Wind jet transition and its localized impact on wave height distribution along the Pacific Coast of Northern Japan

We present a case study of low-level wind jets induced in sequence by orographic effects off the Pacific coast of northern Japan during 7-11 June 2003, and demonstrate that the transition of the wind jets causes areal differences of the wave height variations along the coast. First, we analyze SeaWinds scatterometer wind measurements. Under the easterly wind, a strong wind jet formed after passing by Cape Erimo. As the wind shifted to the southeast, the wind jet started to decay. In turn, the southerly wind along the coast led to another wind jet in the lee of the easternmost tip of the Sanriku coast. Then, we identify onsets and decays of the wind jets from time series of wind speed at meteorological stations. Finally, we demonstrate that the transition of the wind jets has local impacts on wave height variations. Significant wave heights measured by altimeters were correlated positively with local wind energy, i.e., squares of wind speeds. Accompanying the wind jet formation/decline, significant differences of wave height variations became marked among wave observation stations located along the coast at intervals of up to 50 km.