ERBE Wide-Field-of-View Nonscanner Data Reprocessing and revisiting its Radiation dataset from 1985 to 199

Abstract:

The Earth’s radiation budget is a fundamental component of the climate system and should reflect the variation in climate. As such, it is critical to know how it has varied over past decades to ensure that climate models are properly representing climate. Broadband shortwave and longwave irradiances were measured by the Earth Radiation Budget Experiment (ERBE) wide-field-of-view (WFOV) nonscanner instrument from 1985 to 1998. These WFOV nonscanner instruments were onboard NASA’s Earth Radiation Budget Satellite (ERBS) and two NOAA’s satellites (NOAA-9 and NOAA-10). However, earlier studies showed that the transmissivity of the dome for the WFOV shortwave (SW) nonscanner instrument degraded over time. To account for the degradation, WFOV instruments were calibrated assuming constant spectral degradation (gray assumption). Recent developments from analysis of data from the Clouds and the Earth’s Radiant Energy System project (CERES), which has been measuring the radiation budget since 2000, suggest that transmissivity of shorter wavelength degrades faster. Therefore, a spectrally dependent degradation correction is needed for a better calibration. In addition, accounting for the spectrally dependent degradation may eliminate an additional correction applied to irradiances using a time series of daytime and nighttime longwave irradiance differences. Therefore, we have reprocessed WFOV nonscanner data by characterizing the spectrally dependent degradation of the SW dome transmissivity. Time and spectral dependent degradation of the shortwave filter function is estimated using solar data observed by these instruments during calibration days. Because the spectrum of reflected irradiance depends on scene type, we use Advanced Very High Resolution Radiometer AVHRR-derived cloud properties and surface type over the WFOV footprints in addition to time dependent filter function for the unfiltering process. This poster explains the reprocessing approach and discusses the results by comparing the existing ERBE radiation dataset to that obtained with reprocessing using the new correction. This leads to the generation of a long-term radiation datasets consistent with those provided by CERES.