Examining nocturnal jets in the Hudson valley during HVAMS

A low-level weak nocturnal jet is known to flow along the Hudson valley axis in fair weather. It is thought to determine the thickness of radiation fogs in autumn and may be responsible for nocturnal advection of pollutants. However, the jet’s horizontal extent and temporal integrity are not yet understood. To address this problem we analyze a suite of surface observations deployed during HVAMS (Hudson Valley Ambient Meteorology Study during the intensive observation period in September and October 2003. We present several case studies of this phenomenon. Special effort is made to coordinate observations from an 18-station surface station network, two sodars, two wind profilers and tethered balloon-borne instruments. Measurements of the stable boundary layer made during a series of early-morning ‘close approaches’ by the Wyoming King Air research aircraft are used to document the jet condition at the close of the evening