A 25-month database of stratus cloud properties generated from ground-based measurements at the Atmospheric Radiation Measurement Southern Great Plains Site

A 25-month database of the macrophysical, microphysical, and radiative prop erties of isolated and overcast low-level stratus clouds has been generated using a newly developed parameterization and surface measurements from the Atmospheric Radiation Measurement central facility in Oklahoma. The databa se (5-min resolution) includes two parts: measurements and retrievals. The former consist of cloud base and top heights, layer-mean temperature, cloud liquid water path, and solar transmission ratio measured by a ground-based lidar/ceilometer and radar pair, radiosondes, a microwave radiometer, and a standard Eppley precision spectral pyranometer, respectively. The retriev als include the cloud-droplet effective radius and number concentration and broadband shortwave optical depth and cloud and top-of-atmosphere albedos. Stratus without any overlying mid or high-level clouds occurred most frequ ently during winter and least often during summer. Mean cloud-layer altitud es and geometric thicknesses were higher and greater, respectively, in summ er than in winter. Both quantities are positively correlated with the cloud -layer mean temperature. Mean cloud-droplet effective radii range from 8.1 mu m in winter to 9.7 mu m during summer, while cloud-droplet number concen trations during winter are nearly twice those in summer. Since cloud liquid water paths are almost the same in both seasons, cloud optical depth is hi gher during the winter, leading to greater cloud albedos and lower cloud tr ansmittances.