Assimilating Satellite Observations of Clouds and Precipitation into NWP Models

what: Sixty-five experts in numerical weather prediction (NWP) and remote sensing were invited to document progress in cloud and precipitation data assimilation and to recommend pathways for future research and development. when: 15–17 June 2010 where: Reading, United Kingdom S atellite observations in the visible, infrared, and microwave spectrum provide a great deal of information on clouds and precipitation as well as the atmosphere in which the clouds are embedded. A major issue is how to use this information to initialize cloudy and precipitating atmospheric regions in NWP models. Most cloudand/or rain-affected observations are discarded in current data assimilation systems. The major problems are the discontinuous nature, in time and space, of clouds and precipitation, the complex nonlinear and not-well-modeled processes involved in their formation/prediction, and the need for current data assimilation systems to use linearized versions of these nonlinear processes. As a result, cloud/rain-affected radiances are much more difficult to assimilate than clear-sky radiances, which are sensitive to the smoother fields of temperature and water vapor that are controlled by more linear, wellmodeled processes. Since clouds and precipitation often occur in sensitive regions in terms of forecast impact, improvements in their assimilation are likely necessary for continuing significant gains in weather forecasting and, in particular, the prediction of two key weather elements affecting human activities: precipitation and cloudiness (which impacts another key weather factor, surface temperature). In 2005, the National Aeronautics and Space Administration (NASA)–National Oceanic and Atmospheric Administration (NOAA)–Department of Defense (DoD) Joint Center for Satellite Data Assimilation (JCSDA) sponsored an international workshop on assimilating observations in cloudy/ precipitating regions. Papers from that workshop were published in a special section of the November 2007 issue of the Journal of the Atmospheric Sciences AFFILIATIONS: bauer—European Center for Medium Range Weather Forecasting, Reading, United Kingdom; ohrinG—NOAA, Camp Springs, Maryland; Kummerow—Colorado State University, Fort Collins, Colorado; auliGne—University Corporation for Atmospheric Research, Boulder, Colorado CORRESPONDING AUTHOR: George Ohring, NOAA/NESDIS, 5200 Auth Rd., MD 20746 E-mail: george.ohring@noaa.gov