THE DISTRIBUTION OF CARBON DIOXIDE COOLING IN THE LOWER STRATOSPHERE

Abstract

The distribution of radiational cooling due to carbon dioxide is computed for the stratosphere below 30 km in an effort to provide an insight into the role of radiation in the observed seasonal and latitudinal changes of temperature and flow. Laboratory results of Burch, Howard, and Williams for the absorption of the 15 µ band are used as an empirical basis for the computations. When the results are combined with data on solar absorption of ozone provided by Pressman and other radiational factors are assumed negligible, carbon dioxide is found to determine the radiational rates of temperature change below about 40 to 60 mb. In addition, it determines the rates at all heights north of the boundary of polar night. Ozone heating dominates the pattern above 40 to 60 mb south of the polar night boundary. Cooling maxima are 1 to 1.2 K per day near the 60-mb level in spring and summer and the 30-mb level in fall and winter. Heating increases above this level and exceeds 3 to 4 K per day at the highest altitudes considered. In spite of this large solar heating of the ozone layer, the Arctic stratosphere below 30 km is in all seasons a region of net radiational deficit. However, ozone heating in the infrared is probably sufficient to create an excess in southerly latitudes for this layer. The entire stratosphere to 55 km is a region of net deficit in all seasons except Summer as far south as 45 deg at least. Even in summer a deficit exists near the pole. In general, the circulation must supply heat to the Arctic stratosphere in all seasons, as well as maintain a temperature distribution showing large north-south gradients in the face of radiational effects tending to destroy these gradients. In fall and winter the temperature change gradients are such as to favor maximum local temperature gradients at the boundary of the polar night above the 20-mb level, a possible source for perturbations observed in this region.