High-resolution modeling for NYC: coastal ocean and urbanization effects

The challenge of accurate forecasting for coastal cities requires the deployment of sophisticated high-resolution models that account for the combined effects of air-sea interaction and urbanization. We have assembled an NYC forecast system consisting of a 5-nest atmospheric model centered on Manhattan (down to 444 m resolution) linked with sea surface temperature (SST) fields from a high-resolution ocean forecast model for the New York/ New Jersey harbor region. An urban canopy parametrization is used in the data-assimilating atmospheric forecast model (COAMPSŪ*), while the ocean model (NYHOPS) encapsulates dynamic ocean processes such as local coastal upwelling and river discharge that can generate significant horizontal variability in SSTs.

We have previously demonstrated enhanced skill in simulating sea breeze events using this system. Here we evaluate the system using local atmosphere and ocean measurements (including SODAR, meteorological station data, in situ ocean temperature data, and weather balloon data) for several weeks in August 2005, during which time the field component of the Department of Homeland Security Urban Dispersion Program was conducting tracer gas releases in midtown Manhattan. We focus on a quantitative assessment of overall model skill, as well as an examination of conditions such as strong heating and weak winds that occurred frequently during the field experiment.

*COAMPSŪ is a registered trademark of the Naval Research Laboratory.