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Midterm I Review. The most common atmospheric circulation structure. H. L. Cooling or No Heating. Heating. H. L. Imbalance of heating Imbalance of temperature Imbalance of pressure  W ind. Topics we have discussed. Overviews I: Extreme weather and climate

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The most common atmospheric circulation structure
The most common atmospheric circulation structure

H

L

Cooling

or No Heating

Heating

H

L

  • Imbalance of heating

  • Imbalance of temperature

  • Imbalance of pressure

  •  Wind


Topics we have discussed
Topics we have discussed

  • Overviews I: Extreme weather and climate

  • Overview II: Success and failure of weather and climate prediction

  • Overview III: Why is it so difficult to predict weather and climate?

  • Evolution of the atmosphere

  • The incoming solar energy

  • What cause the four seasons?

  • What is the greenhouse effect?

  • Vertical structure of the atmosphere

  • What set the atmosphere in motion?

  • How does air move around the globe?


The mission of the atmospheric sciences is to understand and predict weather, climate, and related disasters


Overview i extreme weather and climate
Overview predict weather, climate, and related disastersI: Extreme weather and climate

  • Atmosphere: A mixture of gas molecules, microscopically small particles of solid and liquid, and falling precipitation

  • Meteorology: The study of the atmosphere and the processes that form weather

  • Weather: The state of the atmosphere at a given time and place

  • Climate: The statistical properties of the atmosphere. (i.e. averages and variability)

  • Weather- and climate-related disasters: tropical cyclones, tornados, floods, droughts, winter storms, extreme heat, extreme cold, lightning, El Nino, global warming

  • Impacts of weather/climate on agriculture, business, international relationships, history, science, philosophy, public health, psychology, social work, education, …


Weather and climate related disasters
Weather- and Climate-related Disasters predict weather, climate, and related disasters



Overview ii success and failure of weather and climate prediction
Overview Transportation, Education, …II: Success and failure of weather and climate prediction

  • The modern climatology (meteorology) was born in the 1940s (a very young science!), but has been growing very fast! Now we have a global observational network with many satellites, ships, radars and surface stations, as well as very comprehensive prediction models running on the world’s fastest supercomputers.

  • The current status of weather and climate predictions: (1) weather prediction good to 10 days, (2) tropical cyclone prediction good in track but not in intensity, (3) climate prediction good to two seasons, (4) climate change projections have a 3-fold difference in magnitude.


Observing the atmosphere
Observing the atmosphere Transportation, Education, …


World s major climate modeling centers
World Transportation, Education, …’s major climate modeling centers


Overview iii why is it so difficult to predict weather and climate
Overview III: Why is it so difficult to predict weather and climate?

  • The main reasons of the difficulties: (1) Teleconnection problem, (2) Feedback problem, and (3) Subgrid-scale problem, (4) Limitation of concept/theory/model.


Problem I climate?: Different parts of the world are strongly connected to each other (The “Teleconnection Problem”)

Global atmospheric flow


Factors affecting us weather and climate
Factors affecting US weather and climate climate?

Arctic

N. Atlantic

Atlantic/ Sahel

Madden-Julian Oscillation

El Nino

Amazon


Any location is climate?affected by all the other locations, and in turn is affecting all the other locations


Problem II: Different components of the earth system (atmosphere, land, ocean, ice, clouds, etc) are strongly interacting with each other (The “Feedback Problem”)


Problem III (atmosphere, land, ocean, ice, clouds, etc) are strongly interacting with each other : The global climate models divide the earth into many small pixels (called grids), but the earth system composes of both very big objects (such as the whole Pacific Ocean) and very small objects (such as the cloud droplets), making it very difficult to draw them on the same page (The “Subgrid-Scale Problem”)


Evolution of the atmosphere
Evolution of the atmosphere (atmosphere, land, ocean, ice, clouds, etc) are strongly interacting with each other

  • The standard units of measurements (SI)

  • Earth’s three atmospheres:

    1st: 4.6 billion years ago, H, He

    Transition: formation of magnetic field, volcano activities

    2nd: 4 billion years ago, CO2, H2O, N2

    Transition: emergence of life, formation of ocean

    3rd: 400 million years ago, O2

    Important event: formation of seven continents

  • What is the residence time? What is the difference between the permanent and variable gases? Name 3 of each. What are the most and second most abundant gases?

  • Given that variable gases are so rare, why are they considered at all? How are CO2 and O3 changing?

  • Earth’s climate history: ice ages (at least 5 have occurred so far. We’re in an ice age!), 100,000-year cycle, little ice age (1350-1850AD)


Standard units of measurement si system international
Standard units of measurement (atmosphere, land, ocean, ice, clouds, etc) are strongly interacting with each other SI (System International)

Quantity Name Units Symbol

Length meter m m

Mass kilogram kg kg

Time second s s

Temperature Kelvin K K

Density kilogram kg/m3 kg/m3

per cubic meter

Speed meter per m/s m/s

second

Force newton m.kg/s2 N

Pressure pascal N/m2 Pa

Energy joule N.m J

Power watt J/s W


Evolution of the sun and the earth
Evolution of the Sun and the Earth (atmosphere, land, ocean, ice, clouds, etc) are strongly interacting with each other

The Earth was born 4.6 billion years ago.


Permanent gases and variable gases
Permanent gases and variable gases (atmosphere, land, ocean, ice, clouds, etc) are strongly interacting with each other

  • Residence time: The amount of time a gas is in the atmosphere

  • The permanent gases: gases having long residence times (N2=42,000,000 y, O2=5,000 y), 99.999% of total atmosphere mass

  • The variable gases: Gases generally having shorter residence times (H2O=10 days, CO2=150 y).


Importance of the variable gases

IPCC (2001) (atmosphere, land, ocean, ice, clouds, etc) are strongly interacting with each other

Importance of the Variable Gases

  • CO2 and water vapor are the major greenhouse gases

  • Water can exist in all three states on Earth. Global water cycle is the process of water being cycled from the planet to the atmosphere and back again.

  • O3 protects us against harmful ultraviolet radiation

Change of CO2

Montreal Protocol in 1987 to ban freons

Change of O3


The incoming solar energy
The incoming solar energy (atmosphere, land, ocean, ice, clouds, etc) are strongly interacting with each other

  • What is energy? 3 methods of energy transfer

  • The names of the 6 wavelength categories in the electromagnetic radiation spectrum

  • Intensity of radiation (Stefan-Boltzman law): I=T4

  • Wavelength of radiation (Wein’s law): max = b/T

  • The wavelength range of Sun (shortwave) and Earth (longwave) radition

  • The 11-year solar cycle


Methods of energy transfer
Methods of (atmosphere, land, ocean, ice, clouds, etc) are strongly interacting with each other Energy Transfer

  • Conduction

    • Molecule to molecule transfer

    • Heat flow: warm to cold

    • e.g. leather seats in a car

  • Convection

    • transferred by vertical movement

    • physical mixing

    • e.g. boiling water

  • Radiation

    • propagated without medium (i.e. vacuum)

    • solar radiation provides nearly all energy

    • The rest of this chapter deals with radiation


The electromagnetic spectrum
The Electromagnetic Spectrum (atmosphere, land, ocean, ice, clouds, etc) are strongly interacting with each other

Sun =

“shortwave”

(0.4-0.7 μm) Peak 0.5 μm (green)

The limitations of the human eye!

Earth =

“longwave”

(4-100 μm) Peak 10 μm (infrared)


What cause the four seasons
What cause the four seasons? (atmosphere, land, ocean, ice, clouds, etc) are strongly interacting with each other

  • The two basic motions of the Earth

  • What causes the four seasons: the Earth’s tilt and the 3 ways it affects the solar insolation (change of length of the day, beam spreading, beam depletion)

  • Change of the Earth’s orbit at longer time scales (Milankovitch cycles): eccentricity, axial tilt, and precession


  • Length of Daylight period (atmosphere, land, ocean, ice, clouds, etc) are strongly interacting with each other

  • Angle at which sunlight hits the surface (“Beam Spreading”)

  • Thickness of atmosphere through which sunlight must travel (“Beam Depletion)

The Earth’s two basic motions: revolution with a period of 1 year, and rotation with a period of 1 day.The change of seasons is caused by the Earth’s 23.5o tilt from the line perpendicular to its orbit plane (toward the sun during summer), which affects the receipt of solar insolation in three ways:


What is the greenhouse effect
What is the greenhouse effect? (atmosphere, land, ocean, ice, clouds, etc) are strongly interacting with each other

  • Earth’s energy balance at the top of the atmosphere and at the surface. What percentage of solar energy is absorbed by the surface?

  • Atmospheric influences on radiation (3 ways)

  • The three types of atmospheric scattering. What causes the blue sky? Why causes the reddish-orange sunsets?

  • What cause the greenhouse effect? What are the major greenhouse gases? Why is methane important?

  • Sensible heat flux (dry flux from warm to cold regions) and latent heat flux (wet flux from wet to dry regions)


Earth s energy budget averaged over the whole globe and over a long time
Earth (atmosphere, land, ocean, ice, clouds, etc) are strongly interacting with each other ’s energy budget (averaged over the whole globe and over a long time

Yellow: shortwave

Red: longwave

  • At the top of the atmosphere (3-way balance):

    Incoming shortwave = Reflected Shortwave+ Emitted longwave

  • At the surface (5-way balance):

    Incoming shortwave = Reflected shortwave + Net emitted longwave (emitted - incoming)

    + Latent heat flux + sensible heat flux

Net Longwave 21%

Sensible heat 7%

Latent heat 23%


Atmospheric absorption the greenhouse effect
Atmospheric absorption - The Greenhouse Effect (atmosphere, land, ocean, ice, clouds, etc) are strongly interacting with each other

Transparent to solar (shortwave) radiation

Opaque to earth’s (longwave) radiation

Major GH gases: CO2, H20(v), CH4

The greenhouse effect helps to keep the earth surface at a comfortable temperature. But when it’s too strong, the temperature becomes too warm.


The importance of methane ch 4
The importance of methane (CH (atmosphere, land, ocean, ice, clouds, etc) are strongly interacting with each other 4)

  • 23 times more powerful as a greenhouse gas than CO2

  • The livestock sector is a major player, which accounts for 35-40% global anthropogenic emissions of methane (their burps!)

  • The livestock sector is responsible for 18% of total greenhouse gas emissions, which is higher than transportation (cars, airplanes, etc)

  • Therefore, consuming less meat is more efficient in reducing global warming than not driving cars.


Vertical structure of the atmosphere
Vertical structure of the atmosphere (atmosphere, land, ocean, ice, clouds, etc) are strongly interacting with each other

  • Thickness of the atmosphere: less than 2% of Earth’s thickness

  • Definition of temperature. 3 units.

  • Definition of pressure and its unit.

  • Definition of pressure gradient. Pressure gradient sets the air in motion.

  • Equation of state (P=ρTR)

  • Vertical Pressure Distribution. How does pressure change with height? What is the hydrostatic equilibrium?


Temperature pressure winds
Temperature, pressure, winds (atmosphere, land, ocean, ice, clouds, etc) are strongly interacting with each other

  • Temperature – measure of average kinetic energy (motion) of individual molecules in matter. 3 units: Kelvin (K), Celsius (C), Fahrenheit (F)

  • Pressure – force exerted/unit area (weight above you). units - Pascals (Pa) or millibars (mb) (1 mb = 100 Pa)

  • Pressure gradient – pressure difference between two locations divided by the distance between those two locations

  • Winds

    • Zonal winds (east-west): Eastward is called westerly

    • Meridional winds (north-south): Northward is called southerly


Temperature layers
Temperature Layers (atmosphere, land, ocean, ice, clouds, etc) are strongly interacting with each other

The names of the 4 layers

What separate them?

The approximate height of tropopause, stratopause and mesopause


Vertical pressure distribution hydrostatic equilibrium
Vertical pressure distribution: Hydrostatic equilibrium (atmosphere, land, ocean, ice, clouds, etc) are strongly interacting with each other

  • Pressure decreases with height

    Becausedownward gravity force is balanced by vertical pressure gradient force (called hydrostatic equilibrium)

    Δp/Δz = ρg

  • Pressure decreases non-linearly w/ height (Because air is compressible, so denser near the surface)

Δp/Δz

ρg


What set the atmosphere in motion
What set the atmosphere in motion? (atmosphere, land, ocean, ice, clouds, etc) are strongly interacting with each other

  • Know 3 Forces that affect wind speed /direction

  • Especially work on Coriolis force, as this is the hardest to understand. Which direction is air deflected to by Coriolis force?

  • What is the geostrophic balance? At which level is it valid? Difference between upper level and surface winds

  • Troughs, ridges, cyclones and anticyclones. Do they correspond to high or low surface pressure? Is the air moving clockwise or counter-clockwise around them?


Forces affecting the horizontal winds (atmosphere, land, ocean, ice, clouds, etc) are strongly interacting with each other

  • Horizontal pressure gradients responsible for wind generation

  • Three forces affecting horizontal winds:

    • Pressure Gradient Force  (PGF)

    • Coriolis Effect  (CE)

    • Friction Force (FF)

CE:

  • The Earth’s rotation deflects any moving object to the right of its moving direction in NH (left in SH). Like walking in a turning bus.

  • CE increases poleward (greatest at the poles, 0 at the equator), and increases with the speed of moving object


Geostrophic balance geostrophic flow
Geostrophic Balance (Geostrophic flow) (atmosphere, land, ocean, ice, clouds, etc) are strongly interacting with each other

  • PGF = - CE

  • When the effects of friction can be neglected (such as in the upper air away from surface roughness), the wind speed/direction is simply a balance between the PGF and CE.

  • Air motion is deflected by the Coriolis force to be perpendicular to PGF

PGF


Cyclones, Anticyclones, Troughs and Ridges (atmosphere, land, ocean, ice, clouds, etc) are strongly interacting with each other

Upper air: isobars usually not closed off

  • Troughs (low pressure areas)

  • Ridges (high pressure areas)

    Near surface: isobars usually closed off due to surface friction

  • Cyclones(Low pressure areas)

  • Anticyclones(High pressure areas)


How does air move around the globe
How does air move around the globe? (atmosphere, land, ocean, ice, clouds, etc) are strongly interacting with each other

  • Three precipitation (heating) belts. Primary high and lows

  • Three-cell model. Mechanism for each cell

  • Two characteristics of zonal mean temperature structure

  • Two characteristics of zonal mean wind structure. Why does westerly winds prevail in the extratropical troposphere? What cause the jet streams?

  • Semipermanent pressure cells. Low pressure is associated with clouds and precipitation. High pressure is associated with warm surface temperature, drought, and desert.

  • What drives the ocean surface currents? In the case of Ekman spiral, what is the direction of surface current relative to surface wind?


Vertical structure and mechanisms
Vertical structure and mechanisms (atmosphere, land, ocean, ice, clouds, etc) are strongly interacting with each other

  • Polar Cell (thermal):

  • Driven by heating at 50 degree latitude and cooling at the poles

  • Ferrel Cell (dynamical): Dynamical response to Hadley and polar cells

  • Hadley Cell (thermal): Heating in tropics  formssurface low and upper level high air converges equatorward at surface, rises, and diverges poleward aloft  descends in the subtropics

Polar

Hadley


Vertical structure of temperature
Vertical structure of temperature (atmosphere, land, ocean, ice, clouds, etc) are strongly interacting with each other

Two characteristics:

  • Horizontally uniform in the tropics

  • Steep gradient in the extratropics


Vertical structure of zonal wind
Vertical structure of zonal wind (atmosphere, land, ocean, ice, clouds, etc) are strongly interacting with each other

Two characteristics:

  • Westerly winds in the extratropical troposphere (caused by the Coriolis force)

  • Jet streams: local maximum of winds (caused by sharp pressure gradient across the boundary between warm tropical air and cold polar air)


General circulation of the oceans

Ocean surface currents (atmosphere, land, ocean, ice, clouds, etc) are strongly interacting with each other – horizontal water motions

Transfer energy and influence overlying atmosphere

Surface currents result from frictional drag caused by wind - Ekman Spiral

General circulation of the oceans

  • Water moves at a 45o angle (right)

  • in N.H. to prevailing wind direction

  • Due to influence of Coriolis effect

  • Greater angle at depth


About the midterm
About the midterm (atmosphere, land, ocean, ice, clouds, etc) are strongly interacting with each other

  • There will be ~50 multiple-choice questions

  • Please pay special attention to the key points highlighted in red on the review slides (some easy grades)

  • Sample questions


  • In the SI system, the standard unit of length is: (atmosphere, land, ocean, ice, clouds, etc) are strongly interacting with each other

    A) yard, B) meter, C) gram, D) pound.

    2) Which of the following is NOT a variable gas?

    A) water vapor. B) nitrogen. C) carbon dioxide. D) ozone.

  • In the northern hemisphere, when the surface wind blows toward the east, the underlying ocean current flows toward:

    A) the west. B) the north. C) the southeast. D) the northwest.

    4) Anticyclones:

    A) are associated with low-pressure systems in the northern hemisphere.

    B) experience Coriolis effects that deflect air to the left in the Northern Hemisphere.

    C) are associated with supersonic winds.

    D) are associated with counter-clockwise flow in the southern hemisphere.


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