Validation of MODIS and AVHRR sea surface temperature using bulk measurements

Abstract

The development of algorithms for the production of reliable Sea Surface Temperature (SST) data sets from space borne infrared radiometers has been pursued by different agencies since late 1960's. The current state of the art in SST retrieval from space is limited by radiometer window placement, radiometer noise, quality of pre-launch characterization, in-flight calibration quality, viewing geometry and, mainly, atmospheric correction. The correction to eliminate the atmospheric effects is a critical and complicated step in the validation process, because although the satellite observations are approaching sufficient quality for routine use, unfortunately the thermal structure in the upper 10 in of the ocean is complex and highly variable, so SST may be significantly different depending on the vertical depth of the in situ measurement, the local time of day, local conditions at the air-sea interface and the instrument used; so in order to properly merge skin and bulk temperatures, daytime match-ups have been excluded from the validation process. In this context, the validation of the NOAA-AVHRR/3 and TERRA-MODIS atmospheric correction algorithms for the retrieval of sea surface temperature from the Canary Islands-Azores-Gibraltar area is performed by using more than 1500 in situ temperature measurements, derived from the ARGO Data Collection System and by the Oceanographic Service of the University of Las Palmas Gran Canaria, over the period from December 2000 to September 2003.