Earth's Radiation to Space at 15 Microns: Stratospheric Temperature Variations

Abstract

Nimbus III carried a Satellite Infra-Red Spectrometer (SIRS) with which the temperature structure of the atmosphere can be observed. The most opaque spectral interval on SIRS was centered at 669.3 cm?1 (?15 ?). At this frequency only the stratosphere essentially contributes to the outgoing radiation. A description of the measured radiances at 669.3 cm?1 is also a description of a weighted mean stratospheric temperature for the upper 100 mb of air. With the aid of additional spectral intervals, however, the temperature structure in thinner layers of the stratosphere can also be investigated. Radiance measurements at 669.3 cm?1 are discussed in relation to several different stratospheric phenonmena. The phemomena discussed are: Moving and stationary ?waves.? In May 1909, westward moving waves were discernible in the tropics. A stationary wavenumber 1 pattern was also seen. Wave motions were also shown at latitudes 60N and 60S. A stratospheric warming area was present in early May over the Indian Ocean area near 45S. A minimum of radiance was observed in July at the equator; the July minimum of stratospheric temperature above 10 mb was apparently responsible for the observed low radiance. Non-seasonal variations of radiance appear almost simultaneously over large areas of the world; although large-scale internal dynamical adjustments may account for the observations, extraterrestrial causes cannot be ruled out as contributing factors. The diurnal variation of stratospheric temperature (integrated in the vertical) is small. Observations which claim large stratosphere temperature variations between midnight and noon are probably erroneous.