What determines our climate?

 Climate refers to the average yearly conditions of temperature and precipitation. ◦ Contrast with weather, the day-to-day conditions.  The biggest difference between climate and weather?  Weather changes frequently each day, but climate rarely changes from year to year.

 Climate is determined by several factors. 1. The latitude (north-south position) of each region. 2. The presence of wind and ocean currents. 3. The amount of precipitation present. 4. How well heat is trapped by the atmosphere.

 Due to Earth’s shape and its tilted axis, the Earth does NOT receive sunlight evenly.  Sunlight is the primary means of heating up the atmosphere. Therefore, certain parts of Earth get a lot of direct sunlight, and are quite warm.  Other parts of Earth get little direct sunlight, and are quite cold.

 The polar zones are at the very top and bottom of Earth.  They get very little direct sunlight; the sun’s rays are at very low angles.  These regions are cold year-round.

 The tropical zone is located around the equator.  This region gets direct sunlight almost all year round.  As such, this region is quite warm year- round.

 The temperate zones are located in between the polar and tropical zones.  The angle of sunlight varies greatly during the year.  As such, climate changes from hot to cold, based on the seasons.

 As altitude increases, local climates will become increasingly cold. Temperatures drop by 6 degrees Celsius (11 degrees Farenheit) for every 1000 meters of elevation you go up.  As a result, regions at high elevations will be much colder than other regions at the same latitude, but closer to sea level.  Local ecosystems are similarly affected – at high elevations, you will see more taiga and tundra biomes.

1. What is the difference between climate and weather? 2. The [polar, temperate, tropical] zone(s) have the largest range of possible climates. 3. The [polar, temperate, tropical] zone(s) receive little direct sunlight. 4. Both Denver, Colorado and Dover, Delaware are found at around 40⁰ north, but Denver has a much higher elevation than Dover. Predict their relative climates, given this information.

 Throughout Earth, warm air and water rises, and cool air and water sinks. This principle is known as convection.  Convection causes air currents, better known as wind.  Convection also causes many ocean currents. Wind also produces ocean currents.  Currents transport heat all over Earth. Warm currents keep climate moderate, and cool currents make climate cold.

 The existence of air currents affects precipitation patterns over Earth. ◦ For example, the equator receives a large amount of solar energy, which heats a large percentage of air. Warm air can hold a lot of moisture, but as air rises, it cools, producing heavy precipitation. ◦ Also look at polar regions, which get relatively little solar exposure. Since very little air is warming, there is little moisture in the atmosphere. Polar regions are often quite dry as a result.

 Prevailing winds are those that primarily move in one direction throughout the year. ◦ Note that winds are deflected into moving from east to west, due to Earth’s rotation.

 Trade winds are found between 30⁰ north and south. They always blow to the west, and towards the equator.  Westerlies are found between 30⁰ and 60⁰ north and south. They always blow to the east, and away from the equator.

 Easterlies are winds found beyond 60⁰ north and south. These winds blow towards the west, and towards the equator.

 Areas close to large bodies of water are likely to see a lot of precipitation. ◦ Why?  Mountain ranges create rain shadows.  Basically, clouds are forced upward due to the mountain range, which cools them down. This makes precipitation much more likely, and the cloud disappears.  As a result, the other side of the mountain is a lot less likely to get precipitation, creating a dry climate behind the mountain range.

 Our atmosphere contains trace amounts of important greenhouse gases – gases that are capable of trapping heat energy. ◦ Greenhouse gases include carbon dioxide, methane and water vapor.  Greenhouse gases trap heat energy, which keeps our atmosphere warm. ◦ Without them, Earth would be 30 degrees Celsius cooler. That amounts to 86 degrees Fahrenheit!  However, too many greenhouse gases is not a good thing, either!

1. Tropical rain forests are found near the equator. They are often warm and humid. Explain why this is. 2. With regards to climate, what is the biggest difference between temperate rainforest and temperate grassland?