Near Surface Radiation Balance
EFD
ME 7710
Spring 2013
Energy Balance over Salt Flats
(Utah’s West Desert)
1
Energy Balance over Salt Flats
RN = H + LE + G + η
Energy Balance over Salt Flats
Components of the Residual
RN = H + LE + G + η
2
Electromagnetic Spectrum
Type of change
Orbital changes
Vibration changes
Range of Interest for Atmospheric
Radiative Transfer
Solar ~ 0.15-4 mm (Short wave)
Terrestrial ~ 3-100 mm (Long wave)
Rotation changes
EPFL Raman Lidar
Discuss on Whiteboard
3
Shortwave & Longwave Radiation
ultraviolet
infrared
Wien’s Law – Wavelength
of maximum spectral
emissive power
λmax =
2897
Tabs
Average Global Radiation Balance
4
Radiative Properties of Surfaces
α=
ε=
4 µm
RS ↑
=
α λ dλ
RS ↓ 0.15∫µm
100 µ m
∫
ε λ dλ
3 µm
Albedo Variability
Murray Utah
5
Clear Atmospheric Flux Density of
Solar Radiation
Top of the atmosphere
Sea Level
Absorption of energy by gases
Energy depletion due to
scattering
~97% of total irradiance
Cloudless Absorption Spectra
lmax
6
Surface Irradiance
Direct Solar Radiation
Diffuse Solar Radiation – scatter radiation
Global = Direct + Diffuse
From Boundary Layer Climate, Oke
1987
Radiation Balance
(Clear Diffuse Component)
K – Shortwave; L – Longwave; Rn – Net Radiation
From Nadeau et al., Q. J. R. Meteorol. Soc. (2012)
7
Solar Constant
From Principles of Environmental Physics,
Monteith & Unsworth
Radiation Balance
K – Shortwave (Solar)
L - Longwave
8
N
latitude
equator
f
ecliptic
Solar
declination
ds
S
N
Local
Azimuth
Angle
a
y
Solar
Altitude
9