Atmospheric Sciences & Global Change Division
For Estimates of Cloud Optical Thickness, Simple Equation is Good Enough
In contrast to complicated algorithms and extensive computer time required to obtain cloud optical thickness from surface measurements, researchers funded by the DOE's Atmospheric Radiation Measurement (ARM) Program have developed a simple equation that does the job—as long as only reasonably close estimates are needed. Using data from several geographically diverse ARM sites, the researchers calculated cloud optical thickness from both their empirical method and a well documented transmission-based algorithm developed by Min and Harrison (1996). When compared, the median distributions were well within 10% of one another, and the shapes of the distributions were very similar. Because this new expression relies only on readily available solar flux measurements, it provides a much wider base of cloud optical depth values on a global basis than have previously been available.