Vertical velocities and turbulence in midlatitude anvil cirrus: A comparison between in situ aircraft measurements and ground-based Doppler cloud radar retrievals

Description

This study introduces a statistical comparison of vertical velocity observations within cirrus from aircraft and ground-based Doppler cloud radar. Two cases of midlatitude anvil cirrus forming under very similar environmental conditions are examined. The case studies benefit from simultaneous observations of vertical velocities in cirrus collected at and around the Atmospheric Radiation Measurement Southern Great Plains site during the U.S. Department of Energy Small Particles in Cirrus field campaign. Observations from both platforms suggest that the majority of vertical velocities in the examined midlatitude anvil cirrus cases are roughly within ±1 m s−1 although higher vertical velocities are occasionally observed. The quality of the vertical velocity comparison between in situ aircraft measurements and ground-based Doppler radar retrievals depends on the case. For the first case on 23 April 2010, the comparison suggests that the radar retrieval may underestimate vertical velocities in the range between roughly 50 cm s−1 and 1 m s−1. For the second case on 14 June 2010, the agreement between radar and aircraft is excellent, and the differences are largely within the observed variability of vertical velocities within cirrus. Differences in the spatial scales of vertical velocities and turbulence sampled by the aircraft and Doppler radar, which arise due to differences in the temporal resolution of the observational platforms are not found to explain the observed discrepancies. Estimates for the dissipation rate of turbulent kinetic energy agree to within 1 order of magnitude between the two observational platforms.