Mass flux equations

[maddykelley]

Howdy AeoLiStars!!

I have a few questions about the different transport models currently available in AeoLiS. Below are some of the commonly referenced models from Kok et al. (2012):

In AeoLiS, I’ve been looking at the transport.py file, specifically around lines 304–406.

• The 'bagnold' model (in which q scales cubically with shear velocity) is the modified Bagnold equation, since it includes a shear velocity threshold—correct?
• The 'bagnold_gs' model includes Dref as 250 µm (reference grain diameter).

Question: Shouldn't the Lettau model also include grain size scaling using Dref?

Question: What exactly is the 'dk' model in AeoLiS?

I’d like to compare results from the Bagnold, Kawamura, and Lettau models to the Durán and Kok model (Q_DK in the table above). However, I don't think the current 'dk' implementation in AeoLiS matches that. I believe it should look something like this:

        elif p['method_transport'].lower() == 'durankok': # Durán & Kok (2011) 
            s['Cu'][ix]  = np.maximum(0., p['Cdk'] * rhoa / g * uth[ix] * ustar[ix]**2 *
                              (1 - (uth[ix] / ustar[ix])**2))

Does that seem right?

Has anyone tested results using different transport models? It’s interesting to consider these differences in light of papers by Doug Sherman and many others:

I know Bagnold tends to be the go-to model, but I agree with the critiques in the literature regarding the assumption that particle speed scales linearly with u∗—which would imply that q actually has a quadratic, not cubic, relationship with shear velocity. That’s one reason I’m particularly interested in testing the Durán and Kok model.

Appreciate any thoughts!
THANKS :)