Mid-term review 1Chapter 1

1. Weather and Climate

Climate: “average” weather conditions

Weather: state of the atmosphere at a given time and place. It is constantly changing.

Climate is what you expect, but weather is what you actually get.

2. Four “Spheres” in the Earth System:

Geosphere, Atmosphere, Hydrosphere, Biosphere

3. Systems

A group of interacting parts (components) that form a complex whole.

Reading: P4-6

Reading: P12-P16

Open System:Open System: Energy and Matter can be exchanged between systems

Closed System:Closed System: Exchange of Matter greatly restricted, but may allow exchange of energy

Isolated System:Isolated System: No Energy or Matter can be transferred in or out of the system

4. Feedback

Processes in one system influences processes in another interconnected system by exchange of matter and energy.

Positive Feedback:Positive Feedback: Change in one system causes similar change in the other system. Can cause runaway instability.e.g., water vapor feedback, ice cover feedback

Negative FeedbackNegative Feedback: A positive change in one system causes a negative change in the other.e.g., cloud cover feedback

Reading: P397

5. Composition of the Atmosphere

Major components: Nitrogen (N2), Oxygen (O2), Argon (Ar), Carbon dioxide (CO2), Minute trace gases: water vapor (H2O),Methane (CH4), Ozone (O3), Nitrous Oxide (N2O)Variable components: Water vapor, Aerosol, OzoneAerosol: direct and indirect effect

Ozone: depletion and ozone hole

6. Extent of the Atmosphere

Pressure: Force F acting on unit area due to the weight of the atmosphere. Surface atmospheric pressure: 1000 hPa or 1000 mb

Temperature F C, K, :unit o

273.16 t T 32); (t 9

5 t 32; t

5

9 t FF

Reading: P17-P24

Reading: P24-P25

Thermal Structure of the Atmosphere

Troposphere

Stratosphere

Mesosphere

Thermosphere

•Averaged Surface temperature is 288.16K, or 15C.•Decreases 6.5C per km up to 11 km (lapse rate).•Nearly all weather happens in this layer.•Height of the tropopause varies with latitude with an average of 10 km.

Inversion: Negative lapse rate, temperature increases with height.

Temperature is constant in the lower part of the layer, and then, increases with height due to O3 absorption of solar UV. ~ 99% of the atmosphere is below the stratopause.

Temperature decreases with height in this layer

Temperature increases greatly because air absorbs sunlight.

Reading: P26-P30

Chapter 2

1. Sun-Earth relationship

2. Forms of energy

Earth’s motion, Seasons, Earth’s orientation, Solstices and Equinoxes

Kinetic energy Potential energy

3. Mechanisms of Energy Transfer

Conduction, convection, and radiation

4. Laws of blackbody radiation

Stefan-Boltzman law, Wien’s displacement law, Plank’s law

Heat

6000K

300K

Reading: P36-P42

Reading: P43-P44

Reading: P44-P47

Reading: P47-P48

5. Selective absorption and emission of atmospheric gases

Electronic excitationPhotoionization

M M e

overlap

Almost all solar radiations shorter than ultraviolet are used up in the upper layer for photoionization, electronic excitation, and molecule dissociation. Since most of solar energy is in the visible band, they have nothing to do with molecule vibration and rotation transition, so solar radiation can reach Earth's surface almost without any attenuation. On the other hand, terrestrial radiation in the infrared band, which is involved with atmospheric molecule vibration and rotation transitions, can be absorbed by the atmosphere to cause greenhouse effect.

6. Greenhouse Effect

Shortwave solar radiation is nearly transparent to the atmosphere, but longwave terrestrial radiation is trapped by greenhouse gases, causing the increase of surface temperature.

7. Atmospheric windowHighly un-reactive greenhouse gases containing bonds of fluorine-carbon or fluorine-sulfur, such as Perfluorocarbons (CF4, C2F6, C3F8) and Sulfur Hexafluoride (SF6). These trace gases have strong absorption lines right in the atmospheric window.

Clouds can also absorb longwave radiation in the atmospheric window.

Reading: P54-P55

Reading: P53-P54

8. Solar constant: incoming solar radiation per unit area at the top of the atmosphere

9. Radiative Equilibrium, Radiative-covection Equilibrium

10. Heat Budget of Earth’s Atmosphere Reading: P56

11. Latitudinal energy balance

12. Transport by atmospheric motion and ocean currents

Chapter 31. Air Temperature Isotherms

2. Controls of TemperatureDifferential heating of land and water; Ocean currents; AltitudeGeographic position; Cloud cover and albedo

Temperature gradient Reading: P66-P67

Reading: P68-P75

3. Daily Cycles of Air Tmperature (diurnal)

5. Temperature measurement

Maximum and minimum temperature

Instrument shelters

4. Heat island effect

•Buildings absorb and store more solar radiation.•City surface results in reduction of evaporation.•Heat sources from heating system, air-conditioning, and industry.•Air pollution

Heat stress is caused by high temperature and high humidity.

Wind chill is the cooling power of moving air.

6. Heat stress and wind chill

What controls the diurnal variation?

Reading: P81-P82

Reading: P84-P85

Reading: P86-P90

Reading: P91-P94

7. Temperature Scale Reading: P89-P90

T=t+273

Chapter 4

1. Phase change and latent heat

2. Equation of state, gas law of dry air

K kgJ

dd 287R T;R p

3. Measuring water vapor in the air

Water vapor pressure

K kgJ

vvv 461R T;R e

Mixing ratio, r

Moist virtual effect

Virtual temperature 0.608r)T(1Tv 4. Saturation

Saturated water vapor pressure, E=E(T)

Reading: P98-P102

Reading: P103

Reading: P104-P105

5. Relative humidity, h

6. Dew-point )e(e

9. First law of thermodynamics in the atmosphere

The change in internal energy of a system is equal to the heat added to the system minus the work done by the system.

7. Internal energy U

Energy associated with the random, disordered motion of molecules. U=U(T)

10. Dry adiabatic process

Lifting mechanisms

K/100m 98.0 d 11. Adiabatic lapse rate

Lapse rate of ambient environment

12. Lifting condensation level (LCL)

8. Hydrostatic balance: the balance between upward pressure gradient force and downward gravitational force.

Reading: P106-P108

Reading: P109-P111

Reading: P112-P116