Tiny cloud droplets called “drizzle” influence the structure of clouds and their persistence—two factors important to climate. To accurately depict this process in climate models, scientists need better information about the genesis of drizzle. Scientists currently rely on airplanes to measure details like drizzle within a cloud, but flights are expensive and measurements are confined to a limited area. A less expensive and more comprehensive approach uses cloud radars on the ground, augmented by other remote sensors. Scientists have developed a new technique that uses spectra from cloud profiling radars to distinguish between air motion, cloud, and drizzle. Researchers used the extensive dataset collected during the deployment of the U.S. Department of Energy’s Atmospheric Radiation Measurement (ARM) Mobile Facility on Graciosa Island in the Azores to test the technique. The research team found that the method’s estimate of drizzle inside the cloud aligned very well with observed drizzle below the cloud, and that this observation held true whether the air was moving up or down. The newly established ARM research facility in the Azores will generate a long-term dataset to allow additional studies of this type.
Luke, E., and P. Kollias. 2013. “Separating Cloud and Drizzle Radar Moments During Precipitation Onset Using Doppler Spectra,” Journal of Atmospheric and Oceanic Technology 30(8), 1656-71. DOI: 10.1175/jtech-d-11-00195.1.