Wind Channeling in the Hudson Valley, NY

This study presents the preliminary results from the Hudson Valley Ambient Meteorology Study (HVAMS). The study region, the mid Hudson Valley, is located from –74.1 to –73.6W and 41.6 to 42.8 N. Valley walls range mostly from 200-300m. During September to October 2004 a network of 9 micrometeorological flux stations and 5 meteorological stations were assembled in this valley. Also, vertical profiles from several platforms are available for this period. The above-valley predominant climatological winds are westerly, but in the Valley most of the surface winds are oriented with the valley axis (North/South) direction indicating channeling controlled by the pressure gradient. We present several case studies of convective boundary layer development, with the aim to detect the controlling pressure gradients (along- and cross-valley) in data from aircraft, sounders, and from a network of surface weather stations. A study of the pressure measurements sensitivity is presented to determine the validity of these measurements. The amplitude of the semi-diurnal pressure oscillation is used with the air temperature to allow us to obtain the maximum accuracy for the pressure gradient measurement based on data from different sensors. With the pressure gradient at the surface, the geostrophic wind at the surface can be obtained and the thermal wind estimated. This allows us then to study the balance of forces in the valley boundary layer and estimate the direction and magnitude of the friction force.