Comparison of Simultaneous Rain Drop Size Distributions Estimated from Two Surface Disdrometers and a UHF Profiler

Christopher R. Williams

CIRES, University of Colorado and NOAA, Aeronomy Laboratory, Boulder, Colorado

Anton Kruger

The Iowa Institute of Hydraulic Researach, The University of Iowa, Iowa City

Kenneth S. Gage

NOAA, Aeronomy Laboratory, Boulder, Colorado

Ali Tokay

NASA, Goddard Space Flight Center, Maryland and Joint Center for Earth Systems Technology, University of Maryland at Baltimore County

Robert Cifelli

Joint Center for Earth Systems Technology, University of Maryland at Baltimore County and Atmospheric Science Department, Colorado State University, Fort Collins

Witold F. Krajewski

The Iowa Institute of Hydraulic Researach, The University of Iowa, Iowa City

Christian Kummerow

Atmospheric Science Department, Colorado State University, Fort Collins

ABSTRACT

In support of the NASA Tropical Rainfall Measuring Mission (TRMM) Ground Validation Program, a suite of surface instruments and vertical pointing Doppler radar profilers were deployed in central Florida to quantify the number and size of the rain drops reaching the surface. Analyzing 276 minutes of simultaneous observations from two surface disdrometers and one profiler revealed good agreement among the instruments for drop sizes > 1.5 mm diameter but poor agreement for smaller drop sizes. The magnitude of the difference in small drop estimation was proportional to the reflectivity (and rainrate). At rellectivities greater than 40 dBZ, the differences in the estimation of the number of small drops yielded differences in estimates of mass?weighted diameter of > 13% and of rainrate > 25%. The combined effect of these uncertainties impact the interpretation of the precipitation processes and the development and validation of space?based precipitation retrieval algorithms.