Cirrus Cloud Microphysical Property Retrieval Using Lidar and Radar Measurements. Part II: Midlatitude Cirrus Microphysical and Radiative Properties

Abstract

The lidar?radar algorithm described in Part I of this set of papers is applied to ?1000 h of Raman lidar and millimeter wave cloud radar (MMCR) data collected at the Atmospheric Radiation Measurement program Southern Great Plains Clouds and Radiation Testbed site in Oklahoma during the period from November 1996 to November 2000. The resulting statistics of cirrus microphysical and radiative properties show that most cirrus clouds are optically thin (mean optical depth of 0.58 with a standard deviation of 0.67) with low ice water path (mean 12.19 g m?2 with a standard deviation of 19.0). The seasonal changes of cirrus properties are relatively small except for the general effective radius (Dge). Strong temperature dependencies of ice water content, Dge, and extinction coefficients are found in the dataset, which are well described by second-order polynomial functions. The temperature and thickness dependencies of the cirrus properties are studied in detail, providing information useful in the validation and improvement of cirrus parameterizations in general circulation models. The limitations of the MMCR for cirrus detection are also considered through comparisons with results from the Raman lidar, which show that the MMCR fails to detect most thin cirrus with τ ≤ 0.1 and consistently underestimates physical cloud thickness. Comparisons with available data describing cirrus microphysical and radiative properties are made, and an improved cirrus particle extinction coefficient parameterization based on the combined lidar?radar approach is offered.