Towards a bias correction of the AVHRR Pathfinder SST data from 1985 to 1998 using ATSR

Abstract

There are many sea surface temperature (SST) datasets derived from various satellite instruments with different characteristics in terms of orbit, coverage, retrieval, calibration, accuracy and measurement type. This paper presents the results of a project to combine SSTs from two instruments: the Along-Track Scanning Radiometer (ATSR) SSTs and the Advanced Very High Resolution Radiometer (AVHRR) Pathfinder SSTs. The dual-view nature of the (A)ATSR series of radiometers enables high-quality sea surface temperatures to be retrieved. These SSTs are ideal for using as a reference in order to bias-adjust the AVHRR series of instruments. In addition a method to correct for aerosol effects in the AVHRR SSTs is employed using aerosol optical depth from the Total Ozone Mapping Spectrometer. The method enables positive characteristics of both datasets to be combined to provide a dataset of potentially high-quality, long time-series, large data coverage satellite sea surface temperatures for climate monitoring purposes.An AVHRR SST dataset at ¼ degree spatial resolution with associated systematic biases and uncertainties is produced for climate research covering the period 1985 to 1998. The method is used to produce improved AVHRR SSTs for the period 1991 to the present (when the ATSRs are available) and additionally the method can be used to estimate biases on AVHRR SSTs prior to the first ATSR launch (1985 to 1991).The bias-correction has the effect of reducing an observed cool bias in the AVHRR SSTs, relative to the Hadley Centre Sea-Ice and Sea Surface Temperature dataset (HadISST), especially in cases of high volcanic and Saharan dust aerosol. The time-series indicates that the bias correction scheme is effective during the 1990s at decreasing the cool bias in the AVHRR SSTs. The scheme is especially effective in times of high atmospheric volcanic aerosol levels such as the period following the Mount Pinatubo eruption in 1991.