Satellite observations and numerical simulations of low-level easterly winds
blowing through the Tsugaru Strait and Mutsu Bay
Teruhisa Shimada (1), Masahiro Sawada (2), Weiming Sha (2), and Hiroshi Kawamura (1)
(1) Center for Atmospheric and Oceanic Studies,
Graduate School of Science, Tohoku University, Sendai, Japan
(2) Atmospheric Science Laboratory,
Graduate School of Science, Tohoku University, Sendai, Japan
Corresponding author: Teruhisa Shimada
Email: shimada@ocean.caos.tohoku.ac.jp
We have investigated structures and diurnal variations of the low-level easterly winds
blowing through the east-west passage comprising the Tsugaru Strait, Mutsu Bay, and
circumjacent terrestrial gaps in northern Japan during summer months. Using observational and
reanalysis data, we have presented a representative case study in June 2003 and supplement
statistical analyses. The cool easterly winds accompanied by clouds and fog are blocked by the
central mountain range. This condition increases an along-strait sea level pressure (SLP)
gradient, which induces strong winds in the west of the strait. Stronger (weaker) and easterly
(east-northeasterly) winds are observed during the nighttime (daytime), corresponding to the
cool air intrusion from east (retreat from west). Differences in SLP observed at meteorological
observation stations on the east and west can be a good indicator of wind speed in the west of
the strait. Furthermore, we look into the easterly wind event on 5-10 June 2003 using model
simulations. The diurnal variation of the cool air intrusion into the strait and the bay below the
height of 500 m induces the diurnally-varying strong winds in the east inlet of the strait, Mutsu
Bay, and the west exit of the strait. During the daytime, air temperature difference becomes
large between the inflowing cool air and the air with rising temperature within the strait. This
increases the SLP gradient in the east inlet and Mutsu Bay, inducing the strong winds. During
the nighttime, the cool air arrives at the west exit and the air temperature difference increases
the SLP gradient due to the cool air and the warm air over the Japan Sea. The resulting
accelerated wind shift to the west from the west-southwest mainly due to the large Coriolis
force.
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