Physical Geography: GEOG 1301

Spring 2005

Chapter Four: Atmosphere and Surface Energy Balances

Input- insolation

Output- reflected light & emitted infrared energy

Determines net energy available for work

Energy Essentials

· Energy flows in weather patterns, ocean currents and distribution of vegetation

· Clouds can make up to a 75% difference in amount of energy to reach surface

· Surface heated by solar energy- distributed by latitude with seasonal variation

Radiation Basics:

http://itg1.meteor.wisc.edu/wxwise/museum/a2main.html

http://www.strategies.org/LESSON8.html (check out links)

University of Florida lecture: http://ess.geology.ufl.edu/HTMLpages/ESS/GLY1033_Notes/lecture2.html

Transmission- passage of short/long wave energy through atmosphere

Scattering- redirected radiation, direction changed, not wavelength, 7% of earth's albedo. The shorter the wavelength, the greater the scattering- cause the sky to be blue and sunrise/sunset red. Direct, overhead rays experience less scattering than oblique angle rays. Pollution causes all wavelength to scatter, resulting in a white sky.

Refraction- distortion of atmosphere by movement from one phase of matter to another. Changes speed and direction (bending) of rays. Atmospheric distortion of setting sun is refraction (adds 8 minutes of daylight)

Insolation- single energy input driving the atmosphere. Inputs: Page 96- Note areas of high radiation related to arid/desert lands.

Albedo- reflective quality (intrinsic brightness) of a surface (Figure 4.5 on page 96.) Dark reflects 0%, Light reflects 100%. 31% of insolation reflected over a year.

Clouds- reflect insolation (shortwave) - cool surface and trap longwave radiation (cloud-greenhouse forcing.)

Absorption- assimilation of radiation by molecules. Insolation converted to either infrared radiation or chemical energy. Land and water absorb energy at different rates.

Conduction- transfer of energy from warmer to cooler materials (land-water heating differences)

Convection- transfer of energy by vertical movement of gas or liquid. (weather/oceanic circulation)

Advection- transfer of energy by horizontal movement of gas or liquid. (winds/fog/etc.)

Energy Balance in the Troposphere

System is in equilibrium

NASA Fact Sheet (very good)

http://www.gsfc.nasa.gov/gsfc/service/gallery/fact_sheets/earthsci/terra/earths_energy_balance.htm

Earth- cool-body radiator

Sun- hot-body radiator

Greenhouse effect- infrared radiation absorbed by gasses, etc. (change in steady-state equilibrium of atmosphere.)

Earth-Atmosphere Radiation Balance

Radiation- 31% reflected (albedo) in upper atmosphere. Remaining 69% reradiated from surface.

Figure 4.14 (page103) is very important! Equatorial surpluses move to polar deficit

Equator and tropics – energy surpluses, polar regions- energy deficits.

Energy Balance at Earth’s Surface

Daily routine of heating via insolation and reradiative heating creates daily radiation patterns. Absorbed insolation at noon, Peak temperature around 3 pm, coldest (most re-radiated by dawn)

Figure 4.15 (page104) is very important! Daily radiation curves- must know

Net radiation- result of heating/reradiative processes. Mostly zonal patterns with strong continental land mass effect. Expended by latent heat of evaporation, sensible heat and ground heating/cooling.

Urban heat islands- effect that cities have upon radiation and temperature (page 109)