Considerations for Modeling Thin Cirrus Effects via Brightness Temperature Differences

• Published in: Journal of applied meteorology (1988) Vol. 34; no. 2; pp. 447 - 459
• Main Authors: Schmidt, E. O., Arduini, R. F., Wielicki, B. A., Stone, R. S., Tsay, S.-C.
• Format: Journal Article
• Language: English
• Published: Legacy CDMS American Meteorological Society 01-02-1995
• Subjects: Cirrus clouds; Cloud physics; Clouds; Crystals; Earth, ocean, space; Exact sciences and technology; External geophysics; Hexagonal crystals; Hexagons; Ice; Meteorology; Meteorology And Climatology; Optical thickness; Particle size classes; Signatures; Surface areas; Temperature difference; Phase function; Ice crystals; Particle size; Artificial satellite; Hexagonal crystals; Cloud physics; Cirrus; Space remote sensing; Brightness temperature; Radiative transfer; Legendre polynomial
• ISSN: 0894-8763; 1520-0450
• DOI: 10.1175/1520-0450-34.2.447

Brightness temperature difference (BTD) values are calculated for selected Geostationary Operational Environmental Satellite (GOES-6) channels (3.9, 12.7 μm) and Advanced Very High Resolution Radiometer channels (3.7, 12.0 μm). Daytime and nighttime discrimination of particle size information is possible given the infrared cloud extinction optical depth and the BTD value. BTD values are presented and compared for cirrus clouds composed of equivalent ice spheres (volume, surface area) versus randomly oriented hexagonal ice crystals. The effect of the hexagonal ice crystals is to increase the magnitude of the BTD values calculated relative to equivalent ice sphere (volume, surface area) BTDs. Equivalent spheres (volume or surface area) do not do a very good job of modeling hexagonal ice crystal effects on BTDs; however, the use of composite spheres improves the simulation and offers interesting prospects. Careful consideration of the number of Legendre polynomial coefficients used to fit the scattering phase functions is crucial to realistic modeling of cirrus BTDs. Surface and view-angle effects are incorporated to provide more realistic simulation.