Download Weather Systems

Weather Systems
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Air masses
Types of front (cold, warm, occluded)
Traveling cyclones and anticyclones
Tornadoes
Tropical Weather Systems
Air Masses
c = continental (dry)
m = maritime (wet)
T= tropical (warm)
T
P = polar (cold)
A = Arctic (cold)
(from Arctic oceans
and fringing
g g lands))
Warm Fronts
Cold Fronts
In a warm front, warm air
advances toward cold air and
rises up and over the cold air.
Rain falls from the dense
stratus cloud layer
At a cold front, a cold air
mass lifts a warm air mass
aloft
The upward motion sets off
a line of thunderstorms
In an occluded
front, a warm front
is overtaken by a
cold front
front.
The warm air is
pushed aloft and it
is not longer in
contact with the
ground
Cyclone Tracks
• Wave cyclones tend
to form in certain
areas and travel
common paths
• Mid-latitude wave
cyclones tend to
travel eastward
• Tropical cyclones
tend to move
westward
Tornadoes
• a small but very intense
cyclonic
l i vortex
t
• appear as dark funnel
cloud hanging down from
cumulonimbus clouds
• Wind speeds may be as
high as 100 meters per
second (225 miles per
hour)
• Cause great damage
Tropical Cyclones
• hurricanes (western hemisphere) and
typhoons (western Pacific in Asia) and
cyclone in Indian Ocean
• develop over warm ocean surfaces
between 8° and 15° latitude, migrate
westward and curve toward the poles
poles.
• tropical cyclones often create
tremendous damage due to high winds,
high waves, flooding and heavy rains.
Hurricanes (Typhoons)
• characteristic central
“eye”
eye (clear skies and
calm winds)
• air descends from high
altitudes, warming
• wind speeds are
highest
g
at the “eye
y wall”
• winds spiral outward
creating high wind
speeds
Simpson-Saffir Scale of
Tropical Cyclone Intensity
• Categories 1 to 5 (5 is most devastating)
• (注意: 台灣分輕度、中度和強度三級)
• measured by central pressure, storm
surge and mean wind speed
Impact of Tropical Cyclones
• low pressure,
pressure high winds and
the shape of bays can
produce sudden rise in water
level (storm surge)
• flooding may occur inland
• activity varies from year to
year (number and strength)
• season usually from May to
November in Atlantic
Global Climates
• Climate refers to
average weather
conditions over long
periods of time
• classification based
on temperature and
precipitation.
Köppen’s Climate Classification
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Tropical Climates (A)
Mesothermal Climates (C)
Microthermal Climates (D)
Polar Climates (E)
Dry Arid and Semiarid Climates (B)
Tropical Climates (A)
• Tropical Rain Forest
Climates (Af)
• Tropical Monsoon
Climates (Am)
• Tropical Savanna
Climates (Aw)
Mesothermal Climates (C)
• Humid Subtropical
Hot-Summer Climates
(Cfa, Cwa)
• Marine West Coast
Climates (Cfb, Cfc)
• Mediterranean DryDry
Summer Climates
(Csa, Csb)
Microthermal Climates (D)
• Humid Continental
Hot-Summer Climates
(Dfa, Dwa)
• Humid Continental
Mild-Summer
Climates (Dfb, Dwb)
• Subarctic Climates
(Dfc, Dwc, Dwd)
Polar Climates (E)
• Tundra Climate (ET)
• Ice Cap Climate (EF)
Dry, Arid, and Semiarid Climates (B)
• Desert Characteristics
• Hot Low-Latitude Desert
Climates (BWh)
• Cold Midlatitude Desert
Climates (BWk)
• Hot Low-Latitude Steppe
Cli t (BSh)
Climates
• Cold Midlatitude
Steppe Climates
(BSk)
Strahler’s Climate Classification
• Based on the scheme first developed by
Koppen first in 1918
• Low Latitude Climates
• Mid-latitude Climates
• High Latitude Climates
Low latitude climates
• occupy equatorial, and much tropical
and
d subtropical
bt i l zones.
• range from very wet to very dry.
• influenced by the intertropical
convergence zone (ITCZ), tropical
easterly systems and subtropical high
highpressure cells.
• experience travelling lows such as the
easterly wave and tropical cyclones.
1. Wet equatorial
• dominance of the
intertropical
convergence zone (ITC),
• mE and mT air masses.
• uniform, very warm
temperatures in all
seasons.
• ample precipitation,
heaviest when the ITC is
nearby.
2. Monsoon and trade wind
coastal climates
• heavy rainfall with strong
seasonal patterns.
• larger temperature range
than wet equatorial climate.
• dominance of the ITC during
the heavy rainfall period and
the subtropical
p
high
g
pressure system during the
dry season.
• trade wind coast climates
are a result of mT and mE
air masses.
3. The wet-dry tropical climate
• a warm climate but with a
more marked temperature
range.
range
• during high sun season,
proximity to ITC brings
heavy rains.
• during cooler period,
subtropical high produces
very dry conditions
conditions.
• vegetation is rain-green
(dormant during dry season
and leafs out in rainy
season)
4. The dry tropical climate
• dominated by subtropical
high pressure cell
high-pressure
cell.
• experiences very low
precipitation and intense
daytime heating under
predominantly clear skies.
• includes many of the world's
greatt deserts.
d
t
• semi-arid areas on the
edges of the desert may
have a short wet season.
Midlatitude and high-latitude
climates
• occupy midlatitude zone
zone, part of
subtropics zone and extend poleward
into the subarctic
• affected by poleward portion of the
subtropical high, westerly winds and
meeting of warm and cold air masses
along the polar front zone.
5. The dry subtropical climate
• poleward extension of dry
p
climate,, but with
tropical
greater annual temperature
range (higher latitude).
• dominated by cT all year.
• cool season (air from higher
latitudes) and occasional
precipitation from midlatitude
cyclones.
cyclones
• divided into arid and semiarid subtypes.
• more vegetation than dry
tropical (lower temperatures
and more precipitation)
6. The moist subtropical climate
• warm, moist air flowing out of
the subtropical
p
high
g onto
eastern sides of continents.
(mT dominated)
• abundant summer rainfall,
mainly convectional with an
occasional tropical cyclone.
((cP mayy reach in winter))
• Southeast Asia experiences
strong monsoon.
• winter precipitation from wave
cyclones
7. The Mediterranean climate
• very dry summer due to
migration of the subtropical
high-pressure cell into the
area. cT air masses
dominated.
• winter is dominated by rainfall
provided by mP air masses
and cyclonic storms.
storms
• has a moderate temperature
range.
• limited to narrow coastal
zones.
8. The marine west coast climate
• mild temperatures with a
small temperature range for
its latitude.
• moist mP air moving inland.
• moist climate with a winter
precipitation maximum due to
frequent
q
cyclonic
y
storms.
• summer the northward
movement of the subtropical
high pressure cell reduces
precipitation.
9. The dry midlatitude climate
• interior regions of North
America and Eurasia
Eurasia. (far
from mP source region)
• summer rainfall is
convectional associated with
occasional maritime air
masses. (cP dominated)
• strong
t
annuall temperature
t
t
range with hot summers to
cold winters.
• includes arid cold desert to
semi-arid steppes.
10. The moist continental climate
• central and eastern North
America and Eurasia
Eurasia. (lies
in the polar front zone)
• large seasonal temperature
variation and strong day-today variation.
• ample precipitation peaking
i the
in
th summer with
ith mT
T air
i
masses
• winter is dominated by cP
and cA air masses.
The high latitude climates
• located in the westerly wind belt
belt.
• influenced by mP air masses conflicting
with cP and cA air masses and wave
cyclones which develop along the
arctic-front zone.
• experience higher summer precipitation
brought in by mT air masses.
11. The boreal forest climate
• long,
g, bitterlyy cold winters and
short cool summers.
• very large annual
temperature range
(continental location)
• source region for cP air
masses and invasions of cA
air masses are common.
• low total annual precipitation
with a summer precipitation
maximum.
12. The tundra climate
• is found along arctic coastal
areas.
• long severe winters
dominated by cP, mP, and
cA air masses.
• smaller temperature range
for its latitude (moderating
effect of ocean))
• consists of grasses, sedges,
lichens and some shrubs.
• cold enough to create
permafrost.
13. The ice sheet climate
• source region of arctic and
antarctic air masses.
• ice sheets of Greenland and
Antarctica and over the
Arctic ocean ice.
• lowest mean annual
temperature,
p
no month has a
mean temperature above
freezing.
• very low precipitation