HR: 0800h
AN: A41B-0447    [Abstracts]
TI: 3D Thermal Infrared Radiative Transfer in Mountains
AU: * Lee, W
EM: wllee@atmos.ucla.edu
AF: University of California, Los Angeles, 405 Hilgard Ave, Los Angeles, CA 90095, United States
AU: Liou, K
EM: knliou@atmos.ucla.edu
AF: University of California, Los Angeles, 405 Hilgard Ave, Los Angeles, CA 90095, United States
AU: Hall, A
EM: alexhall@atmos.ucla.edu
AF: University of California, Los Angeles, 405 Hilgard Ave, Los Angeles, CA 90095, United States
AB: We developed a 3D Monte Carlo photon tracing program for radiative transfer in inhomogeneous and irregular terrain coupled with the correlated k-distribution method for gaseous absorption in the atmosphere for the calculation of broadband thermal infrared (IR) fluxes at mountain surfaces. The thermal IR radiative transfer program includes emission from the atmosphere to the surface and vice versa as well as emissions between mountain surfaces. Both the atmosphere and the land surface are discretized by using finite cubic cells characterized by the spectral optical properties of molecules and background aerosols (absorption coefficient, single-scattering albedo, and scattering phase function) and terrain configuration (albedo, elevation, slope, and orientation). The emissivity of gases is parameterized in terms of the vertical optical depth of cubic cell. We selected an area of 100×100 km² in the Tibetan Plateau near Lhasa city with a horizontal resolution of 1 km² and used the surface temperature and albedo available from MODIS/Terra dataset for this study. We show that surface temperature is the dominating factor in radiative transfer calculations and that subgrid variability of the net surface IR flux distribution relative to a flat surface (1D) with average elevation and temperature can be as large as 50 W/m² at cold mountain surfaces.
DE: 0360 Radiation: transmission and scattering
DE: 3359 Radiative processes
SC: Atmospheric Sciences [A]
MN: 2007 Fall Meeting