Weather and Climate – Part 1

Weather or Climate? The terms “weather” and “climate” are often used interchangeably. However, they are not the same. Weather is the state of the atmosphere at a specific time (e.g. current atmospheric conditions) Climate refers to long-term atmospheric trends. Climate is “average weather” measured on different time scales (usually 30 years) Both involve characteristics such as precipitation, temperature, atmospheric pressure, wind speed

Current Weather Updated: Sunday, October 25, 2009, 14:00 EDT What is Weather? Defined as: Day-to-day characteristics such as temperature, precipitation, humidity, wind speed/direction, cloud cover and air pressure example: Weather Forecast - Ottawa, Ontario Current Weather Updated: Sunday, October 25, 2009, 14:00 EDT 11°C a few clouds Wind: W 22km/h Wind gusts: 35km/h Sunrise: 7:32 Sunset: 18:00 Relative Humiditiy: 50% Pressure: 101.74 kPa Visibility: 32.0 km Ceiling: unlimited

example: CLIMATE - Ottawa, Ontario What is Climate? Defined as: The weather conditions of a place averaged over a long period of time example: CLIMATE - Ottawa, Ontario Ottawa has a semi-continental climate, with a warm, humid summer and a very cold winter Winters in Ottawa are severe Ottawa, like other cities in Ontario, enjoys a sunny climate

FACTORS AFFECTING CLIMATE Use the acronym: “LOWER Water” L.O.W.E.R.N. Latitude Ocean Currents Wind Currents (air masses) Elevation Relief Near Water

LATITUDE As latitude increases (North or South from the Equator) the temperature decreases. This is due to a decrease in ‘concentrated’ solar radiation towards the poles.

Latitude Canada’s southern most point is Middle Island in Lake Erie (41N) Canada’s northern most point is Cape Columbia, NU (83N) This range of 42 degrees latitude is almost the same as the distance between Ottawa and the Equator Distance from the Equator is very important as locations nearer the equator have warmer climates as the Sun’s energy is more concentrated over a smaller area

Latitude

Ocean Currents

Ocean Currents Ocean currents transfer heat (or cold) from one area to another. For example the Gulf Stream carries warm water from the Gulf of Mexico along the East coast of North America. The Labrador current carries cold water from the Arctic south towards Newfoundland.

Labrador Current/ Gulf Stream Temperature of an ocean current affects the air mass above Warm, North Pacific current heats air above it, warming coastal B.C. Cold Labrador current meets warm Gulf Stream moving north off coast of Newfoundland, creating foggy conditions (100 foggy days per year)

Winds (Air Masses) Air masses carry heat and moisture across the landscape as they move from one area to another. m: Maritime - coastal (high precip.) c: Continental –inland (low precip.) T: Tropical - between the tropics (warm) P: Polar – originating at higher latitude than the circles (cool) Examples: mP: Maritime Polar cT: Continental Tropical

Winds and Pressure air masses that form over continents are typically dry air masses that form over oceans contain moisture and release precipitation when they reach land air has weight which is measured as air pressure

Winds and Pressure warm air rises, creating a low pressure system cold air falls, creating a high pressure system

Wind and Pressure

Prevailing Winds air moves from high to low pressure areas, this is called wind prevailing wind in Canada is west to east (called westerlies) this means that most weather systems move west to east across Canada

Polar Front / Jet Stream the Jet Stream is a current of fast moving west to east air at high altitudes

THE NORTH AMERICAN JET STREAM

Elevation Temperature decreases with elevation. It is increasingly cooler at higher elevations in the troposphere (first layer of the atmosphere)

Youtube Earth: Climate and Weather - National Geographic - 24hToday (3:23mins) http://www.youtube.com/watch?v=zz_CRzcIT-Q Strangest Weather On Earth - S01E02 - Thunder Snow: (21:14mins): http://www.youtube.com/watch?v=hgbqaM6nQ9o