What version of the code are you using? Relevant for all CAM versions, to the best of my knowledge (checked the CAM6 code based on the Github repository).
Describe your problem or question:
This question is related to cloud sampling in the radiation transfer module as part of the implementation of the MC-ICA approach for clouds. To the best of my understanding within
CAM6 the parameter permuteseed is hard-coded with a certain fixed value for short-wave (SW) and another fixed value for long-wave (LW). This parameter is passed to the function generate_stochastic_clouds as the input parameter changeSeed as part of the implementation of the MC-ICA cloud parametrization approach (Monte-Carlo Independent Cloud Approximation). The result is basically that the same configuration is sampled again and again. The only seed permutation is done between columns and not between function calls.
In fact, in the comments of the function generate_stochastic_clouds the following statement appears: "If the stochastic cloud generator is called several times during the same timestep, one should change the seed between the call to insure that the subcolumns are different. This is done by changing the argument 'changeSeed'". This suggested seed shift is not done to the best of my understanding in CAM6. I would be happy to be mistaken, please let me know where I am wrong in this post.
Describe your problem or question:
This question is related to cloud sampling in the radiation transfer module as part of the implementation of the MC-ICA approach for clouds. To the best of my understanding within
CAM6 the parameter permuteseed is hard-coded with a certain fixed value for short-wave (SW) and another fixed value for long-wave (LW). This parameter is passed to the function generate_stochastic_clouds as the input parameter changeSeed as part of the implementation of the MC-ICA cloud parametrization approach (Monte-Carlo Independent Cloud Approximation). The result is basically that the same configuration is sampled again and again. The only seed permutation is done between columns and not between function calls.
In fact, in the comments of the function generate_stochastic_clouds the following statement appears: "If the stochastic cloud generator is called several times during the same timestep, one should change the seed between the call to insure that the subcolumns are different. This is done by changing the argument 'changeSeed'". This suggested seed shift is not done to the best of my understanding in CAM6. I would be happy to be mistaken, please let me know where I am wrong in this post.