Four years of global cirrus cloud statistics using HIRS

Abstract

Trends in global upper-tropospheric transmissive cirrus cloud cover are begining to emerge from a four-year cloud climatology using NOAA polar-orbiting High-Resolution Infrared Radiation Sounder (HIRS) multispectral data. Cloud occurrence, height, and effective emissivity are determined with the CO2 slicing technique on the four years of data (June 1989-May 1993). There is a global preponderance of transmissive high clouds, 42% on the average; about three-fourths of these are presumed to be cirrus. In the ITCZ, a high frequency of cirrus (greater than 50%) is found at all times. A significant change in cirrus cloud cover occurs in 1991, the same time as the 1991-1992 El Nino/Southern Oscillation (ENSO) and the eruption of Mt. Pinatubo. The cirrus changes persist into 1993. -from Authors