EVALUATION OF INFRARED EMISSION OF CLOUDS AND GROUND AS MEASURED BY WEATHER SATELLITES.
Abstract
Infrared signals received in the 8 to 12 micron window by weather satellites and aircraft depend, in clear air, on surface temperature, atmospheric interference, and surface emissivity. For the latter, the literature contains very different data for clouds, water, rocks, etc. This paper discusses three methods that were tried for securing correct emissivity data: (1) Testing the reflectivity of polished rock samples in an infrared spectrograph for 5 to 16 micron wavelengths. Using Kirchhoff's law, this method yields emissivities for near-normal incidence. (2) Measuring the emissivity of many surfaces directly, using an 8- to 13-micron-sensitive radiometer and an aggregate (called an emissivity box). (3) Evaluating data obtained on a summer noontime flight of Tiros over the Mediterranean and the Sahara. The Mediterranean served for calibration of the 8 to 13 micron Tiros radiometer and the atmospheric effects. The large discrepancy between the Tiros temperatures of the Sahara and the expected true desert-surface temperatures can only be explained as caused by a substantial deviation from blackbody emissivity. This deviation seems to be caused by the 9 to 10 micron reflection of quartzites. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Nov 01, 1965
- Accession Number
- AD0629081
Entities
People
- Clifford D. Kern
Organizations
- Air Force Cambridge Research Laboratories