Chapter 6 Climate Climate . Canada's climate is not as cold all year around as some may believe. In winter, temperatures fall below freezing point throughout most of Canada. But the south- western coast has a relatively mild climate. Along the Arctic Circle, mean temperatures are below freezing for seven months a year. Climate . During the summer months the southern provinces often experience high levels of humidity and temperatures that can surpass 30 degrees Celsius regularly. Western and south-eastern Canada experience high rainfall, but the Prairies are dry with 250 mm to 500 mm of rain every year. Weather/Climate . Weather – Is the result of the day-to-day conditions of the atmosphere. Climate – A long term pattern of weather – Climate Is The Weather + Weather + More Weather . Climate is what you expect, weather is what you get! Weather . Types of things given in a weather forecast: – Temperature Precipitation – Humidity Wind speed/direction – Cloud cover Air pressure Climate . Factors that affect climate (J.BLOWER); – Jet Stream (air masses) – Bodies of water – Latitude – Ocean Currents – Winds – Elevation – Relief . Note: Different parts of Canada have different climates. Factors that affect Climate A. Jet Stream (Air Masses) Air Masses -- is a large body of air that has similar temperature and moisture properties throughout. For example: Winds blowing from a cold region will bring cold temperature conditions to an area over which they pass Factors that affect Climate . B. Bodies of water – Water warms up more slowly than land and cools off more slowly – As a result of this, land near bodies of water are affected by the weather over these bodies of water. Factors that affect Climate . Bodies of water – The ocean make the temperature on land cooler in summer and warmer in winter. –This is called a maritime climate. Factors that affect Climate . Bodies of water – Continental Climate— Land in the interiors are not influenced by the sea and experience extremely cold winter and hot summers. PG 63 This climate is characterized by winter temperatures cold enough to support a fixed period of stable snow cover each year, and relatively moderate precipitation occurring mostly in summer, Factors that affect Climate C. Latitude – Distance from the equator . Angle at which sun rays strike the earth . Length of daylight period . The tilt of the earth’s axis combined with the earth’s rotation in orbit around the sun results in different day lengths. Factors that affect Climate D. Ocean Currents – The movement of large quantities of ocean water due to the unequal heating of the top layer of the water by the sun. – For countries on the east side of the Atlantic, winters are a balmy holiday compared with the same latitudes on the west: the frigid coasts of Newfoundland and Labrador. Factors that affect Climate . Ocean Currents – There are warm ocean currents and cold ocean currents. These currents affect the air above them in two ways: . Warming or cooling air masses . Warm air absorbs moisture, cold air does not absorb moisture. Factors that affect Climate E. WINDS – Wind is the flow of air. – Created by differences in air pressure – Winds are also caused by temperature differences . Note: Differences in air pressure produce convection currents and wind Factors that affect Climate . Prevailing Winds – are the trends in speed and direction of wind over a particular point on the earth's surface. – Canada’s prevailing wind pattern blows from west to east. – Prevailing winds bring different types of weather and are the causes of waves as they push the ocean. Factors that affect Climate . Prevailing Winds – The direction of wind is measured in terms of where the air is coming from. – A northerly wind blows air from north to south. A southwesterly wind blows air from the southwest to the northeast. Factors that affect Climate F. Elevation: the height above sea level. – Virtually anywhere that has a high elevation will be colder than lower elevations at the same latitude. – As air rises it expands because there is less air pressure (cont.) – As air expands it becomes less dense and less dense air holds less heat than dense air, so the farther above sea level you are, the lower the temperature will be. – The rate of cooling varies according to the moisture content of the air. – When air has a relative humidity of 100%, condensation begins and this affects the cooling rate. Factors that affect Climate Air pressure Air at sea level is what we're used to, in fact, we're so used to it that we forget we're actually feeling air pressure all the time! . Less air pressure at high altitudes than at sea level. How much pressure are you under? – Earth's atmosphere is pressing against each square inch of you with a force of 1 kilogram per square centimeter (14.7 pounds per square inch). The force on 1,000 square centimeters (a little larger than a square foot) is about a ton! . Why doesn't all that pressure squash me? – Remember that you have air inside your body too, that air balances out the pressure outside so you stay nice and firm and not squishy. Elevation . When condensation is not occurring, an air mass loses 1c0 for every 100 m it rises. When condensation is occurring, an air mass loses 0.6c0 for every 100 m it rises. Diagram of air rising up a mountain Factors that affect Climate . G. Relief –Refers to the difference in elevation of the earths surface. –Mountain ranges affect climate because they act as barriers to the movement of air masses. Factors that affect Climate . Relief – Mountain barriers also tend to cause precipitation to occur. Factors that affect Climate . Sea breezes Factors that affect Climate . Sea breezes – During the day the land becomes warmer than the sea. – A low pressure system is created over the land and a high pressure system is created over the sea. – Winds move from highs to lows – Therefore the winds move from the cooler water towards the land creating a sea breeze Factors that affect Climate . Land breeze Factors that affect Climate . Land breeze – During the night the land cools faster than the sea. – A high pressure system is created over the land and a low pressure system is created over the sea. – Winds move from highs to lows – Therefore the winds move from the cooler land towards the sea creating a land breeze Types of Precipitation . Precipitation – is any product of the condensation of atmospheric water vapor that is deposited on the earth's surface. Precipitation that reaches the surface of the earth can occur in many different forms, including rain, freezing rain, drizzle, snow, sleet, and hail. Types of Precipitation . 1. Relief Precipitation (orographic) . 2. Convectional Precipitation . 3. Cyclonic/Frontal Precipitation Relief Precipitation . Occurs when an air mass is forced from a low elevation to a higher elevation as it moves over rising terrain Relief Precipitation . As the air mass rises it expands and cools. This cooler air cannot hold the moisture as well as warm air can. When the dew point is reached the air becomes saturated with water vapor and condensation occurs, creating clouds and frequent precipitation. Relief Precipitation . As the cool air descends on the leeward slope of the mountain it gets warmer. Since warm air is able to hold more water vapour than cooler air, the clouds decapitates and the relative humidity drops creating rain shadow conditions. Evaporation rather than condensation occurs. Relief Precipitation Convectional Precipitation . Develops as a result of uneven heating of the earth’s surfaces by the sun. Air above this area becomes warmer than the surrounding air and starts to rise . This process creates convection currents or updrafts Convectional Precipitation . The rising air expands and cools, and water vapour condenses to form clouds . Water droplets get larger and eventually the weight forces them to fall. As the precipitation reaches the ground it cool it and the air and stops more updrafts from forming. Convectional Precipitation Cyclonic/Frontal Rainfall . Warm Moisture laden air meets cold air; . Warm air is less dense & is forced up over the cooler, more dense air; . Warm moisture laden air cools at higher altitude; . Cool air holds less moisture; . Clouds condense and rain falls. Cyclonic/Frontal Precipitation . A Cyclonic storm is a large low pressure cell that forms when a warm air mass and a cold air mass collide. In Canada these low pressure storms move from west to east at all times of the year. Cyclonic/Frontal Precipitation Interpreting Climate Graphs What is a climate graph? •a type of chart or graph that displays for a place the annual pattern of the two most important climate variables: precipitation and temperature Temperature is shown by the line, with the Precipitation is degrees on the shown by the left Y-axis. bars, with the amounts on the right Y-axis. The data shown are monthly averages, with the months across the X-axis. Of what value are climate graphs? •Climate graphs can be used to compare the climate of selected locations quickly and simply. •Especially useful to tell if a place has a continental or a maritime climate. •Continental: low annual precipitation; large annual temperature range because of no moderating effect of a large a body of water. •Maritime: high annual precipitation; low annual temperature range because of the moderating effect of large a large body of water. Low (fairly low) annual temperature range. Winters are mild. Summers are not hot. High annual precipitation, with no seasonal maximum. Therefore, it’s a maritime climate. Moncton, NB Low annual precipitation High annual temperature range Therefore, continental climate. Yellowknife, NWT Fairly low annual precipitation Large annual temperature range Therefore, continental climate Timmins, ON Very low annual precipitation Large annual temperature range Therefore, continental climate Resolute, NWT Very low annual precipitation Large annual temperature range Therefore, continental climate Wait a minute …..! Resolute is on water yet it has a continental climate.