1. Factors Controlling Climate
Climate – average weather of a region

2. Factors Controlling Climate
Daily & annual cycles
Daily rotation of the Earth (day/night)
Annual revolution around the sun (seasons)
Longer-term cycles:
El Nino – several years
Continental Glaciation – hundreds of thousands of years
Factors influencing annual cycle of air temp:

8. Factors Controlling Climate
Factors influencing annual cycle of air temperature:
Latitude
Altitude
Coastal vs. Continental location
Factors influencing precipitation:
The three above, plus:
Annual & daily air temperaturess
Prevailing air masses
Relation to mountain barriers
Position of persistent low & high pressure center
Prevailing winds & ocean currents

14. Temperature Regimes
Temp Regime – Annual cycle of temp driven by latitude & location
Insolation is main control on temperature
Variation in insolation due to latitude
Effect of marine or continental location moderates variation

17. Precipitation Regimes
Seven global precipitation regions:
1. Wet Equatorial Belt - >2000 mm (80 in) rainfall
mE air masses – heavy convective rainfall
2. Trade-wind Coasts – mm precip
Narrow belts from Equator to 30° N & S on east coast of continents
mT air masses carried on trade winds bring rainfall
3. Tropical Deserts - < 250 mm rainfall
Located on or near tropics
cT air masses under subtropical highs

18. Precipitation Regimes
4. Midlatitude deserts & steppes – mm precip
In centers of continents, 30-50°N
In rainshadow of mountain chains to west
5. Moist Subtropical – mm precip
25-40° N & S on moist, western side of subtropical high
mT air masses from ocean provide moisture for precip

19. 6. Midlatitude West Coast – 1500-2000+mm precip
On west coasts of continents in path of moist westerlies
mP air masses & orographic precipitation
7. Arctic & Polar Deserts - <300 mm precip
Above 60°N & S
cP & cA air masses can hold little moisture

20. Precipitation Regions
Isohyets – lines drawn through areas with equal annual precipitation

21. Seasonality of Precipitation
Timing of precipitation during year key to climate
3 types of precipitation patterns:
Uniform throughout year
Precipitation maximum during summer
Precipitation maximum during winter

24. Climate Classification
Based on mean monthly values of temp & precip
13 climate types based on:
Air mass movements
Frontal zones
Climate types broken into 3 groups:
Group I – low latitudes - cT, mE and mT air masses
Group II – midlatitudes - Polar front, varied air masses
Group III – high latitudes - cP, mP and cA air masses

25. Climograph Tool for defining the climate of a given location or region
Mean monthly temp on line chart
Mean monthly precip on bar chart
May include dominant weather
systems

26. Low-Latitude Climates (Group I)
Wet Equatorial (1) – warm to hot w/abundant rainfall
Example – Amazon Basin or Congo
Trade Wind Coastal (2) – warm to hot w/very rainy season
Example – any coastal region exposed to trade winds

27. Low-Latitude Climates (Group I)
Wet-Dry Tropical (3) – warm to hot w/distinct wet & dry seasons
Example – Sahel or monsoon region of central India
Dry Tropical (4) – very hot in high-sun season, cooler in low sun
Little to no rainfall
Examples – Sahara Desert, Central Australia

28. Midlatitude Climates (Group II)
Dry Subtropical (5) – not as hot as dry tropical
Example – Death Valley, CA
Moist Subtropical (6) – hot, humid summers, mild winters, ample rain
Example – Southeastern US
Mediterranean (7) – hot, dry summers, rainy winters
Examples – Southern California, Mediterranean Sea

29. Midlatitude Climates (Group II)
Marine West Coast (8) – warm summers, cool, wet winters
Expls – Northwestern US
Dry Midlatitude (9) – warm to hot in summer, cold winter, little precip
Expl – Great Plains of North America
Moist Continental (10) – warm summer, cold winter, ample precip.
Expl – Northeastern US

30. High-Latitude Climates (Group III)
Boreal Forest (11) – short, cool summers, long, very cold winters
Example – Siberia, Central Alaska
Tundra (12) – short, cool summers, winters slightly warmer than (11)
Example – western Alaska coast
Ice Sheet (13) – bitter cold all year
Examples – inland Greenland and Antarctica