Inter-seasonal and inter-annual variations of mean and eddy atmospheric energetics over India

Abstract

Using daily upper air data from 1000 to 250 hPa of 20 stations during the period 1983-87 , the inter-sasonal and inter-annual variations of vertically intearated mean and eddy sensible and latent heat fluxes over India were examined. Vertically intearated meridional, sensible and latent fluxes (both mean and eddy fluxes) were generally southwards over the country except over northeastern parts. Large seasonal variation of mean sensible heat and latent heat flux values occur in association with the seasonal shifts of Hadley circulation. Maximum sensible heat fluxes were observed during pre-monsoon season over northern parts of India. Maximum latent heat fluxes were observed over central parts of India during monsoon season. Eddy fluxes were two order smaller than fluxes due to mean flow during all seasons. Maximum eddy fluxes occur in winter and are accomplished by large scale transient eddies. The eddy fluxes were practically negligible equatorwards of 15°N. Seasonal variations of fluxes over low latitudes were, however, different from the zonal pattern of annual cycle obtained by Oort (1971).

There were significant differences in meridional mean and eddy flux values between 1983 (a good monsoon year) and 1987 (a bad monsoon year). During 1983 (1987) the sensible heat flux values due to transient eddies were equatorwards (polewards) during the premonsoon as well as monsoon seasons. Similarly during monsoon season of 1983 larger northward mean sensible and latent heat fluxes were observed. In addition there were significant differences in vertical structure of zonal sensible and latent heat fluxes between 1983 and 1987 also.