Powerpoints Flashcards
Geostationary Satellites (GOES)
Stationary with respect to a fixed point on Earth’s surface (revolves at the same rate as Earth)
Farm from earth (~36,000 km away) => coarse spatial resolution, but good temporal sampling
Polar Orbiting Satellites
Orbit the earth from pole to pole
Closer to the Earth (~900km) => better spatial resolution, poorer temporal sampling
Study Surface Station Model Diagram
in powerpoints 1
90% of earth’s atmosphere (by mass) is below ________
16km (10 miles)
Weather
Specific state of the atmosphere at a given time/place
Climate
Accumulation or average of weather conditions over a long period of time
What is the atmosphere?
A fluid
A thin layer surrounding the Earth
Mainly a mixture of invisible gas with some solid and liquid particles, that stays in place due to the force of gravity
Major permanent gases of the atmosphere
Nitrogen N2 - 78%
Oxygen - O2 - 20%
Argon - Ar - 0.9%
Source of Nitrogen
Bacterial dentrification during decay of biological matter
Sink of Nitrogen
N-fixation by lightning, fires, or bacteria
Sources of Oxygen
Photosynthesis
Photolysis
Sink of Oxygen
Oxidation
Decomposition
Respiration
Hydrogen/Helium:
Earth’s first ATM ( probably)
light => easily escape Earth’s gravity
Water in the Atmosphere
Greenhouse gas
Variable concentration
Invisible
Carbon Dioxide
Greenhouse gases: “Trap” energy in lower atmosphere
Anthropogenic: caused by human activity
CO2 increases with plant decay during winter
CO2 decreases with plant growth during summer
Aerosols
Particles suspended in the air (dust, soot, salt)
Provide “nucleus” for cloud droplet formation (cloud condensation, nuclei, or CCN)
Can shade surface
Earth’s early atmosphere:
H2, He
Volcanic outgassing and the origins of our oceans:
CO2, H2O, and some N2
Life and the origin of our present atmosphere:
Drawdown of CO2, increase in O2
How old is the Universe:
~10 - 20 Ga (billions of years) 13 in specific
How do we know? - expansion, and the hubble constant
Earth’s First ATM
Earth forms via acretion (stuff clumps together)
Whatever happened to be hanging around at the time (H2)
Atmosphere rapidly lost to space; ripped off planet by bombardment
Earth’s second ATM
Volcanism and Heavy Bombardment (4.5-3.8 ga)
Earth’s third ATM
3.8 - 3.5 ga
LIFE!
Cyanobacteria
Photosynthesis
Red Beds
Form in more oxygen-rich environments (1-2% ATM)
Start around 2 Ga
Banded Iron Formations
Form in oxygen-depleted water environments (1-2%)
Stop around 2 Ga
Ultraviolet radiation does not permit =>
life on land, or in surface locations
O3 (ozone) layer is needed
As oxygen increases =>
Ozone increases via photochemical reactions
=> Ozone layer
What next?
Early life: anaerobic bacteria (photosynthesis)
Aerobic bacteria develop ~2 Ga (respiration)
Eukaryotic cells develop ~1.5 Ga
~0.5-0.1 Ga meiosis (sexual reproduction)
~600Ma - Present =>
Life takes off
Vertical sounding
Measurement of how temperature changes with height in the atmosphere
Water balloons lift “radiosondes” into the air
Graph with two bars
Right bar on graph is Temperature
Left bar on graph is Dewpoint Temperature
Lapse Rate
Rate at which temeprature decreases with height (positive when temperature gets colder with height)
Typically ~6.5C in the troposphere
Temperature Inversion
Vertical layer of the atmosphere where temperature increases with height
Lowest pressure ever recorded in the Atlantic
882 Mb
Density =
Mass / Volume
Pressure =
Force / Area
Force =
Mass * Acceleration
Weight =
Mass * Gravitational Acceleration
Pressure:
supports weight of air above a given location
Order of Atmosphere
Thermosphere
Mesopause
Mesosphere
Stratopause
Stratosphere
Tropopause
Troposphere
Troposphere
Tropo (turning) sphere - where weather happens
- heated from below
Lapse rate = ~6.5 C/km
Tropopause: where temperature stops decreasing (isothermal layer)
~16 km in the tropics
~6km in polar regions
Stratosphere
Stratum (layer) sphere - no weather
Temperature increases with height (inversion)
- heated from above by ozone
Stratopause: where temperature stops increasing
=> ~50 km in the tropics
Weight of water per cm^2
10g/cm^2
Air pressure:
1013 g/cm^2
Energy
The ability to do work
units: Joules, or calories
Potential energy
Potential to do work
Kinetic energy
Energy of motion
Internal (thermal) energy
Energy of molecular motion in a substance
ex. random “jiggling”
Internal energy “Heat”
Total energy produced by random motions of molecules and atoms; total kinetic energy of a sample
“Energy of random jiggling”
Conservation of Energy
Energy cannot be created or destroyed - it can only change forms
Temperature
Measures the average kinetic energy of molecule in a substance (related to average molecular speed)
~500m/s at room temperature
Heat Capacity
Amount of heat needed to raise the temperature of an object 1 degree Celsius
=> proportional to mass
=> Depends (somewhat) on composition
Specific Heat
Amount of heat needed to raise 1 gram of an object 1 degree Celsius
=> not proportional to mass
First Law of Thermodynamics: Ch
Change in Internal Energy =
Heat added to system
- Work done by system
Why is beach sand so hot on a sunny day, but the water stays comfortable?
Same amount of heat added to both, so same change in internal energy
Sun’s energy absorbed in 1 cm of sand
- Small mass, small heat capacity, large temperature change
Sun’s energy absorbed in 10 m of water
- large mass, large heat capacity, small temperature change
Second Law of Thermodynamics
Heat will transfer from a warm object to a cold object
Three modes of heat transfer
- Conduction
- Convection
- Radiation
Conduction
Heat transfer from molecule to molecule
Conductivity: Rate of heat transfer across object
Conduction
Katabatic winds: Winds caused by cool air sinking down a slope
Air next to surface cools via conduction / radiation
Cold / dense air sinks down the slope
Convection
Heat transfer via fluid motions (hot air rises, cold air sinks)
Buoyant plumes are called “thermals”
If most buoyant air is already on top, convection does not occur (stable situation)
Advection
Heat transfer via horizontal fluid motion
Heat transfer via horizontal fluid motion
Advection
Latent heat
Heat required for a substance to change phase
Ice => vapor
Sublimation
Vapor => Ice
Deposition
Vapor => liquid
Condensation
Liquid => vapor
evaporation
Why does evaporation cool liquid water?
Only the most energetic molecules break free of attraction to other molecules
Remaining molecules are “less jiggly” on average, so temperature decreases
Condensation is a source of energy for ___________ in clouds
rising air
Latent Heat: Source of energy for hurricanes
Water vapor evaporates from warm ocean surface
Water vapor condenses (latent heat release) into clouds/rain
Latent heat release provides source of energy for hurricane intensification
Radiation
Energy transfer by electro-magnetic waves
Dual personality: can be thought of as
- wave (electric and magnetic field)
- packet of photons (photon: a discrete bundle of energy)
*Ultimate source of energy (from Sun) to Earth
Wavelength
Distance between crests of electromagnetic radiation
Hotter objects emit more ______________
radiation
*Stefan-Boltzman
Wien’s law
Hotter objects => shorter wavelengths
Sun => “shortwave” radiation
Colder objects => longer wave lengths
Earth => longwave radiation
*warmer objects have maximum emission at shorter wavelengths
The Sun radiates more energy with _________ wavelengths
short
The Earth radiates more energy with _________ wave lengths
long
Fate of Incoming solar radiation
- Absorption
- Scattering
- Reflection
Absorption
Incoming radiation absorbed by molecule or particle in the atmosphere (or at the ground)
Scattering
Incoming radiation interacts with molecules or particles in the atmosphere and is sent in all directions
Reflection
Incoming radiation reflects back to space
Albedo - fraction of radiation that gets reflected
Albedo
Fraction of radiation that gets reflected
= Amount of reflecting radiation / Amount of incoming radiation
Bright (ice, snow) => High albedo
Dark (wet dirt, water) => low albedo
Radiative Equilibrium
Balance between incoming shortwave and outgoing longwave radiation
Shortwave absorbed = longwave emitted
Radiative equilibrium temperature:
Temperature required for radiative equilibrium
Selective Absorption
Capability of greenhouse gases in the atmosphere to absorb and emit longwave radiation, but only at selected wavelengths
The Greenhouse Effect
Sun-to-Earth
Shortwave radiation from the sun is trasmitted through the Earth’s atmosphere, and absorbed at the surface
The Greenhouse effect
Earth-to-atmosphere
Earth radiates energy to the atmosphere
Some passes through, but most is absorbed by the atmosphere, warming the atmosphere
Also, energy is transferred to the atmosphere via convection, warming the atmosphere
The Greenhouse Effect
Atmosphere
Energy is radiated back to earth and to space
Additional energy available to warm the surface
Thre Greenhouse Effect Equation
Shortwave absorbed (solar) + Longwave absorbed (atmosphere) = Lonwave emitted (earth)
Selective Absorbers in the ATM
Oxygen and Ozone
Absorbs UV high in the atmosphere (Stratosphere and above)
Ozone absorbs around 9-10 um (in the atmospheric window)
Selective Absorbers in the ATM
Carbon Dioxide
Absorbs infared radiation - plays an important role in the greenhouse effect
Absorbs wavelengths at greater than 13 um
Adding more CO2 gradually “fills in” the atmospheric window
Selective Absorbers in the ATM
Water VApor
Most important greenhouse gas: absorbs throughout the infarred range
Absorbs wave lengths at <8 um and >13 um
Liquid water (clouds) absorb all IR wavelengths (why cloudy nights do not get as cold as clear nights)
Anthropogenic
Human generated
Greenhouse effect
Sun-to-earth
Shortwave radiation from the sun is transmitted
through Earth’s atmosphere, and absorbed at the
surface
The Greenhouse Effect
Earth-to-Atmosphere
Earth radiates energy to the atmosphere
Some passes through, but most is absorbed by the atmosphere, warming the atmosphere
Also, energy is transferred to the atmosphere via convection, warming the atmosphere
CO2 concentrations undergo _________________ over hundreds of millions of years
large fluctuations
More Carbon Dioxide coincides with ____________
more temperature
Emissions
Rate at which a particular gas is being added to the atmosphere
Concentration
How much of that gas is actually in our atmosphere
Chance in concentration =
Natural emissions + Anthropogenic emissions - Natural sink
If sources exceed sinks:
Concentration increases
Sinks of Carbon Dioxide
Ocean: Oceans absorb about 20% of emitted Carbon Dioxide. But Cold water absorbs more than warm water
Land: Growth of vegetation absorbs about 20% of emitted CO2 as vegetation grows (CO2 fertilization). CO2 fertilizaiton is limited as temperature increases
Longwave emitted (earth) =
Shortwave absorbed (solar) + Longwave absorbed (atmosphere)
How much warming should we expect?
Answer depends on:
- How much warming is produced by a doubling of CO2? ~2-4.5 degrees Celsius
- How much CO2 will we put in the atmosphere?
Climate Sensitivity
The equilibrium global temperature change at doubling of CO2
Earth’s orbit
Spins about its axis at a 23.5 degree tilt with respect to its orbit
North Pole faces the sun during (northern) summer, faces away from the sun during (northern) winter
Earth is closest to the sun at Perihelion (january 3) and farthest at Aphelion (July 4)
Receives ~6% more sunlight at Perihelion
Angle of incidence
Zenith angle
Angle at which sunlight hits the earth’s surface
(measured from directly overhead)
Winter solstice 66.5 degees
Summer solstice 19.5 degrees
Large zenith angle =>
Solar energy is spread over a larger area, so Less heating
Smaller Zenith angle =>
solar energy is spread over a smaller area, so more heating
Clouds and the diurnal cycle
Daytime: Reduce the amount of solar radiation reaching the surface
Nighttime: Reduce the amount of longwave radiation excaping
Water molecule:
Unique design gives rise to positive and negative polarity
Polarity => molecules are sticky
Solid (ice)
Least energy
Molecules held together in crystal form (vibrate, but dont move around)
Liquid
Molecules have more energy (they move around)
but still “sticky”
Vapor
Molecules have much more energy
Bounce off each other rather than sticking together
Humidity
How much water vapor is in the air
How do we measure humidity?
Mixing ratio
Vapor pressure
Relative humidity
Dewpoint temperature
Mixing ratio
ratio of the mass of water vapor in a given volume of air to the mass of other molecules in that volume
Mass of water vapor / Mass of dry air
Mixing ratio does not change if the temperature changes
Evaporation __________ mixing ratio
increases
Condensation ___________ the mixing ratio
decreases
Vapor pressure
“Partial” pressure exerted by only water vapor
Water vapor exerts pressure on sides of container:
vapor pressure
Eventually, rate of evaporation = rate of condensaiton:
saturation
Saturation:
Occurs when rate of evaporation equals the rate of condensation
Mixing ratio
Measures how much water vapor is actually in the air
Saturation mixing ratio
Mixing ratio that air would have if it were saturated at its current temperature
Warm air
more energetic molecules => higher saturation mixing ratio
Cold Air
less energetic molecules => lower saturation mixing ratio
Relative Humidity
Ratio of actual water vapor in the air to the amount of water vapor required for saturation
actual mixing ratio / saturated mixing ratio
How do we change relative humidity?
- Change the amount of water vapor in the air
- Change air temperature
What determines the saturated mixing ratio?
Actual temperature
Actual mixing ratio is determined by what?
dew point temperature
Dew Point Temperature
Temperature the air must cool to, to become saturated
Actual mixing ratio determined by Dew Point Temperature
how to remember?
Q: how do we determine how much water is actually in the air?
A: Cool the air until condensation occurs, then measure it’s temperature
*this is the dew point temperature
Problem: it’s harder to condense onto a curved surface than onto a flat surface
Solution: Some aerosols in the atmosphere facilitate droplet formation
Aerosols
Small particles (dust, soot, sulphuric acid droplets, salt) suspended in the atmosphere
- water does not readily condense into drops on its own
- water DOES condense onto “hygroscopic aerosols”
Continental Aerosols
>100,000 per cm^3, Anthropogenic 30% of all aerosols
Crustal Aerosols: erosion of earth’s surface (dust storms, desert)
Combustion and secondary aersols: anthropogenic activities; primarily N. America, Europe, Asia
Carbonaceous Aerosols: Soot, biomass burning, pollen, spores; many tropical sources
Marine Aerosols
~1,000 per cm^3
Salt (as bubbles pop), Di-methyl sulfide (DMS)
___________ aerosols over continental regions than over maritime regions
Many, many more
*For the same amount of liquid water in a cloud, continental clouds have smaller, and a lot more cloud droplets than marine
Hygroscopic (water seeking)
Sulfate aerosols, salt
Hygrophobic (water fearing)
Oils, gasoline, paraffin waxes
Radiation fog
Cooling on clear nights
- light winds required
- Common in valleys
Advection fog
As warm air is advected over a cold surface, it cools to the dewpoint temperature
Evaporation / steam / mixing fog (frontal fog)
Form when water evaporates into the air, eventually saturating the air
- Can occur with rainfall - associated with inversions and warm fronts
- Also when cold air flows over a warm lake (steam fog)
Upslope fog
Rising air cools to saturation
Lifting mechanisms that form clouds
Most clouds form when air cools to the dew point as a parcel of air rises vertically as an updraft
Lifting Condensation Level (cloud base)
As unsaturated air rises, it cools at 10 degrees Celsius/km
The dewpoint temperature cools at 2 degrees Celsius/km
Eventually, the actual air temperature catches up to the dewpoint, any further rising and condensation will occur
Cloud base is _______________ difference between the temperature and the dew point (125 m per degree)
1 km per 8 degrees Celsius
Ways that air can be forced upward
Orographic lifting
Frontal lifting
Convection
Convergence
Orographic lifting
Air flows up over a mountain
Frontal lifting
When less dense warmer air is forced to rise over coler, denser air
Convection
Air near the surface warms and rises
Convergence
When air near the ground converges, or is squeezed together, and rises
Dry adiabatic lapse rate =
10 degrees Celsius / 1000m
*adiabatic means that no heat is added/removed from the parcel
Dry Adiabatic
No heat is exchanged with the environment, no condensation - only work is done
Moist adiabatic lapse rate =
6 degrees Celsius / 1000 m (in lower troposphere)
Moist adiabatic
No heat is exchanged with the environment - work is done and latent heat is released
Latent heat adds 4 degrees Celsius per km
Cloud Condensation Nuclei (CCN)
~0.2um
Cloud droplets
~20 um
Rain drops
~2000 um (2mm)
Largest raindrop ever recorded
8.8 mm
Condensation
Air cools to dew point, condenses into drops
Saturated vapor pressure for flat surface is ________ than that for curvy surface
less
*very difficult for “more curvy” (small) drops to form than big drops
Terminal Velocity
Occurs when gravitaitonal force equals force due to air resistence
Air Resistence
Slows rate at which drops fall
Proportional to velocity times surface area
Gravitational force
Causes rain drops to fall
Proportional to mass
Terminal velocity is proportional to the ______________
size of the raindrop
Large drops grow by colliding with small drops:
coalescence
Thin clouds, weak updrafts
Small drops form, may produce drizzle
Thick clouds, strong updrafts
large drops form, may produce heavy rain
Cloud droplets don’t:
spontaneously freeze at sub-zero temperatures, until about -40 degrees Celsius
May more ____________ than ice crystals in non-glaciated, supercooled cloud regions
liquid cloud droplets
Saturated mixing ratio for liquid water drops is _____________ than that for ice
GREATER
Ice particle that happens to be next to a liquid water droplet
Air is saturated for the liquid water droplet
Air is super-saturated for the ice particle
=> ice particle GROWS
Ice particles grow at the expense of ____________
liquid water droplet
Accretion
Crystals grow as supercooled drops instantly freeze
Forms “graupel”
Aggregation
Falling crystals stick together, form snowflakes
Stratus
“Layer” => sheetlike clouds
Cumulus
“Heap” => puffy clouds
Cirrus:
“Hair” => wispy clouds
Nimbus
“Rain” => rain clouds
High clouds
Cirrus
Cirrostratus
Cirrocumulus
Middle clouds
Altostratus
Altocumulus
Low clouds
Stratus
Stratocumulus
Nimbostratus
Clouds with vertical development
Cumulus
Cumulonimbus
Stratus
like fog hovering above the ground
Nimbostratus
Preciptating stratus
Stratocumulus
low-lying clouds combining layered and convective cloud types
Cumulus
Flat bases and intricately contoured domed tops
- fair weather cumulus
- cumulus congestus => tall relative to their width
– can produce brief heavy rain
Altostratus
Layered clouds made up mostly of water droplets
Altocumulus
Similar to stratocumulus with a higher base
Cirrocumulus
Similar to altocumulus but made of ice and have smaller elements
Cirrostratus
layerlike, uniform, made of ice
Cirrus
Wispy, fibrous clouds made of ice
Cumulonimbus
Thunderstorm clouds
- extend to high altitudes
- produce large amounts of precipitation, severe weather, and even tornadoes
- flattened anvil shape of the top of the cloud
- Under the anvil, sinking air may create pouches called mammatus
Temperature is a measure of:
the average kinetic energy
infared atmospheric window
Atmospheric gases only weekly emit and absorbe in the 10µm-12um
This spectral region is referred to as the infared atmospheric window because the atmosphere is relatively transparent to infared radiation emitted by the surface at these wave lengths
Greenhouse gases
Gases that are transparent to solar energy while absorbing terrestrial energy will warm the atmosphere because they allow solar energy to reach the surface and inhibit longwave radiation from reaching outer space
examples: CO2, water vapor, ozone, nitrous oxide, and CFCs
Methane and CFCs are important despite their small concentrations
What factors influence temperature cycles?
Latitude
Surface type
Elevation and aspect
Relation to large bodies of water
Advection
Cloud cover
Diurnal temperature cycle
The repeating pattern of daily temperatures
Includes the maximum and minimum daily temperatures and the times of day that they usually occur
Temperature inversions
Regions of the atmosphere in which the temperature increases with altitude
Cloud Condensation nuclei (CCN)
Aerosols that asist in forming liquid droplets
examples: dust, salt, pollen, and other small particles
Ice nuclei - particles around which the ice crystals form, important in the beginning stages of ice crystal formation
Fog Formation
Radiation fog
Advection fog - blown horizontally
Evaporation fog
Upslope fog
Collission - Coalescence
The process by which precipitation forms in warm clouds
Drops of different sizes collide and merge, leading to rapid growth into a raindrop
The Bergeron process
Ice particles grow at the epense of liquid water droplets
This occurs because the saturated vapor pressure over ice is less than that over liquid water
This process is most important in cold clouds
Stages of a cyclone
- Birth (frontal wave)
- Young adult (open wave)
- Mature (occluded cyclone)
- Death (cut-off cylone)
Cyclogenesis
The cycle of cyclone birth and growth
Preferred regions of cyclone development
Panhandle Hooks (Colorado to Oklahoma and Texas Panhandles)
Nor’easters (develop along the East Coast over the Gulf Stream near Cape Hatteras, North Carolina)
Alberta Clippers (Pacific Northwest)
Pineapple express (jet stream blowing northeast from Hawaii)
The Normal is:
The direction perpendicular to the surface
Reflection
The incident angle with the “normal” equals the outgoing angle
Refraction
Light slows as it enters a medium of greater density - speeds as it enters of medium of lesser density
*light bends toward the normal as it enters a more dense medium
*light bends away from the normal as it enters a less dense medium
Refraction and Dispersion
Refraction and Dispersion: Refraction causes somewavenths to bend more than others: blue bends more than red light
Scattering
Incoming light gets sent in all directions
Why are sunsets red/orange
Near the horizon, light travels through more atmosphere than when directly overhead, so more blue light is scattered away
Crepuscular Rays
Light is “equaly scattered” by large particles
Mirages: Refraction
Sunrise / Susent occur about 2 minutes before / after than the sun actually passes above / below the horizon
Inferior Mirage:
Light enters a LESS dense medium (very warm near surface
Superior Mirage
Light enters a LESS dense medium (through a surface inversion)
Halos and Sundogs
Light refracts through columnar ice crystals high in the atmosphere
Sundogs
Occur when light refracts through hexagonal ice crystals high in earth’s atmosphere
Rainbows
Occur when sunlight enters a raindrop and the light bends (refraction) then reflects off the back of the raindrop
Rainbows are at the apex of a ____________ degree angle between you and the sun
42
hen do secondary rainbows form?
When there is a double internal reflection
