ClimateMeteorology

Factors Affecting Climate

Climate includes not only the average weather conditions of an area, but also any variations from those norms.

Powered by the sun, the climate system is a complex exchange of energy and moisture among Earth’s different spheres.

Factors Affecting Climate

The varied nature of Earth’s surface and the many interactions that occur among Earth’s spheres give every location a distinctive climate.

Latitude, elevation, topography, large bodies of water, global winds, and vegetation affect the two most important elements of climate—TemperaturePrecipitation

Latitude

Latitude is the distance north or south of the equator.

As latitude increases, the intensity of solar energy decreases.

Latitude

Notice that near the equator the sun’s energy strikes the planet at nearly right angles, and at less of an angle as the latitude increases.

Latitude

The region, between about 23.5°N (Tropic of Cancer) to about 23.5°S (Tropic of Capricorn), is called the tropics or the tropical zone.

Temperatures in the tropical zone are generally warm year-round.

Latitude

In the temperate zones, between about 23.5° and 66.5° north and south of the equator, the sun’s energy strikes Earth at a smaller angle than near the equator.

Latitude

The smaller angles causes the solar energy to be spread out over a greater area.

In the temperate zones, the length of daylight is longer in the summer than the winter.

Latitude

Temperate zones have cold winters and hot summers.

Latitude

In the polar zones, which are between 66.5° north and south of the equator and the poles, the energy from the sun strikes at an even smaller angle, causing the light and heat to spread out over an even larger area.

Latitude

The polar regions experience cold temperatures, even in the summer, these regions experience long periods of daylight, and long periods of nighttime.

Elevation

Elevation, or height above sea level, is another factor that affects climate of an area.

Air temperature decreases with elevation by an average of 6.5 °C every 100 meters.

Elevation

The higher the elevation is, the colder the climate.

Elevation

The elevation of an area also determines the amount of precipitation it receives.

Topography

Topographic features such as mountains play an important role in the amount of precipitation that falls over an area.

Water Bodies

Large bodies of water such as lakes and oceans have an important effect on the temperature of an area because the temperature of the water body influences the temperature of the air above it.

Water Bodies

Places downwind of large bodies of water generally have cooler summers and milder winters than places near the same latitude, but farther inland.

Atmospheric Circulation

Global winds are another factor that influences climate because they distribute heat and moisture around the Earth.

Global Winds

Winds constantly move warm air toward the poles and cool air toward the equator.

The low-pressure zones at the equator and in the subpolar regions lead to the formation of clouds that drop precipitation.

Vegetation

You probably already know that the types of plants that grow in a region depend on climate.

Did you know that vegetation affects climate?

Vegetation

Vegetation can affect both temperature and the precipitation patterns in an area.

Vegetation

Vegetation influences how much of the sun’s energy is absorbed, and how quickly the energy is released.

This affects temperature.

Vegetation

During a process called transpiration, plants release water vapor into the air, influencing precipitation.

Studies also indicate the some vegetation release particles that act as cloud seeds, which promote the formation of clouds.

Review

What are the two things most important elements

of climate?

World Climates

If you were to travel around the world, you would find an incredible variety of climates.

Despite the diversity, climates can be classified according to average temperatures and amount of precipitation.

World Climates

Many classification systems have been used to group climates.

The best-known and most commonly used system is the Köppen climate classification system.

Köppen Climate Classification

The Köppen climate classification system uses mean monthly and annual values of temperature and precipitation to classify climates

Köppen Climate Classification

This system is often used because it classifies the world into climatic regions in a realistic way.

Köppen Climate Classification

The system has five principal groups:–Humid Tropical Climates–Dry Climates–Humid Mid-Latitude Climates–Polar Climates–Highland Climates

Köppen Climate Classification

All the groups, except climates classified as dry, are defined based on temperature.

Dry climates are classified according to the amounts of precipitation that falls over an area.

Köppen Climate Classification

Each of the five major groups is further subdivided.

Humid Tropical Climates

Humid Tropical Climates are climates without winters. Every month in such a climate has a mean temperature above 18 °C. The amount of precipitation can exceed 200 cm.

Humid Tropical Climates

Two types of Humid Tropical Climates:–Wet Tropical Climates–Tropical Wet and Dry Climates

Wet Tropical Climates

Tropical rain forests is typical of a wet tropical climate.

Wet tropical climates have high temperatures and much annual precipitation.

Wet Tropical Climates

The intensity of the sun’s rays in the tropics is consistently high.

The winds that blow over the tropics cause the warm, humid, unstable air to rise, cool, condense, and fall as precipitation.

Wet Tropical Climates

Regions with humid tropical climates form a belt on either side of the equator.

Tropical Wet and Dry Climates

Bordering the wet tropic climates are climates classified as tropical wet and dry climates.

Tropical Wet and Dry Climates

Tropical wet and dry climates have temperature have total precipitation and temperatures similar to those in the wet tropics, but experience distinctive periods of low precipitation.

Tropical Wet and Dry Climates

Savannas, which are tropical grasslands with drought-resistant trees, are typical of tropical wet and dry climates.

Humid Mid-Latitude Climates

Humid mid-latitude climates include climates with mild winters as well as those with severe winters.

Humid Mid-Latitude Climates

Climates with mild winters have an average temperature in the coldest month that is below 18 °C but above -3 °C. Climates with severe winters have an average temperature in the coldest month that is below -3°C

Humid Mid-Latitude Climates

There are three types of humid mid-latitude climates with mild winters:–Humid subtropical climates–Marine west coast climates–Dry-summer subtropical climates

Humid Mid-Latitude Climates

Humid Subtropical Climates are between about 25° and 40° latitude on the eastern side of continents.

This climate region dominates the southeastern United States.

Humid Mid-Latitude Climates

The humid subtropical climates experience hot, sultry weather as daytime temps are high.

Winters are mild, frosts are common in the higher latitude areas.

Humid Mid-Latitude Climates

Marine West Coast Climates are between 25° and 40° in coastal areas.

Maritime air masses hang over these regions results in mild winters, cool summers, with ample rainfall throughout the year.

Humid Mid-Latitude Climates

In North America the marine west coast climate covers a narrow strip from northernmost California into southern Alaska.

Humid Mid-Latitude Climates

Dry-Summer Subtropical Climates are between about 30° and 45° latitude.

These climates are unique because they are the only humid climates that have a strong winter rainfall maximum.

Humid Mid-Latitude Climates

Dry-Summer Subtropical climates in the United States is found only in California.

Also sometimesreferred to asMediterraneanClimate.

Humid Mid-Latitude Climates

There are two types of humid mid-latitude climates with severe winters:–Humid Continental Climates–Subarctic Climates

Humid Mid-Latitude Climates

Continental landmasses strongly influence both of these climates.

Both of these climates are absent in the Southern Hemisphere, where oceans dominate the middle-latitude zones.

Humid Mid-Latitude Climates

The areas with these types of climate lie between approximately 40° and 50° north latitude.

Winters are severe, while the summers are typically quite warm.

Precipitation is generally greater in summer than in winter.

Humid Mid-Latitude Climates

North of the humid continental climate and south of the tundra is an extensive subarctic climate region.

Area stretches from western Alaska, to Newfoundland, and from Norway to Pacific coast in Russia.

Humid Mid-Latitude Climates

Winters in subarctic climates are long and bitterly cold.

Summers are remarkably warm but very short.

Humid Mid-Latitude Climates

The extremely cold winters and relatively warm summers combine to produce the highest annual temperature ranges on Earth.

Dry Climates

A dry climate is one in which the yearly precipitation is not as great as the potential loss of water by evaporation.

Dry Climates

Dryness is not just related to precipitation, but evaporation also.

Evaporation is closely dependent on temperature.

Dry Climates

There are two types of dry climates:–Arid or Desert–Semi-Arid or Steppe

Dry Climates

Arid and semi-arid climates have many features in common.

The difference between them is slight.

Dry Climates

The steppe is a marginal and more humid variant of the desert.

The steppe represents a transition zone that surrounds the desert and separates it from humid climates.

Dry Climates

Dry climates exist as the result of global distribution of air pressure and winds.

When air sinks, it is compressed and warmed, which is opposite in order for clouds to form precipitation.

Dry Climates

Regions with dry climates experience clear, sunny skies and dry climates.

Dry Climates

Other dry climates happen when prevailing winds meet mountains.

These arid regions are called rain shadow deserts.

Polar Climates

Polar Climates are those in which the mean temperature of the warmest month is below 10°C.

Polar Climates

Winters in these regions are periods of perpetual night, or nearly so, making temperatures extremely cold.

Temperatures remain cool despite the perpetual daylight.

Polar Climates

Very little precipitation falls in polar regions.

Evaporation, too, in these areas is limited.

Polar Climates

Two types of Polar Climates:–Tundra Climate–Ice Cap Climate

Polar Climates

The tundra climate is a treeless region found almost exclusively in the Northern Hemisphere.

Polar Climates

Ice cap climate does not have a single monthly mean above 0°C.

Little vegetation grows and the landscape is covered in permanent ice and snow.

Ice cap climates occur in scattered high mountain, Greenland, and Antarctica.

Highland Climates

The other climates are similar from place to place and extend over large areas.

Some climates are localized, they are much different from climates in surrounding areas.

Highland Climates

Conditions of highland climates vary from one place to another.

South-facing slopes are warmer than north-facing slopes.

Air on the windward sides of mountains is wetter than on the leeward sides.

Highland Climates

In general, highland climates are cooler and wetter than nearby areas at lower elevations.

Climate Changes

Like most conditions on Earth, climate is always changing.

Some changes are short term, while others occur over long periods of time.

Some are the result of natural processes.

Natural Processes

Many different natural processes can cause a climate to change.

Some include volcanic eruptions, changes in ocean circulation, solar activity, and Earth motions.

Volcanic Eruptions

Volcanic eruptions can emit large volumes of ash and dust into Earth’s atmosphere.

Volcanic eruptions also send minute particles of sulfur into the air.

Volcanic Eruptions

If the volume of the sulfur is great enough, it can cause short-term changes in Earth’s surface temperature.

Volcanic Eruptions

The presence of aerosols (volcanic ash, dust, and sulfur-based aerosols) in the air increases the amount of solar radiation that is reflected back into space.

Volcanic Eruptions

The more solar radiation reflected back into space due the increase in aerosols causes Earth’s lower atmosphere to cool.

Ocean Circulation

Changes in ocean circulation also can result in short-term climate fluctuations.

Ocean Circulation

El Nino is a change in ocean circulation that causes parts of the eastern tropical Pacific Ocean to become warmer than usual.

This can cause arid areas to receive large amounts of rainfall.

Ocean Circulation

Arid regions may experience more rain due to changes in ocean circulation changes.

Wet regions may experience dry periods when ocean circulation patterns change.

Solar Activity

The most studied hypothesis for the causes of climate change are based on changes in the output of solar energy.

Although variations in solar output may cause short-term climatic changes, no evidence for long-term changes exist.

Solar Activity

When the sun is most active, it contains dark blemishes called sunspots.

The formation of these spots appear to correspond with warm periods in North America and Europe.

Earth Motions

A number of Earth motions are thought to cause changes in climate.

Most of these changes are long-term changes.

Earth Motions

Tectonic plate movements, cause the crust and upper mantle to move slowly over the Earth’s surface.

These movements cause ocean basins to open and close.

They also cause changes in the position of landmasses.

Earth Motions

These geographic changes in Earth’s land and water bodies cause changes in climate.

Earth Motions

Changes in the shape of Earth’s orbit and the tilt of Earth on its axis are other Earth motions that affect global climates.

Earth Motions

Earth’s orbit around the sun is always elliptical.

Over a 100,000 year period, the path becomes more and then less elliptical.

This change brings Earth closer to and farther from the sun.

Earth Motions

The tilt of Earth on its axis changes, precession, about 2 degrees over a 41,000 year period.

The changing angle of the tilt varies the severity of the seasons.

Natural Processes

Identify four natural processes that can result

in climate changes.

Human Impact

Natural processes have contributed to many climatic changes throughout history.

Besides these processes, human activities have contributed and will contribute to global climate change.

Greenhouse Effect

The greenhouse effect is a natural warming of both Earth’s lower atmosphere and Earth’s surface.

Greenhouse Effect

The major gases involved in the greenhouse effect are water vapor and carbon dioxide.

These gases are “transparent” to incoming solar radiation, but then absorb the energy reflected from the Earth.

Greenhouse Effect

The greenhouse effect is very important to life on Earth, without it Earth would be much too cold to support complex life forms.

An increase in the gases could also prove devastating to Earth’s organisms.

Greenhouse Effect

Studies indicate that human activities for the past 200 years or so have had a huge impact on the greenhouse effect.

Greenhouse Effect

Carbon dioxide levels have risen at a rapid pace since about 1850.

Much of this gas has been added by burning fossil fuels.

The clearing of forests also contribute to the increase in CO2.

Global Warming

As a result of increases in carbon dioxide levels, as well as other greenhouse gases, global temperatures have increased, called global warming.

Global Warming

Scientists predict that by the year 2100, temperatures will increase by 1.4 °C to 5.8 °C.

How will these temperature increases affect Earth?

Global Warming

Warmer surface temperatures increase evaporation rates, which increases water in the atmosphere.

Temperature increases also cause sea ice to melt; ice reflects more radiation than water.

Global Warming

The melting sea ice and ice sheets will also cause a rise in global sea level.

This will lead to shoreline erosion and coastal flooding.

Global Warming

Scientists also expect that weather patterns will change as a result of the projected global warming.

More intense heat waves and droughts in some regions and fewer such events in other places are also predicted.