Climate Connections What is the difference between weather and climate? Weather is… the day to day atmospheric conditions Describe our weather characteristics: - precipitation, temperature, wind speed and direction, humidex, air pressure, UV index, wind chill, visibility, cloud cover, hourly forecast, 7 day forecast Climate is… long term pattern of (weather) the day to day atmospheric conditions Describe our climate characteristics: - cool winters, warm summers http://www.theweathern etwork.com/weather/c aon0512 How does weather affect How does climate affect our lives in Ottawa? our lives in Ottawa? - prevent/cancel outdoor - what we grow, where we activities, deciding what live, construction of to wear day to day, snow buildings (peaked roof, storm may cancel double-paned windows, activities, will affect furnace, insulation), local driving conditions. - what we wear over the course of a year, fuel costs, electrical costs, winter/summer sports, underground pathways (winter city concept). Four basic facts to remember when considering Canada’s varied climate: 1. Canada extends a great distance from North to South and East to West - from Pelee Island in Lake Erie at 41̊ N to Alert at the northern tip of Ellesmere Island at 83̊N for a distance of 4620 km north to south and from Victoria to St John’s for a distance of 5260 km west to east. 2. Different elevations produce different climate conditions. - the higher the elevation the colder it can get. 3. Coastal regions have different climates from inland regions. - oceans and very large lakes, such as the Great Lakes have an effect on climate. 4. Wind and pressure systems move weather conditions from one part of the country to another. - the winds in Canada generally blow from the west, therefore most weather comes from the west. Six specific factors that effect climate: Remember... LOWER near Water Latitude Ocean currents Winds and Air Masses Elevation Relief near Water LATITUDE - distance from the equator... Canada’s wide range in latitude has a major impact on our climate. Using the following three average annual temperatures: Pelee Island (41 N) 9.1̊C, Yellowknife at -5.2̊C (62 N) and, Alert -18.1̊C (82 N), it is clear the locations closer to the North Pole experience colder temperatures than those nearer to the Equator. Distance from the equator is a key factor (but not the only one) in determining whether a region has a warm or cold climate: Two factors are represented in the following diagram. Can you identify them? First: The sun’s energy has to pass through more atmosphere at areas closer to the poles because of the curvature of the earth. Second: The sun’s energy is spread out over a larger area because of the curvature of the earth. The suns energy passes through more atmosphere. Fig 13-2 page 146: Earth’s curvature causes the sun’s energy to be less concentrated at the poles than near the equator. Complete Weather and Climate 1 - Latitude Ocean Currents: Temperature of an ocean current affects the temperature of the air mass that passes over it. What determines whether an ocean current is designated a cold or warm current? (See page 147) Add your answer to your note. http://www.youtube.com/watch?v=xusdWPuWAoU East Coast: Cold Labrador Current which flow south from the Arctic cools coastal locations in Labrador and northern Newfoundland. Gulf Stream, flowing north from southern Atlantic warms coastal areas in Nova Scotia and southern Newfoundland. These two currents meet on the Grand Banks creating damp and foggy conditions which produces fog more than 100 days per year. This is also an area of extreme marine importance because of the large, valuable fishing ground called the Grand Banks. Oil is also being removed from several oil fields below the ocean floor: White Rose, Terra Nova and the largest, Hibernia. Fig 13-3 Canada’s weather and climate are affected by air masses and ocean currents West Coast: Warm North Pacific current heats the cold moist air which passes over it, giving a mild climate to the coastal regions of BC. The temperature rarely goes below 0 ̊C along the coast of BC. Wind and Air Masses - air masses will take on the climatic conditions of the area where it was formed and wind results from air moving along the earth’s surface from an area of high pressure to low pressure. Air masses originating over the ocean contain a considerable amount of moisture and as it passes over land the moisture may be released as precipitation. Therefore, maritime locations receive more precipitation then inland locations. The opposite is true of air masses originating over land, far from the ocean. This air mass will be dry because it lacks any source of moisture. Complete Weather and Climate 2 - Air Masses and Ocean Currents Pressure Systems: - air has weight Differences in air pressure are created when the earth is heated to different temperatures. Remember: Warm air raises creating an area of Low Pressure. Cool air falls toward the earth creating an area of High Pressure Wind Wind 1. Heating of the ground by the sun warms the air above it and causes the air to rise producing a LOW PRESSURE. 2. The air cools and sinks producing a HIGH PRESSURE 3. Air ground level moves along the surface of the earth from a…. HIGH LOW = WIND Wind Wind Differences in Air Pressure Average air pressure at sea level is 101.3 kPa (kiloPascals) Lowest ever recorded: 87 kPa in a Pacific Typhon (hurricane) Highest ever recorded: 108.4 kPa in Siberia http://www.theweathernetwork.com/weather/caon0512 Today in Ottawa the air pressure is ______ kPa Today’s weather is… Complete Weather and Climate 3 - Differences in Air Pressure 4 - Highs and Lows 5- Cloud Formation Prevailing winds are created by high and low pressure belts around the earth. In Canada, these come from generally from the west and move the air masses which effect our weather. The winds shift north or south with the season. The degrees of latitude shown as the location of the pressure and wind belts are yearly averages. When you see the diagram below remember Canada is between 41̊N and 83̊N. Air rises high into the atmosphere at low pressure belts and descends at high pressure belts. The air then flows across Earth’s surface from high pressure belts to low pressure belts creating prevailing winds. Fig 13-4 Global pattern of prevailing winds. Complete the handout Weather and Climate 6 - Wind Belts The boundary between cold, dry polar air and warm moist tropical air is called the polar front and high in the atmosphere above the polar front is the jet stream. Complete Weather and Climate 7 - Jet Stream ELEVATION and RELIEF - differences in elevation of the earth’s surface... Mountain ranges act as barriers to the movement of air masses. The temperature drops steadily as you climb a mountain at a rate of 6.4̊C for every 1000 m which is called the environmental lapse rate. Temperature decreases with elevation As air rises up the side of a mountain it expands because of the lower air pressure. As the air expands, it cools. When air is cooled, it eventually reaches a temperature at which it is saturated with water vapour. Meaning, it is holding as much water as it possibly can at that temperature and air pressure. This is called the dew point and further cooling leads to condensation. Condensation is the change of water vapour into liquid water. This process will form clouds and if the droplets grow large they may become rain, snow or hail depending on the weather conditions. Figure 16-6 Calculating changes in temperature of a rising air mass. When condensation occurs, heat is given off. Cooling of the air mass is still occurring, but since heat is being released by condensation, the overall rate of cooling is less than 1C°/100m. The rate of cooling when there is condensation can vary somewhat: 0.6C°/100m is an average figure for this cooling. Complete Weather and Climate 8 - Temperature Calculation Steps Complete - Temperature Calculation I - Temperature Calculation II Quiz tomorrow, bring your own calculator NEAR WATER Areas located in the interior of large land masses, far from oceans, and far from large lakes have a continental climate. The temperature range in these areas is great because there is no large bodies of water to moderate the hot temperatures of summer and the cold temperatures of winter. These areas have low amounts of precipitation. Coastal locations (or near very large lakes) have a maritime climate. In a maritime climate, the range between the highest and lowest average monthly temperatures is relatively small because of the moderating effect of the large body of water. The level of precipitation is relatively high compared to that of a continental climate because of proximity of large bodies of water. Areas near the Great Lakes are a special case, while they are far enough from the oceans to be continental, the lakes are large enough to provide a partial maritime influence. The climate here is sometimes call modified continental. Complete Weather and Climate 9 - Maritime and Continental Climates Oceans and lakes heat up and cool down more slowly than land masses. - this is because land is denser than water therefore absorbs suns energy faster. In winter (or at night), bodies of water retain their heat and are warmer than the land. Winds blowing off the water keep the surrounding countryside warm. Land Breeze In summer (or during the day), a body of water remains cooler than the land surrounding it. Winds blowing from over the water keep the surrounding countryside cooler. Water Breeze Complete Weather and Climate 10 - Land and Water Breezes Precipitation: To help you understand why precipitation occurs remember these 2 points: 1. Air cools as it rises. 2. As air cools, water vapour condenses more than it evaporates. Air may rise for any of the following 3 reasons: 1. It rises to cross an area of high elevation. This causes RELIEF precipitation (also known as orographic precipitation). This occurs in mountainous regions. 2. It rises because it has absorbed heat from the earth’s surface. This causes CONVECTIONAL precipitation. This occurs mostly in the summer months. 3. It rises because there is a cooler, denser air mass flowing beneath it that forces it up. This causes CYCLONIC precipitation (also known as frontal precipitation). This occurs year round. Complete the handout “Relief Precipitation”