Professor Mandia's Extra Help

CHAPTER 2

PART I

Electromagnetic Spectrum

Energy moves through space in a wide range of wave forms that vary by wavelength. See Fig. 2-1.
The sun emits all wavelengths of radiation but the radiation that reaches the top of the earth's atmosphere is primarily in the form of visible light (0.4 µm to 0.7 µm.) 1 µm = 1 millionth of a meter.
Wavelengths of visible light or shorter are referred to as shortwave radiation.
Wavelengths of infrared radiation (IR) or longer are referred to as longwave radiation.
Earth primarily emits IR radiation.

Receipt and Storage of Solar Heat

The energy received at the top of earth's atmosphere is 342 W/m² (Watts per meter squared) and is called the solar constant.
The amount reaching the Earth's surface averages 240 W/m². See Fig. 2-3.
The Earth's average temperature is 59 ^oF (15 ^oC) which is mostly the result of the greenhouse effect which traps much of the outgoing IR radiation.
The three primary greenhouse gasses are water vapor (H₂O), carbon dioxide (CO₂), and methane (CH₄).
Sun angle also influences the amount of radiation reaching the Earth's surface. See Fig. 2-4.
The amount of solar radiation reflected vs. received is called albedo. Higher albedos mean more reflection. See Table 2-1.
Fig. 2-5 shows pole to equator heating imbalance.
The albedo of liquid water is highly variable and depends on the angle of sunlight. See Fig. 2-6.
Figure 2-7 shows the seasonal variation of radiation received by Earth. The tilt of the Earth strongly influences temperatures.
Box 2-2 shows the albedo-temperature feedback: When there is less incoming solar radiation reaching the earth's surface, temperatures cool. Cooler temperatures mean more ice (high albedo) can be formed. Ice reflects incoming sunlight which further cools the temperature - allowing even more ice to form, etc. Scientists estimate that an initial global cooling of 1 ^oC will be amplified to a total cooling of 1.4^oC due to this feedback.

Heat Capacity

Heat capacity is the ability of a material to store heat and is quantified as density x specific heat.
Water has a very high heat capacity (1 cal/cm³) which is 60 times the heat capacity of land. See Fig. 2-9 and 2-10.
Box 2-3 shows the hydrologic cycle.

Methods of Heat Transfer

See Fig. 2-11.
Conduction - heat that is transferred via molecule to molecule contact. Ex. surface air is heated by touching the warmer surface of the earth.
Radiation - heat that is transferred by wave-like energy (ex. photons) without any molecular contact and with no air movement involved. Ex. Earth is warmed by the sun via radiation.
Convection - heat that is transferred by moving air or water. Ex. warm air rising into the atmosphere transfers heat from the lowest levels to above.
Latent - heat transfer due to a phase change of water. Evaporation requires energy so it is a cooling process while condensation releases energy so it is a warming process.

Adiabatic Process (See the mathematical argument.)

The process which involves a rising or sinking air parcel and the temperature changes associated with that motion.
As an air parcel rises it moves into an area of lower pressure aloft. This lower pressure causes the air parcel to expand. The expansion allows more room for the air molecules inside the parcel to move about. More room means less collisions between the molecules. Fewer collisions means less average KE. Less average KE means cooler temperatures. Therefore, RISING AIR ALWAYS COOLS.
As an air parcel SINKS it moves into an area of higher pressure below. This higher pressure causes the air parcel to compress. The compression allows less room for the air molecules inside the parcel to move about. Less room means more collisions between the molecules. More collisions means greater average KE. Greater average KE means warmer temperatures. Therefore, SINKING AIR ALWAYS WARMS.
The rate of warming or cooling is constant and is known as the adiabatic lapse rate (ALR). The ALR = 5.5 ^oF/1,000 ft. or 10 ^oC/1 Km.

Wind & Global Circulation

There are three major forces that govern wind:
1. PGF
2. Coriolis Effect (Force)
3. Friction
PART II
See Fig. 2-16 for locations of semi-permanent high/low pressure systems. Areas of lower pressure are typically wetter while areas of higher pressure are typically dry.
Along the equator, the area of low pressure is called the Inter-Tropical Convergence Zone (ITCZ).
Between 0^o and 30^o latitude surface winds generally flow from east to west and are called the Trade Winds.
Between 30^o and 60^o latitude surface winds generally flow from west to east and are called the Prevailing Westerlies.
Between 60^o and 90^o latitude surface winds generally flow from east to west and are called the Polar Easterlies.

Monsoons

A monsoon is an atmospheric circulation caused by unequal heating of land vs. water. See Fig. 2-17 and 2-18.
The strongest monsoons occur over India due to the Himalaya Mts. (discussed later in Chapter 7.)
There is a seasonal shift of the ITCZ, partly due to the influence of the Indian monsoon. See Fig. 2-19.

Orographic Lift

Mountain ranges greatly influence climate because air must rise up one side (windward side) and sink down the other side (leeward side.) See Fig. 2-20.
Rising air cools (due to the adiabatic process) on the windward side which causes water vapor to condense into clouds and precipitation. Therefore, the windward side of mountains are cool and wet.
Sinking air warms (due to the adiabatic process) on the leeward side which inhibits condensation. Therefore, the leeward side of mountains are warm and dry.

Heat Transfer in the Oceans

Fig. 2-21 shows the major horizontal surface ocean currents.
Fig, 2-24 shows the major vertical ocean current often called the North Atlantic Conveyor Belt.
Temperature and salinity (salt content) control the formation of deep water. Colder and more salty water sinks while warmer, less salty water tends to remain at the surface.
Ocean water can become more salty at low latitudes by increased evaporation (which leaves the salt behind) or it can become more salty at higher latitudes by the formation of sea ice (called salt rejection.) Sea ice is freshwater so the salt is left behind.
Fig. 2-26 shows the vertical structure of water in the North Atlantic Ocean.
It can take 1000 years for surface water to sink to the "deep water" and then return to the surface.
Deep water may return to the surface due to upwelling. See Fig. 2-27 for examples.

Ice on Earth

Sea ice can greatly influence air temperatures above the ocean. See Fig. 2-28.
Land-based ice can either be mountain glaciers (Fig. 2-29) or continental ice sheets (Fig. 2-30.)
Continental ice sheets are much larger than mountain glaciers. The two existing ice sheets today cover Antarctica and Greenland.
Ice grows by accumulation and ice is lost by ablation.

Earth's Biosphere

The Carbon Cycle describes how carbon moves throughout the earth-atmosphere system. See Fig. 2-32.
Carbon in the atmosphere is primarily CO₂ gas.
Carbon on land in vegetation and soil is primarily "organic" (C₆H₁₂O₆).
Carbon in the ocean is typically dissolved C ions.
Fig 2-35 shows photosynthesis in the oceans. As the plankton die, they sink to the deeper ocean leaving behind a nutrient-depleted surface water.
Areas where nutrient-rich water upwells, rates of photosynthesis (also called productivity) are higher. See Fig. 2-36.
Fig. 2-37 shows increases of CO₂ and CH₄ in recent decades that cannot be due to natural causes.

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