Naval Research Laboratory (NRL) scientists are leading a multi-agency study which reveals that a very high-resolution Doppler radar has the unique capacity to detect individual cloud hydrometeors in the free atmosphere.
This study will improve scientists’ understanding of the dynamics and structure of cloud systems.
This Doppler radar was previously used to track small debris shed from the NASA space shuttle missions during launch. Similar to the traces left behind on film by sub-atomic particles, researchers observed larger cloud particles leaving well-defined, nearly linear, radar reflectivity “streaks” which could be analyzed to infer their underlying properties.
Scientists could detect the individual particles because of a combination of the radar’s 3MW power, narrow 0.22 degree beamwidth, and an unprecedented range resolution as fine as 0.5m. This combination of radar attributes allows researchers to sample a volume of cloud about the size of a small bus (roughly 14 m3) when operating at a range of 2 km.
With such small pulse volumes, it becomes possible to measure the properties of individual raindrops greater than 0.5mm in diameter due to the low concentration of such drops in naturally occurring cloud systems and the overwhelming dominance such drops have on the measured radar reflectivity when present in a field comprised of smaller particles.