Both weather and climate communicate data on temperature and precipitation. Weather is a “snapshot” in time. It’s the data collected for one day. Climate on the other hand is a long term trend.

Weather answers questions such as: What should I wear today? Will my baseball game be cancelled? Should I put on sunscreen?

While climate answers questions such as: What should I pack for my vacation? If I move to Ottawa, should I purchase a snow blower?

Climate is affected by 6 main factors which can be easily remembered with the following acronym: L atitude O cean Currents W ind and Air Masses E levation R elief N ear Water

Latitude is the factor that has the greatest influence on a region’s climate. Latitude refers to a region’s proximity to the equator. The closer a region is to the equator, the warmer it is. Why is this so?

Because of the curvature of the Earth, regions that are more northerly (or southerly) from the equator do not receive the same amount of concentrated sunlight as those close to the equator.

How can ocean currents affect climate?

Ocean currents can increase or reduce temperatures. The temperature of an ocean current affects the temperature of the air that passes over it.

The three Ocean Currents that affect Canada’s climate are: 1.The North Pacific 2.The Gulf Stream 3.The Labrador

What is an Air Mass?

An air mass is a large volume of air that takes on the climatic conditions of the area where it is formed.

Air masses that form over the ocean tend to contain large amounts of moisture and as it passes over land, will release the moisture in the form of precipitation. Air masses that form over land tend to be dry because they lack a steady source of moisture.

As a result, maritime regions tend to receive more precipitation than do inland or continental regions.

Air Mass TypeTemperature CharacteristicMoisture Characteristic Arctic or Antarctic (A or AA) Extremely cold, formed over poles. Very dry due to extreme cold. Polar Continental (cP) Very cold, having developed over sub-polar regions. Very dry, due to the cold and having developed over land. Polar Maritime (mP) Very cool because of the high latitude but not cold, due to moderating influence of the sea and the warm ocean currents at these latitudes. Moderately moist because of the cool temperature, but not as dry as polar continental air because of evaporation from the water surface. Tropical Continental (cT) Very warm because of the lower sub-tropical latitude of formation. Dry because it formed over land Tropical Maritime (mT) Very warm because of the sub- tropical latitudes at which it forms. Very humid because of the warm tropical waters below. Equatorial (E) Hot.Extremely humid. Continental is not differentiated from maritime because much of equatorial land is covered with humid tropical rainforests.

 Mountains receive more rainfall than low lying areas because the temperature on top of mountains is lower than the temperature at sea level. That is why you often see snow on the top of mountains all year round. The higher the place is above sea level the colder it will be.   This happens because as altitude increases, air becomes thinner and is less able to absorb and retain heat.   As you move up a mountain you will find that the temperature gets colder the higher you climb (generally about 1˚C per 100m).  The reason is that as air masses move higher into the atmosphere they expand due to lower air pressure.  As the air expands, it cools. As the air continues to cool, it becomes saturated with water vapour.  Further cooling leads to condensation of water vapour which leads to increased cloud cover and eventually greater precipitation (rain or possibly snow).

 Mountain Barriers form what is called relief precipitation. Moist air moving up the windward side of the mountain (west or weather facing side) expands and cools – increasing condensation leading to more rain, and if sublimation occurs (gas – solid) snow will fall.  On the leeward side of the mountain (east facing – away from weather) the cool air descends and contracts, it becomes warmer. Because it has lost most of its moisture on the windward side, the resulting climate is much more dry.

Depending on its proximity to large bodies of water, regions can be classified as Maritime (close to water) or Continental (inland).

Let’s take a look at two case studies: Vancouver which is on the Pacific Ocean (Maritime Climate), and Ottawa which is landlocked (Continental.

MARITME CLIMATE: VANCOUVER Temperatures are moderate not much variation between summer and winter Plenty of precipitation CONTINENTAL CLIMATE: OTTAWA Temperatures are extreme tremendous variations between summer and winter Precipitation amounts tend to be lower