The Physical Environment Climate Climate vs Weather Climatelongterm

The Physical Environment Climate

Climate vs. Weather Climate—long-term average pattern of weather --local, regional, or global Weather—the combination of factors --temperature --humidity --precipitation --wind --cloudiness --atmospheric conditions

The greatest constraint Availability of heat and water n Influences amount of solar energy that plants can capture n Controls distribution and abundance of plants and animals n

I. Solar radiation A. The earth is covered with solar radiation as photons. --51% reaches surface of earth --most of this % is converted back to heat warming the atmosphere --small % used in photosynthesis --this radiation causes thermal patterns

B. Thermal patterns + earth’s rotation + movement around sun = prevailing winds and ocean currents These winds and ocean currents influence distribution of rainfall.

II. Greenhouse effect Intercepted solar radiation varies with latitude— 2 influencing factors A. • • The radiation hits earth’s surface at a greater angle, spreading over a larger area Also traveling through more atmosphere, or a deeper layer of air

B. Tilt of earth is 23. 5 o with respect to sun —results in seasonal variation in temperature and length of day 1. Spring (vernal) equinox 2. Fall (autumnal) equinox 3. Summer solstice—June 22 nd 4. Winter solstice—December 22 nd

III. Seasonality of solar radiation n Temperature variation /day length increases with latitude n Arctic and Antarctic –day length varies from 0 -24 hours

Variations in solar radiation n n Explain latitudinal changes Seasonal changes Daily changes in temperature BUT, do not explain why temperature gets colder with altitude…

BUT, do not explain why temperature gets colder with altitude…

As air reaches a higher altitude it becomes less dense— Adiabatic cooling—results from the fewer collisions of the air molecules --the rate of temperature change with elevation is called adiabatic lapse rate

IV. Circulation of air masses Air masses circulate globally n Warmest air at equator n Moves north and south toward poles n Cools, becomes heavier n Sinks over Arctic/Antarctic regions n Then flows toward equator —replacing warm air n

V. Rotation of earth n East-west rotation of earth – Deflects pattern of air – Causes Coriolis force/effect – Causes right deflection in N. hemisphere » Including air masses – Causes left deflection in S. hemisphere » Including air masses

Wind flows Prevailing winds formed by Coriolis force Series of belts of prevailing winds Polar regions—Polar easterlies Equator region—Easterly trade winds Middle latitudes—Westerlies Doldrums— low pressure around equator

Wind patterns Initiate surface flow in oceans n Each ocean dominated by 2 great circular water motions—gyres n – Northern hemisphere— clockwise currents – Southern hemisphere— counterclockwise current

VI. Temperature/moisture 1. Influences amount of moisture air can hold » 2. 3. 4. Warm air holds more moisture than cold air Amount of water vapor held in a volume of air = saturation vapor pressure Amount of water expressed as percentage of saturation vapor pressure = relative humidity Temperature which saturation vapor pressure is dew point temperature

VII. Global patterns Precipitation exhibits a global pattern n Temperature, wind and ocean currents determine global pattern of precipitation n Westerly winds move across tropical oceans—gather moisture n Warm air cools as it rises—dew point reached n Clouds form—precipitation falls n

Annual world precipitation

VII. Global patterns con’t Winds move northward and southward —cooling n Cool air descends n 2 belts of dry climate encircle the world n Descending air warms/holds more moisture n Draws water from the surface of earth n

VIII. Microclimates A. Small areas where environmental conditions are different – Organisms find their niche in microclimates – Vegetation can reduce ground temperature 7 -12 o. C – Heavy grass cover can reduce wind at ground level

B. Common microclimates North facing slopes Exhibit one type of microclimate South facing slopes Exhibit another microclimate

C. Mountainous topography 1. Influences local/regional microclimates » 2. 3. 4. 5. Changes patterns of precipitation Intercepts air flow Air mass reaches mountains-ascends-coolsbecomes saturated Releases moisture on windward side Cool, dry air descends other side—picks up moisture from land

Phenomenon is called rain shadow n Found at continental divide n Found on Hawaiian Islands n