Ground-Based Remote Sensing of Cloud Particle Sizes during the 26 November 1991 FIRE II Cirrus Case: Comparisons with In Situ Data

Abstract

The paper presents the results of retrieving characteristic particle sizes for the November 26 1991 FIRE II case using two methods that utilize ground-based remotes sensors. The size information for the complete vertical depth of the cloud was obtained for a 3-hour period from 1830 to 2130 UTC using combined Doppler radar and IR radiometer measurements and for two shorter periods using radar reflectivity and CO2 lidar backscatter measurements. The results obtained with both remote sensing techniques are compared for these two periods. Possible retrieval uncertainties are discussed. Comparisons yielded an agreement with a relative standard deviation of 15%-20% between the two methods. Particle sizes retrieved by both methods were compared with 2D particle probe data sampled during 10 time intervals when a research aircraft was crossing the hub area. The relative standard deviation of particle sizes retrieved with the radar-radiometer method from those obtained from 2D probes is about 30% for nine compared times. The corresponding deviation for the lidar-radar method is about 35% for three compared times. The relative standard deviation between particle concentrations retrieved with the radar-radiometer method and those obtained from 2D probes is about 60% for nine compared times.