The Earth’s major air masses originate in
polar or subtropical latitudes
. The middle latitudes constitute essentially a zone of modification, interaction, and mixing of the polar and tropical air masses. Air masses are commonly classified according to four basic source regions with respect to latitude.
Where are air masses found?
Air masses can
extend thousands of kilometers across the surface of the Earth
, and can reach from ground level to the stratosphere—16 kilometers (10 miles) into the atmosphere. Air masses form over large surfaces with uniform temperatures and humidity, called source regions.
Where an air mass originates is called its?
The area where an air mass originates is called a:
source region
.
Where do tropical air masses originate?
Maritime tropical air masses originate
over the warm waters of the tropics and Gulf of Mexico
, where heat and moisture are transferred to the overlying air from the waters below. The northward movement of tropical air masses transports warm moist air into the United States, increasing the potential for precipitation.
What are the source regions for air masses?
Parts of the Earth’s surface where the air can stagnate and gradually gain properties of the underlying surface are called source regions. The main source regions are the
high pressure belts in the subtropics
(giving rise to tropical air masses) and around the poles (the source for polar air masses).
What causes air masses?
An air mass forms
whenever the atmosphere remains in contact with a large, relatively uniform land or sea surface for a time sufficiently long to acquire the temperature and moisture properties of that surface
. The Earth’s major air masses originate in polar or subtropical latitudes.
Why do air masses move?
An air mass is a large body of air that has about the same conditions throughout. Air masses take on the conditions of the area where they form.
Winds and air currents cause
air masses to move. Moving air masses cause changes in the weather.
What are the 5 types of air masses?
The air masses in and around North America include the
continental arctic (cA), maritime polar (mP), maritime tropical (mT), continental tropical (cT), and continental polar (cP) air masses
.
Why is there no such thing as a maritime arctic air mass?
But
mA-type (maritime Arctic) does not exist
. Continental Polar air masses form over large, high- latitude land masses, such as northern Canada or Siberia. cP air masses are cold and extremely dry. Wintertime cooling over these land areas cause the atmosphere to become very stable (even inversion).
What is the boundary between air masses called?
Where air masses converge, they form boundaries called “
fronts”
. 3-D view of a cold front. Fronts are identified by change of temperature based upon their motion. With a cold front, a colder air mass is replacing a warmer air mass.
Why do tropical air masses have lower air pressure?
Once again, the characteristics of an air mass depend on the temperatures and moisture content of the region over which the air mass forms. Since temperature affects air pressure, cold, dense air has a higher pressure, while warm,
less dense air has a lower pressure
. Warm, humid air masses form over tropical oceans.
What air masses affect the US?
Five air masses affect the United States during the course of a typical year:
continental polar, continental arctic, continental tropical, maritime polar, and maritime tropical
. Continental air masses are characterized by dry air near the surface while maritime air masses are moist.
What type of weather does an air mass usually bring?
Continental air masses are usually relatively dry and usually bring
fair weather
. Maritime air masses are usually humid and may bring precipitation.
What is the best source region for an air mass?
The best source regions for air masses are
large flat areas where air can be stagnant long enough to take on the characteristics of the surface below
.
Where do air masses get their temperature and humidity properties?
Temperatures
and humidities vary gradually with latitude, longitude, and altitude throughout the
air mass
. The
air masses obtain their
characteristic
temperature and humidity
by sitting at a location on earth for a period of time. This location is the source region.
What are the characteristics of an air mass source region?
Where an air mass receives it’s characteristics of
temperature and humidity
is called the source region. Air masses are slowly pushed along by high-level winds, when an air mass moves over a new region, it shares its temperature and humidity with that region.
