Assessment of the MODIS and AMSR-E-Derived SST Products in joining area of Asia and Indian-Pacific Ocean

The Moderate Resolution Imaging Spectroradiometer (MODIS) and the Advanced Microwave Scanning Radiometer (AMSR-E) aboard the NASA Earth Observation System's Aqua satellite have been measuring the sea surface temperature (SST) since 2002. Although satellite-derived SST data complement the ground-based SST field data in better understanding the role of SST in coupling the ocean and atmosphere, they need to be validated in order to determine the spatiotemporal variation of their availability, and their error features, and then to decide how they can be used for further applications. In this paper we assess the spatiotemporal coverage and error variation of MODIS and AMSR-E level-3 mapped SSTs during 2003 to 2005 over the joining area of Asia and the Indian-Pacific Ocean. Drifting buoy SST data obtained from the Atlantic Oceanographic and Meteorological Laboratory (AOML) is used as a benchmark for the study. The results show that multi-year and annual average availabilities of MODIS SSTs are lower than those of AMSR-E SSTs due to their different cloud penetration. Weekly mean availability of AMSR-E SSTs is nearly constant during 2003-2005 whereas that of MODIS SSTs shows obvious seasonal variation, i.e. it is low in summer and high in spring and autumn. The intra-annual variation of MODIS and AMSR-E availability is similar for the three year period. The geographical signal of annual mean availability of MODIS is more obvious than that of AMSR-E, i.e. it is high at about latitudes 20 degrees N and 20 degrees S and low around the equatorial regions. For error feature, the overall accuracy and precision of MODIS SSTs are lower than those of AMSR-E SSTs due to their slight differences in atmospheric effects, cloud penetration, spatial resolution, measured depths, and retrieval algorithms. Even so, annual mean biases of these two datasets are both within 0.5 degrees C. The intra-annual variation of the error feature of MODIS is much more obvious than that of AMSR-E due to the wider range of mean bias and standard deviation. The intra-annual variations of MODIS and AMSR-E error are similar for the three year period. We also find that the accuracy and precision of MODIS and AMSR-E have an obvious geographical signal for the three year period. That is, the accuracy and precision become higher moving from mid-latitudes of the northern hemisphere through equatorial regions to mid-latitudes of the southern hemisphere.