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Verification of ESAS-Light demonstration version - Task 4

During the ESASLight study two completely new algorithms are developed: one is for the calculation of Raman scattering, the other is for the computation polarization using the Monte Carlo method. These new algorithms are carefully validated.

We have collected published results that can serve as benchmark for validation. Furthermore we have defined several test cases for solver intercomparisons as well as for physical consistency tests. We also compare the simulations of polarized radiances to measurements and take part in a model intercomparison study for models including polarization.

Details are given in the verification plan.

Polarization

Comparison against benchmark results by Coulson, 1960

Seven test cases have been defined for the verification of the implementation of polarization in MYSTIC. The following figure shows the result of one case as an example:

Test case 6

In general there is a very good agreement between the results by Coulson et al. (1960) and MYSTIC. The small differences are due to Monte Carlo noise and could further be reduced by using more photons. The error bars correspond to two standard deviations (2σ). The noise is larger where the polarized radiance is very small (close to 0). In all test cases there is a systematic difference of about 1% between Coulson et al. (1960) and polradtran.

Test reciprocity principle for realistic 1D atmospheres with molecules, aerosols, and clouds

Realistic simulations in spherical atmospheres including molecules, aerosols, and clouds have been simultated. The computations have been performed in the solar principal plane for a solar zenith angle of 60° at 350 nm wavelength. All simulations were done in forward and backward tracing mode. This test shows that the reciprocity principle (von Helmholtz, 1867) is fullfilled in MYSTIC.

 
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