Drought Monitoring and Hydrologic Forecasting with VIC

Forecast System Layout

The seasonal hydrologic forecast system consists four components as illustrated in the figure. The pre-forecast processor creates the initial condition for the forecast. This can be done uising the hydrologic model (VIC) forced with observational atmospheric forcing. In our case, the observational atmospheric forcing comes from the realtime NLDAS. The spinup period is set to 2 years. Other possible alternatives are remote sensing, data assimilations. The Atmospheric Ensemble Processor is the unit to create atmospheric forcing for the forecast period in an ensemble fashion. This critical unit determines the skill of the seasonal forecast. Our current method is to merge seasonal forecasts from multiple climate models with climatology in a Bayesian framework. This merging produces a pdf of monthly total precipitation at 1/8 degree. Then multiple member ensemble is selected from the pdf. (To be cont'd)