Climate
General conditions of temperature and precipitation for an area over a long period of time.
Determined by temperature and precipitation
Factors that affect temperature
1. Latitude: areas close to equator receive direct rays of the sun so they are warmer…
polar regions have cold climates because of the elongated angle of the sun
2. Elevation: as distance above sea level increases the air becomes less dense. This air
cannot hold as much heat so the temps. Are lower
3. Ocean Currents: river of water that flows in a definite path in the ocean, some are
warm others cold and they affect temp. of air above them. Water flowing away from
the equator is warm, water flowing toward the equator is cold.
4. Nearness to center of large landmass: location near center have wide range in
temperatures
5. Nearness to large body of water: large bodies of water have a moderating effect on
temperatures in coastal areas
6. Location relative to mountains: windward sides are warm, leeward sides are cooler
Temperate Zones
Factors that affect precipitation
1. Latitude: 0-60 N/S heavy precipitation, 30 N/S drier deserts located here, Warm air
can hold more moisture than cold air
2. Nearness to large landmass: center of landmasses are dry. Region with little
precipitation is called a desert, wind direction can allow a desert to exist near a large
body of water (The Sahara Desert lies next to Atlantic Ocean)
3. Nearness to large body of water: have a higher precipitation, A land breeze carries
less water than a sea breeze
4. Location relative to mountains: Mountain ranges act as a barrier to prevailing winds.
Windward side receives precipitation, wet climate. Leeward side receives little
precipitation, dry climate. Rain Shadow Desert: Desert on the leeward side of
mountain… Great Basin is on the east side of the Sierra Nevada mountain range
1. Prevailing wind direction: wind that blows more often from one direction, determines
the windward and leeward side of mountains and large bodies of water
Microclimates
A microclimate is a weather pattern that’s localized in a small area and different in some
significant way from the weather of nearby areas.
For example, there are parts of San Francisco that barely see the sun all summer long;
along the coast it’s frequently cold, foggy, and windy. In other parts of the city, though, fog is
virtually unknown; it may be sunny and 10 or even 20 degrees hotter than spots just a mile or
two away.
Smoky Mountains: Valleys are foggy (smoky) and peaks are clear
Climate Zones
Three Climate types on Earth
Polar Zone
Extends from 90 to 60 degrees latitude, Coldest average temperatures (below 0 c), No
summer, Little precipitation, Icecaps of Greenland, Antarctica, S. America tip
Temperate Zone
60-30 degrees latitude, Areas far from equator, snow in winter, Areas close to equator rains
year round, Temperatures vary from 5 c to 20 c, Includes cool rain forests of Washington
State, and the hot rainforests of S. China, Most of USA falls in this zone, Deserts are not
always hot, cool to freezing or lower at night and are inland (Gobi Desert)
Tropical Zone
0 to 30 latitude, High humidity and temperature, Precipitation is heavy, Warmest
temperatures, no winters, coldest is about 18 c, Deserts exist on western coasts (leeward
mtn. sides, cold deserts form from cold ocean currents
Biomes within the USA
2. Tundra: (Alaska) extremely cold and dry, cold desert
3. Coniferous Forest (Taiga): swamp forest, few trees can survive except conifers (firs,
spruces, pines)
4. Deciduous Forest: trees shed leaves in fall
5. Tropical Rain Forest: (Hawaii) a lot of rain, different plant types, warm temperatures
6. Grasslands: (mid-western plains) hot summers, cold winters
7. Deserts: (Arizona) less than 25 cm of rain/year, hot
8. Marine vs. Continental Climates
9. Marine: more precipitation, summers not as hot and winters not as cold
10. Continental: drier, hot summers, cold winters
Ice Ages
Four major ice ages have occurred in the last 2 million years according to research, these
are called Major Glaciations
Average temperature was 10 – 15 Celsius below today’s temperatures
Each lasted about 100,000 years, the most recent ended 10,000 years ago, Great sheet of
ice covered US as far south as Iowa and Nebraska (formed Great Lakes)
When glaciers melted sea level rose 90 meters (as tall as a 20 story building)
Little Ice Age: cold periods that last for a few hundred years
Exact cause of ice ages is not known
Inter-glacial: time between ice ages
El Nino
Temporary warm current that arrives with little warning usually around Christmas, not
known why these occur
1982-1983 strongest occurred causing severe droughts, heavy rains and floods, and
resulting in 1,000 deaths
La Nina: Follows after El Nino and is associated with extremely cold weather