AIRBORNE BRIGHTNESS TEMPERATURE-MEASUREMENTS OF THE POLAR WINTER TROPOSPHERE AS PART OF THE AIRBORNE ARCTIC STRATOSPHERE EXPERIMENT-II AND THE EFFECT OF BRIGHTNESS TEMPERATURE-VARIATIONS ON THE DIABATIC HEATING IN THE LOWER STRATOSPHERE

In this paper we report radiometric measurements of tropospheric brigh tness temperatures obtained during the AASE II experiment. These measu rements represent the first attempt to characterize effective radiativ e temperatures as seen from above the troposphere during the Arctic wi nter. The reported measurements include brightness temperatures at 6.7 and 10.5mum as seen from the NASA DC-8 aircraft flying at about 11 km altitude. We also present radiative transfer calculations to estimate the effect of tropospheric brightness temperature on the lower strato spheric heating rates. Because of the recent massive eruption of the P inatubo volcano, we also discuss the effects of a volcanic aerosol lay er. It is concluded that small particles like the volcanic aerosol or PSCs type 1 do not affect stratospheric heating rates by much; on the other hand, larger particles, PSCs types 2 and 3, may have significant effects on heating rates and consequently on dynamics of the lower st ratosphere. The dynamical effects of local stratospheric temperature v ariations are briefly discussed.