P4.3 Methods for Evaluating Microwave-derived Satellite Liquid Water Products

* Corresponding author address: Tom Greenwald, CIMSS, University of Wisconsin, 1225 W. Dayton St., Madison, WI 53706-1695; e-mail: [email protected]. Cloud liquid water path (LWP) observed over the oceans by microwave sensors is one of only a handful of physical cloud parameters measured from space. These observations have had some use in, e.g., climate studies (Greenwald et al. 1995, Zuidema and Hartmann 1995), global model verification of cloud LWP (e.g., Lemus et al. 1997), and aircraft icing studies (Tremblay et al. 1996). They also have value in providing key tests for global climate models in terms of the relationships of physical cloud properties to the radiation budget (Stephens and Greenwald 1991); relationships that are the result of cloud-climate feedback processes, which are currently poorly represented in these models (Cess et al. 1990; Cess et al. 1996). In addition, these products may have future application in data assimilation in numerical weather prediction. Although continuous cloud LWP data over the oceans have been available for nearly 15 years, these data are greatly underutilized. We believe one reason is that little is known about their error characteristics. This study uses previously developed multi-sensor satellite techniques to evaluate and interpret cloud LWP products from the TMI (TRMM Microwave Imager) under different cloud conditions and provides estimates of their accuracy over the global oceans. These methods include cloud clearing TMI LWP products using VIRS (Visible and Infrared Scanner) data and comparing TMI products to similar products derived from VIRS for cloudy scenes. Two different months in 1998 were chosen for analysis.