Vertically integrated water vapor transport (IVT) integrated with respect to time from 0000 UTC 1 May to 0000 UTC 3 May 2010, calculated from the 6-hourly 0.5° NCEP Global Forecast System operational analyses.
A flow connectivity grid developed for the Russian and Napa Rivers in California is intended to route excess precipitation from each grid cell to the stream network and thence downstream. Soil moisture accounting procedures are applied for each grid to determine infiltration and the excess precipitation.
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Contact:  Lynn Johnson
February 17, 2012

Hydrological and Surface Processes (HASP) Plan Completed

An updated plan has been completed for Hydrological and Surface Processes (HASP), one of HMT's major activity areas. The vision for HASP is to advance the state-of-the-science for monitoring, modeling and decision support for water forecast operations and management. A near-term focus of the HASP research plan is to enhance the coupling of atmospheric and hydrologic models. A desired outcome is a working prototype and performance assessment of a distributed hydrologic model. Another important component of HMT HASP research is to assess specific aspects of soil moisture dynamics to understand the limits of the measuring systems and the representativeness of in-situ network observations. HASP research involves collaboration between the HMT and the NWS Office of Hydrologic Development (OHD), the California-Nevada River Forecast Center (CNRFC) and the Colorado Basin River Foreast Center (CBRFC).

The distributed model being used is the Hydrology Lab Research Distributed Hydrology Model (HL-RDHM), which was developed by OHD over the past decade. This assessment would involve various precipitation forcings for Quantitative Precipitation Estimation (QPE), Quantitative Precipitation Forecast (QPF) and Ensemble QPF for selected river basins having distinct hydrologic characteristics. The HL-RDHM is intended to become a primary component of NWS hydrological forecasting operations because, in contrast to the current lumped modeling approach, it can account for the spatial variability of precipitation and soil moisture, provides streamflow predictions at any location in a watershed, and affords new gridded products (e.g. soil moisture, soil temperature, evapotranspiration, and snow).

The distributed model is being applied to the Russian, Napa and North Fork American basins in California, and the Babocomari River in Arizona. Its application involves a gridded mesh to represent the terrain and flow patterns (see figure), soil characteristics, and the input precipitation patterns. Distributed model parameter sensitivity, parameter identification, and calibration and verification activities for the Russian River model are currently being conducted. Through collaboration with the CNRFC, the distributed model results will then be compared with those obtained from the lumped mode. The North Fork American River model is being used by OHD to examine the influence of snow level representations with the distributed and lumped approaches. Specific aspects of soil moisture dynamics are the focus of the Babocomari River model developed by the CBRFC. Application of an ensemble of precipitation fields and model parameter variations will allow quantification of predictive uncertainty associated with the principal forecast elements in hydrology. The ultimate intent is to determine what measurements of precipitation, snow accumulation and melt, soil moisture and stream flow are most critical for accurate hydrological modeling.

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