Climate

Climate is defined as the overall weather patterns of an area over a long period of time.

A "long" period being between 30-100 years, though a location can have the same climate for much longer.

Climate Types:

Climographs

A climograph shows the average monthly temperature and precipitation for a location.

The data from climographs will be essential in your conceptual relationship to many of the climates of the worlds past, present, and future.

Climate Factors

The temperature and moisture conditions that a location experiences are the result of many geographic factors that influence air masses.

Latitude and Temperature

Temperature is mostly dependent on latitude.

Due to:

1. Angle of Insolation

* higher angle = higher temperature

2. Duration of Insolation

* longer duration = higher temperature

CLICK the image above to activate the daylight simulator

Latitude and Rainfall

Latitude, Temp/Pecip, Time of Year

Inter-Tropical Convergence Zone (I.T.C.Z.)

The ITCZ can also be referred to as the heat equator. It is generally the hottest location between the tropics on a given date of the year. The high temperatures produce low pressure, which attract airmasses from the north and south to the area.

Sailors commonly refer to the ITCZ as the doldrums. This belt of heavy rainfall migrates around the equatorial region throughout the year as the direct rays of the Sun move between the tropics .

The dry, high pressure regions (horse latitudes) are generally located at 30 degrees north and south, though their location also shifts according to the location of the Sun's direct rays (see diagram to the right).

The 3 climographs to the left are from different locations around the world.

Note the month each reaches their maximum average temperature.

Locations in the the northern hemisphere reach their maximum temperatures during the months of June and July, while a southern hemisphere location observes its highest temperatures in December and January.

Moisture Levels also vary with latitude and time of year.

The lower density of warm air allows more room for water vapor to fit between the molecules.

The equator has the most humid climates in the world. Most of the worlds rain forests are located at or near the Equator (see map below). This is because the warm air can hold a lot of water vapor, and it rises, which leads to heavy precipitation (RECCP). This is true on a smaller scale at low pressure located at 60º north and south latitude.

In a similar fashion, 30º and 90º north and south have arid climates.
The worlds deserts are all located at or near 30º north or south (see map on left). This is because of cool-dry air sinking at those high pressure latitude belts.
No Rising air, NO RECCP

Global Wind Patterns

In the northern hemisphere, as air moves from high pressure to low pressure belts, the Coriolis Effect causes a rightward curve in the paths fluids travel.
The Prevailing Winds that blow between latitudes are controlled by this effect. They play a major role in determining the climate an area receives, as they transport air masses across regions, carrying the temperature and moisture characteristics of the source region across those regions.

The direction the prevailing winds blow also controls the normal storm track for locations. This affects aspects of local climates that will be detailed as it relates to local trends at the appropriate time.

Local Winds

Locations close to large bodies of water have wind patterns that are controlled by the unequal heating rates of land and water. As we have discussed in a previous section, this is due to their differences in specific heat.
A sea breeze occurs during the day, and a land breeze occurs during the night time. Explore the file to the right to view the processes in action.

Elevation:

The orographic effect takes place at mountain barriers. The prevailing winds blow warm-moist airmasses up mountain sides, causing the "RECCP" process to occur. This occurs frequently on the west coast, at the Sierra Nevada and Cascade mountain ranges (see diagram above).
The side of the mountain that the wind goes up is known as the windward side. This side of the mountain will have a humid climate with lots of precipitation.

The leeward side of the mountain can also be called the "rainshadow" area. This is because all of the moisture that was in the airmass on the windward side has been squeezed out, leaving a hot-dry wind to come down the mountain. Native American cultures referred to this hot wind as the Chinook Wind (snow eater).

This is a great example of latent heat (the hidden heat of phase change). The energy released into the air as the water vapor condensed is added to the energy of the air mass. What started as warm-moist air reaches the same elevation on the opposite side as hot and dry.

Due to:

Adiabatic Cooling
AKA… the “RECCP” for precipitation

- Rising air
   -  Expands
   -  Cools to the dew point
   - Condensation occurs
   -  Precipitation

Prevailing wind direction varies with latitude, so the side of the mountain that is considered windward and leeward changes accordingly.

Earth's Atmospheric Circulation Diagram from page 14 of the ESRT

Island of Maui. Located between 19 degrees north and 20 degrees north latitude.

Distance from a Large Body of Water

Winter temperatures in the United States. Note that while at the same latitude, the difference in coastal and inland temperatures.

Summer temperatures show extreme hot locations inland.

The difference in specific heat of land and water causes them to warm and cool at different rates.

1. Coastal Climates:

Water has a high specific heat, so it warms and cools slower than land
Have warmer winters and cooler summers
Small yearly temperature range

2. Terrestrial (inland) Climates:

Warms & cools quickly due to low specific heat of land
Heat to extreme temperatures during the winter and summer
Large yearly temperature range

3. Ocean Currents:

The direction that surface ocean currents circulate is controlled by the Coriolis Effect. These currents, along with the ocean conveyor current, play a major roll in distributing heat on Earth. They take warm water from the Equator toward the poles and bring cold water from the poles toward the equator.

A similar ocean currents map is available in your ESRT on page 4

The warm Gulf Stream current meets the cold Labrador.

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Climate Trends:

Global Warming and the Greenhouse Effect

Global Warming Trends: Ice, Sea Level, CO2, and Temperatures

Methane in the Tundra

Water Heating Curve Connection

One of the most fundamental connections to be made between shrinking sea ice and global warming is through the water heating curve. The temperature of a mixture of liquid water and ice remains the same while heat energy is added to a system. The energy is used to melt the ice. Once the ice has all melted, water temperatures rise.

Global Warming & Mass Extinctions:

We hear a lot about potential changes to sea-level affecting human civilizations as the worlds icecaps melt. It is a legitimate concern for the billions of people living close to sea-level, but to gain an understanding of exactly what threats global warming poses to us all, watch (at least) the first 20 minutes of the video to the left.

Phytoplankton produce roughly 50% of all oxygen on Earth. They are also a vital part of the ocean food chain. They may not be able to survive changes in ocean temperatures.

The pink water is the result of no oxygen, which allows a deadly form of bacteria to grow in the hydrogen sulfide rich environment.

Acid Rain Interactive

Acid rain occurs when Sulfur Dioxide & Nitrogen Oxide emissions turn water vapor in the atmosphere acidic. The pollutants act as condensation nuclei, lowering the pH of the water vapor.

The prevailing winds blow factory pollutants from Detroit, Michigan for hundreds of miles until they precipitate into the land, streams, lakes, and vegetation of the region.

Acid Lake Interactive

Plants and Aquatic Life

CLICK to activate the Acid Lake Interactive

Maps

Adirondack Mountain area trees that are suffering from the effects of acid rain

The Adirondack Mountains in New York State have been exposed to heavy amounts of acid rain. The acidification of the area most directly endangers plant and aquatic life who are susceptible to changes in pH level.

"Clean" Coal:

Energy Production: Past, Present, and Future

Click to open external link to ca.gov

Solar Cookers Project

Lake Effect Snow

Cold (cP) air moves over warm water, which adds moisture to the air. The moist air then travels over cold land, which cools the air to the dew point, and then... SNOW!!!

Monsoon Seasons

India’s wet and dry seasons are based on variations in the location of the ITCZ. As always, the locations of high and low pressure determine the wet and dry areas.

Land heats to extreme temperatures, so in the summer, the warmth produces low pressure and the storms that come with it. During the.winter, the cold produces high pressure (dry) over the land.

Note: The ITCZ (heat equator) bends farther into the northern hemisphere during the month of July than it does into the southern hemisphere during January.

This is due to land warming faster than water (land has a lower specific heat), and the fact that there is more land in the northern hemisphere.

El Nino

An El Niño event occurs when warm water builds in the eastern Pacific Ocean, causing low pressure and heavy precipitation in the region. Cold waters accumulate in the western Pacific Ocean at the same time, bringing high pressure and dry conditions.

The abnormal pressures can weaken and sometimes reverse the trade winds, causing the ocean to flow with an equatorial counter current. This delivers more warm water to the west coast of South America, further lowering atmospheric pressure in the region.

The low pressure brings heavy precipitation to the Western United States, even some mild Hurricanes. The precipitation leads to many forms of erosion (see the photos to the right for examples).

During these times, the East coast of the Unites States experiences warmer than average winters, with heavy snowfalls common in the northeastern region.

Coastal land slides are extremely dangerous to certain houses.

A sinkhole forms under a highway in San Diego

Large scale mass wasting event. The 1983 El Nino affected Thistle, Utah, where a landslide buried parts of two State highways and tracks of the Denver and Rio Grande railroad. Photograph provided by the USGS

La Nina

Cold waters in the eastern Pacific creates high pressure and blows the surface ocean currents strongly east towards Indonesia, where there are generally violent hurricane seasons.