Wind speed and moisture sensitivity tests of the NRL limited area dynamical weather prediction model : an OSSE study of ERICA IOP-4

Abstract : An Observing System Simulation Experiment (OSSE) is conducted to investigate the sensitivity of the Naval Research Laboratory (NRL) mesoscale model to atmospheric water and surface wind speed input. The explosively deepening ERICA IOP-4 storm which occurred off the North Carolina coast on 4 January 1989 is used as a case study. Wind speed and water vapor output from the full physics version of the model is shown to reasonably simulate data available from the Special Sensor Microwave/Imager. Assimilating this modeled satellite information into the degraded version of the model shows ERICA IOP-4 to be a dynamically driven storm. Assimilation of simulated wind speed observations yields the best performance for the degraded model in terms of surface pressure deepening. The model exhibits sensitivities to the coverage area of updated information. Two treatments for atmospheric water are tested, showing the sensitivity of the model to these inputs despite their secondary importance in forecasts of storm deepening.