Describing the Weather

• Weather is the conditions outside on a particular day

Describing the Weather

• Meteorologists are scientists who study the weather
• Meteorologists usually provide the following information when describing the weather:
  • Temperature
  • Type and amount of precipitation
  • Wind speed
  • Relative humidity (the amount of water vapour in the air relative to the maximum amount of water that it is possible for the air to hold at that temperature)
  • Atmospheric pressure (the force exerted on a surface by the weight of the air above it)
  • Presence of fog, mist, or cloud cover
• A typical description of the weather on a summer day might include: a high of 28 °C, sunny with cloudy periods, probability of precipitation 30 %, wind from the west at 20 km/h, and relative humidity of 40%
• In some parts of the world, the weather stays consistent day to day
• In Canada, the weather can change dramatically from one day to the next
• One would not expect snow in Ontario in August or a temperature of 30 °C in Nova Scotia in February.
• Atmospheric conditions include temperature, precipitation, wind, and humidity in a particular location over a short period of time, such as a day or a week.
• Water vapour forms when liquid water evaporates and mixes with air
• Warm air can hold more water vapour than cold air
• Warm air is often more humid than cold air

Predicting the Weather

• Meteorologists gather weather information around the world to forecast the weather for specific areas
• Environment Canada maintains thousands of weather stations across the country
• Weather information has been collected and recorded daily since the 1800s in some parts of the world
• Methods of collecting weather data include weather stations, weather balloons, aircraft, and satellites
• Interactions between water and air on Earth and energy from the Sun contribute to our weather
• Energy from the sun heats Earth’s atmosphere, creating winds and other air movement
• Water evaporates, cools and condenses forming clouds that can produce rain or snow
• Ocean water moves in currents from the poles to the equator and back again
• Air and water movement together create weather
• The Earth's tilt causes seasons; during part of Earth's orbit, the northern hemisphere is tilted away from the sun (winter), and during another part it is tilted toward the sun (summer).

What is Climate?

• Climate is the usual pattern of weather in a region over a long period of time
• Climatologists collect weather measurements made over 30 years or more and average the results to determine the climate of a region
• Scientists who study climate include climatologists, paleoclimatologists, atmospheric scientists, and climate modellers.
• The climate of a region gives a range of temperatures that you might expect at a certain time of year
• Climate also describes expectations of rain, snow, or high winds in certain seasons
• Southern Ontario has a warm and humid climate during the summer and is cold with snow during the winter
• Weather describes the atmospheric conditions over a short period of time, while climate describes the typical weather you can expect in a region based on weather data gathered over many years
• Climate determines the types of plants and animals that live there
• Animals like polar bears and seals live in the Arctic and must be able to survive the cold, dark winters
• The climate of southern Ontario encourages the lush growth of a variety of trees, bushes, and other plants
• Many insects, birds, and mammals live in central and southern Ontario forests