EOS Validation Program

Institution: National Center for Atmospheric Research
Phone: (303) 497-8943
E-mail: heyms1@ncar.ucar.edu

Larry Miloshevich, National Center for Atmospheric Research
Gregory McFarquhar, National Center for Atmospheric Research
Sergei Matrosov, National Oceanic and Atmospheric Administration
Steven Ackerman, University of Wisconsin - Madison

September 2001
Final Report, January 2003

We propose to acquire in situ microphysical measurements from aircraft for developing, validating, and improving several methods that retrieve cloud optical depth and effective particle radius from remote sensors, where the retrieved values represent the entire vertical cloud column. We will provide the measurements of cloud optical depth and effective particle radius to the MODIS Science Team, as well as information on cloud top pressure and thermodynamic phase, and collaborate with them on evaluating their algorithms that retrieve these properties from colocated MODIS or MAS radiance measurements. The proposed approach maximizes the accuracy of the remote sensor retrievals by developing and validating them based on critical in situ measurements on a flight-by flight basis.

We will use the in-situ measurements to develop a "two-parameter" empirical correlation technique that relates both re and the visible extinction coefficient (ext), from which is derived) to the radar-measured equivalent radar reflectivity factor (Ze) and the mean Doppler particle terminal velocity (vd); the radar/aircraft correlations will be validated on a day-by-day basis to avoid the inaccuracies of "universal" relationships. We will also use a second, independent technique to retrieve and re based on the combined radar-radiometer method of Matrosov et al. (1995, 1997). Similarly, we will use lidar measurements to develop empirical retrievals of and re for optically-thin clouds, and to provide accurate measurements of cloud top height and information on the vertical cloud structure. We will also use direct measurements of from sun photometers.

Our techniques will first be applied to data from the recent SUCCESS experiment, in which we acquired microphysical measurements. We will also acquire measurements during the upcoming EOS validation experiments at the ARM Southern Great Plains CART site (ARM-1 and ARM-2), and during the FIRE-III/SHEBA Arctic experiment. In addition to using size distribution measurements from a 2D-C imaging probe on-board the aircraft, we will deploy a Video Ice Particle Sampler (VIPS) and a Gerber PVM probe to measure the radiatively-important small particle portion of the size distribution, and to provide a direct measure of the extinction coefficient.