Climate monitoring with the HIRS outgoing longwave radiation data

Twenty-five years of global outgoing longwave radiation (OLR) data at the top of the atmosphere were retrieved with the narrowband radiance measurements from the High Resolution Infrared Sounder (HIRS) onboard the TIROS-N series of the operational polar orbiting environmental satellites (POES). This product is a result of the rigorous reprocessing efforts of the HIRS level 1b data with careful and consistent procedures. In order to meet climate data record quality, we have devised methods to remove the inter-satellite biases in the orbital data and to minimize the orbital drift effects in the monthly means. For quality control and validation purposes, we inter-compared several OLR products from independent sources, including the NCEP/NCAR Reanalysis, ECMWF Reanalysis, the TOVS Pathfinder Path A, the Advanced Very High Resolution Radiometer (AVHRR) Pathfinder Atmosphere (PATMOS) project, and the ERBE and CERES broadband observations.

The inter-comparison showed favorable characteristics among these OLR products and strong similarities in climate monitoring capability. However, it also revealed various degrees of discrepancy and disagreement that are intrinsic to the OLR derivation procedures. We investigated the sources of these differences and their implications for climate monitoring.