CLIMATECLIMATE

The Six Factors

WeatherWeather

Weather is the result of the day to day conditions of the atmosphere.Descriptions of weather include details about temperature, precipitation, humidity, wind speed, direction, cloud cover and air pressure.

ClimateClimate

Climate is the pattern of weather that has occurred over a long period of time. Example 100 years.

Global Warming - Red, orange, and brown coloring indicate areas where temperatures measured in 2000 are warmer than the averagetemperature from 1951 to 1980.

The Six FactorsThe Six Factors

There are six factors that affect climate.

- Latitude

- Ocean Currents

- Winds and Air Masses

- Elevation

- Relief

- Nearness to Water

LatitudeLatitude

The earth is tilted on an axis of 23.5 degrees.The Earth’s axis is always pointing in the same direction (North Star). In June the North Pole is leaning most directly toward the sun (N.H - summer),while in December it is leaning away from the sun (N.H - winter)Sun’s rays become less and less direct and spread out as they fall closer to the poles. The farther a region is away from the equator, the cooler the climate will be.

Ocean CurrentsOcean Currents

In general, warm air and water both flow away from the equator and towards the poles.Cold air and cold water flow away from the poles towards the equator.

Winds and Air MassesWinds and Air MassesAir has weight, and the pressure is created by the force of gravity.

An increase in the amount of air molecules above and around anObject will increase the amount of pressure placed on that object.Winds are created by the differences in pressure.Winds move from areas of high pressure to areas of low pressure.Air masses are large volumes of air with the same characteristics throughout (temperature and air moisture).

ElevationElevation As air rises it expands (its pressures decreases),

losing its heat. As air rises condensation may occur(clouds). This

depends on the moisture content of the air. Rising air will cool, condense (if it has enough

moisture content) and will precipitate if the clouds reach their saturation point/dew point.

As air cools it is unable to hold as much water vapour.

ReliefRelief

All precipitation comes from clouds, but not all clouds precipitate. With an increase in elevation, the air temperature, pressure and ability to hold moisture decrease.

Mountain ranges act as barriers to movements of air masses.

Nearness to WaterNearness to WaterAs an air mass moves over a body of water it absorbs moisture.Areas that are close to an ocean have a maritime climate (high precipitation and mild temperatures).Areas that are far from oceans/large bodies of water have a continental climate (low precipitation levels, and extreme temperatures of cold winters and hot summers)

PrecipitationPrecipitation

There are three types of precipitation:-Relief-Convectional -Cyclonic/Frontal

Relief PrecipitationRelief Precipitation

Air rises, cools, condenses and precipitates (if?)

Convectional PrecipitationConvectional Precipitation

The heating of the ground by the sun warmsthe air above it causing it to rise (forms low pressure area. Why?)Air cools and sinks producing a high pressure areaAir at ground level moves from high to low pressure.This is known as?

Cyclonic (Frontal) Cyclonic (Frontal) PrecipitationPrecipitation

Caused when a warm moist air mass is forced to rise by a cool, dry air mass.

The colder more dense air forces the less dense warm air to rise. As the air rises it …

The faster the warm air is forced to rise, the quicker the air coolsand the greater chance of the possibility of severe weather.

Fast-moving cold front and cumulonimbus clouds. Often thunderstorms occur if the warm air is unstable

In the diagram above, was there a good opportunity for severe weather?The midlatitude cyclone (low pressure cell) is the most importantstorm of the midlatitudes.All precipitation comes from low pressure cells!!!! Why???

A warm front is produced when warm air glides up overa cold air mass. Precipitation is moderate and occurs within a few hundred kilometers of the surface front

Mid-latitude cyclonic storms develop along the boundaries of different air masses.

This is because the air masses have different temperature and moisture characteristics. They are, therefore, of different densities. Like oil and water, they don’t mix easily.

The following slides trace the development of a theoretical mid-latitude cyclonic storm.

The view is from above.

Air starts to rise as it beings to circulate around the center of the storm.

The storm dissipates or disappears eventually.

What does a mid-latitude cyclonic storm look like from the side or in cross-section?

A

B

Note the line A to B

Cross-section of a mid-latitude cyclonic storm

Because the air is being forced to rise, mid-latitude storms are also called low pressure cells or systems.

AB

Warm Front

Warm Air

Cold Air

Cold Air

Cold Front

Air rises

Air cools

Condensation

Precipitation

.

Look out the window.

Is there a chance for precipitation today?

Why or why not?