Multi-pass objective analyses of radar data: Preliminary results

Radar data commonly are interpolated to a Cartesian grid via an objective analysis in order facilitate operations such as three-dimensional isosurface viewing, dual-Doppler wind synthesis, or simply two-dimensional contouring by a canned algorithm. Objective analysis typically is much more than just simple interpolation, rather, judiciously chosen tuning parameters (which typically are based on the data spacing, D) allow one to filter scales that are poorly resolved. Furthermore, it has been shown that multiple passes ("successive corrections") of an objective analysis "steepen" the response of the filter, i.e., such techniques are less damping at well-resolved scales (e.g., 8-20D) while still removing scales that are poorly resolved (e.g., <4D). I.e., a multi-pass objective analysis can provide a better fit to the observations than a single-pass objective analysis, yet still suppress small-scale noise. Curiously, we are unaware of any attempts to use multi-pass objective analysis on radar data, despite the fact that the use of such algorithms on other types of data (e.g., surface and upper-air observations) is very common. The added computational expense of a multi-pass objective analysis is significant in a relative sense compared to a single-pass objective analysis, but this is much less of an issue for today's personal computers.

At this conference we will present comparisons between single-pass and multi-pass Barnes objective analyses of synthetic radial velocity data obtained from a three-dimensional thunderstorm simulation. The objectively analyzed radial velocity data will be used to produce dual-Doppler wind syntheses, and comparisons will be made between the kinematic fields of the simulation (which will be regarded as the "truth") and those derived from dual-Doppler wind syntheses utilizing single- and multi-pass objectively analyzed synthetic radial velocity data. The improvement of multi-pass objective analyses on higher-order calculations such as trajectory calculations also will be assessed. Dual-Doppler wind syntheses based on single- and multi-pass objective analyses of Doppler On Wheels data obtained in a supercell thunderstorm will be presented as well.