Backscatter and Propagation Observations of Radar and Lidar in Marine Cumulus Clouds: Simulations and Measurements

This paper presents backscatter and propagation observations of marine cumulus clouds. During the Cloud Systems Evolution in the Trades (CSET) field campaign, airborne measurements from the High-Performance Instrumented Airborne Platform for Environmental Research (HIAPER) Cloud Radar (HCR) and the High Spectral Resolution Lidar (HSRL) were made in the North Pacific. The HCR operated at a frequency of 94 GHz (3 mm wavelength) and collected observations at high temporal (0.1 s) and range (30 m) resolution. The capability of HCR is enhanced by the coordination with the HSRL. The HSRL made high temporal (0.5 s) and range resolution (7.5 m) observations of calibrated backscatter and extinction at a wavelength of 532 nm.

Cloud and drizzle in situ probe measurements are used for simulating backscatter and propagation observations. The in situ hydrometeor particle size measurements were collected during the VOCALS (VAMOS [Variability of the American MOnsoonS] Ocean-Cloud-Atmosphere-Land Study) and CSET field campaigns. For particle diameters between 1.2 and 46 microns, a cloud probe gathered size spectra. Drizzle probe size spectra correspond to particle diameters between 25 and 1565 microns. A Mie scattering program capable of producing converged scattering cross-section of non-absorbing and absorbing droplets of large sizes compared to wavelength are used for simulating the lidar and radar observations. Simulated observations of merged droplet spectra from cloud and drizzle probes are discussed in relation to lidar and radar measurements during the CSET.