test 3 Flashcards
Primary circulation
General worldwide atmospheric circulation
Secondary circulation
This consists of migration of high and low pressure systems
Air mass thunderstorms
They are short lived and rarely produce severe weather
Super cell thunderstorms
produces hail at least 3/4 of an inch in diameter and has surface wind gusts of 58 mph, or creates a tornado
Why are surface winds generated?
When two regions have different temperatures, they soon begin to have different air pressures as well. Differences in air pressure allows air molecules to move from one place to another (which is what wind is)
synoptic scale: Across two latitudes
regional scale: Between two surface
What is pressure gradient force?
wind speed proportional to the pressure difference between high and low pressure regions. The greater the PDF, the greater the wind flow
What is the corolis force?
This is the way that the wind flows due to the fact that it spins on an access..it does not have an effect on wind flows
why is the corolis force stronger at the poles than at the equator?
Because at the poles it is perpendicular to the earths surface but it is parallel at the poles
How does the corolis force affect the direction of the wind?
Wind is deflected to the right in the Northern hemisphere and to the left in the Southern hemisphere
What is a geostrophic wind and how is it created?
This is when the wind has reached a constant flow. It is created by the pgf that acts on an air parcel and deflects it to the right. As the air parcel increases in speed, it gets closer and closer to the pgf. This is the point at which it is balanced and becomes constant
Free atmosphere
This occurs when wind flow is above the level of friction . On average this is reached at about 1000m. Creates a geostrophic wind
What is the impact of friction on wind flow?
Reduces wind speed and it alters the direction of the wind. The deflection of wind flow on the ocean is about 8 degrees while it is about 25 degrees on land
Poleward air flow (western side)
air flow carries a lot of moisture. This affects continental margins of the US. Creates adibiatic cooling and condensation
Equatorward air flow
air carries dryness because of strong air subsidence. This air cannot cool and condense. Many of the deserts are located on the eastern side of the subtropical high cells because of this
polar front
the boundary between continental polar air mass (cold/dry) and tropical maritime air mass (warm/moist)… where frontal precipitations can take place. It seperates the polar easterlies from the westerlies
The westerlies
they are generated from substropical high pressure cells They take place between 30 degrees and 60 degrees and are more active in the southern hemisphere than in the northern because of the unbroken belt of oceans
what happens when tropical air mass carried by the westerlies collides with the polar front?
condensation, development of mid latitude cyclones, and frontal precipitation
Polar easterlies
cold and dry wind flow moving from the polar regions. They have a greater velocity of Antarctica because of the strong polar high that develops at the south pole
Upper air circulation
It controls the movement of air masses at the surface and is responsible for the development of mid latitude cyclones
zonal flow
fast moving wind from west to east. maintains air masses from within their natural boundaries
Meriodinal flow
slow moving flow moving across the latitudes in both directions. allows very cold air from the arctic to move toward lower latitudes. also very warm air from the tropics to move north ward
What is air mass
a large body of air whose physical properties (e.g., density, temperature, moisture) are more or less
uniform horizontally for hundreds of kilometers.
Why is weather variable in the mid latitude regions
It has to do with the traveling air masses and how they interact with one and other
mE
maritime equtorial. warm oceans in the equatorial zone. warm and very moist
mT
maritime tropical. warm oceans in tropical zone. warm and moist
cT
Continental tropical. Subtropical deserts. warm and dry
mP
maritime polar. Midlatitude oceans. cool and moist
cP
contiental polar. Northern continental interiors. cold and dry
cA
Continental arctic. Regions near north and south pole. very cold and very dry
what happens when an air mass starts to move?
it will gain (or lose) heat and gain (or lose) moisture
Secondary air masses
these are created because of thermodynamic and dynamic changes.
Thermodynamic change
Takes place when a cold air mass is moving south over areas where the land mass is warmer
dynamic change
Takes place when an air mass has to go over a topographic barrier
mid latitude wave cyclone
a common situation along the polar front in the continental United States
3 phases of mid laittude wave cyclone
- ) Frontogenesis and cyclogenesis stage
- ) Mature (or open) stage
- ) Occluded (or dying) stage
frontogensis
this is the first stage that refers to the creation of fronts delimiting air masses with different physical properties
stationary front
develops at the surface when two air masses remain in the same place. (typical of zonal flow conditions aloft)
Frontal waves
Frontal waves at the surface indicate that the upper air flow is starting to enter a meridional phase. Warm air mass is starting to move above the ground