Monday, 12 January 2004
Assimilation of surface cloud, visibility, and current weather observations in the RUC
An initial technique with the RUC analysis has been developed for assimilation for surface observations of clouds (using ceilometers), visibility, and current weather to modify background fields of water vapor and cloud/hydrometeors. Use of these observations in data assimilation is critical to improved short-range numerical forecasts of low ceiling and low visibility, including fog events. The initial RUC technique uses interconsistency checks with satellite, radar, and background values to quality-control these observations, which are subject to various error problems. We will present a detailed description of the technique, including assumptions about the expected horizontal and vertical correlation of hydrometeor and relative humidity errors near the surface. The paper will also include description of a case study and demonstration of improved short-range forecasts of ceiling and visibility.