A Large Eddy Simulation of Cloud Radar Observations

Poster PDF


General Topics – Cloud


Mark A. Miller — Rutgers University Steven G Decker — Rutgers University
Virendra Prakash Ghate — Argonne National Laboratory Bryan Raney — Rutgers University


Figure 1. A 35-GHz cloud radar "umbrella" scan based upon WRF-LES simulations for November 15. 2012 at the AMF deployment location on the shore of Cape Cod in Massachusetts. Effective reflectivity factor is color-contoured and the axial scan designated (1)-(2) is parallel to the shoreline. The umbrella scanning pattern consists of six horizon-to-horizon Range-Height-Indicator (RHI) scans separated in 30 degree azimuth increments.
A wealth of new information is available from new scanning cloud radars that have been deployed at ARM sites and these instruments represent a new era in cloud radar remote sensing. These new systems have generated wide interest and a host of new science questions, whereupon many questions have arisen about the optimal operation of these new radars and the interpretation of the data that they produce. An effective way to address these questions is to use numerical radar simulators to examine various strategies for sampling cloud systems and to decipher how the radar systems may represent the physical processes that are occurring within the cloud. We have created a radar simulator that interfaces with the output from Large Eddy Simulations from the Weather Research and Forecast (WRF) model using 50-meter resolution and variable vertical resolution. The radar simulator produces simulations with specified elevation and azimuth angles and samples a cone-shaped volume with a width matching the actual radar's 3-dB beam width (Figure 1). It currently simulates each radar pulse volume of specified resolution, which is currently set at 25-m. The simulator calculates the intersection of each pulse volume with volumes of the WRF grid, including advection, and melds the WRF cell data (mixing ratio, temperature, pressure, etc.) into the pulse volume. Simple microphysical parameterizations are currently used to compute radar reflectivity, although more sophisticated parameterizations will soon be implemented, and attenuation is computed.