Relationships Between Meteorological Conditions and Cloud Properties Determined form ARM Data

The cloud vertical structure, including top and base heights, layer thickness, and the characteristics of multilayered clouds, has been examined by Wang et al. (1995) by using radiosonde data. Cloudy layers are identified by relative humidity (RH) values above a threshold value of 84%. Cloud-layer top and base are identified by sudden changes in RH. These changes are positive at the base and negative at the top. The use of a constant threshold value for RH might misclassify clear moist layers as cloudy layers in boundary layer, and drier cloudy layers as clear layers in middle to upper troposphere. With the availability of the Active Remotely Sensed Cloud Location (ARSCL) (Clothiaux et al. 2001) cloud product at the Atmospheric Radiation Measurement (Program) Southern Great Plains (ARM SGP) central facility site, the RH threshold values changing with temperature can be examined.