TURBULENT HEAT-FLUX VARIATION OVER THE MONSOON-TROUGH REGION DURING MONTBLEX-90

Tower data collected during the Monsoon-Trough Boundary Layer Experime nt (MONTBLEX-90) have been analysed to understand the observed structu re of the surface layer over an arid region (Jodhpur) and a moist regi on (Kharagpur) during active and weak phases of the 1990 southwest mon soon. Turbulent heat and momentum fluxes are estimated by the eddy cor relation method using sonic data. The turbulent momentum flux at both Jodhpur and Kharagpur was larger when the winds were stronger, reachin g a maximum of the order of 0.5 N m(-2) on 5 and 6 August when a low p ressure system was located over the region. The heat flux at Jodhpur i s high during weak monsoon days, the maximum being 450 W m(-2), wherea s during active days the flux never exceeds 200 W m(-2). At Kharagpur, the flux does not vary significantly between active and weak monsoon days, the maximum in either phase being 160 W m(-2) At Jodhpur, there is significant contrast in the near-surface air temperature, being hig her during weak monsoon days as compared to active days. Cloud cover d id not vary significantly in both the regions. The turbulent heat flux variation at both the sites appears to be correlated mainly with soil mixture, and less sensitive to cloud cover.