FY 2006

Using SAR remote sensing, field observations, and models to better understand coastal flows in the Gulf of Alaska

Winstead, N.S., B. Colle, N. Bond, G. Young, J. Olson, K. Loescher, F. Monaldo, D. Thompson, and W. Pichel

Bull. Am. Meteorol. Soc., 87(6), 787–800, doi: 10.1175/BAMS-87-6-787 (2006)

The steeply rising coastal terrain of southeast Alaska can produce a wide variety of terrain-induced flows such as barrier jets, gap flows, and downslope wind storms. This study uses a combination of satellite remote sensing, field observations, and modeling to improve our understanding of the dynamics of these flows. After examining several thousand synthetic aperture radar (SAR) high-resolution wind speed images over the Gulf of Alaska, several subclasses of barrier jets were identified that do not fit the current conceptual model of barrier jet development. This conceptual model consists of an acceleration and turning of the ambient cross-barrier flow into the along-barrier direction when the ambient low-level flow is blocked by terrain; however, the SAR imagery showed many barrier jet cases with significant flow variability in the along-coast direction as well as evidence for the influence of cold, dry continental air exiting the gaps in coastal terrain. A subclass of jets has been observed where the transition from the coastal to the offshore flow is abrupt.

The results from these climatological studies have motivated modeling studies of selected events as well as field observations from the Southeast Alaska Regional Jets (SARJET) experiment field campaign in the Gulf of Alaska during fall of 2004. This paper will highlight preliminary results obtained during SARJET, which collected in situ measurements of barrier jets and gap flows using the University of Wyoming's King Air research aircraft.