Measurements of infrared radiative fluxes over India

Abstract

The results of 66 upper air soundings made over India during 1963 and 1964 with Suomi-Kuhn radiometersondes show that, although significant day-to-day and seasonal variations in the upward, downward, and net infrared radiative fluxes in the atmosphere over Poona occur, the mean values for the winter, summer, and monsoon months show remarkable features in common: an increase in the net upward flux with height, with a maximum at about 12 km, and a decrease at the tropopause followed by an increase in the stratosphere. Steady values of the order of 0.35 ly/min are reached at about 25 km in the winter and summer seasons when the sky is clear, in good agreement with satellite observations of net infrared flux over the tropics. During the cloudy monsoon months the net flux is much less, 0.22 ly/min, and the net loss to space is reduced by over 50%. Mean radiative cooling in the troposphere is of the order of 1 to 2°C/day up to 200 mb, with pronounced maximums at 3, 6, and 10 km and a marked warming just below the tropopause. Radiative cooling in the troposphere during the clear seasons is about 50% more than that during the cloudy months except over cloud decks. The effect of dust in the lower layers is conspicuous during the summer months. Tropospheric warming immediately below the tropopause is largest during the monsoon and least during winter. Stratospheric cooling is large and variable and in the mean about 5 times that in the troposphere.