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Strange patterns in WRf-solar irradiance variables

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Dear ones, I am using WRF with the WRF-Solar reference configuration. I'm using two domains: the parent domain has 9 kilometers of resolution and the innermost domain has 3 kilometers of resolution. I'm not using cumulus parameterization, but I'm using Deng shallow cumulus parameterization for both domains. As initial and boundary conditions I am using data from ERA5 (0.25°x0.25°) every 1 hour. I'm simulating for a region close to the equator, central latitude = 5°S.

I'm seeing some strange patterns in the SWDDNI and SWDOWN variables, these patterns occur at various times and end up influencing the monthly averages. An example of the pattern can be seen in the following image, for the SWDOWN variable:

What could be leading to this?

These spots represent a marked decrease in irradiance compared to neighboring areas (more than 400 Wm^-2 in some cases) - the output is hourly.

Could it be the influence of cumulus clouds? Because these spots start to appear from midday... If so, isn't the feedback of these clouds on radiation very strong?

Thank you very much in advance,
Those patterns appear to be the effects of clouds. You can take a look at the variables from the solar diagnostic package that characterize the integrated hydrometeor content. Take a look to the README.tslist file in the run directory for a description of the available variables.
Dear Dr. Jimenez, Thank you very much for your response. In fact, these patterns are the effect of clouds. However, the shape of these patterns still seems strange to me. Look at this other example below, it's the GHI variable:


It doesn't seem reasonable for clouds to have this pattern, they look like horizontal lines. I ran a test and simulated the same period without any cumulus parameterization, and it looks like the patterns disappeared. Still, I did another test inserting the Grell and Freitas parameterization only in the 9 km domain and the result was very similar to the test without parameterizations. See below:


So my question is whether this kind of pattern is expected for the WRF-Solar configuration mentioned above.

Thank you in advance for your solicitude.
The model is generating broken clouds. If you have a satellite image available for this day you can check if there were broken clouds this day.