Class7 (June 15) Radiation Measurements

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THE RADIATION BUDGET
(Exercise)
Exercise: Monitor radiation budget at 2 sites (urban rural) using
instruments
RADIATION BUDGET:
Balance between incoming energy from the sun (SWR) and
the outgoing long-wave (LWR) and reflected shortwave
energy from the Earth.
R = INPUT – OUTPUT
R = SWR + LWR - SWR - LWR
RADIATION BUDGET
• R (Net Radiation) in W m-2
Energy available for us, vegetation, environmental processes (ex: heat
the air)
• (Q+q): total solar radiation in W m-2
•a : albedo (no dimension)
•I : outgoing LWR (W m-2)
I : atmospheric counter radiation (absorbed by the surface)
MEASUREMENT OF SOLAR RADIATION AND ALBEDO
Instrument: Pyranometer
(Q+q) total solar radiation: direct measurement with pyranometer
right side up
Albedo:
a = [(Q+q) a] / (Q+q)
Reflected solar radiation (pyranometer upside down)
MEASUREMENT OF OUTGOING LONG WAVE RADIATION
Instrument: Infrared thermometer (“gun”)
I =  T4
 Boltzmann constant
T in °K
Ts: Target temperature associated with the surface
Te: Target temperature associated with sky and
sorrounding environment
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