrophic geopotential flux and the weaker gain resulted from the smaller decrease of the barotropic energy conversion, the remarkable net loss of the eddy kinetic energy during midwinter is possibly the direct reason for midwinter suppression of the North Pacific storm track.
storm trackmidwinter suppressionbaroclinic energy conversionbarotropic energy conversioneddy ageostrophic geopotential flux
国家科技期刊平台
NSTL
万方数据
维普
