Sensitivity of net thermal flux to the abundance of trace gases in the lower atmosphere of Venus

Abstract

We calculated the net thermal flux in the atmosphere of Venus from the surface to 100 km altitude. Our atmospheric model was carefully constructed especially for altitudes below the clouds (<48 km), using recent CO<SUB>2</SUB> absorption data. It includes updated collision-induced absorptions in the <250 cm<SUP>-1</SUP>, 1200-1500 cm<SUP>-1</SUP>, and 2650-3130 cm<SUP>-1</SUP> wave number ranges. We studied sensitivity of the net thermal flux below the clouds on the abundances of trace gases that were varied within the range reported by observations. Our results reveal a considerable effect of trace gases on radiative budget. We successfully simulate net thermal flux profiles measured in situ by the Night and North probes of Pioneer Venus using 20-50 ppmv H<SUB>2</SUB>O, suggesting that the high H<SUB>2</SUB>O abundance of 200 ppmv derived in the earlier analysis is not required. Our sensitivity study shows that the trace gases SO2, H2O, and OCS are effective thermal agents, while CO and HCl influences are rather weak. We suggest that the influence of the former three gases should be taken into account to estimate the net radiative energy in the deep atmosphere.