Differences between infrared and microwave sea surface temperature products

Infrared and passive microwave satellite sensors provide highly complementary information for the creation of sea surface temperature (SST) products. Infrared sensors provide high resolution and high accuracy estimates of the SST but the measurements are completely obscured by clouds. Passive microwave sensors, in contrast, have poorer resolution but are able to obtain measurements through non-precipitating clouds. By combining the measurements from the two sensors it is possible to produce an all-weather, high resolution SST product. We are currently preparing a blended SST product using infrared data from the advanced very high resolution radiometer (AVHRR) and passive microwave data from the Tropical Rainfall Mapping Mission (TRMM) Microwave Imager (TMI).

Our presentation will examine two aspects of the preparation of the blended SST product. We will first explore the differences between individual infrared and microwave SST products in light of the temperature gradient that commonly exists at the skin of the ocean. Infrared sensors measure radiation emitted only from the top 10 microns of the ocean while microwave radiometers measure radiation from depths down to approximately 1 mm. The skin layer of the ocean can lead to significant and variable differences between the temperatures at these depths. We discuss whether differences between the products are consistent with the presence of the skin layer and whether there are circumstances where the skin layer complicates or prevents the combination of the products. We next explore the results of different techniques for combining the two data sets. These techniques range from simple compositing methods to optimal interpolation. Accuracy statistics of the blended products will be presented and compared with the accuracy of the independent products.