Daily SST fields produced by blending infrared and microwave radiometer estimates

Abstract

Measurement of Sea Surface Temperature (SST) using satellite based sensors have matured during the last decade. The infrared measurements, using the AVHRR sensor, flown onboard the NOAA satellites, have been used for the generation of high resolution operational products on daily basis, since 1982. However, the intrinsic problem of the infrared radiation prevents the retrieval of SST in the presence of clouds. This causes heavy loss of SST data over the north Indian Ocean especially during the summer monsoon (June-September). The recent advances in the microwave remote sensing of SST provides an alternative for the retrieval of SSTs in the presence of clouds. The microwaves, though they can measure the SSTs in the presence of clouds, their spatial resolution is poorer than that of infrared measurements. Near land boundaries the retrievals of the SSTs using microwaves are inferior due to the contamination from the emissions from land. In this study we take the advantage of the SST retrievals from infrared (NOAA/AVHRR) and microwave (TRMM/TMI) sensors and produce a new SST filed. An objective analysis scheme is used to combine the SSTs retrieved using AVHRR (9 km daily ascending and descending passes) and TMI (25 km ascending and descending passes) sensors to produce a daily field at a spatial resolution of 18 km. The new SST fields when compared with in situ measurements (drifting buoy SSTs) showed improvement (Root Mean Square Error of 0.659 degrees C). The corresponding root mean square error of the SSTs derived from AVHRR and TMI were 0.642 degrees C, and 0.783 degrees C respectively.