Cirrus cloud statistics: Temperatures and optical depths

Measurements of the upwelling infrared radiance at 10.5 and 6.5 microns were obtained during the FIRE cirrus Intensive Field Observations using a radiometer with a 15 deg cone nadir field-of-view flown on the NASA Ames ER-2. Data are recorded at a frequency of 1 Hz and the radiometer is continuously calibrated with a liquid nitrogen blackbody source, thereby providing a large number of very accurate radiance values during the course of a several hour flight. For this study, the focus is on the statistical properties of the cirrus deck as deduced from the radiance data. The data acquired on 28 October 1986 is stressed, but some data from the other flights are also shown for comparison purposes.