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intercomparisons:c2_cubiccloud

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intercomparisons:c2_cubiccloud [2016/11/16 11:51] claudia |
intercomparisons:c2_cubiccloud [2018/01/08 12:22] (current) |
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//Setup:// | //Setup:// | ||

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+ | {{ :intercomparisons:phase_c:c2_cubic_cloud:cubic_cloud.png?300 |Definition of cubic cloud}} | ||

* simple cubic cloud | * simple cubic cloud | ||

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# case theta_0 z theta phi i_x i_y I Q U V Istd Qstd Ustd Vstd | # case theta_0 z theta phi i_x i_y I Q U V Istd Qstd Ustd Vstd | ||

+ | ==== Data of model results ==== | ||

+ | |||

+ | {{:intercomparisons:phase_c:c2_cubic_cloud:iprt_case_c2_mystic.dat.gz|Results of MYSTIC model.}} | ||

+ | |||

+ | {{:intercomparisons:phase_c:c2_cubic_cloud:results_all_models_c2.tar.gz|Results of all models (MYSTIC, SHDOM, SPARTA, 3DMCPOL, MSCART).}} | ||

==== Results without atmosphere ==== | ==== Results without atmosphere ==== | ||

- | The following plots show the results obtained with MYSTIC. For all other models the patterns look the same. | + | == Plots of MYSTIC results == |

+ | The following plots show the results obtained with MYSTIC. For all other models the patterns look the same. | ||

{{:intercomparisons:phase_c:c2_cubic_cloud:c2_mystic_noatm.png|C2 without atmosphere, MYSTIC results}} | {{:intercomparisons:phase_c:c2_cubic_cloud:c2_mystic_noatm.png|C2 without atmosphere, MYSTIC results}} | ||

- | ** General ** | + | ** General remarks:** |

- | + | * Generally we find a very good agreement between all Monte Carlo models | |

- | * Generally we find a very good agreement between all Monte Carlo models, only for a few cases they do not agree within 2 standard deviations. | + | |

* The polarization patterns are the same in all models, also the pattern for V when variance reduction methods are applied | * The polarization patterns are the same in all models, also the pattern for V when variance reduction methods are applied | ||

- | * For SHDOM a quantitative comparison is difficult because it does not provide a standard deviation and systematic differences are expected (different treatment of cloud boundary. Smaller differences due to different solution method of VRTE). | + | * For SHDOM a quantitative comparison is difficult because it does not provide a standard deviation and systematic differences are expected (different treatment of cloud boundary, smaller differences due to different solution method of VRTE). |

* MSCART (backward mode) shows systematic differences to the forward calculations, Wang Zhen already mentioned this. MYSTIC gives the same results in forward and backward mode. | * MSCART (backward mode) shows systematic differences to the forward calculations, Wang Zhen already mentioned this. MYSTIC gives the same results in forward and backward mode. | ||

- | * The agreed number of photons for this case is 49e9, this number has been used for 3DMCPOL, MSCART and MYSTIC. For SPARTA, 10e11 photons were used | + | * The agreed number of photons for this case is 49e9, this number has been used for 3DMCPOL, MSCART and MYSTIC. For SPARTA, 1e11 photons were used |

* Circular polarization (Stokes component V) is very noisy in Monte Carlo results, especially for models without variance reduction. | * Circular polarization (Stokes component V) is very noisy in Monte Carlo results, especially for models without variance reduction. | ||

- | The following plots show the mean radiance (for each Stokes component), mean absolute difference with respect to MYSTIC (forward Monte Carlo), mean standard deviation, fraction of pixels which agree within 2 standard deviations (2σ), please note the non-linear scale of the colorbar. Only pixels with non-zero radiances are included into the statistics. | ||

- | |||

- | {{:intercomparisons:phase_c:c2_cubic_cloud:c2_statistics_1.png|Summary plots, statistics C2 without atmosphere}} | ||

- | {{:intercomparisons:phase_c:c2_cubic_cloud:c2_statistics_1.pdf|Summary plots, statistics C2 without atmosphere}} | ||

- | * Stokes component I (upper row): The mean radiance (average over all non-zero pixels) is very similar for all models. The mean absolute difference is smaller than 1\% of the mean radiance. The mean differences are largest for SHDOM. Models without variance reduction (3DMCPOL, SPARTA) show larger differences than models with variance reduction (MSCART, MYSTIC-backward). Also the standard deviations are much smaller when variance reduction techniques are used (as expected). \\ The match fraction shows that all Monte Carlo models agree within 2σ for cases 5-9 (down-looking). The match fraction is between 0.9 and 0.95 for some up-looking cases 1-4, which might indicate a small bias between other models and MYSTIC. MYSTIC (forward and backward mode) agree perfectly. | + | == Statistics of model intercomparison == |

- | * Stokes component Q (second row): The first column shows the mean absolute radiance (since Q can be positive or negative). The only visible difference in mean radiance is seen for case 5, here SHDOM is smaller than the Monte Carlo models, the difference is about 10%. \\ Mean standard deviations again are larger for models without variance reduction. The match fraction shows obvious systematic differences for mscart_bmc (all cases), mscart_fmc (cases 5 and 7) and SPARTA (case 6). | + | {{:intercomparisons:phase_c:c2_cubic_cloud:c2_statistics_rms_std_match_1_nstokes4.png|Statistics C2 without atmosphere}} |

- | * Stokes component U (third row): Largest difference for case 7, mean difference between SHDOM and MYSTIC is about 5% of mean radiance. The match fraction shows obvious systematic differences for mscart_bmc (all cases), mscart_fmc (case 7). | + | Statistics of the Stokes vector results for scenario C2 (cubic cloud |

+ | in vacuum). The panels in the left column show the mean radiance | ||

+ | $I_{\rm mean}$ (for Q, U, and V the mean of the absolute values) for | ||

+ | all models and all 9 cases. The panels in the second column show the | ||

+ | standard deviations $\sigma_{\rm rel}$. The third column shows the | ||

+ | root mean square differences $\Delta_{\rm RMS}$ with respect to MYSTIC | ||

+ | in per cent and the right column shows the match fractions $q$. | ||

+ | | ||

+ | ** Notes: ** | ||

+ | * Stokes component I: The mean radiance (average over all non-zero pixels) is very similar for all models. The RMS difference is < 1% for all MC models, <1.5% for SHDOM. Standard deviations are much smaller when variance reduction techniques are used (as expected). \\ The match fraction shows that all Monte Carlo models agree within 2σ for cases 5-9 (down-looking). The match fraction is between 0.9 and 0.95 for some up-looking cases 1-4, which might indicate a small bias between other models and MYSTIC. However, the number of non-zero pixels included in the statistics is only 200, so that values between 0.9 and 0.95 are still ok. | ||

+ | * Stokes component Q (second row): The first column shows the mean absolute radiance (since Q can be positive or negative). \\Mean standard deviations again are larger for models without variance reduction. The match fraction shows obvious systematic differences for mscart_bmc (all cases), mscart_fmc (cases 5 and 7) and SPARTA (case 6). RMS difference for mscart case 1 looks too large, CE will check this. | ||

+ | * Stokes component U (third row): The match fraction shows obvious systematic differences for mscart_bmc (all cases), mscart_fmc (case 7). | ||

* Stokes component V (bottom): Very noisy, without variance reduction (SPARTA, 3DMCPOL) noise is much larger than mean radiance. The match fraction shows systematic differences for mscart_bmc and mscart_fmc (all cases). These differences might be numerical because the mean radiance is very small (about 2e-6). Since the standard deviation is an order of magnitude larger than the radiance for SPARTA and 3DMCPOL, the results mostly match within 2σ, but this does not show whether the models really agree. | * Stokes component V (bottom): Very noisy, without variance reduction (SPARTA, 3DMCPOL) noise is much larger than mean radiance. The match fraction shows systematic differences for mscart_bmc and mscart_fmc (all cases). These differences might be numerical because the mean radiance is very small (about 2e-6). Since the standard deviation is an order of magnitude larger than the radiance for SPARTA and 3DMCPOL, the results mostly match within 2σ, but this does not show whether the models really agree. | ||

* Generally the standard deviation for SPARTA is below 3DMCPOL because for SPARTA more photons were used (10e11 vs. 49e9). MYSTIC and MSCART used 49e9 photons and variance reduction techniques which decrease the standard deviation approximately by almost one order of magnitude. | * Generally the standard deviation for SPARTA is below 3DMCPOL because for SPARTA more photons were used (10e11 vs. 49e9). MYSTIC and MSCART used 49e9 photons and variance reduction techniques which decrease the standard deviation approximately by almost one order of magnitude. | ||

- | | + | * RMS differences should only be looked at when mean radiance value is not too small (>1e-3). Here it is genearally <5% for Q and U for all cases and all models. For I it is <1%. |

==== Results with atmosphere ==== | ==== Results with atmosphere ==== | ||

+ | == Plots of MYSTIC results with atmosphere == | ||

The following plots show the results obtained with MYSTIC. As for the cases without atmosphere the patterns look the same for all models. | The following plots show the results obtained with MYSTIC. As for the cases without atmosphere the patterns look the same for all models. | ||

{{:intercomparisons:phase_c:c2_cubic_cloud:c2_mystic_atm.png|C2 without atmosphere, MYSTIC results}} | {{:intercomparisons:phase_c:c2_cubic_cloud:c2_mystic_atm.png|C2 without atmosphere, MYSTIC results}} | ||

- | The following plots show the mean radiance (for each Stokes component), mean absolute difference with respect to MYSTIC (forward Monte Carlo), mean standard deviation, fraction of pixels which agree within 2 standard deviations (2σ), please note the non-linear scale of the colorbar. | + | == Statistics of model intercomparison == |

- | {{:intercomparisons:phase_c:c2_cubic_cloud:c2_statistics_2.png|Summary plots, statistics C2 with atmosphere}} | + | {{:intercomparisons:phase_c:c2_cubic_cloud:c2_statistics_rms_std_match_2_nstokes4.png|Statistics C2 with atmosphere}} |

- | {{:intercomparisons:phase_c:c2_cubic_cloud:c2_statistics_2.pdf|Summary plots, statistics C2 with atmosphere}} | + | Statistics of the Stokes vector results for scenario C2 (cubic cloud |

- | * Stokes component I (upper row): Mean radiance agrees very well for all models. Mean difference is largest for SHDOM (about 5e-4), for all other models below 1e-4. The mean standard deviations are in the range from 2e-5 to 5e-5, here the difference between models with variance reduction and without is not as large as for the cases without atmosphere. The reason is that for cases with atmosphere, there are no pixels with zero radiance and all pixels are now included in the statistics. In the clearsky region the standard deviation is not reduced by variance reduction. The match fraction shows a perfect agreement between all Monte Carlo codes over the full image. | + | in vacuum). The panels in the left column show the mean radiance |

- | * Stokes component Q (second row): Mean absolute radiance agrees well for all models, again largest mean difference for SHDOM As for I the standard deviations are similar for all codes. The match fraction shows a perfect agreement between all Monte Carlo codes, except MSCART (backward mode). MYSTIC (backward mode) agrees perfectly to MYSTIC run in forward mode. | + | $I_{\rm mean}$ (for Q, U, and V the mean of the absolute values) for |

+ | all models and all 9 cases. The panels in the second column show the | ||

+ | standard deviations $\sigma_{\rm rel}$. The third column shows the | ||

+ | root mean square differences $\Delta_{\rm RMS}$ with respect to MYSTIC | ||

+ | in per cent and the right column shows the match fractions $q$. | ||

+ | | ||

+ | **Notes:** | ||

+ | * Stokes component I (upper row): Mean radiance agrees very well for all models. The mean standard deviations are in the range from 2e-5 to 5e-5, here the difference between models with variance reduction and without is not as large as for the cases without atmosphere. The reason is that for cases with atmosphere, there are no pixels with zero radiance and all pixels are now included in the statistics. In the clearsky region the standard deviation is not reduced by variance reduction. The match fraction shows a perfect agreement between all Monte Carlo codes over the full image. | ||

+ | * Stokes component Q (second row): Mean absolute radiance agrees well for all models. As for I the standard deviations are similar for all codes. The match fraction shows a perfect agreement between all Monte Carlo codes, except MSCART (backward mode). MYSTIC (backward mode) agrees perfectly to MYSTIC run in forward mode. | ||

* Stokes component U (third row): Mean absolute radiance agrees well. Match fraction again shows perfect agreement for all Monte Carlo codes except MSCART (backward mode). | * Stokes component U (third row): Mean absolute radiance agrees well. Match fraction again shows perfect agreement for all Monte Carlo codes except MSCART (backward mode). | ||

* Stokes component V (fourth row): Mean radiances agree within noise. Largest differences (still below 5e-6) for MSCART. Standard deviation is significantly reduced by variance reduction, because V is only non-zero in cloud (only cloud scattering causes circular polarization, molecular scattering does not). Pixels with zero V are not included in statistics, thus standard deviation is more influenced by variance reduction. Very small systematic differences (may be numerical) between MYSTIC and MSCART (forward and backward). | * Stokes component V (fourth row): Mean radiances agree within noise. Largest differences (still below 5e-6) for MSCART. Standard deviation is significantly reduced by variance reduction, because V is only non-zero in cloud (only cloud scattering causes circular polarization, molecular scattering does not). Pixels with zero V are not included in statistics, thus standard deviation is more influenced by variance reduction. Very small systematic differences (may be numerical) between MYSTIC and MSCART (forward and backward). | ||

- | * Standard deviations are smaller in forward than in backward mode, when the same number of photons/pixel (i.e. 1e7) is used. This can be seed for MYSTIC and also for MSCART. | + | * Standard deviations are smaller in forward than in backward mode, when the same number of photons/pixel (i.e. 1e7) is used. This can be seen for MYSTIC and also for MSCART. |

+ | * RMS mostly for I<1%, for Q and U<2% (for mean Q,U > ~1e-3) and for V <20% (for models with variance reduction and SHDOM). | ||

==== Detailed plots for all models, no atmosphere ==== | ==== Detailed plots for all models, no atmosphere ==== |

intercomparisons/c2_cubiccloud.1479297108.txt · Last modified: 2016/11/16 11:51 by claudia

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