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Wind Notes.docx

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Department
Environmental Science
Course
EESA09H3
Professor
Tanzina Mohsin
Semester
Fall

Description
Wind Lecture 1 9/14/2013 9:57:00 AM Eurus – all natural disastrous storms Zephyrus – fall/spring Boreas – winter Notos – summer - balance of wind based on equilibrium, input = output - always should have a balance (dynamic system) - natural environment adjusts itself for its best needs - why switch from anaerobic conditions to aerobic conditions??? Life will automatically switch itself to whatever is happening in its environment - After 2.3 billions year solar output increased and earth was becoming too warm, the switch to aerobic life, reduced the greenhouse gases (CO2, CH4) and cooled the planet (suited itself based on its surroundings) - disrupt the environment (air) due to dumping of garbage, etc on grounds - right side of composition of the atmosphere slide is all green house gases: they trap heat, retain the heat coming from the sun and keep the warmth (trap radiation) - natural greenhouse effect: is just there **same gases in both effects but emitting more co2 , - enhanced greenhouse effect: causes global warming - troposphere: temp decreases with height(altitude) 0-11km tropopause : transition zone stratosphere: temp increasing with height mesosphere: temp decreasing with height again thermosphere: temp increasing with height **all four show the structure of the atmosphere ** know wet bulb temperature ** concept of rising/sinking air when air RISES: it cools ; cooling leads to condensation goes from high pressure zone to low pressure zone and then essentially requires energy to expand to cool down (adjusts in order to fulfill equilibrium, change in environment) SINKING air: warms! as you go up temp decreases Wind Lecture 2 9/14/2013 9:57:00 AM RECALL: Troposphere- decrease temperature with increase of height (Altitude) unstable, all lectures focus on troposphere, why is it decreasing? All energy is absorbed at the surface, as you go up there is mixing, so you essentially lose energy, which contributes to losing temperature Stratosphere – increase temperature with increase of height, why is it increasing? Ozone absorbs ultraviolet radiation, this layer has the highest amount of ozone, ozone causes the layer to be warmer Mesosphere- decrease temperature with height, loosing energy as well = decrease temperature Thermosphere- increase temperature with height ------------------------------------------------------------------------------------- What is wind? Movement of air in an “ordered” fashion Pressure Gradient Force causes air to move Isobars- lines of constant pressure** Smaller space between isobars = STRONGER PGF = strong wind Larger space between isobars = WEAKER PGF = weak wind Coriolis Force: fictitious force due to the rotation of the earth Northern hemisphere: wind moves towards the right Southern Hemisphere: wind moves towards the left Thought exercise: Starting at North Pole, you aim your plane towards Toronto? What city are you more likely to arrive at? Toronto, Montreal, Winnipeg? Right at the equator, there is no affect of the Coriolis force As you go towards the pole, the C.F gets stronger What happens when these two forces act together?? Geostrophic wind : the balance between PGF and the Coriolis force Geostrophic wind is wind that is blowing parallel to the isobars, based on the balance between PGF and CF, GW is 1km above the earths surface Surface Winds: Below 1km is surface winds influenced by friction - Is not parallel to the isobars, it bends at certain angles - balanced between 3 forces - High pressure center, wind bends clockwise - Low pressure center, wind bends counter clockwise (air is rising) Global Circulation (10,000’s of km) Synoptic scale (100’s to 1000’s of km) Small Scales ( <100km) Observation: There is more energy released in the polar regions than is received from the sun. The reverse is true for the equatorial region. (more is received than released) HOW ?? something is there that is carrying all the energy from the equatorial region WIND IS CARRYING THE ENERGY WOW ONE CELL THEORY: Warm air rises at the equator, moves towards the pole and then sinks at the pole the equatorial region will only have summer all other latitudes will have winter don’t agree with this theory, because it states that 4 seasons is not possible cannot explain the phenomena we experience and the seasonality Sensible heat : heat I can feel Latent Heat: heat stored as water vapour, heat is released when water condenses, heat is absorbed when water evaporates The rotation of the earth can not be explained according to the one cell theory, tilt seasonality, THREE CELL THEORY: Hadley Cell- Air rises at the equator, moves pole ward and then sinks at 30N and 30S Ferrell Cell- 30 and 60 Polar Cell – 60 and 60 - Winds are named from where they are coming from, not where they are going DEFINITIONS Intertropical Convergence Zone (ITCZ) -area of rising air at or near the equator, heavy precipitation. Trade Winds - Winds that blow to the south west, surface component of Hadley cell Subtropical high - - little precipitation, referred to as the horse latitudes. (subsiding air, sinking air =low precipitation) threw horses of the boat Westerlies - winds blowing to the east and north in the midlatitudes - surface component of the Ferrel cell Polar Front - division of polar air and midlatitude air Polar easterlies - winds that blow south west from the North Pole (southwest from South Pole). Seasonality: summers & winters Continentality: land masses heat and cool faster than water - land also has more friction than water Convergence: air/wind coming towards the center Divergence: air/wind moving away from the center LPC- air is rising HPC- air is sinking Winter in the northern hemisphere Summer in the southern hemisphere Upper Level Flow- associated with geostrophic wind Why does this differ from the surface flow? FRICTION is at the surface Jet Streams: between Hedley and Ferrell : subtropical Between Ferrell and polar - swift flowing current of air moving from west to east - on top of stratospheric zone, jet streams can be found Effects on air plane flying: pilots take advantage of the jet steams to save time and fuel Polar Jet: very cold weather if its on the south Warm if its in the north AIR MASSES: An air mass is a large body of air whose properties of temperature and moisture are fairly uniform in any horizontal direction at any given altitude. Source region: the area where an air mass originates (northwest territories, Nunavut, northern Mexico) Stratospheric winds: DBC- thermally driven - provides equator to pole transport - some exchange between the layers QBO- Quasi-biennial oscillation - linked to ozone hole, hurricane frequency - 2 to 3 year oscillation in the upper troposphere and stratosphere equatorial winds - shifting of upper level tropospheric winds / lower level stratospheric winds from east to west - has seasonal variation and altitude Air Masses: 6 air masses rather than 4 Why does sinking air warms? Wind Lecture 3 - Hurricanes 9/14/2013 9:57:00 AM Hurricane – north American term, Taino language of Caribbean meaning “god of evil” (tropical cyclones) Typhoon- term used in Western Pacific, “Taifung” is Chinese for big wind Cyclone – term used in Australia and in the Indian ocean - definition of a storm is usually related to its origin What is a tropical storm? • Storm (tropical region) with sustained winds of 18 ms-1 to 33 ms-1 What is a hurricane? • Tropical storm with sustained winds ranging from 33 ms-1to 50 ms-1 What is
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