Understanding Local Diurnal Winds Sea Breezes and Land

Understanding Local Diurnal Winds • Sea Breezes and Land Breezes dependent on the differences in heating and cooling between land water. • Upslope and downslope winds forced by the differences in heating and cooling between terrain and lowlands.

Diurnal Local Winds

Diurnal Winds 101

Why?

Sea and Land Breezes Influence Clouds!

The Peninsula Effect with colliding sea breezes Can enhance convection and precipitation during the day

Stepped Art Fig. 7 -6, p. 175

Summer Diurnal Winds

The Sound Breeze Viewed Using Ferry Data

Picture take in Sequim looking N Strong Regional Sea Breeze Winds During the Summer

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.

Southern Oregon Coast Near Brookings

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

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-50 s…similar to the temperature of the Sound and the Pacific Ocean. • But it can happen in winter during unusually cold periods.

Stepped Art Fig. 7 -5, p. 174

Land Breeze example during a cold period.

Slope Winds Upslope Flow on Heated Slopes Downslope Flow on Cooled Slopes

Fig. 7 -11, p. 178

Fig. 7 -12, p. 179

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

The Columbia River Gorge An Example of Diurnal Gap Flows

Regional Diurnal Circulations

Total Diurnal Wind Pattern Can Be a Superposition of Many Diurnal Circulations • Sea breezes and land breezes along coasts and between inland areas and oceans/bodies of water • Upslope and downslope flows, both in valleys and between higher elevations and lowlands.

The End

Fovell (UCLA) Sea Breeze Simulations • http: //www. atmos. ucla. edu/~fovell/ASother /mm 5/LA_seabreeze. html