3/26/2023 0 Comments And yet it moves map![]() ![]() The river's current is generally the strongest in the center with decreasing strength as one approaches the river's bank. One way of visualizing this is to consider a river. However, jet streams are wider and not as distinct as a single line but are actually regions where the wind speed increases toward a central core of greatest strength. Jet streams are often indicated by a line on a weather map indicating the location of the strongest wind. Canadian border.) As Autumn approaches and the sun's elevation decreases, the jet stream's average latitude moves toward the equator. (By Summer in the Northern Hemisphere, it is typically found near the U.S. Jet streams also "follow the sun" in that as the sun's elevation increases each day in the spring, the average latitude of the jet stream shifts poleward. They meander around the globe, dipping and rising in altitude/latitude, splitting at times and forming eddies, and even disappearing altogether to appear somewhere else. The actual appearance of jet streams result from the complex interaction between many variables - such as the location of high and low pressure systems, warm and cold air, and seasonal changes. Jet streams occur in both the Northern and Southern Hemispheres. Jet streams vary in height of four to eight miles and can reach speeds of more than 275 mph (239 kts / 442 km/h). The 50°-60° N/S region is where the polar jet located with the subtropical jet located around 30° N. Therefore, the regions around 30° N/S and 50°-60° N/S are also regions where the wind, in the upper atmosphere, is the strongest. In addition, with the three-cell circulations mentioned previously, the regions around 30° N/S and 50°-60° N/S are areas where temperature changes are the greatest.Īs the difference in temperature increases between the two locations the strength of the wind increases. North hemisphere cross section showing jet streams and tropopause elevations. ![]() The speed of the rotation is great enough to cause you to weigh one pound less at the equator than you would at the north or south pole. Someone standing on a pole is not moving at all (except that he or she would be slowly spinning). Someone standing on the equator is moving much faster than someone standing on a 45° latitude line (graphic, above right). Your speed relative to the Earth's axis depends on your location. The reason has to do with momentum and how fast a location on or above the Earth moves relative to the Earth's axis. ![]() The motion of the air is not directly north and south but is affected by the momentum the air has as it moves away from the equator. The earth's rotation is responsible for the jet stream as well. We saw that the earth's rotation divided this circulation into three cells. (The warm air rising at the equator will move toward both poles.) Why do the jet stream winds blow from west to east? Recall from the previous section what the global wind patterns would be like if the earth was not rotating. Since these hot and cold air boundaries are most pronounced in winter, jet streams are the strongest for both the northern and southern hemisphere winters. ![]() Jet streams follow the boundaries between hot and cold air. The winds blow from west to east in jet streams but the flow often shifts to the north and south. Jet streams are relatively narrow bands of strong wind in the upper levels of the atmosphere. The Jet Stream How the earth's rotation effects the west to east direction of the jet stream. ![]()
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