Daytime Precipitating Clouds Identification Scheme Relying on Optical Thickness and Effective Radius

Satellite remote sensing is currently the most important way of global-scale precipitation observations.The identification of precipitating clouds based on the satellite-borne measurements is still one of the most challengable problems.In order to get a universal precipitating-cloud identification method available for common optical satellite measurements,the relationship between cloud parameters and precipitating-cloud pixels is analyzed by using matched TRMM Visible and Infrared Scanner(VIRS) and Precipitation Radar(PR) long time scale measurements in the selected regions.According to the derived characteristic cloud parameters of precipitating clouds that is contrast to non-precipitating clouds,a daytime precipitating clouds detection scheme,called Identification of Precipitating Clouds from Optical Thickness and Effective Radius(IPCτ Re),is proposed relying on both cloud optical thickness and effective radius.As the cloud parameters are retrieved from the visible and infrared signals that cannot penetrate the precipitating clouds,the IPCτ Re scheme can be used operationally over both ocean and land areas.Comparison to PR standard rain products is conducted to verify the IPCτ Re results,in which three dimidiate-forecast factors are utilized and two other precipitating-cloud identification schemes are also evaluated,with one proposed by Inoue and Aonashi(2000) and the other proposed by Nauss and Kokhanovsky(2006).The study proves that IPCτ Re scheme gives better spatial depiction of precipitating clouds.Especially,in oceanic areas,precipitating and nonprecipitating clouds are well separated by current method,with the probability of detection near 0.84 and probability of false detection remaining just 0.06,indicating a satisfying accuracy for satellite monitoring and forecasting of precipitation operations.