GEO101: Physical Geography
Lecture 12: Monday, March 9, 2009
Topics
1. Earth's Climate System and Its Classification
2. Tropical Climates
3. Mesothermal Climates
4. Microthermal Climates
5. Polar Climates
6. Dry Arid and Semiarid Climates
Earth's Climate System and Its Classification
• Climate is weather over time
• Climatology is the study of climate
• Climatic regions are areas with similar weather statistics
• Climate components:
Insolation
Temperature
Pressure
Air Masses
Precipitation
• Classification of Climatic Regions:
Empirical classification: based on statistical data, e.g., temperature and precipitation
Generic classification: based on causative factors, e.g., the interaction of air masses
We are focused on a classification based on temperature and precipitation measurements, and for the desert areas, moisture efficiency
• Tropical Climates (equatorial tropical latitudes):
Rain forest (rainy all year)
Monsoon (6 to 12 months rainy)
Savanna (less than 6 months rainy)
• Mesothermal Climates (midlatitudes, mild winters):
Humid subtropical (hot summers)
Marine west coast (warm to cool summers)
Mediterranean (dry summers)
• Microthermal Climates (mid and high latitudes, cold winters):
Humid continental (hot to warm summers)
Subarctic (cool summers to very cold winters)
• Polar Climates (high latitudes and polar regions):
Tundra (high latitude or high altitude)
Ice caps and ice sheets (perpetually frozen)
Polar marine
• Highland Climates (highlands at same latitudes)
• Desert (permanent moisture deficits):
Arid deserts (tropical and midlatitudes)
Semiarid steppes (tropical midlatitudes)
Read Fig. 10.5 and the slides, trying to understand the general climate patterns across the globe.
Tropical Climates
• Tropical Rain Forest Climates
Constantly moist and warm (rainy all the year)
Precipitation follows the migration of ITCZ
Annual temperature range is only 2 degree C
• Tropical Monsoon Climates
ITCZ migrates to affect these areas 6 to 12 months
A dry season that lasts for one or more months
Along coastal areas within the tropical rain forest climate
• Tropical Savanna Climates
Poleward of the tropical rain forest climates
ITCZ reaches these areas 6 months or less
Summers are wet than winters
Temperatures vary more than rain forest areas
Mesothermal Climates
• Humid Subtropical Hot-Summer Climates
Maritime tropical and continental polar air mass interacts to generate midlatitude cyclones and precipitation
Hot and wet summer but dry winter
• Marine West Coast Climates
Maritime polar air masses - cool, moist, unstable - dominate
Weather is quite unpredictable
Rainy and foggy
• Mediterranean Dry-Summer Climates
Dry summer but wet winter
Continental dry air masses block the maritime air masses in the summer
Microthermal Climates
• Humid Continental Hot-Summer Climates
Humid and hot in summer
Dry and cold in winter
NY and Dalian in China
• Humid Continental Mild-Summer Climates
Humid but not hot summer and dry winter
Lower temperature, precipitation from snow
E.g., Duluth, Minnesota
• Subarctic Climates
Greater seasonal changes and annual T changes
Dry and very cold winter
Alaska, Canada, Siberia in Russia
Polar Climates
• Tundra Climate
Continuous snow cover for 8-10 months
Mainly in northern hemisphere, except for high mountains
Warmest months can be above 0 degree C but never exceeds 10 degree C
• Ice Cap and Ice Sheet Climates
Most of the Antarctic and central greenland
• Polar Marine Climate
Moderate than ice sheet climates, T > -7 degree C
Cold than the Tundra climates
Dry Arid and Semiarid Climates
• Dry subsiding air; rain shadow; away from moisture-bearing air masses
• Hot Low-Latitude Desert Climates
• Cold Midlatitude Desert Climates
• Hot Low-Latitude Steppe Climates
Exists around the periphery of hot deserts
Shifting the subtropical high pressure cells creates a summer-dry and winter-wet pattern
• Cold Midlatitude Steppe Climates
Mostly northern hemisphere