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A new microwave satellite water vapour retrieval for use in polar winter conditions is presented. The retrieval employs a priori information and an iterative approach. It is tested using simulated and actual measurements from the Microwave Humidity Sounder (MHS) satellite instruments. Ground truth is provided by the G-band vapor radiometer (GVR) at Barrow, Alaska. For water vapour columns less than 6 kg m−2, comparison with the GVR gives a standard deviation of 0.39 kg m−2 and a systematic bias of 0.08 kg m−2. The errors are shown to be significantly less than for other satellite measurement systems. The errors are comparable to those from atmospheric reanalyses; however, the MHS data come at much higher horizontal resolution (< 40 km) and are shown to reveal more structure. The retrieval can be used to obtain pan-Arctic maps of water vapour columns of unprecedented quality. The retrieval may also be applied to the Special Sensor Microwave Imager/Sounder (SSMIS) and the Advanced Technology Microwave Sounder (ATMS). |
