Regional Ocean-Atmosphere Prediction System (ROAPS) and its application to land-air-sea interaction processes in the southeastern United States

In this study, a three-dimensional Regional Ocean-Atmosphere Prediction System (ROAPS) using a terrain-following vertical coordinate is developed by coupling the Advanced Regional Prediction System (ARPS) with the Princeton Ocean Model (POM) to provide ocean-atmosphere prediction. The three models: ARPS, POM, and ROAPS are used to study coastal land-air-sea interaction in the southeastern U.S. during the second Intensive Observation Period (IOP 2) of the Genesis of Atlantic Lows Experiment (GALE). Both coupled and uncoupled simulations are conducted and compared with each other to investigate the importance of the coupled air-sea interaction processes.; Coastal fronts are simulated using ARPS with fixed SST in the control run of atmospheric simulations. Results show that coastal fronts can be simulated within the half-a-day simulation, and the existence of the SST gradients in coastal water is a primary factor for the frontogenesis along the Carolina coast. A simulation with hourly SST data generated from POM is used to compare with the control run. The simulated coastal front is sensitive to the SST distribution in the coastal waters and fixed SST cannot capture the detailed mesoscale features with a time scale of one to two days. Results from a series of sensitivity experiments indicate that low level easterly ambient winds are most favorable for the Carolina coastal frontogenesis and cold-air damming east of the Appalachian Mountains helps maintain the coastal front.; Short-term shelf oceanic responses to surface turbulent fluxes across air-sea interface are simulated using POM with realistic ocean bottom topography under different atmospheric forcings. The initial state of the SST and ocean currents is generated by a 30-day dynamic adjustment toward the observed characteristics and a feature model of the Gulf Stream. Results indicate that surface atmospheric cooling can decrease the SST in the shelf water within 24 hours and increase the vertical mixing to produce a well-mixed layer in the shelf water, and thus weaken the shelf ocean circulation. Surface wind stress plays a key role in the shelf ocean circulation and coastal upwelling and downwelling.; The fully coupled mesoscale air-sea interaction in coastal regions with complex ocean bottom and land surface topography is studied using ROAPS. In ROAPS, the surface fluxes of momentum, heat and moisture across air-sea interface exchange every ocean time step. The results suggest that the atmosphere and shelf ocean can respond to each other quickly, with a time scale of approximately half a day. The development of the coastal front and its associated surface wind pattern exert an influence on the shelf ocean circulation which further modifies the coastal front. Comparisons between the coupled and uncoupled simulations indicate that the fixed SST for the atmospheric simulation and the simplified atmospheric forcing for the ocean simulation tend to over-estimate the responses of the atmosphere and the shelf ocean. The fully coupled mesoscale model is necessary to capture detailed mesoscale features in the coastal weather and the shelf ocean prediction. (Abstract shortened by UMI.)...