evaporation from the ocean transport through the atmosphere condensation and precipitation return to...
TRANSCRIPT
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 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.
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.
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