| Popis: |
Airborne measurements of mid and far infrared (IR) sea radiances were obtained using a calibrated dual-wavelength band thermal imaging system (AGEMA 900). The measurements were used to evaluate a sea radiance model which is based on the Cox-Munk wave slope statistics and is incorporated into a modified version of LOWTRAN 6. The measured and modeled IR blackbody sea temperatures for three days (which included low, moderate and high wind speeds) are compared as a function of the observation altitude. For all three data sets, the far IR modeled sea temperatures are less than the measured values by 1 degree(s)C to 3 degree(s)C at all altitudes. There is slightly better agreement (1 degree(s)C to 2 degree(s)C) between the measured and modeled temperatures for the mid IR band. In these instances, however, the modeled temperatures are greater than the measured values, except at altitudes where the sea backgrounds were contaminated by sun glint. Observations are presented which show that the far IR sea radiances are more closely influenced by the actual sea temperature than are those for the mid IR band, and that the strong `close-in' absorptions of carbon dioxide and water vapor control the mid IR radiances. |
