A Doppler-radar-based cloud-scale dynamics climatology of cirrus

 

Authors

Pavlos Kollias — Stony Brook University
Heike Kalesse-Los — University of Leipzig
Matthew Gruber — University of Alaska, Fairbanks

Category

Dynamics/Vertical Motion

Description

Cirrus microphysical properties are strongly controlled by vertical air velocities and their mesoscale variability (Kärcher and Ström 2003). It has been argued that adequate parameterization of cirrus in global climate models requires cloud-scale vertical velocity probability density functions (Kärcher and Lohmann 2002). Dynamical properties of cirrus can only be directly determined through the use of Doppler measurements from cloud radars at ground-based profiling sites or using aircraft penetrations. Here, probability density functions of vertical velocity as well as turbulence and updraft fractions are presented. The study is based on 15 years (1997–2011) ground-based cirrus cloud observations from the profiling millimeter-wavelength radar at the Atmospheric Radiation Measurement (ARM) Southern Great Plains (SGP) climate research facility in Oklahoma, USA. In addition, the Doppler measurements are used to detect gravity waves whose correlation with cirrus microphysical properties is investigated. ECMWF re-analysis model output is used to relate the cirrus clouds dynamics to large-scale meteorology.

References:

Kärcher, B, and U Lohmann. 2002. “A parameterization of cirrus cloud formation: Homogeneous freezing including effects of aerosol size.” Journal of Geophysical Research 107: doi:10.1029/2001JD001429.

Kärcher, B, and J Ström. 2003. “The roles of dynamical variability and aerosols in cirrus cloud formation.” Atmospheric Chemistry and Physics 3: 823–838.