Exam #2 Weather & Climate

Greenhouse gases

water vapor and CO2 (also known as variable gases), water vapor/CO2 retain heat that is released up from ground

How do clouds affect temperature?

clouds trap/retain heat from below so not as much air can escape, therefore clouds and moisture are huge components of global warming because keeping more heat at earth's surface, more heat--> more moisture able to coexist

Atmospheric origins

hot particles in solar winds slowly came together to form earth, particles began cooling down through outgassing of water vapor which added water/oceans to planet, then clouds began to form & precipitate

How did oxygen increase on earth?

very little at first but now 20.95% O2 in atmosphere largely from process of photosynthesis due to rise of bacteria/algea in oceans--> rise of plants also releasing O2

thermal structure of the atmosphere from bottom to top

troposphere: 8-15 miles up, deep at equator, shallow at poles, temp decreases

tropopause: rawindsondes detect temp at this level

stratosphere: top is 30 miles up from ground, lower third temp is steady, in upper 2/3rds ultraviolet radiation received in ozone so temp rises

ozone: absorbs UV radiation from sun

stratopause: transitory zone between layers

mesosphere: steady temp before temp drops again

mesopause

thermosphere: stead temp then increase

How is ozone distributed in the stratosphere?

very fickle (changing frequently), good/max ozone found in lower/middle part of stratosphere while temp increase in middle/top of stratosphere, less ozone over southern hemisphere

Homosphere

The lower layer of earth's atmosphere, from ground level to roughly 55-60 miles up, very well mixed region as far as chemicals, not v intuitive

Heterosphere

The upper layer of earth's atmosphere, 55-60 miles above ground and up, chemical contingents (few) begin to layer up depending on their molecular/atomic weight, very few atoms/gases

Ionosphere

the lower part of the thermosphere, 45-50 miles above ground and up, electrically charged region of atmosphere where molecules/atoms ionized by incoming shortwave radiation (sun), seen in northern lights

How do radiowaves interact with the ionosphere?

lowest layer of ionosphere is D, then E, then F; D & E layers highly absorbent of radiowaves when sun shining through (charged by sun during the day), however at night, F layer extremely reflective of AM radiowaves because passed through D & E layers and reflected back down off of F layer

How much of the sun's energy does the earth receive?

2 billionths, but solar energy from sun is 99.9% of all energy that heats earth's surface

What would happen if sun disappeared?

Global winds would slowly shut down

Which hemisphere is facing the sun in the summer?

The northern hemisphere

What buys us seasons?

The earth revolving around the sun every 365 days (one revolution)

What is the altitude of the sun?

The angle of the sun above the horizon, where you are in latitude distinguishes where sun is in sky

Solar moon

when the sun is highest in the sky for a given place on earth/when sun most directly overhead

What type of rays distinguish the sun at the horizon?

most indirect rays

90 degrees overhead

Most direct sun rays, in austin: sun never directly overhead and always in southern sky

Tropic of Cancer and Capricorn

23.5 degrees north and south latitude of the equator, cancer basically crosses Mexico city, sun will only ever be directly overhead between tropic of cancer, equator, and capricorn

"Atmospheres"

unit of measure (sun rays traversing x number of atmospheres), when sun directly over equator suns rays traversing 1 atmosphere (90 degrees overhead), sun traversing 2 atmospheres when it's 30 degrees above horizon

How many atmospheres does the sun traverse as it rises/sets?

11 atmospheres until gets to 30 degrees above horizon and then at 2 atmospheres (morning & afternoon)

Autumnal Equinox

September 22-23, sun directly overhead equator at noon, then goes more over southern hemisphere and we begin autumn

Winter Solstice

December 21-22, when the sun is at its southernmost point directly over tropic of capricorn, weakest rays of the year but sun starts to get higher and higher in the sky everyday--lag/march of temperature

Vernal Equinox

March 20-21, sun directly over equator again and begins spring

Summer Solstice

June 21-22, sun directly above tropic of cancer, hottest day in Austin mid August because of lag/march of temp (earth takes a while to heat up/cool down)

How does the sun behave in the Arctic circle?

sun sets/remains set in summer & winter solstice, remains in sky in vernal/autumnal equinox

What time of day is the coldest during winter?

10/15 minutes after sunrise

Which hemisphere is closest to the sun in the winter?

The northern hemisphere

Circle of allumination

boundary separating light and dark parts of the planet, defines sunrise and sunset

Heat Budget

51% of sun's radiation absorbed by the earth

20% scattered/reflected by the clouds back upwards

19% absorbed by the atmosphere and clouds

6% scattered from the atmosphere back upwards

4% reflected by the surface

Why is water near the equator warmer?

Because sun is directly overhead (low albedo)

Water absorption/reflection of sun rays

70-75% of earth's surface covered by water, amount of rays absorbed/reflected depends on sun angle (causes unequal heating of earth's surface), more sun absorbed when sun directly overhead (low albedo)

What does budget mean?

What goes into atmosphere has to equal what comes out

Conduction

transfer of heat energy across an object from hot to cold, metal is good conductor or heat, best conduction within 1 to 2 inches of ground because atmosphere is not a good conductor

Convection

Vertical transfer of heat energy, heat released upwards into air-->expands-->cools, thunderstorms are sign of convection because heat rising (parcels of air rising) then cooling (becomes saturated) then forming clouds

Advection

The horizontal transfer of any atmospheric property typically by wind, cold front transfers air this way, moisture returned back to Gulf of Mexico (can advect in any type of air)

Radiation

short wave radiation is solar radiation, sun to earth/hot to cold, radiation absorbed into earth only a couple of inches down then released back up as long wave/terrestrial radiation, reason why temp typically decreases in troposphere w altitude (besides areas of inversion)

Scattering

Dust particles and gases in the atmosphere reflecting light in all directions

-non-selective scattering: wavelengths of light scattered equally w larger particles in atmosphere, shows white clouds

-rayleigh scattering: ultraviolet radiation hitting gas molecules, turns sky blue

-mie scattering: hazing conditions

Albedo

the percentage of incoming sunlight reflected from a surface, varies from place to place/time to time, affected by cloud coverage, angle of sun rays, nature of earth's surface

Earth's average planetary albedo

about 30%

Albedo of freshly fallen snow

80-85%

Albedo of old "dirty" snow

50-60%

Albedo of thin clouds

25-50%

Albedo of thick/layered clouds at very top

70-80%, causes street light to come on

Albedo of sand surfaces

20-30%, lots absorbed (color & grain size matter)

Albedo of green, grassy surfaces

20-25%

Albedo of heavily forested/thick leaved areas

5-10%

Albedo of dry/freshly plowed earth

15-25%

Albedo of wet/freshly plowed earth

10%

Albedo of water w sun directly overhead (equator)

3-5%, lowest on earth, hot water because sun absorbed

Albedo of water w low sun angle (near poles)

50-80%

Atmospheric Greenhouse Effect

The relatively easy transmission of shortwave radiation by the atmosphere coupled with the selective absorption of long wave radiation (variable gases)

Absorption and Emission

if an object gives away more energy than it absorbs it will get cooler (emission) and vice versa

Black body object

a perfect absorber or a perfect emitter, both sun and earth black body objects because radiate and absorb at 100% efficiency (earth absorbs/emits depending on time & place), earth's atmosphere is very selective absorber and therefore NOT a blackbody object

radiative equilibrium temperature

The temperature achieved when an object, behaving as a blackbody, is absorbing and emitting radiation at equal rates (earth and sun), RET of earth's surface 0 F or -18 C while actual avg. temp is 59 F or 15 C

Energy

the property of a system that enables it to do work (kinetic, chemical, solar, etc.)

Temperature

A measure of how hot or cold something is, air temp dependent upon molecular motion

Heat

The energy transferred between objects that are at different temperatures, dependent upon mass/type of material (good conductor or not),

Heat capacity

the number of heat units needed to raise the temperature of a body by one degree, ratio of heat absorbed/released by system compared to corresponding temp rise/fall, takes more energy to heat up large body of water than smaller one (higher heat capacity), land heats/cools more quickly than water

Latent heat

hidden, heat energy absorbed or released during a change in state of water

Sublimation

solid to gas, latent heat absorbed (dry ice)

Melting

solid to liquid, latent heat absorbed

Evaporation

Liquid to gas, latent heat absorbed, cold when you get out of the pool with process of evaporative cooling, water droplets form on skin and heat is hidden/locked up energy within this water vapor, after air rises latent heat is released, parcel expands & cools as it rises then condenses & saturates into clouds

Desposition

gas to solid, latent heat released (snow/snowflakes)

Freezing

liquid to solid, latent heat released

condensation

Gas to liquid, latent heat released (air becoming saturated)

Why do we feel turbulence?

latent heat in clouds being released, heat re-released in condensation affects atmospheric stability

Latitudinal Heat Balance

earth balances out short and long wave radiation but works differently north/south of equator, causes atmospheric conflict in certain places (between 30-50 N & S, mostly in north because of land distribution)

Where is there an energy surplus?

Between 36 N and 36 S latitude, area where more short wave radiation received, "haves"

Where is there an energy deficit

N of 36 N and S of 36 S, losing more longwave radiation than gaining because sun less rays are less direct, "have nots"

How is energy redistributed?

wind blows cold air from polar region to cool northern hemisphere, wind transfers surplus to deficit, ocean currents also working but at much slower rate

Temperature measurement

most accurate through anal temp, original thermometer was mercury inside glas tube (expansion/contraction of liquid) but in cold temps mercury gets sluggish so switched to alcohol-- mercury banned in federal buildings so moved to temp sensors (electronic), still measuring molecular motion but more accurately now

How is air temperature measured?

-mushroom shaped device consists of thermometer and hydrometer, about 5 feet off ground, air temp always measured in shade, white (albedo)

-radiometers: remote sensor device by satellite (infrared cloud top temp & water vapor), 22-23000 miles up

-thermograph: uses biometallic sensor to plot temp graph, outside in white shelters, uses drum and ink graph that functions by energy transfer

Thermometer shelter/exposure

thermometers are much better energy absorbers than air...

-Cotton region shelter (CRS): sheltering device to keep therms/thermographs, loopers pointed down so sun can't enter, 5 feet up, device door faces 360 N so don't never faces sun directly

-thermometer radioactive shield (TRS): same type of thing

Rules for measuring temperature

1) no direct sunlight on temp sensor at any time

2) well ventilated, free air movement, shade

3) shielded from radiating surface, away from black surface/wall of building

4) 5 feet above ground, coldest air sinks which is why you can have frost at 36 F

5) typically measured over naturally vegetated area

6) typically the more inconvenient, the better siting

Fahrenheit scale

widely used mostly in US (besides some smaller, undeveloped countries), Gabriel Fahrenheit created in early 1700s, used liquid (mercury) in glass thermometer based upon a "zero point--" 32 degrees F is freezing point of water/melting point of ice, 98.6 F internal body temp, 212 F boiling point of water at sea level

Celsius scale

widely used around world, created by Anders Celcius in 1700s, devised using decimal scale and zero point, 0 degrees C is freezing point, 37 C is body temp, 100 C is boiling point,

How large are celcius degrees compared to fahrenheit degrees?

degree of celcius is 1.8x size of degree of fahrenheit (so bigger)

Kelvin scale

largely used in scientific experiments, zero point is the stopping/cessation of any molecular motion, 0 degrees K is stopping point so no negative numbers, 273 K is freezing point, 373 K is boiling point, 310 K is body temp

How large are celcius degrees compared to kelvin degrees?

exactly the same size

F to C

(F-32)/1.8=C

C to F

1.8C + 32=F

C to K

C+273=K

Air temperature controls

(sun primary control but doesn't exactly heat the atmosphere)

-differential heating of land and water: don't reflect back up terrestrial radiation the same

-ocean currents: attempt to bring earth into thermal equilibrium, slower than wind currents, west cold cold because cold water brought down from poles, cold water translates to a more stable atmosphere (less tornados)

-elevation: pressure decreases and thins out w altitude, if you're in rockies, less molecules-->harder to breathe

-latitude/geographic position: being on diff sides of montain affects exposure to sun

Air temperature data/uses

temp data gathered at thousands of stations worldwide on an hourly basis

-measuring snow coverage: wanna know snow depth and water content as well

specific uses: air density for aerodynamics, highs and lows/avg. temps for annual analysis, temps at specific times for crime scenes

Heating/Cooling Degree Days

unit of measurement (HDD/CDD), developed in 20th century, based on assumption that heating/cooling of buildings is not required where avg. temperature is 65F, simply a number, HDD/CDD are cumulative, calculated by finding diff between current temp and 65F

CDD season

Jan 1 - Dec 31, equivalent to calendar year, looks like miniature bell curve

HDD season

July 1-June 30, trying to encapsulate seasons, looks like miniature bell curve

Avg annual HDD & CDD in Austin

avg annual HDD: 1185

avg annual CDD: 3375

although HDD lower, causes greater impact on people/schools when there is a freeze, costs $$ to turn up thermostat

Biometeorological Applications

(things that affect humans), heat stress index & wind chill index

Heat stress index

developed early 80s, involves air temp and relative humidity (saturation), more moisture in air causes evaporation to be less effective & body can't cool as well, WGBT (wet bulb globe temp): futuristic measurement, takes temp, humidity, sun exposure/angle, & wind into account

Wind chill index

developed by polar scientists is 1940s, involves air temp and wind speed, not made for people in mid latitudes (Austin), initially misused/doesn't make much difference in hotter regions

What is the #1 weather related killer on earth?

Heat, 85% body heat loss is from neck up

Where are flood problems most prominent?

-urban areas because the rain not absorbed by concrete

-limestone areas causes run off into hill country

(austin is flash flood capital of US)

Where does atmospheric moisture come from?

-transpiration: plants give off moisture

-big bodies of water: primary source of moisture in Austin from Gulf of Mexico (7 day shelf life before falls back down as precipitation)

Absolute humidity

amount of moisture in air, weight/mass of water vapor per volume of air in a parcel of air (think of parcel as balloon rising)

Specific humidity

weight/mass of water vapor per volume of air in a parcel compared to total weight/mass of parcel of air including water vapor

Mixing ratio

weight/mass of water vapor per volume of air in a parcel compared to weight of remaining dry air in parcel

Relative humidity

expressed as a percentage, ratio of air's actual water vapor content compared with amount of water vapor required for saturation at given temperature, RH is 100% when actual temp=dew point temp (saturated), RH tells us how close we are to saturation but NOT how much moisture is in the air

What is the relationship between air temp and relative humidity?

on a clear day, air temp and relative humidity have inverse relationship