Gr 8 - Social Studies: Climate

The prevailing southwesterly winds also have an important large climatic effect by moving the air masses and frontal low pressure storms across the contiguous United states generally from west to east. The paths of these air masses and storm movements are often called

"tracks". Much of the precipitation in the mid-latitudes is the result of these tracks and associated weather.

Range of average monthly temperatures

Average difference between the average temperature of the hottest month and the coldest month, calculated using data for many years

belts of prevailing winds are caused by the air pressure differences (from unequal heating of Earth by the sun) and the effects of

Earth's rotation (the Coriolis effect).

The factors that determine climate include

Latitude; planetary wind and pressure belts; oceans and other large bodies of water; ocean currents; mountains; elevation; amount of cloud cover; vegetation

Large bodies of water-oceans, seas, and large lakes-serve to modify the

Latitudinal climate patterns.

The two major aspects of climate are

Temperature and moisture (water conditions)

In terms of climate, 2 characteristics of the temperatures of a region are most important

The average temperature over the year and the range of average monthly temperatures (average temperature range)

An area's climate is called arid or dry if

The average total precipitation during the year is less that the average yearly potential evapotranspiration

Climate is not just average weather; it includes extremes like

The number of hurricanes and the number of days of damaging hail

The combination of the temperature and the moisture effects of latitude results in

a basic distribution of climate types around the world-latitudinal climate patterns

Latitude is

a major factor in determining climates because of its influence on both temperature and moisture conditions.

Thunderstorm clouds often cover the area around the equator, and these clouds

absorb a large percentage of the insolation or reflect it back into space

An area's climate is humid, or wet, if the average precipitation for the year is greater than the average potential evapotranspiration. Thus, whether a climate is said to be arid or humid depends not on the amount of precipitation, but on the difference between the

amount of moisture available from precipitation and the potential need for water as determined largely by temperature.

Potential evapotranspiration is largely determined by

an area/s amount of energy available for evapotranspiration thus temperature.

An area's natural vegetation amounts and types are largely determined by the climate. Thus,

an arid area has desert vegetation and a hot, humid climate has tropical rainforest vegetation.

Coastal climates are often modified by surface ocean currents. Currents flowing away from the equator carry warm water to higher latitudes, while currents flowing toward the equator

carry cool water to lower latitudes.

Global warming, El Nino, the greenhouse effect, the ozone "hole" problem, the effects of volcanic ash and other aspects of climatic change

cause changes in Earth's climates over time.

The overall view of a regions weather conditions over a long period if time (tens to thousands of years ) is called

climate

greater amounts of precipitation are due to the fact that warmer air can hold more water vapor and that warmer air-because it is less dense-will tend to rise and then cool, so that

condensation can produce the clouds that bring precipitation.

Inland areas away from the effects of large bodies of water have cooler winters and warmer summers and a wider annual range of temperatures. Such areas are said to have a

continental climate.

Building cities-urbanization-also causes-a-

decrease in forests and grasslands and causes changes in climate and weather

Regions where the potential evapotranspiration is much greater than what an area receives as precipitation are called.

deserts

A warm ocean current will cause a coastal area's climate to be warmer and

have more precipitation.

with increasing distance from the equator (increasing latitude) the annual temperature range increases. This is largely because

higher latitudes have a greater amount of change in duration of insolation during the year than areas of lower latitude nearer the equator

dry latitudes without much cloud cover are often

hotter than regions closer to the equator

At elevations above the place the dew point is reached, condensation results

in clouds and then precipitation on the windward side.

Marine climates have cooler summers and warmer winters than inland areas, and thus a small annual range of temperatures compared to

inland areas at the same latitude.

isotherms-

isolines of equal temperature.

The elevation of an area above sea level modifies the latitudinal climate pattern because as air rises,

it expands and cools.

As the air descends,

it is compressed and warmed.

Temperature characteristics vary with

latitude because of the relationships between angle, intensity, and duration of insolation and latitude.

Large bodies of water-oceans, seas, and large lakes-serve to modify the

latitudinal climate patterns

the higher the altitude at any given latitude, the cooler the climate. Another reason higher elevations are cooler is the lower amounts of the greenhouse gases (carbon dioxide, water, and methane) at higher altitudes, and this means

less absorption of long-wave radiation from the sun and Earth's surface.

Moisture conditions vary with latitude because of the

location of the planetary wind and pressure belts. Where there is low pressure at Earth's surface, such as near the equator and in mid-latitudes, the air rises

Mountains that intersect prevailing winds, such as those associated with the planetary wind belts, can

modify the latitudinal climate pattern.

The effects of the prevailing winds and their shifting compared to the simple latitudinal climatic pattern result in the

more realistic climate zones

On the other hand, the vegetation of an area can help determine the climate of an area. When rainforests are cut down and converted into farms or grazing land, the climate often becomes hotter and less humid. Part of the reason for this is that there is

more runoff and less transpiration to add humidity. Also, without all the trees to absorb solar energy and convert it into potential food energy, the solar energy heats the land instead, which then heats the atmosphere it touches.

Most of the contiguous United States is located in the prevailing southwesterly wind belt for much of the year, which means that

most weather conditions move from southwest to northeast-more generally west to east.

The warming of the air raises the temperature above the dew point, and condensation and precipitation stop. As a result, the leeward side is warmer than the windward side at any given altitude. The leeward side also has

much less precipitation because the air has lost much of its moisture, and its water vapor capacity rises as its temperafure increases.

Another way that mountains modify climate is by acting as barriers to moving air masses, preventing cold air or warm air from crossing the mountain to the other side. As a result,

opposite sides of a mountain can have different temperature patterns

There is a direct relationship between insolation received at Earth's surface and

potential evapotranspiration.

Movements of air over Earth's surface that blow in the same direction most of the time are

prevailing winds.

An area's average temperature is often determined by the

solar energy or insolation it receives.

Since the duration of insolation varies from zero to 24 hours a day, and is longest at the times of greatest angle of insolation,

temperatures vary over a wide range from winter lows to summer highs.

cool ocean current humid will cause a coastal area to have cooler temperatures and less precipitation. One reason there is less precipitation is

that cool water results in cool air, which cannot hold much water vapor.

As the wind strikes the windward side of the mountain,

the air is forced to rise. As it does so, it expands and cools.

Potential evapotranspiration is

the amount of water vapor that would evapotranspiration from an area if the water were available.

If an area has a high percentage of cloudy days, this will have a major climatic effect. Without clouds,

the atmosphere is much more transparent to insolation, and more of the sun's energy can reach and heat Earth's surface.

Elevation also affects precipitation. As the elevation increases, the temperature and water Vapor Capacity decrease; the air thus approaches-

the dew point, condensation forms clouds, and precipitation often occurs.

Earth has gone through many times of overall increasing or decreasing temperatures. During the times of cooling, glaciers have advanced from the polar regions into the mid-latitudes and maybe even into the regions that are now considered warm or tropical. These times of advancing glaciers into the mid-latitudes were known as

the ice ages.

At low latitudes,

the maximum angle of insolation is always high, average temperatures are high throughout the year. Because the duration of insolation is fairly constant at about 12 hours per day, there is little temperature variation during the year.

At high latitudes,

the maximum angle of insolation is never large and in some months remains zero, average temperatures are low.

The west coast of the contiguous United States has much more of a marine climate than the east coast because

the west coast's prevailing winds are from the ocean.

Though monsoons are usually associated with

the wet summers and dry winters of southeast Asia----especially India-other areas experience a monsoon effect.

The larger a landmass is, and the farther it is from the effects of large bodies of water;

the wider the annual temperature range. This is why central Eurasia has a more pronounced continental climate than North America.

Monsoons are the

weather changes caused by_the seasonal shifts in the direction of prevailing winds.