Air Pressure and Winds

Largely based on notes from my Introduction To Weather class at Suffolk County Community College

Atmospheric Pressure

The force exerted against a surface by continuous collision of gas molecules. It is the weight of the air above a given location.

Mercury Barometer

Instrument that measures pressure, in which air pressure pushes down on a pool of mercury, which holds mercury up in a vacuum tube.

High Pressure

In a mercury barometer, if the mercury goes further up the tube it is showing….

Low Pressure

In a mercury barometer, if the mercury stays lower down in the tube it is showing….

1013.25 mb

Average sea level pressure in millibars.

980, 1040

Most of the time, sea level pressure lies between_______and_______millibars.

Altimeter

Instrument used to measure the altitude of an object above a fixed level.

Too High, Too Low

An altimeter reads__________in cold air and_________in warm air.

Clockwise, Outflow, Sinking

In a high pressure system in the Northern Hemisphere, air moves_________around the center, and there is an________of________air.

Clouds And Precipitation

High pressure systems often suppress this, while low pressure systems often produce this.

Counterclockwise, Inflow, Rising

In a low pressure system in the Northern Hemisphere, air moves________around the center and  there is an_______of________air.

Trough

An elongated area of low pressure.

Ridge

An elongated area of high pressure.

Milder, Moisture, Trough Axis

In the United States, southwest winds transport______temperatures and increasing_______east of the_________

Cooler, Dryer, Ridge Axis

In the United States, northwest winds transport_________temperatures and________air east of the_________

Four Millibars

On a weather map, isobars are typically analyzed every….

Steep, High

If isobars are close together, there is a _______gradient and_______wind speeds.

Low, Lower

If isobars are far apart, there is a________gradient and________wind speeds.

Pressure Gradient Force

Force that influences wind speed and is the result of differences in pressure across a surface, driving air from high-pressure areas to low-pressure areas.

Perpendicular

The pressure gradient force is________to the isobars.

Pressure Gradient

The difference in pressure over a distance.

Differential Heating

This often causes “local” pressure gradients.

Land, Water, Pressure Gradient

During differential heating, ______warms more rapidly than_____, creating a_________

Sea Breezes

On Long Island and other places worldwide, differential heating can lead to_________developing.

Gravity

This force is the reason wind doesn’t typically blow vertically upward.

Coriolis Force

This force modifies wind direction on a rotating sphere.

Enhanced

Due to their being less friction in the upper troposphere, the Coriolis force is…

Right

In the Northern Hemisphere, the Earth’s counterclockwise rotation results in winds deviating to the…

Left

In the Southern Hemisphere, the Earth’s counterclockwise rotation results in winds deviating to the…

Apparent, Deflecting

The Coriolis force is an_______and_______force.

Right Angles

The Coriolis force is always directed at________to the direction of wind flow.

Does Not

The Coriolis force______control the speed of the wind.

Direction, Horizontal, Vertical

Usually, storms require a change in wind_______, both_________and________

Near Zero, Rarely Form

As a result of the Coriolis Force being_______near the equator, hurricanes________at this region

Geostrophic Winds

Winds that blow parallel to the isobars above the Earth’s friction layer.

Geostrophic Balance

The balance between the pressure gradient and Coriolis forces.

Negligible, Significant Influence

Friction’s effect is_______to winds at higher altitudes, but is a__________near the Earth’s surface.

Aloft, Friction, Balanced

Geostrophic flow occurs when winds are_____due to the negligible amount of______and the pressure gradient force and Coriolis force being______

Move Faster

Winds typically_________over water and flat land than other areas.

Increase

Generally, wind speeds_______with increasing height.

Slows, Geostrophic Balance

Friction______the wind, keeping it from reaching______

Shaft, Direction

The long line sticking out of the circle on the weather station model is known as a_____and is used to show wind______

Barb, Speed

The shorter lines sticking out of the end of the long line on a weather station model is known as a______and is used to show wind_____

From

The orientation of the shaft on a weather station model shows where the wind is blowing….

Centrifugal Force

Apparent outward force that draws a rotating body away from the center of rotation, which can slow or speed up geostrophic wind speed.

Curved

Around cells of high or low pressure, wind moves in______paths.

Gradient Wind

The wind that results from the balance between the pressure gradient force, the Coriolis force, and the centrifugal force.

Parallel

Gradient winds are______to the curved isobars.

Slower

In a low pressure system or trough, the gradient wind blows parallel to the isobars_____than the geostrophic speed.

Faster

In a high pressure system or ridge, the gradient wind blows parallel to the isobars_____than the geostrophic speed.

Vertical

Cyclones and anticyclones are associated with_______airflow.

Vertical Wind Shear

The change in wind speed with increasing height.

Into A Region, Rise

Convergence aloft occurs when net airflow________causes the surface pressure to______

Net Outflow Of Air From A Region, Fall

Divergence aloft results when there is a________, causing the surface pressure to_______

Diverge, Converge

In high pressure systems, winds________at the surface and_______aloft.

Converge, Diverge

In low pressure systems, winds_______ at the surface and________aloft.

Coming From

Wind direction is always measured in the direction that it is…

Prevailing Winds

Average winds over a specific area and long time period.

Wind Vane

Instrument that measures the direction of the wind in degrees. The pointed arrow determines the direction from which the wind is blowing.

Windsock

Device used to measure wind direction and speed, but is more general and less precise than other instruments.

Aerovane

Instrument that measures both speed and direction of the wind.

Vector Quantity

Due to it having both direction and speed, wind can be considered a….

On Your Left

According to Buy’s Ballot Law, in the Northern Hemisphere low pressure will be_________if you stand with your back to the wind.

Significantly Impact

Orographic elements can___________wind speed.

Higher, More Dense

Dry air has_______pressure than moist air and is also______than it

Horizontal Differences

Winds result from______in air pressure

Rising

If fair weather is approaching, the pressure tendency would likely be…

China

Country with the largest wind generating capacity.