What are sea & land breezes?

If you live along a coastline, then you have experienced a sea breeze at some point. No doubt it’s a refreshing wind coming from the ocean on a hot summer afternoon! But, on the other hand, perhaps a bit chilly during the winter season. Sea breezes happen year around and for all seasons. Wherever large bodies of water and land masses join, sea breezes should be expected to develop.

Have you ever thought about why coastlines tend to get breezy in the first place? Remember, from a general meteorological perspective, blowing wind is the result of an atmospheric pressure imbalance trying to correct itself. What causes a pressure imbalance? Variation in temperature! The variety of temperature sensations you encounter spending time on a beach is a major clue that a local atmospheric imbalance is underway. For instance, it’s afternoon and you arrive at the beach. At first you step out of your car, look towards the waves, and are immediately hit with a pleasant breeze. Then you plunge your feet into the sand. Feels pretty warm, right? Wanting to save your feet from the scorching sand, you race off to the ocean and finally meet up with the cooler waters.

Fast forward through the day and past sunset. Not wanting to end the beach outing just yet, you decide to stick around to watch the brilliant moon and stars light the night sky. Sensations begin to change at night, though. Sand, once warm, has quickly become cooler. Hanging out in the water actually feels warmer now! Finally, given enough time after sunset, you continue to gaze out towards the ocean, but now a breeze is at your back coming from the land instead of from the ocean when the sun was out overhead. What you experienced was the diurnal evolution of a sea breeze circulation!

The main driver forcing a “sea breeze” during the day and the opposing “land breeze” experienced at night is the inherent disparity between water and the sand to respond to solar heating. In other words, water naturally takes in or releases a lot more energy before changing temperatures compared to the land. So, head-to-head versus sand, water will tend to heat and cool more slowly throughout the day and night. 

The result is during the day hotter more buoyant air rising over the beach sand creates localized lower pressure. The rising air associated with low pressure is must then be replaced by the adjacent air mass influenced by the cooler ocean sea surface temperatures having relatively higher pressure. Wind flows to from high to low pressure, hence the developing sea breeze. After sunset when the land cools off more quickly than water, a reversal of the pressure gradient and wind circulation occurs resulting in a cooler land breeze heading out into the ocean.

I focused on the ocean and beach environment for this example, but “lake breezes” also are found for large lake systems around the globe, such as the Great Lakes of the United States.

Photo Credit: Jonny William Malloy