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Understanding Local Diurnal Winds. Diurnal-varying over a day Sea Breezes and Land Breezes dependent on the differences in heating and cooling between land and water. Upslope and downslope winds forced by the differences in heating and cooling between terrain and lowlands. Sea and Land Breezes.
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Understanding Local Diurnal Winds • Diurnal-varying over a day • Sea Breezes and Land Breezes dependent on the differences in heating and cooling between land and water. • Upslope and downslope winds forced by the differences in heating and cooling between terrain and lowlands.
Sea and Land Breezes Need to think about the 3D circulation
Sea Breeze Return Flow
Land Breeze Circulation Return Flow
Sea Breeze Facts • Builds up in coastal regions during the day • Best developed in late spring and summer when sun is strongest. • Can cool the coast by 5-15F, sometimes more. • Tends to suppress clouds over water, but enhance over land. • Starts at the coast and extends landward and seeward, 20-50 km
Sea Breeze Winds Along the Southern Oregon Coast • Gusts frequently reach 30-35 knots during the summer during the afternoon. • Very painful to stay on the beach! • Strong pressure gradient normal to the coast between the warm land areas and the cold upwelling water.
2-minute average July-August winds along the Northwest coast.
Summer Diurnal Winds
The Sound Breeze Viewed Using Ferry Data
Picture take in Sequim looking NStrong Regional Sea Breeze Winds During the Summer
Land Breezes Tend to Be Weak in the Northwest • Why? Because the land rarely cools down more than the water. • Local minimum temperatures generally in the low to mid-50s…similar to the temperature of the Sound and the Pacific Ocean. • But it can happen in winter during unusually cold periods.
Slope WindsUpslope Flow on Heated SlopesDownslope Flow on Cooled Slopes
Low temperatures are generally cooler in low spots on cold, cloud-free nights.
H H Warm Cool Cool Warm L L Valley breeze Mountain breeze Editable Text Fig. 7-11, p. 178