Exploration of Supercooled Water Detection in Orographic Clouds Using Differential Attenuation at W-Band

The Seeded and Natural Orographic Wintertime clouds: the Idaho Experiment (SNOWIE) field campaign operated from January 7, 2017 – March 17, 2017 in the Payette Basin just northeast of Boise, ID. The goal of this campaign was to use radar and in-situ measurements to observe seeded and natural orographic clouds to prove the efficacy of orographic cloud seeding over the Payette Basin. One of the platforms used was the Wyoming King Air aircraft equipped with the Wyoming Cloud Radar, a 3 mm wavelength cloud radar, which flew through, and collected data on orographic clouds to obtain fields of reflectivity and radial velocity. This cloud radar has two beams, one that points directly down, and one that points forward of the aircraft at a 30-degree angle from nadir.

Supercooled liquid water (SLW) is required for cloud seeding to be successful. Currently, SLW can only be observed along the path of a specially equipped rawinsonde or research aircraft, or directly overhead with a microwave radiometer.

Liquid water droplets strongly attenuates a radar beam at W-Band. In this paper, we explore how using different beam angles of the cloud radar may provide a way to recover SLW. We are developing a technique to acquire the distribution of liquid water content throughout a cloud using differential attenuation at W-Band. Preliminary results of liquid water content distributions as a function of depth using this technique are presented.