When is sea breeze

In the image above, you get a much clearer look at what is happening. A sea breeze occurs due to the difference in temperature between the ocean and the land. As land heats up during the afternoon, air above it begins to rise forming a low pressure area near the land. Then cool air, situated in high pressure areas, spreads across the water and moves in over land. Again, it heats up and rises. As this warm air is moving over the water, the colder water causes it to cool off and sink.

This process continues until an equilibrium is created. During this cycle, the warm, rising air may form a line of clouds. If conditions are right, smaller thunderstorms may also form along the sea breeze.

The most important thing to recall is that warm air rises and cold air sinks. Without this phenomena, fronts would not form. Land always heats up faster than water. In these cases the use of satellite imagery is clearly problematic for the detection of Sea-Breezes, while it may still be detectable using other remote sensing means, such as sensitive weather radars.

In the afternoon, when the boundary layer heating over land is at its maximum, the Sea-Breeze is normally at its most intense, and can penetrate tens of kilometres - in some cases, even over a hundred kilometres - inland. If the large-scale flow is weak, the direction of the Sea-Breeze often veers with time. This is a result of the Coriolis force having an impact on the air current.

Another factor influencing the wind direction along the coast is the regular existence of thermal lows over land in the afternoon. Later in the day, as solar radiation decreases, the Sea-Breeze dies out, the thermals weaken and the cumuliform clouds gradually disappear. Sufficient temperature contrast between the land and sea surfaces is needed for the initiation of the Sea-Breeze.

In this respect the physical background differs for Coastal Convergence see Coastal Convergence in which the differential friction over land and over the sea is the main component for the development. The coastline shape can either enhance or inhibit sea-breeze development. For example, merging of two Sea-Breezes originating from both sides of a peninsula enhances convection. This is the sea breeze and can be seen at the top of the following image. The bottom of the following image illustrates the land breeze that occurs at night.

Recall that the land surface cools quicker than the water surface at night. Therefore, the warmer air over the ocean is buoyant and is rising. The denser cool air over the land is flowing offshore to replenish the buoyant warm air and is called a land breeze.