BREEZE

air current designation on the Beaufort scale; it is weaker than a wind, which in turn is weaker than a gale. Breeze also denotes various local winds (e.g., sea breeze, land breeze, valley breeze, mountain breeze) generated by unequal diurnal heating and cooling of adjacent areas of the Earth's surface. These breezes are strongest in warm, clear, dry weather, when daytime insolation, or solar radiation, is most intense. They may be reinforced or prevented by winds of passing pressure systems. Land areas warm and cool more rapidly than do water bodies. For that reason, cooler, denser air often flows from water to land (sea or lake breeze) during the day, and from land to water (land breeze) at night. Because the temperature contrast is usually greater during the day in summer, the sea breeze is the stronger; it sometimes reduces maximum temperatures by 8 C (15 F) or more along a narrow coastal strip and greatly modifies the local climate. Similarly, a valley breeze is produced by rapid warming of the valley floor that causes the air to expand and flow up the slopes. The rising currents sometimes trigger thunderstorms over the mountains. Nighttime land-surface radiation cools the slopes, causing cooler, denser air to drain into the valley (mountain breeze). Usually light, a mountain breeze may become a violent, gusty wind when it is funnelled through a narrow gorge into which cold air has drained from many higher valleys. A glacier breeze is a draft of cold air that is cooled by contact with a glacier, descends along its edge, and then dies out within a short distance.