Thermal infrared radiation transfer in the planetary boundary layer.

A high spectral resolution thermal infrared radiation transfer program has been developed. It uses the emissivity growth method to calculate transmittances along inhomogeneous paths from a line-by-line calculated database for homogeneous paths. This program offers high accuracy and reduces the computing time by about two orders of magnitude in comparison with the line-by-line method. Critical to the program are the choice of appropriate grid points for transmittance calculation, the double quadratic interpolation, and an appropriate stratification of the atmosphere. A criterion for evaluating grid points has been developed that can reduce interpolation errors significantly. This research reviewed and evaluated current measurements and theories on water vapor continuum absorption. By including the most current data, this radiation transfer program showed the significant effects of water vapor continuum absorption and produced simulation results which agree with available measurements. The sensitivities of thermal radiation fluxes to a doubling of CO$\sb2$ were significantly affected by the temperature and the water vapor profiles. Sensitivity studies also showed the extreme importance of the lower part of the boundary layer to the diurnal variation of the down-welling flux and the surface radiative energy budget. In the standard atmosphere, about 30% of the down-welling flux comes from the lowest 0.6 millibars and about 50% from the lowest 3 millibars. This-research clearly showed that a widely used extrapolated profile cannot represent a daily average profile. The extrapolated profile overestimated the surface net radiation by 50%. A layer of fog was parameterized as a grey body for certain absorptions in radiation transfer simulations. The primary results of the one parameter model were consistent with observations.PhDAtmospheric and Space SciencesUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/103163/1/9303846.pdfDescription of 9303846.pdf : Restricted to UM users only