Automatic quality control and analysis of airborne Doppler data: real-time applications, and automatically post-processed analyses for research

At the Hurricane Research Division of AOML, we have developed software that allows us to quality control (QC) airborne Doppler-radar data collected aboard the NOAA WP-3D aircraft, analyze the data, and send the analyzed and quality-controlled data from the aircraft to the ground. The QC removes reflections from the sea surface, radar gates with too high a velocity spectral width, and badly de-aliased Doppler radial velocities. The software first uses the Bargen-Brown (Bargen and Brown 1980) de-aliasing scheme followed by a home-grown two-dimensional scan de-aliasing scheme, to quality control the velocities, and then interpolates the data to a cylindrical grid centered on the presumed center of the tropical cyclone. A wind field that is a function of radius, height, and the zeroth and first Fourier components is then synthesized from the interpolation to produce a first guess. The second pass through the data then attempts to find the correct Doppler Nyquist interval for each radial velocity observation using the first guess wind field. This second analysis is Cartesian but uses an interpolation filter that is cylindrical, with greater upwind and downwind influence than radial influence. A third pass through the data produces inbound and outbound vertical cross sections of the vertical, radial, and total wind speed. All three analyses use a three-dimensional variational solution scheme, similar to Gao et al. (1999).

In the past, quality control of P3 airborne Doppler radar data for a single pass through the storm center could require a full person week to accomplish, but the automatic method performs the QC in minutes. Thus, this automatic method allows us to produce analyses for many passes through the hurricane. In fact, virtually all analyses for the 2004 and 2005 seasons are at the HRD website at http://www.aoml.noaa.gov/hrd . By the time of the conference 2006 and 2007 analyses should also be online.

In the process of producing these analyses, the QC Doppler radial velocities are produced and placed in a file. These files will be sent by satellite to the NCEP Environmental Modeling Center for assimilation in real time into the HWRF (Hurricane Weather Research and Forecasting) model. It is expected that these data will improve the initial representation of the inner core wind field in HWRF simulations.

At the conference we will present examples of these analyses and the means to obtain them, as well as the quality-controlled Doppler radial velocities, from http://www.aoml.noaa.gov/hrd .

References:

Bargen, D. W., and R. C. Brown, 1980:Interactive radar velocity unfolding. Proc. 19th Conference on Radar Meteorology, Miami, Amer. Meteor. Soc., 278-283.

Gao, J., M. Xue, A. Shapiro, and K. K. Droegemeier, 1999: A variational analysis for the retrieval of three-dimensional mesoscale wind fields from two Doppler radars. Mon. Wea. Rev., 127, 2128–2142.