During the past decade Doppler radar profilers that operate near 1 GHz and 3 GHz have been developed at the NOAA Aeronomy Laboratory for use in dynamics and precipitation research. The profilers have been used extensively in numerous field campaigns during the past decade. The field campaigns include the Coupled Ocean Atmosphere Response Experiment (COARE) that took place in the western Pacific warm pool region during 1992-93, the Maritime Continent Thunderstorm Experiment (MCTEX) that took place near Darwin, Australia in November - December 1995, the Combined Sensor Program (CSP) that took place in the vicinity of Manus Island, Papua New Guinea in March 1996 and the Tropical Rainfall Measuring Mission (TRMM) Ground Validation Field Campaigns: TEFLUN (Texas and Florida; 1998), TRMM LBA (Brazil, January -February 1999) and KWAJEX (August - September 1999). Additional campaigns include the NAURU99 campaign that took place in July 1999 and the EPIC Campaign in 2001.

Profiler observations yield time height cross-sections of equivalent reflectivity, Doppler velocity and spectral width that illustrate the evolution of precipitating clouds systems. In the presence of precipitating clouds backscattering from hydrometeors is dominant and the Doppler velocity provides a measure of the fall velocity of hydrometeors. The vertical structure of these parameters has been used to classify the precipitating cloud systems into several different categories. These observations document the prevalence of deep anvil cloud systems over the Pacific warm pool region. They also show the relative abundance of rainfall from stratiform and convective components of precipitating cloud systems and the continuous observations reveal the diurnal evolution of the precipitating clouds over the profiler.

The profiler observations provide important information for the calibration and validation of precipitation measurements by other instruments and platforms. For example, direct comparisons of profiler reflectivities with scanning radar reflectivities provide a direct means for calibration of scanning radars. The profilers are calibrated with a collocated disdrometer.

An important objective of the profiler observations is to retrieve drop-size distributions and to determine the variability of the drop-size distributions in diverse precipitating cloud systems. Recent developments provide optimism that drop-size distribution retrievals can be made by profilers operating at 1 GHz or 3 GHz without complementary measurement of vertical air motions. These developments indicate that important future applications of profilers will include their use as part of integrated observing systems at hydrological field sites designed to measure precipitation parameters over an areal domain the size of a catchment basin.