Failures in detecting volcanic ash from a satellite-based technique - Comments

The recent paper by Simpson et al. [Remote Sens. Environ. 72 (2000) 191.] o n failures to detect volcanic ash using the 'reverse' absorption technique provides a timely reminder of the danger that volcanic ash presents to avia tion and the urgent need for some form of effective remote detection. The p aper unfortunately suffers from a fundamental flaw in its methodology and n umerous errors of fact and interpretation. For the moment, the 'reverse' ab sorption technique provides the best means for discriminating volcanic ash clouds from meteorological clouds. The purpose of our comment is not to def end any particular algorithm; rather, we point out some problems with Simps on et al.'s analysis and re-state the conditions under which the 'reverse' absorption algorithm is likely to succeed. (C) 2001 Elsevier Science Inc. A ll rights reserved.