Retrieval of cloud physical parameters from ground based observations of microwave atmospheric radiation and transmitted solar radiation

Several methods are proposed in this study to retrieve some cloud physical parameters from ground-based simultaneous observations with a microwave radiometer and other instruments. When cloud is thin, liquid water path and columnar water vapor amount can be retrieved to be consistent with measured intensities of two frequencies around 20 GHz and around 30 GHz under the assumption of homogeneous cloud temperature. In this retrieval procedure, cloud temperature, which affects the calculated value of liquid water path seriously, is given form measurement with an IR radiative thermometer. The effective radius of cloud particles is also derived from comparing the measured downward solar flux on the ground surface to calculated one. For the thick cloud, which is expected that the temperature difference between top and bottom of cloud is large, cloud top temperature is also retrieved from narrow view angle measurements of transmitted radiance of solar radiation at two wavelengths in addition to microwave measurements. The liquid water path is deduced from the comparison of measured radiances at the two wavelengths to the calculated values, thus the appropriate cloud top temperature can be retrieved to be consistent with the measured microwave intensity at two frequencies. Practices suggested that the observation with a microwave radiometer and a pyrnometer enables to derive the detail of cloud structure.