The objective of this exercise is to examine pressure gradients and the three ba
ID: 111384 • Letter: T
Question
The objective of this exercise is to examine pressure gradients and the three basic wind types.
2. Columbus and Pittsburgh are approximately 300 km apart. What is the pressure gradient (in units of mb/100 km) between the two cities
if the barometric pressure in Columbus is 1021.6 mb and the barometric pressure in Pittsburgh is 1020.7 mb?
if the barometric pressure in Columbus is 991.6 mb and the barometric pressure in Pittsburgh is 988.0 mb?
3. In question 2, which scenario, a or b, would produce the weaker wind? How did you determine this?
4. Fill in the blanks with the appropriate directions. A 270° wind is also known as a
___________ wind and moves from ___________ to ___________.
5. Describe the upper-level flow (gradient wind flow) around an area of low pressure (L) in the Northern Hemisphere.
Use the words (clockwise or counterclockwise) and (parallel, inward, or outward).
6. Describe the surface flow around an area of low pressure (L) in the Northern Hemisphere.
Use the words (clockwise or counterclockwise) and (parallel, inward, or outward).
7. What causes surface winds to flow in a slightly different direction than gradient winds?
Explanation / Answer
2. Pressure gradient = Difference in Pressure / Distance between the points
a) In first case Pressure gradient = (1021.6 - 1020.7)/300 = 0.003mb/km
So, to calculate the gradient in 100 km = 0.003 X 100 = 0.3 mb/100km
b) In the second case, Pressure gradient = (991.6-988)/300 = 0.012mb/km
So, Gradient per 100km = 0.012 X 100 = 1.2 mb/100km
3. Among the two case , Case a will be having weaker wind.
Always steeper gradients result in a stronger push from high pressure to low pressure area. That means higher the gradient, higher will be the wind speed and lower the gradient , the wind will be weaker.
4. 270 degree wind is also called as West wind and moves from west to east
270 degree represents the western side and hence it will starts from west to east.
5. Gradient flow around a low pressure area will be counter clockwise and parellel.
In a low pressure center the pressure gradient force which is directed inward balances the coriolis force and centrifugal force both directed outward because the coriolis force acts to the wind's right in the northern hemisphere and wind's left in the southern hemisphere. So the wind blows counter clockwise along the curved isobars in the northern hemisphere and clockwise in the southern hemisphere.
6. Surface flow around alow pressure area will be counter clockwise and inward
A low pressure system pulls air into centre and hence inward. In the northern hemeisphere coriolis force deflects towards the right and hence creates a counter clockwise rotation in the northern hemisphere
7. In surface winds there is no gradient force to cancel out the effect of coriolis force
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