Surface Energy Budget

1. Surface Energy Budget • R = - (G + H + L ) • R = net solar and terrestrial radiation at the earth’s surface (+ into surface) • Absorbed solar radiation (incoming – reflected) • Incoming longwave radiation emitted by gases and clouds in the atmosphere • Outgoing longwave radiation emitted by the earth’s surface • G- storage of energy into the deep soil (- into soil) • H – heat flux into atmosphere(- into atm) • L – Latent heat flux into atmosphere ( - into atm)

2. Heat Storage Hartmann (1994)

3. Soil Temperature • high intensity of solar radiation at high altitudes can result in high surface temperature • Austria- 80C humus at 2070 m; air temp at 2 m 30C • New Guinea 60C at 3480 m air temp 15C Barry (1992)

4. Net Radiation Whiteman (2000)

5. Surface Energy Budget Whiteman (2000)

6. Surface Energy Budget Whiteman (2000)

7. p/ps = fraction of atmosphere above point = 1 m q Solar Radiation • m= 1/(sin(q) • m = non-dimensional • optical depth at surface • m =1, q = 90o • m =2, q = 30o • m =4, q = 14o • When sun at 14o , • light travelling through 4 atmospheres

8. Solar Radiation • M = m p/ps = non-dimensional optical depth at pressure p • At 500 mb (p/ps = .5): • for zenith angle = 14o, equivalent to path length at sea level for zenith angle of 30o • so, more radiation at higher elevation p/ps = fraction of atmosphere above point M q

9. Solar Radiation- Ideal Atmosphere

10. Barry (1992) Solar radiation reduced in lower atmosphere by: --absorption of radiation by water vapor -- Mie scattering by aerosols

11. Absorbed Solar Radiation • Absorbed solar radiation depends strongly on albedo: Abs Solar = Solar (1 – a) • Snow cover reflects solar radiation and diminishes absorbed solar radiation • Annually, snow cover at high elevation later in season than in valleys tends to cause absorbed solar radiation to diminish with elevation Whiteman (2000)

12. Incoming Longwave Radiation Iijima and Shinoda (2002)

13. Outgoing Infrared Radiation • Stefan-Boltzmann Law: IR = esT4 • As elevation increases: • temperature decreases, IR radiation decreases • Optical thickness of atmosphere decreases (less greenhouse gases, including water vapor), atmospheric transparency to outgoing radiation increases, more IR escapes • Emissivity (e) of snow and ice is high Whiteman (2000)

14. Infrared Radiation: December, Austrian Alps Barry (1992)

15. Net Radiation • Net Radiation = Absorbed solar radiation + downwelling IR – IR • Effect of altitude on net radiation is variable and depends most strongly on decrease with height of absorbed solar radiation Barry (1992)

16. Peter Sinks Clements (2000)

17. Radiation Budget on Slope downwelling IR solar IR Temperature slope Temperature ground

18. Variations in sunrise time Whiteman (2000)

19. Influence of aspect (orientation) Barry (1992)

20. Influence of aspect (orientation) Barry (1992)

21. Influence of slope angle Barry (1992)

22. South – north West - east Inclination angle, valley orientation, season Whiteman (2000)

23. Microclimates • Small topographic irregularities • Differences in slope angle and aspect • Types (Turner 1980) • Sunny windward slope (high radiation; high wind) • Sunny lee slope (high radiation; low wind) • Shaded windward • Shaded lee

24. Microclimates Barry (1992)