Evaporation from the ocean
Transport through the
atmosphere
Condensation and precipitation
Return to the ocean
Many smaller sub cycles
Clouds form when air masses are
cooled to their dew point
Generally cooled by upward
movement
Cloud formation depends on
atmospheric stability
Stable atmosphere
lifted parcel of air to cooler
(and denser) than surrounding air
lifted parcel returns to the
original level
Unstable atmosphere
lifted parcel of air is warmer
(and less dense) than surrounding
air
Moved to a higher level, it will
continue to rise
“thermals”
Rising moist air cools and
eventually reaches the dew point
Droplets condense around
condensation nuclei in saturated
air
no condensation nuclei:
supersaturated air
In a state of atmospheric stability,
the parcel of air will always be
cooler, and therefore more dense,
that he surrounding air at any
altitude. It will, therefore, return
to the original level when the
upward force is removed.
In a state of atmospheric
instability, a parcel of air will
always be warmer, and therefore
less dense, than the surrounding
air at any altitude. The parcel
will, therefore, continue on in the
direction pushed when the
upward force is removed.
Cooling of rising air slowed by
release of latent heat of
vaporization
Huge numbers of droplets
appear as clouds
Precipitation
Water returning to Earth’s
surface
Dew and frost are surface
processes, not precipitation
Precipitation forms in two ways
Coalescence of cloud droplets
Growth of ice crystals
Coalescence process
takes place in warm
cumulus clouds, near the tropic
oceans
clouds contain giant salt
condensation nuclei
Ice-crystal process
Takes place in clouds of
middle latitudes
Ice crystals capture nearby
water molecules and grow
Fall as snow in the winter;
melt and turn to rain in summer
Idealized model
Region 10oN and 10oS of
equator receives more direct
solar energy
Air heats up, rises and
spreads toward poles
Air cools and becomes more
dense as it rises sinking back to
the surface at latitudes 30oN and
30oS
End Result
Band of low pressure near
the equator, bands of higher
pressure 30oN and 30oS of the
equator
Large convective cells form
to equalize pressure
Large, horizontally uniform
bodies of air
Moisture and temperature
conditions nearly the same
Four main types
Continental polar
Maritime polar
Continental tropical
Maritime tropical
Dictate air mass weather
weather conditions remain
the same over several days
weather changes when a
new mass moves in or when the
air mass acquires local
conditions
Boundaries between air masses
at different temperatures
Cold front
cold air mass moves into and
displaces warmer air upward
moist rising air cooled
Warm front
Warm air mass advances over
a cooler air mass
Long, gently sloping front
Clouds and rain may form in
advance of the front
Stationary front
Forces influencing warm
and cold air masses become
balanced
Mechanisms
Bulges or waves often form
between air masses
Overriding, uplifted cold air
produces a low pressure area
Further cold front motion
leads to an occluded front and a
cyclone storm
Cyclone
Low pressure area with
inflowing, upward force winds
Circulation pattern caused
by the Coriolis effect
Anti-cyclone
High pressure area
Air sinks, is warmed,
relative humidity is lowered
Rapid, violent weather changes
Often associated with frontal
passage
Three major types
thunderstorms
tornadoes
hurricanes
Usually develops in warm, very
moist, and unstable air
Three stages
Cumulus – associated with
convection, mountain barriers, or
a cold front
Mature
Updraft can no longer support
growing ice crystals and snow
flakes
Falling frozen water melts and
becomes rain
Hail formed through ice
accumulation cycles
Final
All updrafts are exhausted
Updrafts, downdrafts and
circulating precipitation separate
electrical charges
Charges accumulate in different
parts of the thunderhead
Lightning
Discharge between charge
centers
Can be cloud to ground,
ground to cloud, or cloud to cloud
Expanding pressure wave
from heated air produces crack of
thunder
Smallest, most violent weather
disturbance
Rapidly whirling column of air
diameter of 100-400 meters
wind speeds up to 480 km/h
Damage produced
high winds
drop in pressure at center
flying debris
Associated with intense
thunderstorms
Tropical depression
Tropical Storm
Hurricane
Tropical depression
area of low pressure
winds generally moving at 55
mph or less
Tropical storm
more intense low pressure
areas
Winds between 56 and 120
mph
Hurricanes
Very intense low pressure
Winds in excess of 120 km/h
Fully developed hurricane
has a calm eye surrounded by
intense rain and thunderstorms
Based upon mathematical models
of the atmosphere
Billions of calculations
necessitate use of supercomputers
Fairly accurate forecasts up to
three days possible
Major uncertainty:insufficient
technology to connect small and
large scale events
Ultimately oceanic influences
need to be better understood
Composite, larger weather
patterns occurring over a
number of years.
Determining factor in
types of plants and animals
in a given location
types of houses built
lifestyles
Influences
shape of the landscape
types of soil
agricultural type and
productivity
Two primary factors
1.Intensity of incoming solar
radiation
2.Number of daylight hours
Low altitudes
High solar radiation
Yearly variation small
Temperature uniformly high
Middle latitudes
Higher solar radiation during
one part of the year; lower
during the other
Overall temperatures lower
with greater variation than low
latitudes
High latitudes
Maximum amount of
radiation during one part of the
year; none in the other
Overall temperatures are
lowest with violent variation
Defined in terms of yearly
temperature averages
Tropical climate zone
near equator
receives most solar radiation
hot
Polar climate zone
least solar radiation
cold
constant daylight part of
summer; constant darkness
part of winter
Temperate climate zone
intermediate between
others
Four
Major
Factors
Altitude
Higher altitude air radiates
more energy into space
Mountains
Cooler air at higher altitudes
Upwind slopes receive more
precipitation; downwind slopes
receive less
Large bodies of water
high specific heat of water
moderates temperature
changes
Ocean currents
can bring water nearby that
has a different temperature that
the land
Problems
No sharp boundaries
No two places have exactly the
same climate
Marine climate
Near ocean
Influenced mostly by air
masses from the ocean
Can be polar or tropical
Continental climate
far from ocean
influenced mostly by air
masses from large land areas
can be polar or tropical
Other classifications:
arid
semiarid
humid
Microclimate: a local
pattern in climate
Can be associated with large
cities