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GEOG 205 - Weather and Climate.docx

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Department
Geography
Course
GEOG 205
Professor
John Yackel
Semester
Winter

Description
Weather and Climate GEOG 205 – January 29, 2014 Weather – state of the atmosphere with respect to heat and cold, wetness or dryness, calm or storm, clearness of cloudiness. Climate – the average course or condition of the weather at a place usually over a period of years as exhibited by temperature, wind velocity, and precipitation It is a matter of temporal scale! Due to the time scale and aggregation an individual cannot experience climate! (Time scale – 30 years) Earth’s Temperature depends on: 1. The amount of solar radiation received 2. The amount of solar radiation reflected 3. The amount of solar radiation trapped a. Ocean traps a lot of solar radiation Sunspots - Magnetic storms – releases electromagnetic radiation - Produces flares - Occur on 11 year cycles - Low sunspots numbers have been linked to cold periods (e.g. LIA) - Cycle corresponds to a 0.1% variation in energy output Seasonality - Here in Calgary, there are 3 components of seasonality that we can factor in: o Earth rotates once every 24 hours on an axis, at a tilt of 23*, and that tilt at different times of the year affects our seasons o Orbit around the sun is an ellipse, so at the perihelion (January 3 it’s at its closest) it is closer to the sun, at the aphelion (July 3 it’s at its furthest) it is further away from the o Line of Solstice goes across the orbit (June 21 and December 21) o Equinox goes perpendicular to Line of Solstice (March 21 and September 23) - Seasonality is more pronounced the further you get away from the equator Global Seasonal temperatures (The 4 Main Factors of Temperature) - Latitude (further away from the equator, more pronounced seasonal changes) - Altitude - Cloud cover - Distance from major water body o Oceans and large water bodies hold a lot of heat, so being located next to a body of water can increase the temperature of a location 4 Layers of Atmosphere Troposphere – narrow, little more than 10 km thick, bottom, oxygen rich but chaotic (storms) Stratosphere – air is stable, very dry, virtually no weather, home to ozone layer (filters radiation from space) ~ 50,000 feet Mesosphere – protects us from meteors, home to noctoluscent clouds (thin, wispy clouds usually seen at sunset) Thermosphere – 84km above Earth, considered to be the beginnings of space – where the ISS is – creates the Aurora Volume of the atmosphere is just 5% of the earth. GEOG 205 – January 31, 2014 Milankovitch Cycles - Eccentricity (~100,000 year cycles) - Axial Tilt (~41,000 year cycles) o Halfway through the cycle, the earth changes the axis it rotates on by about three degrees - Precession (~23,000 year cycles) o Earth wobbles like a top throughout the 23,000 year cycle o Axial tilt is what actually changes – still 23.5* Paleoclimate – fancy word for ‘past climate’ Isotope analysis of the ice cores shows what the atmosphere was like when that ice formed. - Did the temperature go up and cause all of these atmospheric changes, or did the atmospheric changes cause a rise in temperature? Bit of a debate. Albedo - The % of solar radiation reflected back - Earth’s average is about 30% - - Albedo of 0.05 = a 5% albedo, 0.40 = 40% - Cutting down the Amazon rainforest means there will be fewer green trees to absorb solar radiation, so more will be reflected, essentially cooling the earth - Why should we care about sea ice? o Ice and snow have a high albedo, and it moderates the warming of the atmosphere with that high percentage of reflection o Water has a low albedo, so it absorbs more radiation, and so it warms the ocean and atmosphere o The loss of ice changes the temperature and salinity which drives ocean currents. GEOG 205 – February 3, 2014 Albedo continued - Many European cities at same or similar latitudes as some N. American latitudes will have warmer overall temperatures because of the hot/warmer air that is blown off the ocean and onto the continent - Lack of sea ice (due to melting) would mean a political dispute over the territory – makes a big difference with the trade path and trade routes Why are the greatest seasonal temperature ranges on land? - Only the surface of
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