Comparisons of Surface Longwave Radiance Between Line-by-Line Radiative Transfer Model and Atmospheric Emitted Radiance Interferometer Observations from the Atmospheric Radiation Measurement Program

Observed surface downward longwave radiances from the Atmospheric Emitted Radiance Interferometer (AERI) were compared with line-by-line radiative transfer model (LBLRTM) calculations from April 1994 to November 1996 for “clear-sky conditions” in the 800-1250 atmospheric The observed radiance data used herein were measured by the window region. Results show that the mean AERI-LBLRTM AERI at the ARM Southern Great Plains (SGP) site. We used radiance differences are generally small and close to the recalibrated AERI prototype (AERI-00) data from April 1994 instrument accuracy during the nighttime. However, during to July 25, 1995, and AERI-01 data from July 26, 1995, to the daytime, the radiance differences are larger and increase as November 1996. the H O amount increases when using radiosonde data as 2 model input. Scaling the radiosonde H O profile by the ratio The atmosphere was considered to be clear when the follow2 of the microwave to the radiosonde precipitable water (PW) ing four conditions were satisfied within a period from reduces the mean and scatter of the radiance differences and 10 minutes before through 25 minutes after a radiosonde makes the day and night differences consistent. launch: