Weather and climate
FOCUS QUESTIONS
What is the difference between weather and climate? What factors influence weather and climate? The sun is ultimately responsible for the weather.
WEATHER
Is what the conditions of the atmosphere at a particular location are over a short period.
Consists of the short-term (minutes to months) changes in the atmosphere. Weather is caused by movement or transfer of heat energy, which influences temperature, humidity, precipitation, cloud cover, wind speed and wind directions.
CLIMATE
Is how the atmosphere ‘behaves’ over relatively long periods of time.
Is the average of weather over time and space.
Is the description of the long-term pattern of weather in a particular area. Is the average weather for a region and time, usually taken over 30 years. Is looking at averages of precipitation, temperature, humidity, sunshine, wind velocity, etc. Climate describes the total of all weather occurring over a period of years in a given place.
The difference between weather and climate is a measure of time; that is, they both describe the same thing – the state of the atmosphere – but at different time scales. Climate is what you expect and weather is what you get.
Weather changes quickly and climate changes more slowly.
Climate is about using the weather data collected in the past to look for longterm trends of 30 years or more to predict changes that may occur in the ocean and atmosphere in the future.
Weather is what you experience when you step outside on any given day. The weather is constantly changing, as temperature and humidity change in the atmosphere.
TERMS TO NOTE
Radiation is how the earth receives solar energy.
Conduction is energy transferred by collisions in heat-carrying molecules. Convection is energy transferred from hotter to colder regions of the earth.
THE FACTORS THAT INFLUENCE WEATHER
1. Air mass is a large body of air that has similar temperature and moisture content. 2. Air pressure is gravity on air mass (99% within 20 miles of Earth’s surface). Low pressure produces stormy weather (usually).
High pressure produces fair weather (usually). 3. Albedo is reflectivity.
Ocean = low albedo
Snow and ice = high albedo
Dust = high albedo (solar radiation does not even hit Earth’s surface) 4. Altitude is height above sea level. 5. Angle of sunlight is the area closest to the equator to receive the most direct angle of sunlight. 6. Clouds are collections of water droplets or ice crystals that are suspended in air. How?
As warmer air rises, it expands due to decreasing pressure, thus drops in temperature (cannot hold as much water vapour).
Vapour condenses, forming water particles or ice crystals.
7. Distance to oceans (oceans are thermally more stable than landmasses) – Changes in temperature are more extreme in the middle of the continents.
In the next lesson, we will recap the factors that influence weather and discuss those that influence climate.