Exam 2 Study Guide (Units 7-12)
Exam 2 Study Guide (Units 7-12) GR 1114
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This 10 page Study Guide was uploaded by Alexandra on Friday October 7, 2016. The Study Guide belongs to GR 1114 at Mississippi State University taught by Elcik in Fall 2016. Since its upload, it has received 22 views. For similar materials see Physical Geography in Geography at Mississippi State University.
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Date Created: 10/07/16
Physical Geography Study Guide Unit 7 1. Temperature is molecules moving in a random motion. a. It is a measure of Kinetic Energy 2. Temperature Scales: a. Celsius (Metric) i. Boiling point: 100C ii. Freezing point: 0C b. Fahrenheit (US) i. Boiling point: 212F ii. Freezing point: 32F c. Kelvin i. Boiling point: 373K ii. Freezing point: 273K 3. Lapse Rate: Rate of change of temperature with height a. Decreases with height because the surface is the heating source. As you get further away from it, the air cools. b. Environmental Lapse Rate (ELR) i. Lapse rate at a particular location ii. Decreases with height iii. We measure it using weather balloons c. Dry Adiabatic Lapse Rate (DALR) i. Constant (10C/km) ii. Non saturated air parcels cool at this rate iii. If a non-saturated parcel is lowered, it will warm at this rate also. d. Saturated Adiabatic Lapse Rate (SALR) i. Do not cool as quickly because of latent heat. ii. NOT a constant, depends on amount of condensation taking place. Usually around 4C/km 4. Stability: Compare ELR to the lapse rate of the parcel a. Stable i. Cooler than environment b. Unstable i. Warmer than environment c. Conditionally Unstable i. Warmer if saturated, cooler if dry. ii. Condensation decreases stability 5. Temperature Inversion a. Increasing temp with increasing height b. Surface is heating source, so when we go up, air cools. 6. Parcel Theory a. Air Parcel: Theoretical bubbles of air b. Air is a poor heat conductor. c. Over a short period, a parcel of air is adiabatic (ie: No transfer of heat) d. IF THE PARCEL IS WARMER: i. Parcel rises ii. Unstable air iii. Clouds/rain (Active Weather) e. IF THE PARCEL IS COOLER: i. Parcel sinks ii. Stable air iii. Clear conditions f. As Parcel rises, it expands and cools environment g. As Parcel sinks, it compresses and heats environment Unit 8 1. Winds a. Movement of air b. Air moves from high pressure to low pressure c. Response to an imbalance of forces acting on air molecules i. Can be horizontal or vertical 2. Pressure Gradient Force a. Difference in surface pressure over a given distance b. Drives all movement of air c. Radiation difference → Temperature difference → Density difference → Pressure difference d. What starts the winds 3. Coriolis Force a. Due to Earth’s rotation b. Force deflects all objects moving over surface of Earth away from original path c. Function of wind speed d. Deflects winds to the right in the Northern Hemisphere e. Max at the poles, minimum at the equator f. Why we have a westerly wind over the united states 4. Frictional Force a. Drag that slows the movement of wind b. Depends on roughness of surface (ie: NYC would have more FF than the ocean) 5. PGF STARTS THE WINDS, CORIOLIS AND FRICTIONAL ALTER THEM 6. Large Scale Wind Systems a. Upper Level Winds i. Geostrophic winds 1. Upper atmosphere, no FF 2. PGF and Coriolis acting on wind balance over time 3. Runs parallel to isobars b. Surface Winds i. Ageostrophic winds 1. Near surface, friction disturbs balance seen in geostrophic winds 2. Run across the isobars ii. Cyclones and Anticyclones 1. Winds blow across isobars at oblique angles 2. Cyclones a. Low Pressure b. Active Weather c. Rising air/convergence d. 3. Anticyclones a. High pressure b. Sinking air/Divergence c. 7. Small Scale Wind Systems a. Sea Breeze i. Land surfaces heat and cool more rapidly than water ii. During day, land heats up quickly iii. Surface pressure on land falls and rises over ocean. Small PGF goes from ocean to land. b. Land Breeze i. Opposite of a sea breeze ii. Happens at night c. Valley Breeze i. Driven by thermal differences between adjacent topographic features ii. Mountain terrain is warmer than valley iii. Generates a valley breeze that flows up slope d. Mountain Breeze i. Opposite of valley breeze ii. Happens at night e. Cold Air Drainage (Katabatic Winds) i. Steady downward oozing of cold air along steep slopes f. Chinook/Santa Ana Winds i. Warm, dry winds on leeward side of the mountain 8. Station Plots a. Weather info from different observation stations b. Provides temperature, dew point, wind speed, pressure, and pressure tendency c. d. Pressure i. Add 9 or 10 to given number, put decimal in front of last number 1. Ex: 986 becomes 998.6 Unit 9 1. Global Atmospheric Circulation a. Multi-Cell Model i. Assume a rotating earth and a uniform body of water ii. Surface Pressure Systems and Wind Systems 1. Equatorial Low (ITCZ): year round low pressure band at the equator. Active Weather. 2. Subtropical High: dry, little wind. a. As air tries to go to the poles, it’s deflected to the right and piles up, creating a high at 30N 3. Trade Winds: Northeasterly trade winds. Air from ST High gets deflected right 4. Subpolar Low: Low at 60N and 60S 5. Westerlies: Westerly wind deflected right 6. Polar High: High at the poles 7. Easterlies: Easterly wind deflected right b. Hadley Cell: From ST High to Equatorial Low, warm air diverges aloft, cools and sinks c. Polar Cell: Polar High to SP low, cold air forms thermal high, sinks and diverges d. Ferrel Cell: ST High to SP low e. Thermally Direct: Warm air rises, cold air sinks i. Hadley cell and Polar cell f. Thermally Indirect: Warm air sinks, cold air rises i. Ferrel cell g. Shifting Cells i. Cells shift with season ii. Location of max solar heating shifts throughout year h. Jet Streams i. Rapidly moving wind within a general direction ii. Polar Jet at 60N**** iii. Flat=zonal iv. Wavy=Meridional Unit 10 1. Ocean Currents a. Large scale movements of water that affect oceans and land masses 2. Temperature Profile of Ocean a. Temp decreases as you go down because you get further away from the heating source b. Mixed Layer i. ~245 ft in depth ii. ~3% of ocean volume iii. Active mixing by currents c. Thermocline i. 245-3,300 ft ii. Sharp decline in temp d. Deep Water i. ≥ 3,300 ft ii. Nearly uniform depth iii. Stays between 1C-3C 3. Ekman Transport a. Coriolis steers surface currents 45 degrees to the right 4. How do ocean currents form? a. Wind hits water and moves it b. Variations in the density of the salt water 5. Gyre Circulations a. Cell like circulation of surface currents that encompass an entire ocean basin (around a ST high) b. Form through prevailing winds, Coriolis effect, and land masses c. 2 in the Northern Hemisphere d. Circulate clockwise around a high. 6. Upwelling a. Cold water rises from depths to replace surface water taken by currents b. Causes dry conditions c. Carries nutrients to surface, making these waters best for fishing 7. Downwelling a. Wind causes surface water to build up along coastline and it eventually cools and sinks b. Poor biological conditions due to lack of nutrients 8. Deep Sea Currents a. Operate in sharp contrast with surface currents Unit 11 1. Water Vapor a. Vapor Pressure (e) i. Amount of water vapor actually present in the atmosphere ii. Ranges 0-4% in the atmosphere (average 2%) iii. Ex: If atm pressure=1000mb, VP is ~20mb b. Saturation Vapor Pressure (e )s i. How much water vapor the atmosphere can support at a given temp. ii. VP when air is saturated iii. As temp increases, SVP increases c. A Saturated air parcel: e=es(hit dewpoint) d. Unsaturated: e<e s 2. How to measure water vapor a. Humidity i. Amount of water vapor in a column of air ???? ii. Relative Humidity: % of saturation ( ∗ 100) ???????? iii. Absolute Humidity: Mass of water vapor per volume of air iv. Mixing ratio: mass of water vapor per mass of dry air v. Specific Humidity: mass of water vapor per mass of air vi. Dewpoint: Temp at which saturation is reached (BEST METHOD) 3. Cloud Types a. Stratus: Layered appearance. Fairly thin, cover a large region. i. Low: Stratus (Below 3km) ii. Middle: Altostratus (3-6km) iii. Upper: Cirrostratus (>6km) b. Nimbostratus: Low level, rain producing. c. Cirrus: Thin and wispy, made of ice. Only form >6km. d. Cumulus: Thick and puffy. i. Low: Cumulus/Stratocumulus ii. Middle: Altocumulus iii. High: Cirrocumulus e. Cumulonimbus: Very tall (500m-12km), Anvil tops, produce violent weather Unit 12 1. Air Masses a. Large, uniform body of air that moves across a surface as an organized whole. b. Has uniform temp, humidity, and density. c. Changes in weather occur along the boundary. d. Source Region: Where the air mass formed 2. Types of air masses a. Continental Tropical (cT): Hot and Dry b. Maritime Tropical (mT): Hot and Moist c. Continental Polar (cP): Cold and Dry d. Maritime Polar (mP): Cold and Moist 3. How they form a. In a warm source region: i. Equilibrium of temp and moisture is established in 2-3 days ii. Air mass is warmed to a height of 3000m iii. Unstable air iv. Forms either mT or cT b. In a cold source region: i. Equilibrium takes a week or more to establish because cooling at base stabilizes lapse rates, prevent vertical mixing, and limit efficient heat exchange ii. Only relatively shallow later of air, up to 900m, cools iii. Forms either cP or mP 4. How they move a. As air moves from source region, it becomes modified by surface conditions and air temp, but retains overall source characteristics b. Easy to forecast c. Size, physical properties, and movement of air masses change throughout seasons due to sun’s location 5. Fronts a. Transitional air masses b. Border between two air masses where sharp temp, density, and moisture gradients exist c. Cold fronts i. Air behind it is colder and drier d. Warm fronts i. Air behind it is warmer and wetter 6. Lifting Mechanisms a. Convergent Lifting i. Forced uplift of air where low level wind converges ii. Air streams come together around a low near the surface. Horizontal convergence of air produces vertical uplift b. Frontal Uplift i. Collision of air of different densities ii. Cold front 1. Cold air forces warm air to rise rapidly 2. More abrupt cooling and condensation in warmer air 3. Not widespread precipitation, but intense iii. Warm front 1. Warm air rides over cooler air 2. Wider areas of light to moderate precipitation c. Orographic Lifting i. Forced uplift of moving air that encounters a mountain ii. Ideal conditions: 1. Mountain range close to and parallel to the coast 2. Prevailing onshore winds (seabreeze) d. Convectional Uplift i. Caused by atmospheric instability ii. During summer, heating by solar radiation can lead to warm air near surface. This air rises and forms convectional precipitation iii. Localized 7. Air Mass Thunderstorms a. A very large and towering cumulonimbus b. Don’t last long c. Move slow d. Form with sufficient water vapor, sufficient instability, and weak winds aloft e. Developing stage i. Convection occurs in unstable environment as moist, hot air rises, condensation occurs, and warms the surrounding air through latent heat f. Mature Stage i. Updraft continues, heavy rain falls creating a downdraft g. Dissipating Stage i. Downdraft dominates updraft, suffocates the storm 8. Severe Thunderstorms a. Defined as severe when one of these occurs: i. Wind gusts of 58mph or more ii. 1 inch hail iii. Produce a tornado b. Form with sufficient water vapor, sufficient instability, and vertical wind shear (winds change speed and direction with height) c. Differences from AMTs: i. Multiple cells possessing unique spatial arrangements ii. Form and persist in vertical wind shear iii. Wider variety of weather conditions iv. Produce heavy rain for hours d. Squall Line i. When individual severe thunderstorms 1-5 miles wide become arranged in a line ii. Typically ahead of a cold front e. Mesoscale Convective Complex i. When multiple single T-storms occur over a large area ii. Can be up to 100,000 square km f. Supercell i. Individual T-storms that assume their own rotation 9. Thunderstorm related Phenomena a. Lightning and Thunder i. Lightning is electric discharge from a thunderstorm 1. Cloud to ground 2. Within cloud 3. Cloud to cloud 4. Cloud to air ii. Thunder is produced by rapid expansion of air by lightning bolt b. Hail i. Ice crystals pass through subfreezing and above freezing layers, collecting water ii. Will take a very layered appearance iii. Once hail grows large enough that updraft cannot support it, hail will fall from thunderstorm c. Tornado i. Vortex of air with very low pressure ii. Averaging 100-500m in diameter iii. Descends down from wall cloud at base of thunderstorm iv. Winds from 110-200mph
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