One of these challenges is to re-scale and downscale atmospheric forecasts to produce appropriate ensemble forcing for hydrologic ensemble Streamflow prediction. One criterion for such forcing is that the long term climatology of the forcing ensemble members (over many forecasts) must be same as the climatology of the forcing used to calibrate the hydrologic forecast model. Another criterion is that the ensemble forcing should preserve both the space-time scale dependent variability of the forcing and the space-time scale dependent uncertainty in this forcing. This is important for at least two main reasons. First, hydrologic processes integrate input forcing over a wide range of space and time scales, depending on the drainage areas above river forecast points. Second, atmospheric forecasts are more skillful at larger space and time scales.
This presentation will show some examples of space-time scale dependency of precipitation variability and forecast uncertainty for a few test locations in the U.S. It will also include some results of a downscaling algorithm to produce ensemble forcing for ensemble Streamflow prediction. Finally, it will discuss some of the science issues that need to be addressed in the future.
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