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PHYS-575/CSI-655PHYS-575/CSI-655Introduction to Atmospheric Physics and ChemistryIntroduction to Atmospheric Physics and Chemistry

Lecture Notes 1 – Part 1 Earth: The water planet Take a deep breath Some basics

ideas/concepts Why study the

atmosphere? Climate change issues Survey of planetary

atmospheres

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Earth – The Water PlanetEarth – The Water Planet

Is there anything in this picture that is not influenced by water?

Is there anything in this picture not influenced by life?

Is there anything in this picture not influenced by the atmosphere?

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What is Atmospheric Science?What is Atmospheric Science?

Atmospheric Science is an applied discipline that is concerned with the structure and evolution of planetary atmospheres and with the wide range of phenomena that occur within them.

Atmospheric Science includes:

- weather and weather forecasting - climate and climate change - atmospheric chemistry

- atmospheric observations Atmospheric Science overlaps many traditional disciplines: - physics, chemistry, geology, biology, astronomy (e.g. biogeochemical cycles of carbon, oxygen, nitrogen….)

In general, Atmospheric Science is the study of the characteristics of the thin gaseous envelope around a planet, its interactions with the planet below and space above, and its evolution over time.

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The EarthThe Earth’’s Atmosphere is Thins Atmosphere is Thin

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Atmospheric LayersAtmospheric Layers

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What is the air we breath?What is the air we breath?

D. Bodanis “It’s in the air: skin, stardust, radio waves, vitamins, spider legs” Smithsonian Magazine, April, 1995.

What is in one breath of air?Atoms and Molecules: ~ 3 x 1022 mostly O2 and N2 molecules; elements forged by nuclear reactions in the interiors of stars.

Oxygen (O2) cycles through the biosphere (photosynthesis and respiration) roughly every 6000 years. Nitrogen (N2) cycles with a 2 million year time scale.

These molecules move at near the speed of sound and experience billions of collisions per second.

How many molecules in one breath of air were at one timebreathed by Julius Caesar?

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What is in the air we breath?What is in the air we breath?

A Few of the Other Gases in the Atmosphere:

Methane (CH4) from cows belching… Argon (Ar) from extinct volcanoes Water vapor (H2O) from impacting comets and

meteorites over 4.5 BYA, or released from the deep interior of the Earth.

Carbon Dioxide (CO2) from respiration and fossil fuel burning.

Hydrogen Sulfide (H2S) from blue-green algae

Overall, there are more than 2000 measurable trace gases in a liter of air.

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ItIt’’s in the Air…s in the Air…

Even the cleanest liter of air has a vast amount of particulate matter.Dust: ~ 100,000 dust particles of wide range of compositions: sea salt – many thousands per cc. pollen, spores – tens of thousands broken bits of insect (mostly spider) legs - thousands smoke (soot) from around the world - thousands meteoric dust from outer space - thousands DNA fragments from decaying bacteria, skin flakes, soil, pet fur, dander, dust mites millions of bacteria from your classmates.

Even the cleanest “Clean Room” has > 10000 particles per liter of air.

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Atmospheric CompositionAtmospheric Composition

Concentration

Number density: molecules/cm3

Fractional Concentration:No. of molecules/total density

Fractional concentration isalso referred to as:

- Mixing Ratio- Molar Fraction- Volume Mixing Ratio

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What Determines the What Determines the Atmospheric Composition?Atmospheric Composition?

Almost all atmospheric gases are produced/consumed or moderated by life.

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Primary Productivity (photosynthesis)

Where does Oxygen (O2) come from?

Biological organisms, via photosynthesis, metabolize water and carbon dioxide to formcarbohydrates and produce oxygen as a by-product.

Photosynthesis: (+sunlight)Water + carbon dioxide glucose + oxygen6 H2O + 6 CO2 C6H12O6 + O2

Green trees and plants are the major sourceof oxygen on land.

Phytoplankton are capable of consuming thenutrients in the euphotic zone of the oceanin a matter of days, requiring continual replenishment.

Respiration is the reverse process which oxidizes organic material and removes O2.

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Oxygen Sources, Reservoirs and CyclesOxygen Sources, Reservoirs and Cycles

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Atmospheric Nitrogen – Sources and SinksAtmospheric Nitrogen – Sources and Sinks

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The Carbon CycleThe Carbon Cycle

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Primary Drivers of Biogeochemical CyclesPrimary Drivers of Biogeochemical Cycles

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Atmospheric Description:Atmospheric Description:Vertical Temperature Structure of the EarthVertical Temperature Structure of the Earth ’’s Atmospheres Atmosphere

The characteristics of thevertical temperature profileare produced by heatingand/or cooling processes.

Troposphere - weather

Stratosphere - ozone

Mesosphere - meteors

Thermosphere - ions

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Fundamental Relationships:

Downward force (weight) due to gravity (g = gravitational acceleration):

(F = force per unit volume; ρ = mass density)Pressure is due to the overlying weight of atmosphere:

Thus, P = mg (where m is mass of atmosphere per unit area)It follows that the change in pressure with altitude is

This is known as the Hydrostatic Relationship. It implies that pressure decreases exponentially with altitude, which we will see later.

0

gdzP

gdz

dP

gF

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The Ideal Gas LawThe Ideal Gas Law

Where R is the gas constant, ρ is mass density,

and T is the temperature in Kelvin.

Alternatively:

Where k is the Boltzman Constant, n = # density

RTP

nkTP

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Vertical Vertical Density Density StructureStructure

If pressure decreasesexponentially with altitude,then density will decreaseat the same rate.

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Horizontal Variation on a Wide Range of ScalesHorizontal Variation on a Wide Range of Scales

http://rst.gsfc.nasa.gov/Sect14/milthorpeincus.jpg

SEAWiFS Image

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Coordinate SystemCoordinate System

Latitude – measured from equator

Longitude – measuredWRT to Greenwich meridian

Altitude – measuredWRT sea level

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The Atmospheric General Circulation:The Atmospheric General Circulation:Driven by Differential Solar HeatingDriven by Differential Solar Heating

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Zonal Zonal Average Average StructureStructure

Zonal averages are2 dimensional averagevalue of winds, temperature, etc., around a latitude circle

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Circulation: Highs and LowsCirculation: Highs and Lows

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Trade WindsTrade Winds

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Winds, Winds, Rainfall, Rainfall, Surface Surface

TemperatureTemperature

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Idealized Surface Winds vs. Actual Surface WindsIdealized Surface Winds vs. Actual Surface Winds

http://z.about.com/d/space/1/7/e/e/pia01347.jpg

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Sea Surface Temperature, Land Surface Sea Surface Temperature, Land Surface Temperature, and CloudsTemperature, and Clouds

http://www.mhhe.com/earthsci/geology/mcconnell/earths_climate/images/temp_cloud_map.gif

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Precipitation (mm)Precipitation (mm)

http://www.geo.arizona.edu/Antevs/nats104/sld15b.gif

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Atmospheric Structure: Atmospheric Structure: Variability and Internal/External InfluencesVariability and Internal/External Influences

http://www-frd.fsl.noaa.gov/mab/scatcat/khwavephoto-opt2.jpg

Kelvin-Helmholtz Breaking Waves

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Volcanic Influences on the AtmosphereVolcanic Influences on the Atmosphere

This eruption occurred at the Chaiten Volcano in Southern Chile on May 7, 2008.

http://cache.io9.com/assets/resources/2008/05/chilevolcano.jpg

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Solar Influences on the EarthSolar Influences on the Earth

http://stereo.gsfc.nasa.gov/img/spaceweather/preview/tricompSW.jpg

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Continued Evolution – Human InfluencesContinued Evolution – Human Influences

Mauna Loa

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The Antarctic Ozone The Antarctic Ozone HoleHole

Ozone Depletion is a Global Phenomena.

But the arctic regions, in particular the Antarctic, actsto magnify the ozone depletionat certain times of the year.This is known as the Ozone Hole.

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Current interest in past and future climates is due to several factors:

Detailed reconstructions of past climates show that the climate has varied on all time scales from decades to millions of years.

Research focused on human activities on the environment has demonstrated that humans are influencing climate.

And finally, there is observational evidence that world climate is changing rapidly (IPCC, 2007).

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Intergovernmental Panel Intergovernmental Panel on Climate Change (IPCC)on Climate Change (IPCC)

Fourth Assessment Fourth Assessment Report (2007)Report (2007)

Global Average Temperature

Global Average Sea Level

Northern Hemisphere Snow Cover

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Weather PredictionWeather Prediction

Weather Prediction is the mostpractical application of atmosphericscience. But refinements in weatherprediction require improvementsin our understanding of the entireatmospheric system and the variousexternal and internal forcing mechanisms.

Furthermore, understanding the structure and evolution of the atmosphere of other planets gives us a clearer understandingof the range of phenomena possible onEarth. In some cases we have recognized important chemical and physical processes on other planets before we knew of theirimportance for the Earth system.

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Observing the AtmosphereObserving the Atmosphere

Observing Platforms:Balloons – RadiosondesWeather AirplanesWeather RadarWeather Satellites

Atmospheric Variables:TemperaturePressureRelative HumidityWindsTrace Gas Abundances

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Atmospheric Observations: Weather SatellitesAtmospheric Observations: Weather Satellites

http://www.eohandbook.com/eohb05/images/fig_03_(weather).jpg

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Mediterranean Dust & Smoke from the SEAWifs SatelliteMediterranean Dust & Smoke from the SEAWifs Satellite

http://jwocky.gsfc.nasa.gov/aerosols/today_plus/yr2000/seawifs_med000825.jpg

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Greek Fires from MODIS SatelliteGreek Fires from MODIS Satellite

http://earthobservatory.nasa.gov/NaturalHazards/natural_hazards_v2.php3?img_id=14469

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Hurricane Katrina from the SEAWifs SatelliteHurricane Katrina from the SEAWifs Satellite

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Gustav – Projected PathGustav – Projected Path

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What is the source of illumination of the rocket trail?