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GEOG 1900 Midterm: OSU [GEOG 1900] Extreme Weather and Climate: Midterm 1 Study Guide

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GEOG 1900
Bryan Mark

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OSU Geography 1900 Extreme Weather and Climate Midterm 1 Study Guide Chapter 1 ● Scientific method: hypothesis, prediction, experiment, analysis, conclusion ● Weather: State of atmosphere at a particular moment ● Climate: the statistics (average & variability) of weather ○ Mean January precipitation in Columbus ○ Expected difference between min. and max. temps tomorrow Composition & Structure of Atmosphere ● Beginning of solar system: Spinning dust-cloud→ electrostatic and gravity ○ More mass & nuclear reactions→ sun ○ Less mass→ planets ● Formation of Earth→ accretion; small particles clump together, begin colliding, gain gravity→ attract more particles (“planetesimals”), becomes larger→ proto-planet ● Very Early Atmosphere ~4.6 Billion years ago ○ Mostly H2 and He--gases present in dust cloud ○ Lost to space (heat, solar wind, and Earth’s small mass) ● Early Atmosphere ~4.6 to 4.2 billion years ago ○ Contraction→ heating→ volcanic activity→ outgassing and potentially impact degassing ○ Surface temperature between 85° - 100° C ○ Potential composition: 85% H2O, 10% CO2 ● Reduced Volcanism- 4.2 to 3.8 billion years ago ○ Atmosphere cools→ clouds→ rain→ oceans formed ○ Cooling and precipitation cause a decrease in: ■ Atmospheric H2O (stored in oceans) ■ Atmospheric CO2 (stored in ocean sediments) ● Increase in atmospheric O2→ caused by advent of photosynthesis (~3.5 billion years ago) ● Earliest photosynthesizers similar to cyanobacteria ○ sunlight→ H2O + CO2 → {CH2O} + O2 ○ Photosynthesis: removes CO2 and adds O2 ○ Respiration: removes O2 and adds CO2 ○ Increase in O2: increase and burial of plant biomass 1/11/17 Lecture ● Present composition of the atmosphere: N2+O2+Ar=99.96% by volume ○ Mostly nitrogen (78%), oxygen (21%), Argon (.93%) ● Variable gases of the atmosphere ○ Water vapor-H2O (.25%), carbon dioxide CO2 (.039%), ozone-O3 (.01%) ○ Spatial-temporal means, these gases are variable after all ■ For example, H2O from trace concentrations to ~4% ● Non-gas components of the atmosphere ○ Aerosols: ​Solid​ and ​liquid​ material in suspension ■ Role in energy budget (radiation absorption & scattering) directly and indirectly (cloud formation and characteristics) ■ Ex: dust, smoke, ■ Have some part in turning sunsets more red/orange ● Thickness of the atmosphere ○ Pressure: force per unit area; measured in millibars (mb); average sea level pressure is 1013 mb ○ The mass of air above a point, and hence pressure, decrease with altitude ■ Earth’s atmosphere becomes thinner at higher altitudes ○ Earth’s diameter ~12,800 km ■ A 100 km high atmosphere would add 200 km or .016% (200/12,800) to this diameter ○ Very thin layer of fluid where horizontal speeds greatly surpass vertical speeds ● Vertical distribution of mass in the atmosphere ○ Air is compressible​. Higher near-surface pressures result in larger air density near the surface. ○ *nonlinear relation b/w pressure & altitude ● Temperature based layers→ density is affected by temperature ○ Earth: warmest near the surface ○ *study diagram above* ● Thermosphere ○ Less particles of air in the upper layers of atmosphere ● Density, temperature, and vertical stability ○ Stable vertical density distribution ■ Heaviest at bottom, lightest at top ■ Perturbation (small push) → system returns to original stable configuration after perturbations ○ Unstable vertical density distribution: heavy at top, light on bottom→ system tends to depart unstable configuration and move to stable configuration ○ Stability in atmospheric layers; refers to the ease of vertical movement occurrence ■ Troposphere ● Cold, “heavier” on top ● Warm, “lighter” on bottom ○ Favors instability; this is what creates weather ● Portion of the atmosphere where we live ● Stage for almost all processes we will study ● ~80% of atmospheric mass ● Heated from below→ heat from the surface ○ Overturning movement (tropo=rotate) ● Thickness decreases from the Equator to Poles ● How is the troposphere heated from below? ○ The Sun radiates mostly in the visible band. ○ The atmosphere is transparent to this type of electromagnetic radiation. ■ (In a similar way that many of our tissues are transparent to X-ray radiation) ○ Most of the electromagnetic energy coming from the Sun in the visible band passes through the atmosphere without interacting (warming) the atmospheric gases. ○ The solar energy warms the surface. Heat from the surface is transported to the overlaying atmosphere. ​The direct source of energy for heating the troposphere is the surface, not the Sun. ■ Stratosphere ● inversion→ temperature in layer increases with altitude, as opposed to troposphere ● Warm, “lighter” on top ● Cold, “heavier” on bottom ○ Favors stability ● ~20% of atmospheric mass ● Where ozone layer is located ● Heated from above as ozone absorbs ultraviolet – vertically stable ○ Some clouds with large vertical development reach the base of the stratosphere ■ Ozone layer & Ozone depletion ● Three atoms of oxygen (O3) ● Concentrated between 10 to 50 km above the surface ● Absorbs harmful UV radiation ● Human activity has decreased ozone by adding chlorofluorocarbons (CFCs) to the stratosphere ● Stratosphere contains 90% of atmospheric ozone(beneficial role: acts as primary UV radiation shield), troposphere contains about 10% (harmful impact, toxic effects on humans and vegetation) ● Ozone depletion by CFCs ○ UV radiation strikes a CFC molecule & causes a chlorine atom to break away. Chlorine atom collides with an ozone molecule & steals an oxygen atom to form chlorine monoxide & leave a molecule of ordinary oxygen. When a free atom of oxygen collides with the chlorine monoxide, the 2 oxygen atoms form a molecule of oxygen. The chlorine atom is released & free to destroy more ozone. ● Ozone “hole” → not really a hole, seasonal decrease of up to 50% of the mean concentration 1/13/17 Lecture ● The Ozone hole is ​not​ causing global warming ○ More UV makes it to the surface when stratospheric ozone concentration decrease ○ UV radiation represents less than 1% of the energy arriving from the Sun ○ Reduction in stratospheric ozone has caused a reduction in absorption of solar energy and a small decrease in lower stratosphere and upper troposphere temperature ○ Ozone is also a good absorber of long wavelength radiation - greenhouse gas ○ Increases in lower troposphere ozone lead to warming ● Mesosphere ○ ~0.1% of atmospheric mass ○ Reaches up to ~100 km altitude ○ Heated from below by absorption of sunlight by gases ○ Small upward heat transport (little mass) ○ Noctilucent clouds are found at around 80 km and are highest clouds ever observed in the atmosphere ● Thermosphere ○ Less than 0.1% of atmospheric mass ○ Imprecise boundary between atmosphere & space ○ Photodissociation (breaking by light) of O2 ● Ionosphere ○ Not temperature based​ (b/w mesosphere & thermosphere) ○ Ions resulting from interaction between gases and sunlight ○ Auroras​ (Northern and southern lights) ● Chapter 2-Energy ○ Solar energy makes it to Earth as electromagnetic radiation (as waves and photons) ○ a=amplitude (m) ○ lamda=wavelength (m) ○ hz= frequency ○ Speed c=frequency*wavelength ○ All electromagnetic waves move at the speed of light (in a vacuum) ○ Higher frequency (shorter wavelength) → higher energy ● Electromagnetic radiation emitted by the Sun ○ All objects with temperature above absolute zero (0 K) emit radiation. ○ The Sun behaves very similarly to a black body (so does Earth) ■ Sun’s temp: ~6000 K ■ Sun emits mostly in the visible and near-infrared portions of the spectrum ■ Wein’s displacement law for blackbodies: The wavelength of the most intense radiation emitted by a blackbody is inversely proportional to the temperature of the objectλmax=C​ /T ■ Stefan-Boltzmann Law for blackbodies: The total energy per unit area radiation by a blackbody (I) is proportional to the 4th power of its temperature. ● I=σT^4 ; σ = 5.67x10^-8  ● Hotter objects radiate more energy ○ Blackbodies emit & absorb radiation in all wavelengths/frequencies. ■ Hotter objects have shorter wavelength of maximum radiation ■ Surface of the sun radiates about 164,000 times more energy than the surface of the Earth. ● How much solar energy arrives at the top of Earth’s atmosphere? ○ Total energy emitted by the Sun / Area of a sphere with Sun-Earth distance as radius = 3.865x10^26 W / 4pi(1.5x!0^11 m)^2 = ​1367 W/m^2 ← solar constant ■ There is some variability in the solar constant because of sunspots ○ If the amount of energy arriving from the Sun is constant, why do seasons occur? ■ Earth’s axis of rotation is tiled in relationship to the ecliptic plane (tilt angle is 23.5°) ■ Tilt causes an unequal distribution of energy on the surface as Earth orbits the Sun ■ Unequal distribution of energy related to 3 factors: ● 1. Solar Altitude, or angle Sun makes with horizon→ the more perpendicular a beam of light is to a surface, the larger the amount of energy per unit area arriving at the surface. ● 2. Length of solar energy path through atmosphere (atmospheric beam depletion) → The length of the path through the atmosphere that must be crossed by solar radiation before it reaches the surface is inversely proportional to solar angle (altitude). ● 3. Period of daylight: June Solstice→ length of day longer in NH (summer) than in SH (winter); December Solstice→ Length of day longer in SH (summer) than in NH (winter) ■ The input and o
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