Gridpoint Statistical Interpolation for Rapid Refresh

The Rapid Update Cycle (RUC) has been operational at NCEP since 1994. The present version (as of June 2005) of the RUC has 13-km horizontal resolution and 50 vertical levels. Every hour it produces analyses and short-range numerical predictions for aviation, severe weather and public forecasting. The RUC assimilates data from diverse sources: RAOBs, wind profilers, commercial aircraft, METARs, buoys, precipitable water estimates, satellite images of clouds, etc. A new version of the RUC, called the Rapid Refresh (RR)is under development at the NOAA Forecast Systems Laboratory in Boulder,Colorado in close collaboration with NCEP/EMC. The RR will incorporate the dynamics and physics of the Weather Research and Forecasting (WRF) model and a three-dimensional variational assimilation scheme based on Gridpoint Statistical Interpolation (GSI). GSI was developed at the Environmenal Modeling Center (EMC), one of the National Centers for Environmental Prediction (NCEP). It is intended for use on both global and regional domains. This presentation will describe the installation of the GSI code on a large Linux cluster and adaptation of the GSI code for use in the RR so as to retain features already present in the RUC, including a cloud/hydrometeor analysis (combining background 1-h forecast, current GOES cloud-top data, and METAR cloud/visibility/current weather observations), quality control, representativeness of surface data using depth of the planetary boundary layer , and the inclusion of data on surface characteristics (snow cover, soil, and vegetation). The Rapid Refresh also includes a larger domain than the current RUC, to include most of North America including Alaska, Puerto Rico, and Canada. The application of the GSI in the Rapid Refresh will also focus on use of satellite data on an hourly cycle over much larger,otherwise-data-sparse regions over oceans and arctic regions.