Transcript Temperate Climate

The Temperate Climate
The Temperate Hadley Cell
• Westerly Prevailing Winds
• Warm inputs (often from the
Tropical Hadley Cell)
• Cold inputs form the Polar
Hadley Cell
• Weather develops where the
cold and warm inputs
collide guided by the Jet
Stream
Weather Systems & Air Masses
• Weather System – recurring
circulation pattern &
associated weather
• Air mass – large bodies of air
with uniform temp & moisture
– Up to thousands of km across
– May extend up to top of
troposphere
– Measured by:
• Temperature
• Humidity
Air Masses
• Develop over source
regions
• Take on characteristics of
the region
• Air masses classified by:
– Latitude (Arctic (A), polar
(P), tropical (T), equatorial
(E))
• Indicate temperature
– Surface type (Maritime (m),
continental (c))
• Indicate moisture content
Source Regions
• Idealized
continent &
oceans show
source regions
for air masses
• Combined air
mass labels (no
cE, mA or mAA)
– mE, mT, cT, mP,
cP, cA, cAA
The Pineapple express
Cold dry air
from Alaska
Warm moist air
from Hawaii
Fronts
• Surface of contact between 2 distinct air
masses
– E.g. boundary between polar & tropical air → polar
front
Fronts
• Cold air is heavier than warm air….the warm air
is pushed over the cold air
Fronts
• Warm Front – moving front → warm air slides
over cold air
– Slower than cold front
– Warm front stimulates nimbostratus clouds & rain
Cyclones
• Converging, inspiraling
air rises → condensation
• Cyclonic storm:
– Intense convection
– Strong winds
– Heavy precipitation
• 3 types of traveling
cyclones:
– Midlatitude cyclone (or
extratropical cyclone)
– Tropical cyclone
– Tornado
• High pressure
• Fair weather system
• Descending air
warms adiabatically
• No condensation
Anticyclones
A “Perfect Storm”
• Intense cyclonic
storm
• L marks the center of
rotation
• Strong wind & precip
hit NE US (blue &
orange)
L
Midlatitude
Cyclones
• Dominant weather
systems in mid & high
latitudes
• Form, intensify and
dissolve along polar
front
• Air converging along
front can create
circulation
• Cyclone may last a few
days, moving west-toeast
Lifecycle of Midlatitude
Cyclone
Upper-Air Disturbances
• Closely related to
midlatitude
cyclone
development at
surface
• Upper-air
convergence →
high surface
pressure
• Upper-air
divergence →
low surface
pressure
Cyclone Tracks & Families
• Certain regions good to develop cyclones
• Upper-level winds consistently steer
cyclones
• So, consistent cyclone tracks are well known
• Sets of tracks form cyclone families
Midlatitude Cyclone
Tracks
Cold Air Outbreaks
• Occasionally cold air
from polar regions
pushes far south
• This February image
shows cold, clear air as
far south as Florida
• White pattern E & SE of
image is clouds from
cold front
• White in NW of image
is snow cover