Surface radiation budget over tropical pacific: Interannual variability

A 21.5-year (July 1983 to December 2004) global dataset of surface shortwave (SW) and longwave (LW) radiative parameters on a 1x1 grid was recently completed under the NASA/GEWEX Surface Radiation Budget (SRB) Project at the NASA Langley Research Center (LaRC). Both SW and LW fluxes were derived with two sets of radiation algorithms: one set designated as primary and the other as quality-check. Cloud and surface properties derived from ISCCP pixel level (DX) data, temperature and humidity profiles from GEOS-4 reanalysis, and column ozone from TOMS archives were used as inputs to the algorithms. Several top-of-atmosphere (TOA) radiation budget parameters were also derived with the primary algorithms. Surface fluxes from all algorithms were extensively validated with ground-based measurements obtained from the Baseline Surface Radiation Network (BSRN), the Global Energy Balance Archive (GEBA), and the World Radiation Data Center (WRDC) archives. Detailed characteristics, analysis, and validation of this dataset are being presented in concurrent papers at this conference.

Since surface radiation represents a large part of energy input into the ocean, we have used the above dataset to examine the interannual variability of SRB parameters over large regions of western and eastern Pacific Ocean, and also over the Nino-3, Nino-4, and Nino-3.4 regions. Significant anomalies were found to occur in both shortwave (SW) and longwave (LW) downward and net fluxes over these regions during El Nino/La Nina episodes. The overall radiative effect was much smaller, however, because SW and LW effects partially cancelled each other. It was also seen that interannual effects related to El Nino/La Nina were not confined to the above-mentioned El Nino regions but extended over much larger areas. Surface flux variability was examined relative to the variability of surface and atmospheric state variables. The two showed a strong correspondence. Similar correspondence was also seen between surface fluxes and concurrently measured top-of-atmosphere (TOA) fluxes from satellite observations. Such relationships between independently derived TOA and surface fluxes greatly enhance confidence in the quality of these SRB parameters.