Add option to derive the override for the net surface shortwave radiative flux #253
Conversation
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
When using ML to predict the surface radiative fluxes, it is important to use an albedo that is at least consistent with the coarse model when computing the net shortwave radiative flux at the surface. This adds an option to do this by computing the absorption (i.e. 1 - albedo) using the RRTMG fluxes, and makes the assumption that the absorption is zero if the RRTMG downward shortwave flux at the surface is zero.
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
Predicting or computing the net surface shortwave radiative flux based on the downward surface shortwave radiative flux outside the physics driver is difficult, because the effective albedo changes throughout the day. In the middle of the day, sunlight is typically more direct and more readily absorbed (notebook).
This PR adds an option to compute the override for the net surface shortwave radiative flux within the physics driver based on the ratio of the net to downward shortwave radiative flux at the surface predicted by RRTMG (this ratio is one minus the albedo). When the RRTMG-predicted downward shortwave radiative flux at the surface is zero, we assume that the override for the net shortwave radiative flux at the surface will also be zero to avoid divide by zero issues.
I tested this in a new ML-corrected run. If we look over the month of August, it has the desired effect. The Sahara-mean bias in net shortwave radiative flux at the surface goes from about -9.1 W/m^2 using the basic derived model to about 1.6 W/m^2 using the derived model enabled via this PR (notebook).