Cirrus Radiative Flux Study at SGP Using Radar/Lidar/AERI Derived Cloud Properties

The role that clouds play in the Earth's radiative balance represents a major source of uncertainty in understanding climate and climate change. A large part of this uncertainty lies in the modeling of the cloud, which requires assumptions and simplifications of the cloud morphology. In this study uniform cirrus cloud events at the Atmospheric Radiation Measurement (ARM) Southern Great Plains (SGP) site are investigated using various data sources (including 3 mm and 8 mm radar, lidar, AERI, and combinations thereof) to derive cloud microphysical and optical properties. The results of a flux closure study are presented where observed top-of- atmosphere and surface flux measurements are compared with computed fluxes. Computed heating rates are compared with the ARM Broadband Heating Rate Profile (BBHRP). Results indicate that combinations of measurement types are needed to accurately characterize thin cirrus. Radar alone can miss significant upper level cirrus impacting the computed fluxes and heating rates. Vertical distribution of cirrus extinction and particle size is significantly less important than the total optical depth in computing heating rates.