What is the difference between weather and climate?
- weather = condition of the atmosphere in a particular area
- climate = the average weather experienced by a region
- both influenced by - solar radiation, topography, water
The Atmosphere
- thin envelope of air that surrounds the earth
- composed of
- nitrogen
- oxygen
- other
- water vapor (humidity)
Structure of the Atmosphere
- 4 layers
1) Troposphere (0 - 14 km)
- most dense, weather systems
2) Stratosphere (15 - 50 km)
- ozone layer
3) Mesosphere (55 - 85 km)
4) Thermosphere (90 - 500 km)
- upper atmosphere
What influences the atmosphere
The engine for weather = solar radiation
- the fate of solar radiation
- filtered - ozone
- reflected - albedo
- absorbed - IR radiation
- uneven heating
Interactions between water and the atmosphere
- the hydrologic cylcle
- evaporation - condensation - precipitationWeather and Water
the three states of water
- solid, liquid, gas
=> What determines the state?
- heat energy released or absorbed
Thermal Properties of Water
Water can absorb or release substantial quantities of heat without any significant
change in temperature.
- specific heat (heat capacity) - very high
- latent heat (energy released or absorbed during change of state)
Weather and Water
What is humidity?
a measure of the amount of moisture in air
which can hold more water - warm or cold air?
Relative Humidity - the amount of water in air relative to the maximum amount
of water the air could hold.
- When does humidity increase
Atmospheric Pressure
- atmospheric pressure decreases with increasing altitude
- local variation related to density of cold vs. warm air
H - cold dry air sinks and compresses
L - warm moist air rises and expands
The Wind - atmospheric circulation
- air (wind) moves from high to low pressure
- uneven heating
- latitude
- seasons
- coriolis
Produces
- global atmospheric circulation cells
- Westerlies & Trade Winds
Weather Systems
- the condition of the atmosphere in a particular place
- the most obvious way that the earth system impacts humans
Air Masses
- changes in weather result of interaction between moving air mass
- source area and temperature (maritime & continental, Arctic, Polar, and
Tropical)
- changed by temperature and topography
- boundary between moving air masses = fronts
Frontal systems
- cold front - heavy rainfall
- warm front - light rainfall
- occluded front
Mid latitude cyclones
- migration of regional low pressure system
- continental polar and maritime tropical
- most weather systems in U.S. are of this type
Thunderstorms
- cold front produces supercells
- latent heat - updrafts - warm, humid air rises to 15 km
- 3 stages = cumulus, mature, and dissipating
Tornadoes
- cold front produces supercells
- extreme pressure gradients
- 3 stages = early, updraft, and tornado
- damage - Fujita Intensity Scale F0-F5
- ~1000/yr in the U.S.
- Tornado Alley
Hurricanes = large, cyclonic tropical storms
- require warm tropical oceans
- start as a tropical depression - low pressure
- convergence and divergence
- build to tropical storm, then finally a hurricane (75 mph)
- Intensity = Saffir-Simpson scale - categories 1 through 5
- Damage - high winds, rainfall, storm surge
- landfall - predictions