Thermal effect of the sea breeze on the structure of the boundary layer and the heat budget over land |
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| Authors: | Tsuneo Kuwagata Junsei Kondo Masatoshi Sumioka |
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| Institution: | (1) Geophysical Institute, Tohoku University, 980 Sendai, Japan;(2) Present address: Tohoku National Agricultural Experiment Station, 4 Akahira, Shimo-Kuriyagawa, 020-01 Morioka, Japan;(3) Present address: Mitsubishi Bank, Marunouchi 2-7-1, Chiyodaku, 100 Tokyo, Japan |
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| Abstract: | The daytime boundary-layer heating process and the air-land heat budget were investigated over the coastal sea-breeze region by means of observations over the Sendai plain in Japan during the summer. In this area, the onset of the sea breeze begins at the coast around 0900 LST, intruding about 35 km inland by late afternoon. The cold sea breeze creates a temperature difference of over 10°C between the coastal and inland areas in the afternoon. On the other hand, warm air advection due to the combination of the counter-sea breeze and land-to-sea synoptic wind occurs in the layer above the cold sea breeze in the coastal region. Owing to this local warm air advection, there is no significant difference in the daytime heating rate over the entire atmospheric boundary layer between the coastal and inland areas. The sensible heat flux from the land surface gradually decreases as distance from the coastline increases, being mainly attributed to the cold sea breeze. The daytime mean cold air advection due to the sea breeze is estimated asQ
adv
local
=–29 W m–2 averaged over the sea breeze region (0 35 km from the coastline). This value is 17% of the surface sensible heat fluxH over the same region. The results of a two-dimensional numerical model show that the value ofQ
adv
local
/H is strongly affected by the upper-level synoptic wind direction. The absolute value ofQ
adv
local
/H becomes smaller when the synoptic wind has the opposite direction of the sea breeze. This condition occurred during the observations used in the present study. |
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