OSE and OSSE Studies to Evaluate the Impact of Real and Simulated Global Hawk Data on Winter Storm Forecasts over Alaska and the Arctic

A key program within the National Oceanic and Atmospheric Administration (NOAA), Sensing Hazards with Operational Unmanned Technology (SHOUT), uses both Observing System Experiments (OSEs) and Observing System Simulation Experiments (OSSEs) to evaluate the impact of real and simulated Unmanned Aircraft Systems (UAS) data on weather forecasts of tropical cyclones and high-impact events over Alaska and the United States. Recently, SHOUT participated in NOAA’s El Niño Rapid Response (ENRR) mission, conducted between January and March 2016, by providing targeted observing support to determine areas sensitive to added observations and evaluating the impact of Global Hawk (GH) data on numerical weather prediction in a global model. Both OSE and OSSE experiments are conducted on an extratropical storm which hit Alaska both during the ENRR campaign and in a realistic OSSE nature run. Results from an OSE data-impact study using the NCEP Global Forecast System (GFS) show that the assimilation of GH dropsonde data reduces forecast error in both sea-level pressure and 500 mb geopotential height. Accompanying OSSE experiments are performed to validate an Ensemble Transform Sensitivity (ETS) method for identifying data sensitive regions and also to investigate uncertainty on impact of targeted data collected from different simulated flight tracks. An objective flight path design that covers sensitive regions identified using the ETS method, as well as subjective flight path designs that sample both data sensitive regions and areas of key meteorological features, such as upper-level divergent regions, frontal systems, and moisture plumes, are studied. Related OSSE results will be presented and discussed.