how does the pressure force gradient change the course of the wind

by Ellis Gottlieb 10 min read

The pressure gradient is the rate of change of pressure with respect to distance. The force of Pressure Gradient produces wind movement by moving from a high-pressure area to a low-pressure area. When the isobars are near together, the pressure gradient is large; when they are separated, the pressure gradient is mild.

Thus, if the upper level divergence is removing molecules faster than the low level convergence the surface low pressure will decrease. This decreases the surface pressure which increases the pressure gradient force, which increases the wind speed and causes the air to rush in faster towards the low pressure center.

Full Answer

What is the relationship between pressure gradient and wind?

Pressure Gradient Forces. Wind ultimately comes from temperature differences because, as we learned in another lesson, temperature differences lead to air pressure differences, and air pressure creates convection currents, which, as we just learned, create wind.

How do you calculate the pressure gradient force?

Two measurements must be taken on barometers to determine the pressure gradient force, and the distance between the barometers must be counted. The pressure gradient force will equal the difference between the pressures, in pascals, divided by the distance.

What is the pressure gradient force in geostrophic flow?

The pressure gradient force is independent of velocity and so is always there for a given geopotential gradient. In a regular low, the centrifugal and Coriolis forces, both dependent on velocity, sum together to equal the pressure gradient force, whereas for geostrophic flow, only the Coriolis force does.

How does pressure affect wind speed?

The change in pressure over a given distance is defined as a pressure gradient. The strength of this pressure gradient determines how fast the wind moves from higher pressure toward lower pressure. A stronger pressure gradient will cause stronger winds, as shown in Figure 2. >> Balanced in the vertical by the force of gravity

How does pressure gradient force affect wind?

Pressure gradient is just the difference in pressure between high- and low-pressure areas. The speed of the wind is directly proportional to the pressure gradient meaning that as the change in pressure increases (i.e. pressure gradient increases) the speed of the wind also increases at that location.

How does pressure gradient determine wind direction?

The pressure gradient force is directed from high heights (or pressures) toward low heights (or pressures). Thus, on upper air charts the wind moves parallel to the height contours, with lower heights to the left of the wind direction.

What does the pressure gradient force do?

The change in pressure measured across a given distance is called a "pressure gradient". The pressure gradient results in a net force that is directed from high to low pressure and this force is called the "pressure gradient force". The pressure gradient force is responsible for triggering the initial movement of air.

How does wind speed change with pressure?

The correlation between barometric pressure and wind velocity is that as pressure increase wind velocity decreases.

How pressure gradient force and Coriolis force respectively influence the course of these winds?

As the wind gains speed, the deflection increases until the Coriolis force equals the pressure gradient force. At this point, the wind will be blowing parallel to the isobars. When this happens, the wind is referred to as geostrophic.

How do the Coriolis force and pressure gradient together affect wind direction?

There are only two forces acting: the pressure gradient force and the Coriolis force. The pressure gradient force acts towards low pressure perpendicular to the lines of constant height while the Coriolis force acts to the right and perpendicular to the wind direction.

Where does the pressure gradient force pull air?

The vertical pressure gradient force results from molecules in the high pressure near the earth's surface trying to move upward where the pressure is lower. Horizontal pressure gradient force- results from the high and low pressure systems (highs, lows, troughs and ridges) in the atmosphere.

What affects pressure gradient force?

The strength of the pressure gradient force can be changed by increasing the pressure difference (DP) or reducing the distance (DZ) of the pressure change.

How do pressure gradients drive local wind patterns?

Whenever a pressure difference develops over an area, the pressure gradient force begins moving the air directly across the isobars. The closer the spacing of isobars, the stronger is the pressure gra- dient force. The stronger the pressure gradient force, the stronger is the wind.

What is pressure gradient force in geography?

Pressure gradient force is created by differences in atmospheric pressure. The pressure gradient is the rate of change of pressure with respect to distance. Force of Pressure Gradient produces wind movement by moving from a high-pressure area to a low-pressure area.

Which factor increases the speed of wind?

The speed of air increases with increase in difference of air pressure. Also, we know that moving air is called wind. Thus, the speed of wind increases with increase in air pressure difference.

Which direction does the Earth's rotation affect the path of wind?

What's especially interesting is that this rotation of Earth affects the path of wind so that it appears to deflect to the right in the Northern hemisphere and to the left in the Southern hemisphere (if you're looking down from one of the poles).

How does wind come from temperature?

Wind ultimately comes from temperature differences because, as we learned in another lesson, temperature differences lead to air pressure differences , and air pressure creates convection currents, which, as we just learned, create wind. Let's back up and see how this works. Say we have a warm location, like the equator, and a cold region, like the North Pole. Air at the equator is warmed with more solar energy than the air at the North Pole, so it rises and then moves horizontally toward the North Pole. As it cools, it sinks back down toward the warmer equatorial region. The air pressure difference between the two locations is called the pressure gradient, and the force that actually drives the air from high pressure areas to low pressure areas is called the pressure gradient force.

What would happen if the Earth didn't rotate?

If Earth didn't rotate (which we know it does, because we have cycles of day and night), this pressure gradient force would create two single-cell circulations of wind - one for the Northern hemisphere and one for the Southern hemisphere.

What does rotation mean in the hemisphere?

Earth's rotation means that air does not circulate in a single-cell convection current for each hemisphere. Instead, we get multiple air cells and the Coriolis effect, which is the apparent deflection of wind due to Earth's rotation.

Why are convection currents at the mercy of temperature differences?

But convection currents are ultimately at the mercy of temperature differences because these are what create pressure differences in the first place. The pressure difference between two locations is called a pressure gradient, and the force that actually moves air as wind is called ...

What is the Coriolis effect?

The Coriolis effect is like being on a merry-go-round. Imagine that you are on one side and your friend is directly across from you on the other. If you were to throw a ball to your friend while the merry-go-round was not spinning, it would go straight to them.

What happens to the air in the atmosphere?

The same thing happens with air in the atmosphere. As warm air rises, it expands and cools. It then sinks back down to fill the space the warm air left behind. This convection current, or circulation of warm air rising and cool air sinking, has some interesting effects on wind.

What is the name of the balance that causes wind to move parallel to isobars?

This balance is known as the geostrophic balance. In a world without friction, the pressure gradient and Coriolis forces would exactly balance one another. This type of balance, called geostrophic balance by meteorologists, causes wind to move parallel to isobars. This case can be seen in Figure 4.

What is the downward force of gravity?

In the vertical, the upward pressure gradient force is balanced by the downward force of gravity. This is known to meteorologists as hydrostatic balance. Hydrostatic balance implies that motions of air in the vertical direction are highly limited. Coriolis Effect.

How does friction affect the Coriolis force?

The force due to friction not only works to oppose the motion of any moving object, but it also has an impact on the amount an object is deflected by the Coriolis force. This is because the Coriolis force not only depends on latitude, but also the speed of the object.

What is frictional force?

The force of friction is a drag force. This force always acts to oppose the motion of an object, whether that object be a car or the wind. The frictional force is most prevalent at the surface and decreases as altitude increases. >> Ultimately reduces deflection due to Coriolis Force.

What is the Coriolis effect?

The Coriolis Effect is a direct result of the fact that the earth is constantly rotating on its axis. This effect causes an object in motion to appear as if it is being deflected to the right (in the northern hemisphere). An object in motion appears to be deflected to the left in the southern hemisphere.

Which direction is the favored location for divergence aloft, upward motion, and a surface low?

So downwind of a trough is the favored location for divergence aloft, upward motion, and a surface low. Downwind of a ridge is the favored location for convergence aloft, downward motion, and a surface high.

What happens to the trough as it goes through the low pressure loft?

As it goes through the trough, around the low-pressure loft, it slows down to subgeostrophic and then speeds up to geostrophic in the next straight section. The speeding up causes divergence aloft. And the slowing down causes convergence aloft, just as you learned in lesson nine.

Is PGF dependent on velocity?

Note that the PGF is independent of velocity but both the Coriolis force and the centrifugal acceleration are dependent on velocity. In the figure the geostrophic velocity is represented by vg and the gradient wind velocity is represented by vgr .

Is pressure gradient force dependent on velocity?

The pressure gradient force is independent of velocity and so is always there for a given geopotential gradient. In a regular low, the centrifugal and Coriolis forces, both dependent on velocity, sum together to equal the pressure gradient force, whereas for geostrophic flow, only the Coriolis force does.

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