Question 5.6: A farmer plans to plant seeds in a field of soil with a sola...
A farmer plans to plant seeds in a field of soil with a solar radiation reflection coefficient \rho _{s} = 0.20. She decides that the soil will be warmer (and germination more rapid) if she spreads a thin layer of black soot over it, decreasing the solar radiation reflection coefficient to \rho _{s} = 0.05. To assess the effect of the change, she prepares adjacent plots and records the following data around noon on a cloudless day:
Incident total solar irradiance S _{t} = 900 W m ^{-2} (same for both plots).
Difference in net radiation R _{n} (soot-covered)− R_{n} (bare soil) = 69 W m ^{-2}.
Radiative temperature of bare soil T _{s} = 303 K.
Estimate the radiative temperature of the soot-covered surface, stating any assumptions that you need to make.
Assuming that the soil and soot are perfect black body radiators,
L _{u}= 545 W m ^{-2}, so T _{soot} = 40 °C.