Seasonal and local winds

Seasonal winds. As the zones of greatest heating and the pressure and wind belts shift with the seasons, the wind pattern changes. The strongest example is the monsoon, especially over southeast Asia.

Local winds come from differences in heating and cooling of surfaces, in daily or yearly cycles:

• Sea breeze and land breeze: by day the land heats faster, so air over it rises, pressure falls, and wind blows from sea to land (sea breeze). At night the land cools faster, the pressure difference reverses, and wind blows from land to sea (land breeze).
• Valley breeze and mountain wind: by day the slopes heat up, air moves upslope, and air from the valley flows up to replace it (valley breeze). At night the slopes cool, and dense air flows down into the valley (mountain wind).
• Katabatic wind: cold air from high plateaus and ice fields draining down into valleys.
• Warm leeward wind: moist air crossing a mountain range drops its moisture as rain on the windward side; as the dry air descends the leeward side it is warmed by compression (adiabatically). It can melt snow very quickly.

Example (new): fishing boats on the Kerala coast traditionally set out before dawn and return in the afternoon: the night land breeze helps carry sailboats out, and the daytime sea breeze helps bring them home.