Satellite‑borne detection of high diurnal amplitude of sea surface temperature in the seas west of the Tsugaru Strait, Japan, during Yamase wind season

Abstract

The purpose of this study is to investigate the variation of diurnal SST amplitude ( SST) in the seas west of the Tsugaru Strait, Japan, which exhibit complex topography that alects the wind pattern during “Yamase” season, when cold easterly winds blow around northeastern Japan. Wefused in rared based satellite SSTs to obtain strong SST signals. The objective analysis data on surface wind, air temperature and relative humidity patterns wasfused to explain possible mechanisms responsible for the observed phenomena. Although easterly winds are frequently accompanied by clouds that hinder frequent observation of SSTs from space, four cases of high SST were obtained under clear sky conditions. The results show that high resolution satellite data can capture SSTs of more than 5f°C. Further, the SST variation was strongly iniuenced by topography. The existence of mountains near the study area have the elect of blocking the easterly winds, creating aflow wind speed area on the leefside of the mountain range, which is responsible for the generation of high SST, especially in the olshore area. Infaddition to the topographic elect, the SST values measured in the in-shore area were iniuenced by the sea breeze. The warm-dry air mass is advected to the coastal seas by the anti-sea breeze which heats the in-shore area and keeps the SST at the same level as that of the olshore area. This nding highlights the importance of understanding air, sea and land interactions in terms of the variation observedfin SST in the study area.