air masses

air mass

immense body of air.

air mass characteristics

similar temp, humidity, n stability throughout

air mass weather

a region w/ generally constant weather conditions because it is under the influence of an air mass.

source regions

are where air masses originate. 

nature of the source region determines

air mass characteristics, must be an extensive n physically uniform area. characterized by a general stagnation of atmospheric circulation. Either water or land. 

Air mass Classification

classification depends on the latitude (temp) n the surface are n are the identified by two-letter code. Air masses at the poles are cold, and air masses at the equator are warm

with latitude, air masses are in 1 of 3 categories

Polar, Artic, Tropic. (Gradient of freezing). Nothings artic until it’s really cold.

There are two surface areas for air masses

Marine (wet), Continental (dry) (cant get marine + artic)

CP-Continental Polar

Cold and dry. Comes out of Northern Canada/ Alaska

cA- Continental Artic

VERY cold, VERY dry comes out of the artic ocean (ice covered) n Greenland ice cap

cT- Continental Tropic

Warm and Dry comes from Mexico (+sw us)

mP- Marine polar

Cold, and Wet. North Pacific, northwestern Atlantic

mT- Marine Tropic

Warm and Wet. comes from gulf of Mexico. Caribbean, pacific, western atlantic

What happens to cA or cP air as it moves over the ocean in winter

it undergoes significant changes, as evaporation from the water surface transfers moisture to the dry continental air, leading to instability. 

Continental polar (cP), and continental Arctic (cA), air masses (during winter)

air masses are dry and bitterly cold. (stable air is the rule because the air is very cold and the surface below is frozen) CONTROLS WINTER. often enter US between Rockies, and the Great lakes.

Maritime polar air masses are

cold/moist. form over cold oceans @ high latitudes over n Atlantic/pacific. mP air is warmer than cP n cA masses in winter. mP air masses from the north pacific influence North American weather more than those generated in the North-west Atlantic. (North Atlantic influence Europe)

Pacific mP air masses usually begin as

cP air in Siberia (Siberian High)

As cP air moves east

it picks up moisture over the warm ocean. When it arrives at the western coast of North America, it is often accompanied by low clouds and shower activity. (cp air traveling turning to mp)

As cP air moves in the summer

it passes over an ocean that is cooler, not warmer, than surrounding continents.

mP air from North Atlantic was originally

cP, only occasionally affects weather on northeast coast of North America. In winter, strong cyclonic winds can draw mP air from the Atlantic into the region, which results in a nor'easter w/ strong northeast winds, freezing temps, high humidity, n precipitation.

Marine Tropical air masses most often originate

over the gulf of Mexico, the Caribbean sea, or the western Atlantic. They’re warm to hot. Moist and unstable. Capable of significant precipitation. SUMMER

(WINTER) North Atlantic Air masses are from

the Gulf-Caribbean-Atlantic source affect the weather of the United States east of the Rocky Mountains. During winter, mT air only occasionally enters the central and eastern United States. When the lower portions of air are chilled n stabilized, mT air is changed to mtw w/ the possibility of FOG n increased PRECIPITATION. Comes in off subtropical high. as move across Atlantic, become humid. WINTER

(SUMMER) North Atlantic mT air masses from

the Gulf-Caribbean- Atlantic source affect the weather of the United States

east of the Rocky Mountains.

In the summer, mT air masses affect a much wider area of North America and are present for much of the winter. As it moves inward, it becomes an Mtk mass as daytime heating increases instability. Hot n Humid.

Isohyets

lines connecting places having equal rainfall

What air mass from the North pacific have less of an impact on North American Weather

North Pacific mT air masses. When air masses move northward, cooling causes the lower layers to become more stable often resulting in fog, drizzle, of moderate precipitation

What air mass is associated with atmospheric rivers

mT Maine tropic

Atmospheric Rivers

narrow zones in the atmosphere that transport significant amounts of moisture to regions outside of the tropics. Winter Phenomena. Warm, moist air coming onto land. (Pineapple Express!)

Pineapple Express

brings extraordinary rains to southern California and other West Coast locations.

SUMMER MT AIR

moves Northeastward from Pacific, into Gulf of California and into southwest United States. Associated w/ Monsoon.

Drylines

narrow zones that trigger severe thunderstorms may occur if the air mass encounters a mT air mass

cT Continental Tropic

More prevalent in the summer. Usually produced in the interior of Mexico and in the southwestern United States. cT masses are hot, dry air masses. It remains nearly cloudless with an almost complete lack of rainfall, which can cause drought. When air masses moves out of source region, it occasional moves into the southern Great Plains

Identifying Air masses on weather maps

Use surface temperature and

dew point. Dew point tells about relative humidity. 

(below 10 significant snowfall inhibited

below 55 minimum for severe thunderstorms to form

below 65 considered humid by most ppl

below 70 typical of the rainy tropics

below 75 considered oppressive by most)

Lake-effect snow

result of a cold air mass over warm water. occurs mainly in autumn and early winter. cP air moves across open water (Great Lakes). Air increases temperature slightly from the warmer water. It picks up more moisture. cP air moves over land. It then cools and drops snow in large amounts.