Calibration of Infrared Radiometers for Cloud-Base Temperature Remote Sensing: Technique and Error Analysis

摘要

Absolute radiometric calibration is required for ground-based infrared remote sensing of cloud-base temperature. This requires associating the radiometer's output voltage with blackbody temperatures over the desired measurement range. Insufficient attention to subtle error sources while performing this conceptually simple calibration results in errors many times larger than the 1.0 C uncertainty achievable with a carefully performed calibration. Inadequate blackbody simulation and imprecise voltage measurements contribute most significantly to calibration uncertainty. The purpose of the report is documentation and error analysis of the technique used at the NOAA Wave Propagation Laboratory for calibrating zenith-viewing infrared radiometers. Additional uncertainties that arise in cloud-base temperature measurements for real clouds in the real atmosphere are discussed briefly.