Climate Determines Global Patterns in the Biosphere Chapter 34 Section 2

Uneven Heating of Earth’s Surface Energy from the sun warms Earth's surface. But because of Earth's spherical shape, different locations on Earth's surface receive different amounts of solar energy. Near the equator, the sun's rays strike the surface most directly.

Earth's surface can be divided into different climate zones based on lines of latitude. Most of the United States is located within the northern temperate zone. POLAR ZONES TEMPERATE ZONES TROPICAL ZONE

Direct heating changes with the Earth’s position around the Sun

Wind, Precipitation, and Ocean Currents The uneven heating of Earth's surface by the sun is also a driving force behind global patterns of winds and precipitation (rain, snow, and sleet). When air is warmed it can absorb more moisture, and it also tends to rise.

Global Wind Patterns

Thus air near the equator, heated by the direct rays of the sun, absorbs moisture and rises. Higher in the atmosphere the air cools again, forming clouds that produce rainfall. This pattern means that many areas of Earth close to the equator tend to have warm temperatures and heavy rainfall year-round.

After losing moisture over the equator, air masses spread away from the tropics. The dry air descends again and warms at latitudes of about 30° N and 30° S. Some of the world's largest deserts are found in these regions.

The rising and falling of air masses, combined with Earth's rotation, produce predictable wind patterns. These wind patterns combine with the uneven heating of Earth's surface, the rotation of the Earth, and the shapes of the continents, producing surface ocean currents. A current is a river-like flow pattern within a body of water.

Surface currents can greatly affect regional climates. For instance, the Gulf Stream carries warm water northward from the tropics. This makes the climate in western Europe warmer than other areas at similar latitudes.

Local Climate On an August day, people in Los Angeles' San Fernando Valley might face temperatures of 38°C (100°F), while just 30 kilometers away, people at the beach are enjoying the comfortable 24°C (75°F) outdoor air. Local climate variations may be influenced by nearby large water bodies. Oceans and large lakes affect climate because water tends to absorb and release heat more gradually than most other substances

The Movement of Air Warm rising air creates low pressure Cool sinking air creates high pressure Wind travels from high to low pressure

Land and Sea Breezes

Mountains also affect local climate Mountains also affect local climate. First, air temperature declines with an increase in elevation. Second, mountains near a coast can block the flow of cool, moist air from the ocean, causing different climates on opposite sides of the mountain range.

Microclimate Organisms living in the same climate region may be exposed to different conditions created by shade, snow cover, or windbreaks. Such small-scale differences in climate result in a microclimate, the climate in a specific area that varies from the surrounding climate region.