An Examination of the Historical Observing System Simulation Experiment Methodology

The accurate characterization of the meteorological and oceanographic environment at tactical scales (5 km or less horizontal scales from 0 to 12 hours of forecast lead time) is an essential need for the U.S. Navy. The domains the Navy operates in are often constrained by limited data, which make it more difficult to form accurate initial conditions for the initialization of numerical weather prediction (NWP) models. Traditionally, observing system simulation experiments (OSSEs) have been performed to evaluate new sensors and platforms designed to help fill data gaps. In an OSSE, a high resolution nature run is used to simulate all observations (including simulated data from the existing observing system as well as data from new sensors and platforms), which are then assimilated by the target data assimilation system. The effectiveness of the new observations are expressed as measures of how close analysis and forecast output are to the nature run. Unfortunately, traditional OSSEs are prohibitively expensive to run for the Navy due to the need of a high resolution nature run, simulation of all observations, and calibration of the observation and background errors.

This research examines the historical OSSE methodology, in which observations from the historical archive are assimilated along with simulated observations from a new platform drawn from an alternate, independent model meant to simulate the true observation. This examination will compare impacts on Coupled Ocean-Atmosphere Mesoscale Prediction System (COAMPS®) forecasts from existing platforms as well as their simulated equivalents drawn from the Coupled-Ocean-Atmosphere-Wave-Sediment Transport Modeling System (COAWST).