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An in-depth exploration of air masses and fronts, their formation, classification, and impacts on weather patterns. topics such as the properties of air masses, source regions, fronts on weather maps, and their association with high and low-pressure systems. The document also discusses the differences between cold and warm fronts, stationary fronts, and occlusions.
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ESS124ESS124Prof. JinProf. Jin-
ESS124ESS124Prof. JinProf. Jin-
ESS124ESS124Prof. JinProf. Jin-
January
July
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The centers of cold air masses are associated with high pressure on surface weather maps.
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In summer, when the oceans are cooler than the landmasses, large high-pressurecenters appear over North Atlantic (
Bermuda high
) and Pacific (
Pacific high
). ESS124ESS124Prof. JinProf. Jin-
-Yi YuYi Yu
-^
In winter, high-pressure centers form over the northern parts of Asian continent( Siberian high
)^ and North America.
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ESS124ESS124Prof. JinProf. Jin-
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ESS124ESS124Prof. JinProf. Jin-
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ESS124ESS124Prof. JinProf. Jin-
Continental Arctic (Continental Arctic (cA
cA) Air Masses
) Air Masses
Continental Arctic (cA)
air represents extremely cold and dry
conditions as, due to its temperature, it contains very little watervapor.
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The boundary between cA and cP air is the shallow (~1-2 km)arctic front.
ESS124ESS124Prof. JinProf. Jin-
cA air masses can extend as far southward as the Canadian-United State.
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Maritime polar air masses form overupper latitude oceanic regions and arepp
g
cool and moist.
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mP air masses form over high-latitudeocean as cP air masses move out from the interior of continents. (i.e., cP
Æ
mP).
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Oceans add heat and moisture into the dryand cold cP air masses.
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Along the west coast of the U.S., mP airaffects regions during winter and may bepresent before mid-latitude cyclonesd
t^
th
ti^
t
advect over the continent.
-^
Along the east coast, mP air typicallyaffects regions after cyclone passage asthe mP air wraps around the area of low
ESS124ESS124Prof. JinProf. Jin-
the
mP air wraps around the area of low pressure.
Maritime Tropical (Maritime Tropical (mT
mT) Air Masses
) Air Masses
p
(
p
(
))
Form over low latitude oceans and assuch are very warm humid andsuch are very warm, humid, andunstable.
-^
mT air masses from Atlantic and Gulff M
i^
i^
h^
i
of Mexico is the primary sourceregion for the eastern U.S.
-^
As air advects over the warm continent in summer the highhumidity and high heat occasionallycombine to dangerous levels.
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mT air masses have an enormousinfluence on the southwestern U.S,particularly in summer.
Advection of mT air also
ESS124ESS124Prof. JinProf. Jin-
p^
y
Advection
of mT air also
promotes the so-called Arizonamonsoon.
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ESS124ESS124Prof. JinProf. Jin-
along a cold front depends on thecharacteristics of the warm air ahead ofcharacteristics of the warm air ahead ofthe front.
diti
ll^
t bl
th
d^
t
conditionally unstable, thunderstormscan be triggered ahead of the coldfront; the thunderstorms will form in ali^
ll d
ll li
if^
ll
line called squall line; if supercellthunderstorms form, tornadoes, hail,damaging wind can occur.
form by lifting only produce light rain.
ESS124ESS124Prof. JinProf. Jin-
-Yi YuYi Yu
If
the warm air is dry and stable, no clouds will form at all.
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ESS124ESS124Prof. JinProf. Jin-
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warm front boundary and progressivelybecomes thinner and higher toward the north.
depends on the stability of the warmdepends on the stability of the warmair.
t bl
th
d^
t^
d^
l
unstable, thunderstorms may developover the warm front.
be layered.
below freezing snow ice pellets or
ESS124ESS124Prof. JinProf. Jin-
-Yi YuYi Yu
below
freezing, snow, ice pellets, or
freezing rain may occur.