How does the wind change direction?
Answers:
Wind is the roughly horizontal movement of air (as opposed to an air current) caused by uneven heating of the Earth's surface. It occurs at all scales, from local breezes generated by heating of land surfaces and lasting tens of minutes to global winds resulting from solar heating of the Earth. The two major influences on the atmospheric circulation are the differential heating between the equator and the poles, and the rotation of the planet (Coriolis effect).
Given a difference in barometric pressure between two air masses, a wind will arise between the two which tends to flow from the area of high pressure to the area of low pressure until the two air masses are at the same pressure, although these flows will be modified by the Coriolis effect in the extratropics.
Some local winds blow only under certain circumstances, i.e. they require a certain temperature distribution.
Differential heating is the motive force behind land breezes and sea breezes (or, in the case of larger lakes, lake breezes), also known as on- or off-shore winds. Land is a rapid absorber/radiator of heat, whereas water absorbs heat more slowly but also releases it over a greater period of time. The result is that, in locations where sea and land meet, heat absorbed over the day will be radiated more quickly by the land at night, cooling the air. Over the sea, heat is still being released into the air at night, which rises. This convective motion draws the cool land air in to replace the rising air, resulting in a land breeze in the late night and early morning. During the day, the roles are reversed. Warm air over the land rises, pulling cool air in from the sea to replace it, giving a sea breeze during the afternoon and evening.
Mountain breezes and valley breezes are due to a combination of differential heating and geometry. When the sun rises, it is the tops of the mountain peaks which receive first light, and as the day progresses, the mountain slopes take on a greater heat load than the valleys. This results in a temperature inequity between the two, and as warm air rises off the slopes, cool air moves up out of the valleys to replace it. This upslope wind is called a valley breeze. The opposite effect takes place in the afternoon, as the valley radiates heat. The peaks, long since cooled, transport air into the valley in a process that is partly gravitational and partly convective and is called a mountain breeze.
Mountain breezes are one example of what is known more generally as a katabatic wind. These are winds driven by cold air flowing down a slope, and occur on the largest scale in Greenland and Antarctica. Most often, this term refers to winds which form when air which has cooled over a high, cold plateau is set in motion and descends under the influence of gravity. Winds of this type are common in regions of Mongolia and in glaciated locations.
Because katabatic refers specifically to the vertical motion of the wind, this group also includes winds which form on the lee side of mountains, and heat as a consequence of compression. Such winds may undergo a temperature increase of 20 °C (36 °F) or more, and many of the world's "named" winds (see list below) belong to this group. Among the most well-known of these winds are the chinook of Western Canada and the American Northwest, the Swiss föhn, California's infamous Santa Ana wind, and the French Mistral.
The opposite of a katabatic wind is an anabatic wind, or an upward-moving wind. The above-described valley breeze is an anabatic wind.
A widely-used term, though one not formally recognised by meteorologists, is orographic wind. This refers to air which undergoes orographic lifting. Most often, this is in the context of winds such as the chinook or the föhn, which undergo lifting by mountain ranges before descending and warming on the lee side.
These winds are used in the decomposition and analysis of wind profiles. They are useful for simplifying the atmospheric equations of motion and for making qualitative arguments about the horizontal and vertical distribution of winds. Examples are:
Geostrophic wind (wind that is a result of the balance between Coriolis force and pressure gradient force; flows parallel to isobars and approximates the flow above the atmospheric boundary layer in the midlatitudes if frictional effects are low)
Thermal wind (not actually a wind but a wind difference between two levels; only exists in an atmosphere with horizontal temperature gradients, i.e. baroclinicity)
Ageostropic wind (difference between actual and geostrophic wind; the wind component which is responsible for air "filling up" cyclones over time)
Gradient wind (like geostrophic wind but also including centrifugal force)
it's to do with pressure. Air travels fromhigh pressure to low pressure. The pressure changes because of the sun.
its down to areas of high and low pressure.
Jet stream, and Air pressure.
Thermal variances
When my sister was young, she asked my mother this question. She asked endless questions back then I guess and my mother told her that there was a button she pushed in the car. My sister believed that for the longest time..
There are many causes for wind direction changes, but the most typical reason is that large masses of air migrate generally from west to east. These masses are either high pressure ridges or low pressure troughs, and, in simplistic terms, the air flows clockwise around the ridges and counterclockwise around the troughs (N hemisphere, with a perspective of looking down from above the earth).
Your local wind direction changes as your relative position within a ridge or trough changes over time.
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