Spectra for Incoming Beam of Solar Radiation Assignment

Assignment Task 

The Excel workbook contains spectra for an incoming beam of solar radiation that hits a vegetated target, and then is reflected back to space. Specifically, it contains five columns of data: wavelength ( micrometers), top of atmosphere downwelling flux (ETOA , at-surface downwelling flux (ESfc, surface-leaving flux ( MSfc) , and top of atmosphere leaving flux (M) (e.g. at-sensor flux) (watts/m^2). ( You can use any software you choose, I have also included a .csv file

For this exercise, we will assume that the target surface is Lambertian, and that the fluxes represent irradiance and exitance values (ie. the cosZ, D^2, and PI corrections have already been applied), so you can use the simplified equations on part 1, slide 5 ( see also part 1 slides 18-19). These values were created by a freeware radiative transfer program for UNIX called SBDART, produced by UC Santa Barbara, and incorporates the effects of Rayleigh scattering, gaseous absorption, and aerosol scattering. Respond to the instructions below. Prepare a Word document with the graphs asked for and your discussion

(a) plot each of the four fluxes against wavelength together on the same graph.

(b) calculate and plot the actual ( i.e,surface) reflectance spectrum for the target on a new graph calculate and plot the "top-of-atmosphere" reflectance spectrum for the target on the same graph.

(c) Describe how do the radiance curves change as the incoming beam travels through the atmosphere, hits the target, and arrives at the sensor? Describe what you see and why there are differences. Hint: Explain the characteristics of the 4 flux graphs and the effects of atmospheric absorption and scattering and the reflective properties of the surface.

(d) assuming that the surface target is a Lambertian reflector, calculate the total visible energy flux (in Watts / meter squared) absorbed by the surface (assume zero transmissivity for the target material). Hint you are, in effect, integrating (summing) the amount of energy over the specified wavelength interval in this case 0.4 - 0.7 micrometer. Therefore you need to consider the contribution for each increment of wavelength. Hint, the data set shows that the wavelength intervals are 0.01micrometer.

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