12-yr Analysis of Cirrus Cloud: Its Radiative Effect and Microphysical Properties over the Midlatitude within the United States

Cirrus clouds play an important role in the atmospheric energy balance and hence in the earth’s climate system. The properties of optically thin clouds can be determined using both active and passive instruments. The goal of this research is to understand the optical properties of cirrus clouds and better estimate their net radiative effect on our earth surface. A combination of ground based active and passive instruments is used to better estimate the occurrence of the cirrus clouds optical properties. Cirrus cloud properties used in this research are retrieved from measurements of direct solar beam transmittance from the MultiFilter Rotating Shadowband Radiometer (MFRSR) (Min et al., 2004). Cloud mask data from a passive instrument, MultiPulse Lidar (MPL) is used coupled with a radiosonde instrument to derive the cirrus cloud optical depth. In this study, a statistical study was performed on cirrus cloud properties based on 12 years of measurements from both (passive and active) instruments at the Southern Great Plain Atmospheric Radiation Measurment (ARM) sites within the United States. Results from MFRSR analysis show over 30% of cirrus cloud present in the atmosphere is within optical depth between (1-2). Cirrus optical depth slightly increases during spring - summer and decreases in fall - winter. Through the statistical studies, the temporal and spatial variation of cirrus clouds are investigated to determine the occurrence of cirrus within these regions listed above and to also investigate their radiative effects on the atmosphere.