IMPROVED MEASUREMENTS OF THE DROP SIZE DISTRIBUTION OF A FREEZING DRIZZLE EVENT

Airborne measurements from a new digital holographic camera are compar ed with PMS 2D-C measurements during the Canadian Freezing Drizzle Exp eriment. The digital holographic camera is not affected by drop sizing errors associated with out of focus particles in the same way as the 2D-C probe. Recent theoretical simulations of 2D-C particle sizing err ors and approaches for statistically correcting the measurements are d iscussed. The theoretical simulations predict that in freezing drizzle with drop diameters from about 50-200 mu m, uncorrected PMS 2D-C meas urements can produce an artificial tail in the drop size distribution that extends out to about 325 mu m. The digital holographic camera doe s not see the artificial tail. 2D-C measurements of drop size distribu tion in freezing drizzle that have been statistically corrected show a n improved agreement with the digital holographic measurements. Some d igital images of drizzle drops and ice crystals from a recently improv ed version of the instrument, called a cloud particle imager (CPI), ar e also shown. (C) 1998 Elsevier Science B.V. All rights reserved.