Search Results

You are looking at 1 - 3 of 3 items for

  • Author or Editor: William R. Kuhn x
  • Refine by Access: All Content x
Clear All Modify Search
Frank Haurwitz and William R. Kuhn

Abstract

The planetary radiation for the Southern Hemisphere troposphere has been calculated from climatological data for January and July. Zonally averaged profiles of cooling/heating rates are presented. In addition, calculations have been made for selected latitudes and longitudes to illustrate the variation from the mean zonal rates. The outgoing planetary radiation and the zonally averaged net flux divergence are also discussed.

The heating/cooling rate calculations show that maximum cooling occurs in the mid-troposphere and is larger over the oceans than the continents, with longitudinal variations reaching 1C day−1. Results are similar to those of Katayama for the Northern Hemisphere with the exception that we find significant heating at the base of the cirrus clouds.

The hemispheric distribution of outgoing flux agrees qualitatively with that derived from satellite measurements. The annual longitudinally averaged results agree closely with those of Sasamori et al. except in the vicinity of the polar front where our outgoing fluxes are about 25 ly day−1 smaller while in the polar latitudes our results are larger by a comparable amount. Many of the variations are directly attributable to cloud cover and the need for additional cloud data is exphasized.

Full access
William R. Kuhn and Julius London

Abstract

The infrared contributions to the heat budget by the 15 µ CO2, 9.6 µ O2, and 80 µ H2O bands are evaluated for the upper stratosphere, mesosphere and lower thermosphere as a function of latitude for both summer and winter. Flux divergences are numerically evaluated for a quasi-random band model with the appropriate line-broadening mechanism. A general discussion of the source function applicable to a multi-vibrational level molecule is given, and this formulation is applied to the 15 µ band of carbon dioxide.

The flux divergence of infrared radiation acts to cool the atmosphere in the 30–110 km height region except in the vicinity of the mesopause. Here there is a small, but nevertheless significant heating which increases in value toward the summer pole (∼4K day−1). Centers of cooling appear near the stratopause for low latitudes (∼10K day−1) and in the lower thermosphere over the winter pole. Thermospheric values may vary by a factor of 4 because of uncertainties in the collisional lifetime of the 15 µ transition; the rates of temperature change in this region have been parametrized in terms of the collisional and the radiative rates.

Ozone makes a significant contribution to the cooling in the vicinity of the stratopause (∼3K day−1). The water vapor contribution is approximately 1K day−1for a mixing ratio of 10−6 gm gm−1. Our calculations indicate that both these gases, when compared with carbon dioxide, give a negligible contribution to the flux divergence in the upper mesosphere.

Full access
C. Bruce Baker, William R. Kuhn, and Edward Ryznar

Abstract

Direct normal and diffuse solar irradiances and 500 nm aerosol optical depths measured at the University of Michigan departed far from normal on 26 October 1982, when it is concluded that the main stratospheric cloud from the El Chichon volcanic eruption arrived at the 42°N latitude of the radiation measurement facility. For clear-sky data analyzed through 19 January 1983, direct solar is about 25% less than normal and diffuse solar is about 85% greater. For the same aerosol optical depths and solar zenith angles, the ratio of diffuse to direct is about 30% greater for about 0.3 cm of precipitable water but nearly the same for 0.9 cm. Aerosol optical depths are nearly three times greater for wind directions that naturally advect the cleanest air. The effect of circumsolar irradiance on the methods used to measure direct normal and diffuse irradiances cause the former to be overestimated and the latter to be underestimated.

Full access