PROFILES OF INFRARED IRRADIANCE AND COOLING THROUGH A JET STREAM

Abstract

Vertical atmospheric cross sections of upward, downward, and net infrared irradiance, infrared cooling, temperature, potential temperature, and water vapor through a jet stream have been constructed for Jan. 7 and 9, 1961, along a line from International Falls, Minn., to Willemstad, Curacao. The profiles of irradiance and infrared cooling determined from filtered radiometersonde measurements clearly portray the influence of clouds. Variations of infrared irradiance and cooling associated with the zonal, secondary, and convective scales are discussed. Primarily attention is focused on radiation features associated with the jet stream and its associated cloud distribution. The contrast between profiles of net irradiance and infrared cooling between clear and cloudy regions is clearly portrayed. The range of infrared heating at the base of the clouds to the cooling at the top of the clouds exceeds 5?7°C./day. Apppreciable variations of infrared cooling are found in the stratosphere indicating the presence of water vapor, dust, tenuous cirrus, or other attenuating particles. The data indicate that a major factor controlling the horizontal variations of stratospheric infrared cooling is the high level cloudiness. The presence or absence of high level clouds primarily controls the source of infrared energy emitted from the earth and the troposphere, i.e., the upward irradiance which is available for stratospheric absorption.