GEOGRAPHY: Introduction the study and analysis of the spatial and temporal distribution of phenomena on the Earth's surface, and the underlying processes which cause the observed pattern (pg. 1-3) ** the spatial science of areas, natural systems, & manmade systems. Four Traditions in Geography: developed by W.D. Pattison in 1964 Earth-Science tradition: physical geography; studying the world around us, climate, landforms, plants & animals, etc. Culture-Environment tradition: the impacts of the environment on people & their impact on the environment; the relationship bewtween human societies & their environment EX: the impact of deforestation on a region, or the impact of a hurricane on a region Locational tradition: the spatial component of geography; being concerned with where things are; the patterns or distribution of the phenomena EX: Location Theory: used yo explain the pattern of an activity or phenomena
Area-Analysis tradition: regional science or study; studying all the various phenomena of a particular area of the world EX: regional study of North America, Asia, or Africa, Five Fundamental Themes of Geography: developed in the 1980's by the National Geographic Society and numerous geographers in the U.S. (Fig. 1.1, pg. 4) 1) Location: absolute and relative 2) Place: characteristics that make a location unique 3) Movement: diffusion across Earth's surface 4) Regions: areas with uniform/similar characteristics 5) Human-Earth Relationships: use of the environment by humans 3 Main Sub-disciplines or areas in Geography (Fig. 1.2, pg. 5) 1) Physical Geography: Biogeography, Geomorphology, Climatology, Hydrogeography, Soils geography 2) Human/Cultural Geography: Economic, Political, Historical, Population, Urban, etc. 3) Techniques: Cartography, Remote Sensing, Aerial
Photography, Geographic Information Systems (GIS) ** In this course we are concerned with Physical Geography. * As an area of study, Physical Geography is quite old. ** Eratosthenes, a Greek who lived from 275 to 195 B.C., is considered one of the first "geographers". * Measured the polar circumference of the earth (Fig. 10, pg. 16) * Became an accomplished cartographer or mapmaker * Developed the idea of environmental zones based on temperature (T) ** Other famous early geographers: * Greek scholars: Aristole, (384-322 B.C.), Hipparchus, (2nd cent. B.C.) * Roman scholars: Strabo, (63 B.C. - 24 A.D.), Ptolemy, (100 - 170 A.D.) * Muslim scholars: Edrisi (1099-1154), ibn-Batuta (1304-1378) * Chinese scholars: Phei Hsiu, (3rd cent. A.D.), Chinese geographical study has been dated as far back as the 5th cent. B.C.
* German scholars: Bernhardus Varenius (1622-1650) * Alexander von Humboldt, (1769-1859), considered by some the "father" of modern physical geography (pg. 616) * Traveled and studied throughout the Americas, and Siberia * Credited with bringing "scientific study" to the field of physical geography ** More recent important geographers: * Vladimir Kppen (1846-1940), developed the Kppen Classification System for climates based on vegetation, temperature & precipitation patterns (pg. 283) * Alfred Wegener (1880-1930), developed the theory of Continental Drift which later became part of the theory of Plate Tectonics (pgs. 341-342) * Charles Thornthwaite (1899-1963), developed another climate classification system based on principles of water balance, precipitation & potential evapotranspiration (pgs. 248 & 280-283) * Tetsuya Theodore Fujita (1920-1998), developed the Fujita Scale for measuring the intensity of tornadoes (pg. 228)
* Robert Simpson (1915- ), developed, along with Herbert Saffir, the Saffir-Simpson Scale for measuring hurricane intensity (pg. 233)
EARTH'S SPHERES (Fig. 1.8, pg. 14) Earth's 4 spheres: 3 abiotic(non-living), and 1 biotic(living) 1) Atmosphere: thin gaseous veil that surrounds the Earth
From sea level to about 60,000 km (37,000 mi) above surface * Composed of different layers based on composition & temperature * Where weather occurs * Decreases in density with increasing altitude
2) Hydrosphere: all the water above, on and in the Earth; in all 3 states (solid, liquid, gas); includes fresh and saline(salt) * Comprises some 71% of Earth's surface * Oceans hold the vast majority of Earth's water 3) Lithosphere: Earth's crust and a portion of the upper mantle
* The rocky, outer shell of the planet; both land & sea bottom 4) Biosphere: interconnection between the living organisms of the planet with their physical environment
* the life zone of the planet
HEMISPHERES: * Arbitrary sectioning of the planet into areas based on compass directions: North, South, East, & West * OR based on land vs water: Land Hemisphere (continents and islands) & Water Hemisphere (Oceans) SYSTEMS: common to study "systems" or all the factors influencing an area or particular phenomena (pgs. 315) (Fig. 1.7, pg. 13) EX: a fluvial (river) system, a thunderstorm or hurricane system, etc Types: Open System = boundaries or interfaces freely permit transfer of energy & matter across them (Fig. 1.3, pg. 6 & Fig. 1.4, pg. 6)
EX: a weather system, a river system, leaves of a tree
Closed System = self-contained system exhibiting no exchange of energy or matter across boundaries - Systems change, but tend to be in, or in the process of being in, some form of an equilibrium state Equilibrium: the changing, or relatively nonchanging conditions of a system; all systems will change over time, but at different rates, thus some are seemingly in equilibrium while others may be moving toward a state of equilibrium (Fig. 1.5, pg. 10) * Steady-state Equilibrium: when a system is in balance over time, is neither growing or contracting but is in full operation; may oscillate around an average level or condition * Dynamic equilibrium: fluctuates around an average value, but demonstrates a trend over time * Feedback: change in one part (variable/factor) of a system causes change in another part (variable/factor) (pg. 6-9) - 2 types:
Negative feedback = keeps system in original condition inhibiting change; are self-regulating Positive feedback = induces a progressively greater change in a system; the "snowball effect" EX: growth of a hurricane (Read Insert 1.1, pg. 7) (Read pgs. 1-37)
LATITUDE & LONGITUDE
Earth is a sphere or has a spheroidal shape. It is a little "squished" at the poles or has what is called a geoidal bulge at the equator. (pg. 15-25) Equatorial diameter: 12, 756 km = 7926 mi (24,902 mi circumference) Polar diameter: 12, 714 km = 7900 mi (24,860 mi cir.) (Fig. 1.9, pg. 15) To Locate Places on the surface we use a grid system. Several types have been developed and are in use. Most common or well known is the latitude and longitude grid system. (Fig. 1.16, pg. 23) Latitude: parallel lines that run East-West and are measured North-South. start at 0 (equator), end at
90 (poles)
(Fig. 1.11, pg. 17)
Longitude: non-parallel lines that run North-South and are measured East-West, start at 0 (Prime Meridian) and end at 180 (International Date Line) (Fig. 1.13, pg. 18) (Read Focus Study 1.2, pg. 20)
* Degree: one part of a circle, with 360 parts or degrees in a complete circle * A degree is sub-divided into 60 equal parts or minutes * A minute is sub-divided into 60 equal parts or seconds EX: 1235'15" N 10455'30" E
* Latitude must have a N or S after it for north (N) or
south (S) latitude designation
* Longitude is similar, with an E or W for east (E) or west
(W) longitude designation Parallels of Latitude are about 111 km (69 mi) apart no matter which two you pick. (Table 1.2, pg. 19) Meridians of Longitude are 111 km (69 mi) apart only at the equator. (Know the major lines of latitude & longitude.) Latitude:
Equator 0 Tropic of Cancer, Tropic of Capricorn, Arctic Circle, Antarctic Circle, North Pole and South Pole Longitude: Prime Meridian International Date Line MAP PROJECTIONS (pg. 25-29) * The problems of transferring a round globe onto a flat surface, a piece of paper (Fig. 1.20, pg. 27) * Do this by an orderly arrangement of parallels & meridians * Several primary types or methods: * Cylindrical * Mercator (one of the most common types used) * Conic (Fig. 1.22, pg. 28)
* equal-area * polar * gnomonic * The matter of Scale of a map: the ratio of distance on the map to actual distance on the ground (Fig. 1.19, pg. 26) EX: 1:24000 means, 1 inch on the map equals 24,000 inches on the ground or 2000 feet; A Large scale map shows a relatively small area of the Earth's surface (Table 1.3, pg. 26) 1:100000 -----> 1 inch on the map equals 1 million inches on the ground, or about 83,333.33 feet or about 15.78 miles; A Small scale map shows a relatively large area of the Earth's surface. The larger the second number shows a larger area of Earth's surface, but is a smaller scale. Conversely, the smaller the second number, the smaller the area of the Earth's surface, yet is a large scale.
EARTH/SUN RELATIONSHIPS
* > 99% of Earth's energy is from the sun * Amount of sunlight striking the Earth varies spatially (over space or area), with latitude * Varies temporally (over time), with the changing seasons and between day & night * Amount varies with day length and intensity * These variations cause an unequal heating of the Earth surface that drives the ocean currents and creates wind, transporting energy across the globe Earth Movements Rotation: the spinning of the earth about its axis
1 turn every 24 hours; defines day & night * Earth turns at different rotational velocity for each degree of latitude; EX: 23.5 deg. = same as tropic
lines
* Turns counterclockwise, when viewed from above the North Pole * Creates a circle of illumination between areas of light and dark * Atmosphere rotates with Earth, held by force of gravity Revolution: movement of the earth in its orbit
around the sun * 1 orbit every 365.2422 days = 1 year hours) (365 days, 5.8
* Moves at ~ 66,660 mph as it travels around the sun * Counterclockwise orbit, when viewed from above North Pole * Orbit is elliptical, so at one time of year it is closer to the sun than another * Perihelion: closest to sun * Aphelion: farthest from sun (aph- means away from) Earth's Seasons Why it occurs: revolve around sun with a tilt. * Revolution * Rotation * Tilt of Earth on its axis * Axial parallelism * Sphericity * Primarily due to earth's orientation to the sun & thus the varying angle the sun's rays strike the earth's surface * This can be seen by the varying daylength & intensity with varying seasons * Earth's orientation caused by the tilt of its axis or the inclination of the axis, 23.5 from a perpendicular to the plane of the ecliptic
* Also, the Earth's axial orientation (axial
parallelism), that it is pointed towards the North Star (Polaris) (* These two aspects, inclination of the axis & axial orientation, along with the elliptical shape of the Earth's orbit, do change over long periods of time) * And sphericity that the Earth appears as an oblate spheroid to the Sun's parallel rays Solstices & Equinoxes * The five above factors cause the seasons, with 4 days being of particular interest: 2 Solstices & 2 Equinoxes ** Vernal (March) Equinox mar 21 ** Summer (June) Solstice June 21 ** Autumnal (September) Equinox - sep 21 ** Winter (December) Solstice - Dec 21 * Amount of day length determined by tilt & revolution * Sun never directly overhead (90) outside 23.5 N or S latitude * Northern hemisphere winter = southern hemisphere summer
* The Earth's rotation and the Meridians of Longitude determine the Time Zones
is this til 10 20 or 10 30? 45 there's a big fellow whose majors are ceramics and Chinese hehe I was thinking ," big fellow? Do you mean the guy in front of me? Haha" Cermaics right on. Chinese = too practical Definitely. Way too practical. She should be cermics and history. Hahahaha I think that was a weird sort onf compliment from you haha Yup this is fun. Maybe I'll drop into this class after all tehehe Have you ever heard a "live in the moment"-type quote that had to do with a hard-working, American businessman talking to his Mexican employees? You should! Or at least come chill here even if you don't sign up for it haha Er, I don't think I have... is there one you had in mind or that I should know? Yeah, I read it in a restaurant in midtown one time. I just remembered it. You know when you hear something, but it's not particularly striking or memorable to you, so it kind of sinks to the back of your mind, but then you hear it again, or you remember it, and now it means more to you? That's what just happened with that quote I'll try to find it to show it to you. I luuurve it Haha
WEATHER
vs
CLIMATE
* Constantly changing * Slow long-term changes * The state or condition of the * A description of aggregate atmosphere at a particular weather conditions time and place * Comprised of various factors: * A sum of the daily and air pressure, air temperature,
seasonal weather events humidity, clouds, precipitation, over decades of years wind, visibility, etc. (averages of these factors) Meteorology: the science that studies the atmosphere Climatology: the study of long-term atmospheric conditions ORIGIN OF THE ATMOSPHERE A B C D --|------------------------------------|------------------------------|------------------4.5 b 3 - 1.5 bya .5 bya
* Main process for increased oxygen levels is photosynthesis
COMPOSITION OF THE ATMOSPHERE *A mixture of discrete gases with solid and liquid particles suspended in it * Some components are fairly stable while others vary spatially and temporally * Constant gases * Variable gases
Constant Gases: 3 gases make-up just under 100% of the atmosphere Nitrogen (N): ~ 78% Oxygen (O): ~ 21% Argon (Ar): ~ .9% Variable Gases: 3 that influence weather and life systems Carbon dioxide (CO2) Water vapor (H2O) Ozone(O3) * Carbon dioxide: ** Water vapor: ** Ozone: * Formation is by splitting an O2 molecule with shortwave (solar) radiation and the single O atoms combining with an O2
** OZONE "HOLE" * Thought to be caused by increased amounts of chlorofluorocarbons in the stratosphere
* 1% loss of O3 leads to a 2% increase in Ultra Violet (UV) radiation absorbed at the earth's surface * Consequences (of less ozone): 1) increased amounts of
UV at surface 2) increased cases of skin cancer 3) increased damage to plants and animals
VERTICAL STRUCTURE OF THE ATMOSPHERE * Air Pressure: force exerted by the weight of a column of air above a given point * At sea level the average air pressure is 1000mb or 1 kg above every square cm * Pressure decreases with increasing height = inverse relationship * 50% of atmosphere is below 5.6 km (~3.36 mi) * 90% of the atmosphere is below 16 km (~9.6 mi) * Temperature (T): measure of the degree of hotness or
coldness of a substance. Different than amount of heat.. larger substance at same temp will have more heat
* T may decrease or increase with increasing altitude * In the troposphere it normally decreases 6.5C/km
* If the T increases with altitude it is called inversion *A change in T with a range in altitude is called the lapse rate or
the temperature lapse rate
Layers of the Atmosphere: 2 general regions: Homosphere: uniform chemical composition; from surface to a height of 80 - 100 km (50 - 63 mi) Heterosphere: changing chemical composition; from top of homosphere upwards 4 main layers: Troposphere: T usually decreased with increasing altitude; 8-10
miles where weather takes place
Stratosphere: T stays constant; where ozone layer is. Mesosphere: T decreases with altitude Thermosphere: increases rapidly with altitude- aurora is here
RADIATION BALANCE
ENERGY: ability or capacity to do work * Potential energy: the potential to do work; energy at rest * Kinetic energy: the energy of motion
* Heat energy: of an object
the sum total of all molecular motion
* Radiant energy: emitted by all objects with a temperature (T) > 0 K = (-273C) * follows the laws of thermodynamics * First Law of Thermodynamics: in all physical & chemical changes, energy is neither created nor destroyed, but it may be converted from one form to another ( Law of Conservation of Energy) * Second Law of Thermodynamics: when energy is changed from one form to another, some of the useful energy is always degraded to lower-quality, more dispersed and less useful energy ** Properties of Radiant Energy or Radiation: * light, heat, radio, X-rays, etc. all part of the electromagnetic spectrum or radiation *
*
* hotter the emitting body, the shorter the wavelength ** Sun's max. energy is radiated at .5 micrometers & its T = 6000K = 5700 C = 10,300 F and this is called Shortwave (SW) radiation ** Earth's max. energy is radiated at 10 micrometers & its T = 300K = 15 C = 59 F and this is called Longwave (LW) radiation
SOLAR RADIATION: * also called shortwave (SW) radiation; ~.4 microns and smaller * visible light is in the wavelengths from .4 microns(violet) to .7 microns(red) * it travels in straight lines * may be scattered reflected or absorbed or go directly to surface Scattering: particles in the atmosphere redirect the incoming solar radiation (SW) from its original path
* *
Reflection: process whereby a surface turns back a portion of the radiation that strikes it ** Law of Reflection ; the angle on incidence(incoming) = angle of reflection(outgoing)
incident radiation striking it * average planetary surface with varying sun angles * *
** Albedo: % of radiation reflected off a surface compared to
* examples: thick clouds 70-80, thin clouds 30-50, fresh snow 80-85, Old snow 50-60, forest 5-10, grass 20-25, dry earth 15-25, water 3-5(high sun altitude), 50-80(low sun altitude)
Absorption: process whereby energy of the incoming SW radiation is transferred into internal molecular motion (heat energy) of the object struck * * * ** SO, of 100% of incoming radiation from the sun: -- 45% reaches the surface -- 24% is absorbed by the atmosphere
-- 31% is loss to space by reflection & scattering
TERRESTRIAL RADIATION: wave (LW) radiation *
* also called Long
* Earth's emissions generally 1-30 micrometers wavelength size; in the infrared portion of the spectrum * carbon dioxide (CO2) and water (H2O) are very good absorbers of these wavelengths * water vapor absorbs 5X what all the other gases do * ** This Greenhouse Effect causes the atmosphere to be heated from the ground up. * LW radiation is "bounced" back & forth between the atmosphere, esp. Clouds, dust, and any CO2, & the ground. This helps to keep the earth's average T some
35 C warmer than -- with H2O & CO2 CO2 15C (59F) (0F)
it would be otherwise. without H2O & -18C
** the actual process of warming the atmosphere is a little more complicated/complex than the simple Greenhouse Effect. The Greenhouse does Effect not incorporate the process of convection and thus a better term would be Atmospheric Effect. * Global Warming is basically an enhanced natural Greenhouse Effect or what could be called, the greenhouse effect on 'overload' short wavelength radiation in, long radiation out thermal
GLOBAL ENERGY/HEAT BALANCE
HEAT: total kinetic energy of all the atoms and molecules of an object or surface * Note: Heat and temperature ARE different! * calorie = heat required to raise the T of 1 gram of water by 1 C
** Heat Transfer: by 3 mechanisms
Conduction: transfer of heat through matter by molecular
activity, the direct contact and transfer from one molecule to the next- solids
* heat flows from high T to low T * good & poor conductors of heat; metal (and ground) is a good conductor * insulators are poor conductors of heat, EX: air
Convection: transfer of heat by mass movement within a
substance happens in liquids or air is the most important mechanism for heat transfer in the atmosphere.
* in the atmosphere, air is heated at the surface and then rises in mass * the sensible heat flux is one component of this, (the dry component) * evaporation/condensation, or latent heat flux, is the other component of convective heat transfer, (the wet component) ** latent heat: heat energy added to a substance without changing the T of the substance, BUT changing the state (solid, liquid, gas) of the substance Radiation: wavelike transfer of energy EARTH'S HEAT BUDGET: the balance of incoming and
outgoing radiation
* can be applied to most any time period, daily, monthly, annually, etc. * if there was no balance of incoming and outgoing energy, then Earth would be too cold or hot Q* = net radiation = incoming minus outgoing
Q* =
QG
+
QH
+
QLE latent heat flux
ground sensible heat heat flux flux (conduction) (convection) (evaporation/condensation)
** Heat Budget varies temporally & spatially ** day vs night, ** summer vs winter ** tropics vs polar regions * Horizontal imbalance of energy over the earth's surface leads to a surplus in the tropics and a deficit at the poles * How is the energy redistributed? 1) Atmospheric circulation (winds)
2) Oceanic circulation (currents) * Most heat transfer takes place between 30 - 50 latitude & a large portion of the stormy weather we receive in the U.S. is attributable to this transfer of heat energy. * QLE is most important in the humid tropics * QH is most important in the arid tropics.
GLOBAL T PATTERNS/DISTRIBUTION
TEMPERATURE (T): average molecular motion ** atoms moving faster means greater kinetic energy, which means the substance will have a higher T * T is NOT heat * amount of HEAT is dependent on volume or mass of an object; the T of an object is not dependent on its volume or mass EX: an 8 oz glass of water and a filled bath tub can have the same T, but will not have the same amount of
heat because of different volumes ** T Scales: of water Celsius 0 Fahrenheit 32 100 180 Kelvin freezing pt 273 212 100 373
boiling pt of water range 100
* 0K = no molecular motion or absolute zero which = -273C = -459 F * C = (F - 32) x 5/9
K = C + 273 or
F = (C x 9/5) + 32
C = K - 273
* isotherm: a line on a map with equal temperature *** T Controls Receipt of Solar Radiation Differential Heating: *** land cools and warms more quickly than water, and to lower & higher T because: * water is more transparent while land is more opaque * specific heat of water is 3X greater than land s.p. = the heat needed to raise 1 gm of a substance 1 C
SO, * It takes more energy (sunlight) to heat up water than it does the same amount of land.
*Water turbulence and convection no soil turbulence or convection occurs.
* Evaporation from water is greater than land, so energy is used to evaporate water, not just raise the temp. Geographic Setting & Position: * Proximity to water * water has a moderating affect on T, average monthly T's will not vary as much between summer and winter * inward locations show greater temp variation between winter and summer * relationship to wind patterns, windward vs. leeward side of a continent * barriers to wind or moisture, i.e. mountains Ocean Currents: * will influence air temperatures of both the ocean area and adjoining land area where the current is located * warm currents: will help keep the T higher than it would be without the current
* cold currents: will keep the temp lower than it would be without the current * will also influence precipitation patterns Elevation:
* as you go higher in elevation, T decreases BUT amount of solar radiation increases * higher elevation often yields greater daily T range
Cloud Cover & Albedo: ** clouds trap-in terrestrial radiation keeping the surface warmer, BUT also reflect solar radiation coming in * cloudy day vs clear day; cloudy night vs clear night (Know the differences in temps due to these
situations.) * cloudy is usually cooler than a clear day * cloudy night is usually warmer (traps heat in)
*** Worldwide T Patterns * variations controlled by the above factors * one of the key factors is that the proportion of land to water varies over the earth's surface ** Southern Hemisphere: 81% water, 19% land
* T variations and range are smaller
** Northern Hemisphere: 61% water, 39% land
* greater T variations (more land, duh) * greater winter time variations with latitude than summer
* coldest T's: over land at high latitudes in winter EX: Siberia & Antarctica * warmest T's: in the tropical deserts in summer EX: Sahara
AIR PRESSURE & WIND
Regions of sinking air are called highs, high pressure regions or anticyclones. Clear skies and fair weather usually occur in these regions. Regions of rising air are called lows, low pressure regions, depressions or cyclones. Clouds rain and strong winds often occur in these regions.
*** Air Pressure: weight if the air pushing down on a surface
low air pressure in areas where heat rises (high temps)
** can vary both spatially and temporally
** avg. surface pressure = 1013 mb, 29.92 inches of Hg (mercury) ** shown on a map as lines of equal pressure or isobars
** Pressure Gradient Force (PGF): ** initiates horizontal air flow or advection = WIND *** air pressure & the PGF determine wind direction & wind strength or speed. ** Steep gradient == strong PGF == fast winds ** Gentle gradient == weak PGF == light(slow) winds *** These diferences in pressure are set-up by differences in Temperature. *** Coriolis Force: apparent deflection in path or movement of
an object due to the earth's rotation
* Earth is a sphere * objects move independent of the earth's rotation * the whole earth's surface does not spin at the same rotational velocity * deflection is: (with your back to the wind)
to the right of the original path in north to the left of original path in south
** Characteristics of Coriolis Force(CF): it is strongest at the poles & zero at the equator * an objects speed will alter the amount of deflection increase speed = increase deflection * CE alters direction, but NOT speed of an object * affects not only wind, but ocean currents, flight paths of planes and missiles
*** TYPES OF WIND:
Geostrophic winds: upper level winds affected by Pressure Gradient Force (H>L) & Coriolis Force net effect is that geostrophic winds blow parallel to
isobars with little to no friction
** 2 main patterns: look up. No, seriously. Know what a rossby wave is. Polar circulation loop and stuff.
Zonal flow: a more flattened air flow with primary an east wet
orientation
Meridional flow: a more curved flow with distinct ridges and
valleys
Surface winds: winds below 1000m altitude * influenced by: Pressure Gradient Force, Coriolis Force, Friction * effect: Low pressure cells: have cyclonic or counterclockwise flow in the NH High pressure cells: Anticyclonic or clockwise low
in the NH High pressure is falling to the earth, then diverges. Low pressure air is rising and converging.
*** Wind Measurements: direction & speed Direction: north, south, east, & west; NE, SW, etc. Winds are always named for the direction they are
coming from!!!! Speed: usually recorded by an anemometer in mph or kph EX: calm = <1mph, moderate wind = 13-18 mph, gale = 39-46 mph, and hurricane = >73 mph ** Winds can viewed at 3 or 4 different scales: Macroscale Planetary 1000 - 40,000 km Westerlies Synoptic 100 - 5000 km hurricanes Mesoscale 1 - 100 km T-storms Microscale < 1 km dust devils *** Types of Local Winds: ** Land/Sea Breezes: created along coastal areas because
of differential heating between land and water
** Valley/Mountain Breezes: warm wind going up
mountin during th day and cool wind coming down at night
** Chinook wind: warm dry wind coming off(down) the mountains named for such winds of the western U.S. ** Katabatic wind: a flow of dense cold air downslope under the influence of gravity in areas of large continental glaciers such as Greenland & Antacrtica
GLOBAL PATTERNS: PRESSURE &
WIND
PRESSURE ** Idealized Pattern: * changes temporally & spatially * is altered from the idealized pattern by land masses, seasonality, and differential heating (of land & water) Low Belts: area of uplift with convergence at the surface; usually unstable EX: Intertropical Convergence Zone(ITCZ), Subpolar Lows (SPL) High Belts: areas of subsidence and divergence at the surface, usually stable EX: Subtropical High(STH), Polar High (PH) WINDS Rotating earth: Pressure Gradient Force Coriolis Force Friction still apply and all three help create the 3-cell or Hadley model
ATMOSPHERIC MOISTURE:
HUMIDITY
Hydrologic Cycle: the continuous movement of water from the earth's surface to the atmosphere and back to the surface, then to the atmosphere, ..... * Basic process: Evaporation & Transpiration (Evapotranspiration), Condensation, Precipitation, Runoff * transpiration = States of Water: solid, liquid, & gas. Know these and the processes that change matter (& water) from one state to another: melting, evaporation, condensation, freezing, sublimation, & deposition (Know whether energy is being added (absorbed) or released for each process.)
HUMIDITY:
the water vapor content of the air
** the amount of water vapor in the air can be measured in different ways or units: * specific humidity: grams of water/ kilograms * absolute humidity: grams of water/ cubic meter * relative humidity (RH): ratio of water vapor actually in
the air compared to the maximum water vapor the air could hold at that temperature and expressed as a percentage
EX: (content / capacity) X 100 = RH
** Terms * partial pressure: each component of the atmosphere makes up a part of the total air pressure * water vapor pressure: that portion of the air pressure which is made up by water vapor * saturation: when the air is holding all the water vapor it
can (cloud)
* the amount of water vapor the air can hold is a function of T * warmer air can hold more water vapor than colder air * saturation vapor pressure the airs capacity increases wit increasing T * specific humidity: the weight of water vapor divided by the weight of the air in gm/kg * Relative Humidity (RH): the amount of actual water vapor in the air as compared to the water vapor capacity of the air equals the RH of the air actual water vapor content -------------------------------- X 100 water vapor capacity ** when RH = 100%, the air is saturated and condensation begins
** this is controlled by the water vapor content & the air's capacity, which is controlled by T * Dew point: The T at which a given mass of air becomes saturated, holding all the water it can. Any further cooling or addition of water vapor results in active condensation. * it is an indication of the moisture level in the air * controlled by vapor pressure, NOT by the air T if air temp and dew point are the same, then relative humidity is 100 percent. Relative humidity is higher in morning, lower in afternoon *** How to change the RH:
* adding or subtracting water vapor
* lowering or raising the temp
Examples of how to bring air to the point of saturation: a) By adding water vapor to air ( T held constant) air T: Sp. Hum.: capacity: 25C 5gm/kg 20gm/kg 25C 10gm/kg 20gm/kg 25C 20gm/kg 20gm/kg
R.H.:
25% {(5/20)X100}
50%
100%
b) By cooling the air ( vapor content constant) air T: Sp. Hum.: capacity: R.H.: 30C 10gm/kg 27gm/kg 37% {(10/27)X100} 20C 10gm/kg 14gm/kg 71% 15C 10gm/kg 10gm/kg 100%
*** So, when the RH varies during the day its because of a change in air temp or a change in the amount of moisture in the air. * the most common way & easiest way for the RH of the air to be changed is by changing the air T. * this is also the most common & easiest way for the air to become saturated and thus for condensation to occur, by changing the air T. ** Water vapor content in the air and thus RH also varies from day to day, month to month, and of course seasonally. * Remember, the colder the air, the less water vapor it can hold. The warmer the air, the more water vapor the air can hold.
ADIABATIC PROCESSES ** warm air is less dense(lighter) and thus rises * as air rises in the atmosphere, it expands * a parcel (or 'bubble') of air comes under less & less pressure as it rises & thus expands * as a gas (air) expands, the molecular action (kinetic energy) decreases thus the T decreases ** cold air is more dense (heavier) and thus sinks * as air sinks in the atmosphere, it compresses. * a parcel of air comes under more & more pressure as it sinks & thus is compressed * as a gas (air) compresses, the molecular action (kinetic energy) increases thus the T increases SO, expanding air = T decrease Compressing air = T increase ** BUT, the T changes WITHOUT heat being added or subtracted.
*** this is Adiabatic Temperature Change: Simply the result of compressing the air or allowing it to expand. RESULT: ** rising air in the atmosphere expands and cools.
** sinking air in the atmosphere is compressed and warms
*** Rate of Adiabatic Change: * varies with humidity condition of air: Dry (unsaturated) air vs. Wet (saturated) air Dry Adiabatic Rate: (DAR or DALR) When air is unsaturated, air T > dew point T; * the DAR is a constant rate of 1 C/ 100 m * Thus, rising air cools at 1C/100 m (10C/1000 m) sinking air warms at 1C/100 m (10C/1000 m) Saturated Adiabatic Rate: (SAR or SALR) RH < 100%
(May also see this as Wet Adiabatic Rate (WAR), or Moist Adiabatic Rate (MAR) When the air is saturated, air T = d.p. T or RH = 100% * the SAR is variable: .5 - .9C / 100 m .5C - .9C/100 m or 5C - 9C/1000 m * It is dependent on the moisture content of the air. The more water vapor there is in the air, the slower the rate (closer to 5C /1000 m). * This is because condensation releases latent heat , thus slowing the rate of cooling (or warming). *** So as air rises by convection it cools and the air T may reach the dew point T (saturation0 & thus condensation may begin. If there is enough water vapor in the air parcel, then a cloud may form. The level of the atmosphere where this occurs is known as the condensation level. ** condensation level: the height at which condensation occurs; where cloud formation begins (bottom of a cloud) RH = 100%; air T = d.p. T
ATMOSPHERIC STABILITY *** STABILITY: refers to the tendency of an air parcel with its water vapor either to remain in place or to change vertical position
* a stable parcel of air resists displacement upward or, when disturbed, tends to return to its starting place * an unstable parcel of air continues to rise until it reaches an altitude where the surrounding air has a density & T similar to its own Rules of Stability 1) When an air parcel is warmer & less dense than the surrounding air, the parcel will rise: UNSTABLE air or condition = low pressure 2) When an air parcel is colder & denser than the surrounding air, it will tend to stay at the same level or sink: STABLE air high pressure 3) the Environmental Lapse Rate (ELR) is the T profile of the atmosphere (air surrounding a parcel of air). The actual (T) lapse rate in the lower atmosphere at any particular time under local weather conditions.
Whether a particular parcel of air will rise (unstable) or not rise (stable) is a function of the T inside the parcel of air as compared to the T outside the parcel of air, thus the ELR determines air stability. Types of Stability Stable: the condition of the air when ELR < DAR; Absolutely Stable Conditions or Absolute Stability * * * associated with High pressure cells * most severe example is a T inversion: when the air T is increasing with increasing altitude in the atmosphere Unstable: the condition of the air when ELR > DAR Absolutely Unstable Conditions or Absolute Instability * usually results in uplift if air * cloudy skies * associated with Low pressure cells * often occurs during the warmest months & on clear days
Conditionally Unstable: the condition of the air when the ELR is between the DAR & the SAR SAR < ELR < DAR * atmosphere will vary between Stable & Unstable * usually if air is saturated then upper portion of the atmosphere is Unstable * usually if air is unsaturated then the lower portion is Stable ** Stability is important in daily weather patterns. * controls whether clouds form or not & the type * partially controls precipitation type & amounts
*** LIFTING MECHANISMS * For air masses or parcels of air to cool adiabatically ( by expansion) and to reach the dew-point T and saturate, condense, and form clouds and perhaps precipitation, they must lift and rise in altitude. * There are 4 principal lifting mechanisms which operate in the atmosphere. Convective Lifting:
* the heating helps produce UNSTABLE conditions * if there is enough moisture in the air parcel, then may get cloud develop & precipitation * common in summertime, producing afternoon thunderstorms especially here in the SE US * part of the process that occurs in Low pressure cells in conjuction with convergence Convergent Lifting: * part of the process that occurs in Low pressure cells in conjuction with convection * both convection & convergence are at work to form the (ITZC) InterTropical Convergence Zone Orographic Lifting: the process by which air is forced to rise over a mountain ranger and thus cool adiabatically. * precipitation occurs on the windward side of the mountain * little to no precipitation occurs on the leeward side * mat create a Rain Shadow Desert on the leeward side Frontal Wedging:
* The leading edge of a mass of cold air is known as a cold front & similarly the leading edge of a mass of warm air is known as a warm front. So this lifting mechanism is associated with cold/warm fronts & Mid-Latitude Wave Cyclones (frontal systems). * usually produces clouds & precipitation; often severe storms or thunderstorms along the cold fronts