Global Wind Patterns Wind is movement of air due to __________ and _________. Air always moves from areas of _________ atmospheric pressure to areas of ________ pressure. Air moves in great spirals from high to low pressure, creating giant wind systems around the Earth. Air also moves horizontally across the Earth’s surfaces. The differences in surface can also affect air movement. ____________ - At the equator, there is little horizontal movement of air. In this windless zone, the air is moving upwards, leaving seemingly windless area. ______ ________- During the day, land absorbs heat from the Sun. The warm air rises and cool sea air blows onto the land. ______ ________ - At night, the land loses it heat, and the warmer air over the water rises. Cooler land air moves out to sea to fill in the space. Wind and Wind Systems _______ __________- These dry, cold air currents move from northeast to southwest over higher latitudes (60° to 90°) of the Northern Hemisphere and from the southeast to northwest over the polar zones of the Southern Hemisphere (60° to 70° south latitude). __________ - In the middle latitudes (30° to 60° north or south of the equator), the prevailing winds blow from ________ to ________. _________ ___________ These winds blow toward the equator from a latitude of about 30° north and south of the equator. They blow from northeast to southwest in the Northern Hemisphere and from southeast to northwest in the Southern Hemisphere. ______ _______- These narrow belts of fast moving air flow in a westerly direction at the higher levels of the troposphere. The rotation of Earth causes air to move fastest at the equator. This creation of eastward winds just below the equator is called the ________ _____________. An instrument called an ____________ measures speed, or velocity, of the wind. Velocity is measured in miles or kilometers per hour. A scale for measuring wind force was developed in 1806 by Sir Frances Beaufort. This is the scale, with an added description of what action might be seen for each level of wind.