SAR-derived gap jet characteristics in the lee of the Philippine Archipelago

Gap jet characteristics were analyzed in the lee of the Philippine Archipelago during the 2004–2009 winter monsoon seasons (November–March) using wind fields derived from ENVISAT synthetic aperture radar (SAR) images. Jet characteristics were derived for the Philippine Island gap jets and compared to those from theoretical literature and experimental studies. It was found that 18 of 31 jets characterized from 13 SAR images followed the defined power laws, or classic case, and were similar to the defined scale equations. The remaining 13 jets did not follow the classic case and resulted from jet interaction with islands, adjacent jets, and variable atmospheric conditions. These non-classic jets were grouped based upon similarities and referred to as decreasing, increasing, and reverse classic cases. Distinct deviations from the classic case included downstream increases in velocity and decreases in jet width. It was found that the orientation of the wind field relative to topography significantly impacted jet classification, and thereby made it difficult to characterize jets by region. For all 31 jets, the initial jet width dictated the distance at which a jet became self-similar, wherein a larger initial jet width required a greater distance for self-similarity.