A global ship track climatology from ATSR-2: January 1999 - January 2001

Abstract

Two years (January 1999 - January 2001) of data from the Along-Track Scanning Radiometer 2 (ATSR-2) aboard the satellite ERS-2 have been processed with an automatic ship track detection algorithm. The distribution of detected tracks shows similar patterns and magnitudes to another satellite-derived dataset and is consistent with locations of shipping lanes. Most tracks are detected in the North Pacific and North Atlantic, between March and August. The derived track masks have been used with ATSR-2 data from the Oxford-RAL Aerosol and Clouds (ORAC) retrieval scheme to reveal differences between track and non-track clouds. Water clouds which are part of a ship track show an approximate 50% increase in optical depth as compared to background cloud conditions (30 km or more from tracks), and a decrease in effective radius of similar magnitude. This is consistent with the first aerosol indirect (Twomey) effect