129 Re-analysis of TOA Radiation Budget using reprocessed ERBS WFOV Nonscanner observed Irradiance in the Period from 1985 to 1998

Monday, 9 July 2018
Regency A/B/C (Hyatt Regency Vancouver)
Shrestha Alok, SSAI, Hampton, VA; and K. Seiji, T. Wong, and P. W. Stackhouse

ERBE Wide-field-of-view (WFOV) nonscanner instrument onboard Earth Radiation Budget Satellite (ERBS) provided outgoing broadband irradiances at the top-of-atmosphere (TOA) from 1985 to 1999. However, earlier studies show that the uncertainty in this radiation dataset (Ed3) is significantly higher after the Mt. Pinatubo eruption in 1991 and battery issue in the second half of 1993. Furthermore, the differences between day and night longwave irradiance increased with time due to degradation of the shortwave dome, which was removed using a user-applied Ed3_Rev1 correction. To correct these Ed3 issues, we re-processed the ERBE/ERBS WFOV data using a new spectral unfiltering algorithm similar to that used in the CERES project. This new algorithm reduces the Ed3 artificial drift in daytime longwave irradiance by about 33%. The remaining daytime longwave drifts artifact is eliminated using linear trend removal technique. The final reprocessed WFOV data set (Ed4) is also corrected with the sampling correction to account for the sampling uncertainties due to ERBS precessing orbit. Further, the Ed4 data is calibrated to the absolute radiometric scale of the CERES-EBAF irradiances and the spatial coverage of ERBE/ERBS irradiances is also extended to global from 60°N to 60°S latitudes using CERES-EBAF climatological 60°N to 60°S latitudes (near-global) to global mean irradiance ratios. Comparing to the previous Ed3Rev1 data, the monthly near-global standard deviation of deseasonalized shortwave anomalies is reduced in the new Ed4 data, 8.0 Wm-2 vs. 3.2 Wm-2. Similar to Ed3Rev1, however, the Ed4 global shortwave irradiance averaged over the 1994 to 1997 period (second period) is smaller by 2.2 Wm-2 compared to that averaged over the 1985 to 1989 period (first period). In addition, the global longwave irradiance in the second period is larger by 0.7 Wm-2 compared to that averaged over the first period. When the difference of two periods is computed (second period minus first period) with the DEEP-C data product (Allan et al. 2014), the difference is -0.5 (-0.3) Wm-2 for shortwave (longwave). The global net imbalance at the TOA computed with ERBS and DEEP-C data sets are, respectively, 0.45 (1.89) Wm-2 and 0.17 (0.96) Wm-2 for the first (second) period. The net imbalance for the CERES period in the 2000s is 0.65 Wm-2. The ocean heating rate at 0-2000m (converted from 0-700m) derived from NODC is 0.31 (0.73) Wm-2 in the first (second) period. Although the net TOA irradiance and ocean heating rate disagree, the difference is within the uncertainty of the net TOA irradiance. Re-processed ERBS data product (Ed4) was released in July 2017 from NASA Langley Atmospheric Science Data Center and available from https://eosweb.larc.nasa.gov/project/measures/long-term-toa-m.
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