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Understanding Local Diurnal Winds

Dive into the world of local diurnal winds, including sea breezes and land breezes, influenced by heating and cooling variations. Learn about the 3D circulation, sea breeze facts, and the impact on cloud formation. Explore examples like the Washington coast sea breeze front and Southern Oregon coast winds. Understand how slope winds create upslope and downslope flows based on terrain temperature differentials.

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Understanding Local Diurnal Winds

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  1. 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.

  2. Sea and Land Breezes Need to think about the 3D circulation

  3. Sea Breeze Return Flow

  4. Land Breeze Circulation Return Flow

  5. 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

  6. Sea Breeze Front: sharp leading edge of cooler air

  7. Can See the Influence of Sea and Land Breezes on Clouds

  8. Washington Coast Sea Breeze Front

  9. Colliding Sea Breezes Can Produce Strong Upward Motion

  10. Fig. 7-7, p. 176

  11. 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.

  12. 2-minute average July-August winds along the Northwest coast.

  13. Southern Oregon Coast Near Brookings

  14. Summer Diurnal Winds

  15. The Sound Breeze Viewed Using Ferry Data

  16. Picture take in Sequim looking NStrong Regional Sea Breeze Winds During the Summer

  17. 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.

  18. Land Breeze example during a cold period.

  19. Slope Winds

  20. Slope WindsUpslope Flow on Heated SlopesDownslope Flow on Cooled Slopes

  21. Low temperatures are generally cooler in low spots on cold, cloud-free nights.

  22. Eastern Washington Slope flows

  23. Fig. 7-11, p. 178

  24. H H Warm Cool Cool Warm L L Valley breeze Mountain breeze Editable Text Fig. 7-11, p. 178

  25. Fig. 7-12, p. 179

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