Thin Cirrus Cloud over the Tropical Pacific

This report summarizes a theoretical study of the detectability of high altitude (10 km) thin cirrus clouds by various remote sensors over the tropical Pacific. The remote sensors considered include: (1) visual detection from the surface, (2) visual detection from an aircraft, and (3) infrared sensor (6.7 micrometers) from space. The radiative transfer technique to compute the atmospheric radiance (intensity) is summarized. The optical properties of ice crystals are presented. The results indicate that the minimum detectable concentration of ice crystals having a dimension greater than 80 micrometers, the critical size which will be hazardous to the RV transition, is around 2 x 10(4) m(-3) for visual detection from the surface and 3-4 x 10(3) m(-3) for both aircraft observation and infrared sensors from space. (Author)