SR SSD 2001-16

Technical Attachment

Improving Precipitation Estimates

Gary M. Carter
Director, Office of Hydrologic Development

Many comprehensive activities are underway in the Hydrology Laboratory at NWS Headquarters to improve the estimation of precipitation and thus enhance river, flood, and flash flood forecasting. This brief note is intended to spread the word to other NWS offices about these activities. Results of the lab's work will directly impact RFC and WFO operations through enhancements to the AWIPS algorithms and the open-RPG (ORPG) system. What follows is an overview. Members of the Hydrology Lab staff will also be making presentations at upcoming AMS and NWA conferences, and they welcome opportunities to participate in local or regional meetings as appropriate, and as resources allow.

The Hydrology Laboratory is part of the NWS Office of Hydrologic Development ( A major part of the OHD mission is to infuse new hydrologic science into NWS operations, so we are naturally active in on-going efforts to improve WSR-88D multisensor quantitative precipitation estimation (QPE) algorithms and products. Major project areas address some of the more important and challenging deficiencies in radar-rainfall estimation which impact both the Weather Forecast Offices and the River Forecast Centers. These enhancements include the following items scheduled for upcoming WSR-88D and AWIPS software builds.

1) A new AWIPS Multisensor Precipitation Estimator (MPE) algorithm to improve utilization of radar and rain gauge data (in AWIPS 5.1) and satellite rainfall estimates (in AWIPS 5.2).

2) A new WSR-88D Range Correction Algorithm (RCA) planned for ORPG 2, and Convective-Stratiform Separation Algorithm (CSSA) for ORPG 3. The latter will perform vertical reflectivity profile corrections to the AWIPS precipitation processing system (PPS) rainfall estimates and improve range performance, particularly for cool season stratiform precipitation events, and mitigate bright band contamination.

Additional major project areas include work on improvements to automated rain gauge quality control procedures, and the development of polarimetric and probabilistic multisensor rainfall products for the future.

These activities and future plans for QPE improvement are described in a presentation on the OHD Hydrology Laboratory web site at Scroll down to the "WSR-88D Rainfall Estimation" section to find the presentation entitled Projects and Plans for Improving WSR-88D Rainfall Algorithms and Products in HTML or PDF formats. Comments or questions about any of these activities can be directed to Richard Fulton in the Hydrology Laboratory (, or other members of the OHD staff.