P14R.12 DSD uncertainties estimated from multi-frequency profiler observations

Friday, 28 October 2005
Alvarado F and Atria (Hotel Albuquerque at Old Town)
Christopher R. Williams, Univ. of Colorado and NOAA/AL, Boulder, CO; and K. S. Gage, R. Cifelli, and S. W. Nesbitt

The vertical air motion, turbulence, and time-space variability of precipitation are factors that contribute to the uncertainties of raindrop size distributions (DSDs) retrieved with vertically-pointing Doppler profiling radars. In order to quantify these uncertainties, six profilers and four surface disdrometers were operated during the Front Range Pilot Program (FRPP) at two different field sites. Doppler profiling radars operating at 449-MHz were used to estimate the vertical air motion and turbulent motions. The 915- and 2835-MHz Doppler profilers were used to estimate the raindrop size distribution after correcting for the observed air motion and turbulence. The different radars with their different dwell times, pulse volumes, beam widths, and sensitivity to the small raindrops provide different views of the same precipitating cloud system. The uncertainties of the DSD estimates are derived using simulations and through comparisons with the surface disdrometer observations.

During the FRPP, surface disdrometers and profilers were operated at two different sites. At the Boulder Atmospheric Observatory (BAO) in Erie, Colorado, a Joss-Waldvogel disdrometer (JWD) was located next to three vertically-pointing Doppler profiling radars operating at 449-, 915-, and 2835-MHz. At the Platteville Atmospheric Observatory (PAO) in Platteville, Colorado, two JWDs were located 0.5 meters apart and were next to Doppler profilers operating at 449-, 915-, and 2835-MHz. A video disdrometer was deployed for the first half of the experiment at BAO and at PAO during the second half of the experiment. While the BAO and PAO field sites had profilers operating at similar frequencies, the radars had significantly different hardware and operating parameters.

The simulations and observations used to estimate the DSD uncertainties will be presented at the conference.

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