soil-dust density (K) and emission area (A) in alternate emission algorithm

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onlyhesam
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soil-dust density (K) and emission area (A) in alternate emission algorithm

Post by onlyhesam »

Hi
I have a question about the "soil-dust density (K)" and "emission area (A)" in alternate emission algorithm. Is "emission area (A)" constant parameter?

for example in one of the global points file -Potential points of Feb- there are 27421 points with a resolution of 0.25 degree (about 25 Km), a part of this points are
-49.75 -72.50 10.0 69.7 0.6700E+04
-44.75 -67.00 10.0 124.7 0.4706E+04
-44.00 -68.25 10.0 131.4 0.1503E+05
-43.75 -68.25 10.0 115.3 0.2184E+04
-43.75 -68.00 10.0 121.3 0.2448E+04
-43.50 -68.25 10.0 130.1 0.1853E+04
-43.25 -68.00 10.0 141.0 0.2673E+04

for the first point whose location is -49.75 -72.50, if the "emission area (A)" is constant, the threshold friction velocity will be 69.7 cm/s and the A is 25*25=625 km^2 and hence, K will be calculated by dividing "KA" into "A" -which is 625 km^2- then "soil-dust density (K)" will be 0.6700E+04/625= 10.72.
Is the preceding calculation correct?
ariel.stein
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Re: soil-dust density (K) and emission area (A) in alternate emission algorithm

Post by ariel.stein »

That will be correct. However, the model already takes that into account when making the calculation for the emission.
NicoCosentino
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Re: soil-dust density (K) and emission area (A) in alternate emission algorithm

Post by NicoCosentino »

But, Ariel, wouldn't that imply that the full area of each grid cell is assumed to emit dust? Isn't it that only a fraction of the area of each grid cell is assumed to emit dust? I've read in Draxler et al. (2010), in section 2.4, that that fraction of the grid cell is calculated based on Ginoux et al.'s (2001) topographic depression analysis.

Draxler, R. R., P. Ginoux, and A. F. Stein (2010), An empirically derived emission algorithm for wind‐blown dust, J. Geophys. Res., 115, D16212, doi:10.1029/2009JD013167.
Ginoux, P., M. Chin, I. Tegen, J. M. Prospero, B. Holben, O. Dubovik, and S. J. Lin (2001), Sources and distributions of dust aerosols simulated with the GOCART model, J. Geophys. Res., 106(D17), 20,255–20,274.
ariel.stein
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Re: soil-dust density (K) and emission area (A) in alternate emission algorithm

Post by ariel.stein »

Not exactly. The A parameter already includes the fraction of the area that is emitting. K and A are empirical parameters, they don't really have an absolute physical meaning.
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