Calibration of the Community WRF-Hydro Modeling System over Southern Wyoming for Simulation With Randomized Cloud Seeding Experiments.

The community WRF-Hydro system is a fully distributed hydrologic modeling system that simulates land surface processes, surface and shallow subsurface flow, along with channel flow within river networks. In addition to forecasting vital surface hydrologic states, the WRF-Hydro system can be used in a research framework to study various hydrologic impacts from anthropogenic processes. This study shows results from efforts to calibrate the WRF-Hydro modeling system over key mountainous regions in southern Wyoming for use with experimental simulated precipitation from randomized cloud seeding experiments in an effort to quantify the hydrologic response.

For years, research has taken place to study and simulate the impact from cloud seeding operations on the local environment and hydrology. Up until recently, studies applied broad estimates on a basin scale from estimated enhancements due to cloud seeding experiments. Recent advances in the Weather Research and Forecasting (WRF) model have allowed for explicit simulated enhancements of precipitation through the development of a specialized cloud seeding parameterization. In addition,recently completed long-term high-resolution (4 km) WRF simulations offer an additional forcing dataset for use in hydrologic model calibration and validation in a region which traditionally has lacked a rich set of precipitation observations. These developments allow for explicit representation of cloud seeding impacts in high resolution WRF simulations. In parallel, the WRF-Hydro system has been developed over the last several years to be run on spatial scales, finer than WRF, which allow for improved process representation of runoff production mechanisms. The overlap of these two activities will be capitalized upon for the study of high resolution hydrologic responses due to simulated cloud seeding experiments.

For this study, a WRF-Hydro modeling domain was established over the Sierra Madre and Medicine Bow regions of Southern Wyoming. Retrospective convective-allowing WRF simulations at 4km resolution developed at the National Center for Atmospheric Research (NCAR) were processed to the WRF-Hydro modeling domain for the 2001-2013 water years. The cloud seeding parameterization developed at NCAR was used for multiple randomized seeding experiments (RSE) for the 2009-2013 water years to produce grids of the simulated change in precipitation. These precipitation changes were applied to the WRF forcings to generate two precipitation datasets. Model calibration was done for key spatial parameters using observed streamflow using unaltered WRF forcings. Two independent model simulations took place to study the impact of the RSE precipitation on the local hydrology.

This study offers a unique approach with the use of the WRF-Hydro modeling system that utilizes a high resolution WRF dataset for calibration that explicitly resolves convective systems. This study also facilitates the application of calibrated parameters to the WRF-Hydro modeling system to explicitly resolve the impacts of cloud seeding impacts over multiple years. This approach allows for a more comprehensive cost benefit analysis of randomized cloud seeding experiments. Specifically, this study allows for high resolution, detailed information within a watershed on where enhanced streamflow likely is occurring , along with alterations to additional land surface hydrologic states.