Climatology of High Cloud Dynamics Using Profiling ARM Doppler Radar Observations

Abstract

ce cloud properties are influenced by cloud-scale vertical air motion. Dynamical properties of ice clouds can be determined via Doppler measurements from ground-based, profiling cloud radars. Here, the decomposition of the Doppler velocities into reflectivity-weighted particle velocity Vt and vertical air motion w is described. The methodology is applied to high clouds observations from 35-GHz profiling millimeter wavelength radars at the Atmospheric Radiation Measurement Program (ARM) Southern Great Plains (SGP) climate research facility in Oklahoma (January 1997?December 2010) and the ARM Tropical Western Pacific (TWP) site in Manus (July 1999?December 2010). The Doppler velocity measurements are used to detect gravity waves (GW), whose correlation with high cloud macrophysical properties is investigated. Cloud turbulence is studied in the absence and presence of GW. High clouds are less turbulent when GW are observed. Probability density functions of Vt, w, and high cloud macrophysical properties for the two cloud subsets (with and without GW) are presented. Air-density-corrected Vt for high clouds for which GW (no GW) were detected amounted to hourly means and standard deviations of 0.89 ± 0.52 m s?1 (0.8 ± 0.48 m s?1) and 1.03 ± 0.41 m s?1 (0.86 ± 0.49 m s?1) at SGP and Manus, respectively. The error of w at one standard deviation was estimated as 0.15 m s?1. Hourly means of w averaged around 0 m s?1 with standard deviations of ±0.27 (SGP) and ±0.29 m s?1 (Manus) for high clouds without GW and ±0.22 m s?1 (both sites) for high clouds with GW. The midlatitude site showed stronger seasonality in detected high cloud properties.