Climate Classification -- Two Approaches• Empiric – Classes are based on observations and the effects of the phenomena – Examples include Koeppen and Thornthwaite• Genetic – Classes are based on causes of the phenomena – Examples include Air-Mass, Synoptic Classifications, etc.
The Elements of Climate• Based on – Temperature – Precipitation – Pressure – Wind Direction/Speed – Cloud Cover – “Climate proxies”
The Koeppen System• The Major Climates – The Tree Climates • A - Tropical Rainy Climates • C - Midlatitude Rainy Climates (mild winter) • D - Midlatitude Rainy Climates (cold winter) – Trees Don’t Grow Here • B - Dry Climates • E - Polar Climates
Koeppen System: Principal Climate Types• Tropical – Af - Tropical Wet (Rains all year) – AW - Tropical Wet/Dry (Dry Winter Season) – Am - Tropical Monsoon (Shorter Dry Season)• Dry – BW - Desert (BWh - hot desert, BWk, cold desert) – BS - Steppe (semi-arid) BSh - hot steppe, BSk, cold steppe)• Mesothermal – Cfa, Cwa - Humid Subtropical – Csa, Csb - Mediterranean – Cfb, Cfc - Marine West Coast
Koeppen System: Principal Climate Types• Microthermal – Dfa, Dfb Dwa, Dwb - Humid Continental – Dfc, Dwc, Dfd, Dwd - Subarctic• Polar – ET - Tundra – EF - Ice Cap (Remember, Eternally Frozen!)• Highland Climates
Koeppen System: The Particulars• First Letter - – Designates Major Type (A, B, C, D, E)• Second Letter – If with A, C, or D climates, denotes seasonality of precipitation (f - all year, w=dry winter, s=dry summer) – If with B, denotes whether hot (h) or cold (k)• Third Letter – Designates different temperature regimes and sometimes other parameters like fog frequency, etc.
The Factors Forming the Koeppen SystemFigure 6.5
Tropical Climates• ~ 12 hours a day throughout the year• There is a greater daily energy change than there is annual energy change• Influenced by the migration of the ITCZ• No temperature constraints on growth leading to large species diversities
The Hydrologic Cycle• A Hydrologic Cycle Model – More Evaporation over Oceans than over Land – More Precipitation over land than over oceans – Amount of water advected to the land equals the amount runoff back to the oceans• Surface Water – Only .333% of all surface fresh water is available for human use. – 11.20% of all fresh water is available for human use in groundwater and soil moisture
Remember…• If the air rises, it’s more likely to rain (or snow…)• Where it sinks, it’s less likely to rain (or snow…)• The less rainfall you have… – The less reliable it is• So, a climate with a dry season, isn’t necessarily guaranteed a wet season either! – Monsoon climates – Steppe and Savannah Climates – Deserts (obviously)
Our Water Supply• Water Supply in the United States• Instream, Nonconsumptive, and Consumptive Uses• Future Considerations
U.S.Water Budget 1. Three-fourths of what falls is evaporated 2. We withdraw and consume one-third of what is left on a one-time basis 3. Some of the water is exchanged into groundwater which might not be recoverableFigure 7.17
Future Considerations• There’s plenty of water (if you like salt with your water!) and we don’t loose any of it…• On a local basis, water resource scarcity is a very real issue• Too much water and the water becomes polluted• Too little water and the water becomes polluted• Water scarcity globally are major issues where: 1. The water is used mostly for agriculture and thus for growing the food supply and… 2. Where competing regions are sharing the same water supply
Global Climate Change• Global Warming• Climate Models and Future Temperatures• Consequences of Global Warming• Political Action to Slow Global Warming