Weather
Weather is over a short period of time
Constantly changing
Climate
Climate is over a long period of time
Generalized, composite of weather
Elements of weather and climate
-Properties that are measured regularly
-Most important elements
Temperature
Humidity
Cloudiness
Precipitation
Air Pressure
Winds speed and direction
Compostion of Earth's Atmosphere
Air is a mixture of discrete gases
Major components of clean, dry air
Nitrogen (N) - 78%
Oxygen (O2) - 21%
Argon and other gases
Carbon dioxide (CO2) - 0.036% - absorbs heat energy from Earth
Water vapor
Up to about 4% of the air's volume
Forms clouds and precipitation
Absorbs heat energy from Earth
Aerosols
Tiny solid and liquid particles
Water vapor can condense on solids
Reflect sunlight
Help color sunrise and sunset
Ozone
Three atoms of oxygen (O3)
Distribution not uniform
Concentrated between 10 to 50 kilometers above the surface
Absorbs harmful UV radiation
Human activity is depleting ozone by adding chlorofluorocarbons (CFCs)
Pressure Changes
Pressure is the weight of the air above
Average sea level pressure
Slightly more than 1000 millibars
About 14.7 pounds per square inch
Pressure decreases with altitude
One-half of the atmosphere is below 3.5 miles (5.6 km)
Ninety percent of the atmosphere
Troposphere
Bottom layer
Temperature decreases with altitude - called the environmental lapse rate
6.5?C per kilometer (average)
3.5?F per 1000 feet (average)
Thickness varies - average height is about 12 km
Outer boundary is named the tropopause
Stratosphere
About 12 km to 50 km
Temperature increases at top
Outer boundary is named the stratopause
Mesosphere
About 50 km to 80 km
Temperature decreases
Outer boundary is named the mesopause
Thermosphere
No well-defined upper limit
Fraction of atmosphere's mass
Gases moving at high speeds
Seasons
Rotates on its axis
Revolves around the Sun
Changing Sun angle
Changing length of daylight
Caused by Earth's changing orientation to the Sun
Axis is inclined 23��
Axis is always pointed in the same direction
Summer solstice
June 21-22
Sun's vertical rays are located at the Tropic of Cancer (23�� N latitude)
Winter solstice
December 21-22
Sun's vertical rays are located at the Tropic of Capricorn (23�� S latitude)
Autumnal equinox
September 22-23
Sun's vertical rays are located at the Equator (0� latitude)
Spring equinox
March 21-22
Sun's vertical rays are located at the Equator (0� latitude)
Mechanisms of Heat Transfer
Heat is always transferred from warmer to cooler objects
Mechanisms of heat transfer
Conduction-through molecular activity
Convection -Mass movement within a substance
Usually vertical motions
Radiation (electromagnetic radiation)
Velocity: 300,000 kilome
Radiation
(electromagnetic radiation)
Consists of different wavelengths
Gamma (very short waves)
X-rays
Ultraviolet (UV)
Visible
Infrared
Microwaves and radio waves
Governed by basic laws
All objects, at whatever temperature, emit radiation
Hotter objects radiate m
Incoming solar radiation
Atmosphere is largely transparent to incoming solar radiation
Atmospheric effects
Reflection - albedo (percent reflected)
Scattering
Absorption
Most visible radiation reaches the surface
About 50% absorbed at Earth's surface
Atmospheric heating
Radiation from Earth's surface
Earth re-radiates radiation (terrestrial radiation) at the longer wavelengths
Longer wavelength terrestrial radiation is absorbed by
Carbon dioxide and
Water vapor in the atmosphere
Lower atmosphere is heated from Earth's su
Temperature measurement
Daily maximum and minimum
Other measurements
Daily mean temperature
Daily range
Monthly mean
Annual mean
Annual temperature range
Human perception of temperature
Anything that influences the rate of heat loss from the body also influences the sensation of temperature
Important factors are
Air temperature
Relative humidity
Wind speed
Sunshine
Temperature variations
Receipt of solar radiation is the most important control
Other important controls
Differential heating of land and water
Land heats more rapidly than water
Land gets hotter than water
Land cools faster than water
Land gets cooler than water
Controls of temperature
Altitude
Geographic position
Cloud cover
Albedo
Clouds
reduce the daily temperature range
Temperature maps
Isotherm - a line connecting places of equal temperature
Temperatures are adjusted to sea level
January and July are used for analysis because they represent the temperature extremes
Global temperature patterns
Temperature decreases poleward from the tropics
Isotherms exhibit a latitudinal shift with the seasons
Warmest and coldest temperatures occur over land
In the Southern Hemisphere
Isotherms are straighter
Isotherms are more stable
Isotherms show ocean curr