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 incr.ease 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 monscon 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 I to 2øC/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. RADIATIVEFLUXES OVER INDIA 4533 426, 1960. Goody, R. M., Atmospheric Radiation, I, Theoretical Basis, Clarendon Press, Oxford, 271, 1964. Houghton, J. G., On the annual heat balance of the northern hemisphere, J. Meteorol., 11, 1-9, 1954. House, F. G., and J. R. Blankenship, Applications of infrared measurements in meteorology, Tech. Rept. 157, Air Weather Service, Scott AFB, Ill., 1961. Kuhn, P.M., Accuracy of the airborne economical radiometer, Monthly Weather Rev., 89, 285-288, 1961. Kuhn, P.M., and V. E. Suomi, Infrared radiometer soundings on a synoptic scale, J. Geophys. Res., 65, 3669-3677, 1960. Kuhn, P.M., V. E. Suomi, and G. C. Darkow, Soundings of terrestrial radiation flux over Wisconsin, Monthly Weather Rev., 87, 129-135, 1959. London, J. A., A study of the atmospheric heat balance, Department of Meteorology, New York University, New York, 1957. Mani, A., and O. Chacko, Measurements of solar radiation and atmospheric turbidity with strSm pyrheliometers at Poona and Delhi during the IGY, Indian J. Meteorol. Geophys., 14, 270-282, 1963a. Mani, A., and O. Chacko, Studies of nocturnal radiation at Poona and Delhi, Indian J. Meteorol. Geophys., 14, 196-204, 1963b. Riehl, H., Radiation measurements over the Caribbean during the autumn of 1960, J. Geophys. Res., 67, 3935-3942, 1962. RSnicke, G., •ber Messungen des Verlaufs der Warmestrahlungsbilanz in der freien Atmosphare in San Salvador, Z. Meteorol., 15, 8-12, 1961. A direct measurement of infrared radiation divergence to 160 mb, Quart. J. Roy. Meteorol.