Reference no: EM131703112
LABORATORY: ATMOSPHERIC ATTENUATION OF SOLAR RADIATION
Objective:
The molecular and aerosol constituents of the earth's atmosphere cause scattering and absorption of the incident solar radiation altering the spectral character of the irradiance reaching the surface as well as generating scattered light into the space borne or airborne sensor. Although the characteristics (brightness and spectral distribution) of the solar radiation outside the earth's atmosphere (known as the exo-atmospheric solar irradiance) has been measured repeatedly and is considered well-known, the characteristics of the radiation field received at the earth's surface is highly variable, dependent primarily on the solar angle and the optical properties of the atmosphere. The objective of this lab is to expose you to methods measuring the direct and diffuse spectral irradiance received at the surface as well as the extinction of the solar beam by the atmosphere.
Assignment -
The practical purpose of this experiment is to familiarize you with the analysis of data from a sun photometer to derive atmospheric optical properties.
Sample SONOTEK data previously acquired by your TA is provided so you can get some experience in its analysis.
1) Using the solar ephemeris spread sheet program (ESSE 4220_EPHEMERIS) provided, calculate the solar zenith angle and the corrected air mass for each measurement time and tabulate the values, and submit these in a form as shown in Table 1.
2) Produce a Langley plot. For each channel and derive the corresponding zero air-mass Calibration constants STOA;λ for the sun photometer. Correct these values to the mean-earth- sun distance values to determine the standard calibration constants So(λ) for this. Enter these results in Table2.
3) The Langley plot analysis also yields the total optical depth of the atmosphere on the day of measurements. Calculate the aerosol optical depth at each wavelength for each of the measurement times and compute the Angstrom exponent. Enter your results in Table2.
Attachment:- Assignment Files.rar