There are four primary air masses that effect the weather in the United States. These are the Continental Polar, Continental Tropical, Maritime Polar, and Maritime Tropical Air masses. These air masses form in their source regions and based on that region is how they get their names. The Maritime Tropical air masses are typically located off the southern east and west coasts. They are responsible for much of the rainfall in the United States due to moving the moisture from the oceans over land and then interacting with the Continental Polar or Continental Tropical air masses depending on the time of year and the season. Once any of these air masses start to move from their source region, this is when the atmospheric stability of the air mass is modified.
We first need to define what an air bulk is and then determine its source region to identify what type of air travel multitude it is and the constancy of the air out mass. Air masses are labeled based on their source region .
There are two primary tune masses that impression the weather in the mid-west and eastern United states. The Continental Polar ( cP ) and the Maritime Tropical ( metric ton ). The Continental vent mass will begin to drop south out of Canada and bring cold tune to the south with a dominant high pressure arrangement.
Semi-permanent eminent blackmail systems determine migration of the vent masses during the summer and winter months .
Air Mass – Definition
An vent mass is a widespread body of air with exchangeable temperature and moisture characteristics in both the horizontal and erect ( homogeneous ). Air masses may cover several thousand square miles.
Locations Of Air Masses In North America
The geographic localization where the air-mass formed is referred to as the Source Region. These regions have uniform surfaces of temperature and moisture characteristics. They are normally flat and uniform ( all down or all water system ) and light come on winds. The properties of any air multitude will be dependent upon where the breeze multitude originates. Dry air masses form over land and moist air masses form over water .
Air mass locations in the United States
Types Of Air Masses
Continental Arctic (cA)
The continental arctic ( calcium ) air-mass forms in the arctic areas of the Arctic Ocean, Antarctica, Greenland, Northern Siberia, Alaska and Canada in the winter. These areas have a uniform surface, normally extremely cold and dry. The abundance of ice and snow, does not allow for increase moisture contented because the sphere in most cases does not have dissolve urine .
Continental Arctic (cA) Air Mass When the continental north-polar ( calcium ) air mass does move south, it is the one that starts the cold dry weather that we know as the diametric whirlpool .
Continental Polar (cP)
Continental Polar (cP) Air Mass This air-mass forms in the northern regions of Canada, Alaska, Siberia and sometimes northern Europe. You will notice an area of higher pressures in the same region where these cP air-masses form. This high imperativeness allows for the homogeneous area an air-mass needs to form. As the cold of winter settles in, the remission helps intensify the highs which besides weaken in the heat of summer. These air-masses are typically cold, dry and stable.
Maritime Tropical (mT)
The meitnerium air travel masses are very warm and moist in low levels. There are probably inversions in this air mass during the evening that prevent moisture from reaching the higher levels in the troposphere. The eastern side of the subtropical high is more stable than the western side. This makes the eastern side drier than the western side where clouds and precipitation are common. Dew-point temperatures are greater than 60°F. These high dew points make it very uncomfortable in a montana air multitude .
Maritime Tropical (mT) Air Mass Maritime Tropical airmass will be very quick and humid. A “ tropical continental ” airmass normally covers much of the United States in the summer. other airmass types include “ arctic ”, “ equatorial ”, and “ monsoon ” .
Maritime Polar (mP)
The source region for the mP air batch is the cold unblock ocean areas poleward of 45°. It is associated with the subpolar lows which intensify and shift equatorward in the winter. They form from the alteration of another air mass, normally continental arctic or nautical tropical, which moves over the cold ocean areas. This is the predominate atmosphere mass west of the Rocky Mountains and in western Europe .
The Maritime Polar air mass over the North Pacific effects the weather in the upper northwest causing the showery season. This air mass is besides responsible for lake effect snow from inshore flow from the pacific .
Continental Tropical (cT)
The entirely actual source area for connecticut air masses in North America is found during the summer in the defect Southwest and northerly Mexico. hera the atmosphere is very hot and the air rises causing a low-pressure area. These lows are thermal lows and are called heat lows .
Continental Tropical (cT) Air Mass In the summer, there is a continental Tropical ( connecticut ) tune mass that settles over the confederacy central United States and if the sub-tropical jet comes far adequate union to cause the warm and dry air aggregate to push east, a dry line can be found at the leading border of the air mass and this dry lineage in known to cause sudden hard weather in the south .
Weather Caused By The Continental Tropical (cT) Air Mass
This air mass forms in the summer and is unique due to dry nature and can cause the hard weather we see much in Texas.
Read more: How Maritime Law Works
An inversion is when temperature increases with stature opposed to decreasing with acme and this causes an inversion in the atmosphere that can trap warm damp air out in the lower levels an with an approaching dry line acting in the warm damp publicize, it can cause the moisture to build up and when the inversion pops, a sudden explosive onset thunderstorms with severe condition and tornadoes can form .
Semi-Permanent High Pressure Systems
There are two semi-permanent senior high school pressure systems. One over the Atlantic Ocean and one over the Pacific Ocean. These press systems migrate north and south during the winter and summer months. This migration allows the nautical tropical air masses over the oceans to move union or south vitamin a well. When the semi-permanent high coerce systems move south in the winter, they can be creditworthy for pumping warm damp atmosphere over land in the south east and west transporting the moisture needed to produce rain showers when interacting with the continental pivotal ( cP ) air travel mass to the north .
These gamey imperativeness systems can besides collide with the Maritime Tropical air mass to the south which is affectionate and damp and induce precarious conditions. As the warm damp air is lifted up over the cold dry publicize clouds will for at the lifting condensation level and if there is adequate moisture associated with the two air masses, rain and thunderstorms can develop .
These press systems are besides creditworthy for steering hurricanes and tropical storms during Hurricane season. 1 June – 30 Nov .
Summary
Continental Polar/Arctic (cP or cA)
- Cold/dry air masses
- Originate over the ice/snow covered regions of northern Canada and Alaska
- Long, clear nights allow for maximum cooling
- Very dry
- Usually stay in place but occasionally break away and are carried southeast by the upper level winds
- Drops in toward the plains so there is not much terrain to impede it.
- Moderate (warm up) as they move southward – Particularly if they move over warm water
- Produce lake-effect snow up north
Maritime Tropical (mT)
- Warm/moist air masses
- Originate: Gulf of Mexico Sub-tropical eastern Pacific Western Atlantic
- Develop afternoon air-mass thunderstorms
- Very stable in the eastern region
- Dew points are in the 70’s causing an uncomfortable humidity
Maritime Polar (mP)
- Cool and moist in the low levels
- Greatest influence on the Pacific Northwest
- Cool, moist. and unstable
- Sometimes causes severe weather along the dry line in the southern plains.
Continental Tropical (cT)
- Hot/dry air masses
- Found in the desert Southwest and northern Mexico
- Responsible for summer drought conditions
- Very unstable in the low levels
- Precipitation usually evaporates before reaching the ground
Equatorial Trough (E)
- Source region is approximately 10°N to 10°S
- The weather is the same year round
- Will produce showers and thunderstorms mainly in the afternoon
- Unstable with high humidity
This gamey blackmail system will then collide with the Maritime Tropical atmosphere mass to the south which is warm and damp and induce unstable conditions. As the warm damp breeze is lifted up over the cold dry atmosphere clouds will for at the lifting compression flat and if there is adequate moisture associated with the two air masses, rain and thunderstorms can develop .
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Garry Ward
Served in the United States Marine Corps as a upwind observer and advanced to a weather forecaster. Stationed at the most active breeze field on the east coast and provided meteorologic and oceanographic support to aircraft squadrons traveling around the worldly concern .