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Xu, F., 1997: Outgoing Longwave Radiation (OLR): Variability and Retrieval. Ph.D. thesis. Columbia University.
The outgoing longwave radiation (OLR) is one of the most important components in the global energy balance for the Earth-Atmosphere system. Both spatial and temporal variations of longwave radiation have direct implications on the climate. Despite its importance, the variabilities of OLR are still not well understood. One of the reasons is that the OLR is not observed with sufficient accuracy. In this study, the spatial and temporal variabilities of satellite observed OLR from three different datasets are examined. Through the comparison, we found that the current observations, although accurate in global average, have considerable uncertainties in smaller scales. Such uncertainties may cause difficulties in understanding some fundamental mechanisms of the atmospheric circulation. Every effort should be devoted to eliminate or minimize these uncertainties. The cause of the uncertainties can arise from many sources. Some of these uncertainties are technical, meaning they can be avoided or minimized by more careful planning and operations. The others are more fundamental, meaning that they are associated with the retrieval methods and can only be eliminated by improving the methods. By this investigation, we conclude that current measurements of OLR are not adequate to monitor/validate climate changes and are of limited value for climate model validations/improvements. The problems associated with current measurements are identified in this study and practical solutions to these problems are suggested.
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