Spatio-temporal variability in sea surface wind stress near and off the east coast of Korea

Sea surface wind stress variabilities near and off the east coast of Korea,are examined using 7 kinds of wind datasets from measurements at 2 coastal (land) stations and 2 ocean buoys,satellite scatterometer (QuikSCAT),and global reanalyzed products (ECMWF,NOGAPS,and NCEP/NCAR).Temporal variabilities are analyzed at 3 frequency bands; synoptic (2~20 d),intra-seasonal (20~90 d),and seasonal (>90 d).Synoptic and intra-seasonal variations are predominant near and off the Donghae City due to the passage of the mesoscale weather system.Seasonal variation is caused by southeastward wind stress during Asian winter monsoon.The sea surface wind stress from reanalyzed datasets,QuikSCAT and KMA-B measurements off the coast show good agreement in the magnitude and direction,which are strongly aligned with the alongshore direction.At the land-based sites,wind stresses are much weaker by factors of 3~10 due to the mountainous landmass on the east parts of Korea Peninsula.The first EOF modes(67%~70%) of wind stresses from reanalyzed and QuikSCAT data have similar structures of the strong southeastward wind stress in winter along the coast but show different curl structures at scales less than 200 kn due to the orographic effects.The second EOF modes (23%~25%)show southwestward wind stress in every September along the east coast of the North Korea.