The Physical Basis of Climate (ATSC5400/4400) Spring 2011

Stellarsphere Slides

• Sun and Plancks Function

• Orbital influences on climate (Croll – Milankovitch)

Solar Radiation Sun - typical main sequence dwarf starRo = 6.95 x 105 km, Mo = 2 x 1030 kg71% H, 26.5% He, 2.5% heavier metalsMean earth sun distance 1.496 x 108 km

Core out to 0.25 Ro Temperature ~ 107 K Hot enough to cause fusion of H in to He provides energy for the sun.

Energy transfer by radiation, temperature ~ 106 K, ~0.7 Ro

Final ~0.3 Ro energy transfer by convection violent small scale (103 km) mixing process granulation

Photosphere ~ 1000 km thick, dominant source of solar radiation - relatively continuous emission - determines sun's blackbody temperature, 5800 K. Sunspots here.

Chromosphere - 5000 - 10,000 km thick, temperature ~ 105 - 106 K. Radiation from emission lines from H, He, Ca.

Corona - region above chromosphere, extending out for several solar diameters, temperature ~ 106 K. Prominences, Solar flares appear here. Origin of solar wind.

Most solar energy in the continuum is from non-quantized electronic transitions (free - free, bound - free transitions)

B(υ,T)=2hυ3/c2 [1/(ehυ/(kT)-1)]

B(λ,T) = -8πhc/λ5 1/[ehc/(λkT) -1]

B(λ,T) = -8πhc/λ5 1/[ehc/(λkT) -1]

B(υ,T)=2hυ3/c2 [1/(ehυ/(kT)-1)]

B(λ,T) = -8πhc/λ5 1/[ehc/(λkT) -1]

B(υ,T)=2hυ3/c2 [1/(ehυ/(kT)-1)]

http://www.pmodwrc.ch/tsi/composite/pics/org_comp2_d41_62_1009.png

http://blog.ltc.arizona.edu/azmasternaturalist/Sunspot%20cycle.JPG

http://solarscience.msfc.nasa.gov/images/ssn_predict_l.gif

http://www.universetoday.com/wp-content/uploads/2008/10/moon_formation.jpg

Precession of 90° implies planet closest to sun in fall

Figure 7.2 Map of July-January surface air temperature differencesFig. 7.2 Map of July-January surface air temperature difference (C).

Milankovich cycles: Eccentricity-100,000 Obliquity-41,000 Precession-23,000 years

41,000 y

100,000 y

23,000 y

CO2today

http://upload.wikimedia.org/wikipedia/commons/5/53/MilankovitchCyclesOrbitandCores.png

Obliquity

Eccentricity Precession

Ecc * Prec

Solar insolation

------- Pleistocene ---------------------Holocene

Croll -

Harvey, 2000

Houghton, 2004