Sea Breeze
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Introduction
The sea breeze is a local coastal wind that blows from the water to the land during the late morning and early afternoon hours in response to strong solar heating of the land. Its nighttime counterpart is a land breeze that blows from land to sea in response to strong radiational cooling over the land.
Objectives
Understand the conditions that can produce sea breezes and recognize their onset in the surface observations of coastal locations that experience them.
References
Sea and Land Breezes in Chapter 7 of your text
Sea Breezes and
Land Breezes
at the University of Illinois Weather World 2010 Project
Instruction
Sea breezes can normally occur at coastal locations under the following conditions:
 | the skies are clear enough to allow strong solar heating of the land |
| there are no fronts passing through |
| the pressure gradients are weak |
The onset of the sea breeze is normally marked by
| the wind shifting from some other direction to onshore or going from calm to onshore |
| the temperature slowing its normal rate of rise, dropping, or reaching its maximum for the day much earlier than normal |
| the dew point rising (reducing the DPD and increasing the relative humidity) |
| the possible formation or advection of low clouds and/or fog |
Consider the following meteograms:
At Portland the skies were cloudless throughout the 24-hour period. The morning of Feb 15 started out with a 5 kt land breeze. The winds shifted to a 5 kt sea breeze between 2 pm and 3 pm local time. Notice the rise in dew point which accompanied the sea breeze. After 8 pm, the winds began to alternate between calm and a 5 kt land breeze.
At Los Angeles on Feb 16, there was a sea breeze from 2 pm until 5 pm. Throughout the late evening and early morning hours of the next day, there was a weak land breeze. By 11 am the next day a sea breeze had set in again.
Web Examples
In the clickable map for Meteograms, find some coastal locations which could experience sea breezes. You may need to consult a map if you're uncertain of the direction of a sea breeze for a given location.
Next, check the current Surface Map to see if the weather conditions look right for a sea breeze to set in at any of the locations you've chosen. Recall that the weather conditions are
| clear skies for strong heating |
| no fronts |
| weak pressure gradients |
Then inspect the Meteograms for those locations where the weather conditions seem right to see if there was a sea breeze, and possibly also a land breeze.
Practice Questions
Inspect the Meteograms for San Francisco (KSFO) and San Diego (KSAN) below. Both are coastal California locations with a north-south orientation to the coastline. Did either location experience a sea breeze (and/or a land breeze) during the 24-hour period? If so, describe it. If not, explain why.
Answers
San Francisco did not have a sea breeze. In fact, they had rain, clouds, and only a 4°F range of temperatures throughout the 24-hours.
San Diego had a sea breeze during the late afternoon and early evening hours of Feb 16, followed by calm winds to a light land breeze overnight, with a sea breeze setting in again the late the following morning.
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Revised 06/16/04