A parameterization for sub-grid emission variability

Stefano Galmarini, DG-Joint Research Center, IES

S. Galmarini1, J.-F. Vinuesa1 and A. Martilli2

1EC-DG-Joint Research Center, Italy2CIEMAT, Spain

A parameterization for sub-grid emission variability




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How to transfer source intensity variability to upper atmospheric layers?

• Turbulent motions are responsible for creating and generating scalars concentration variance

• In RANS scalar variance is accounted for by means of the variance conservation equations

• The source variability at the surface can be though as a boundary condition of scalar variance equation that will take care of describing its transport in x, y and z, creation and dissipation


Formulation


Equation closure


Approach

10 Km

LES =100 x 100 grid cells, 100 m resolution

10 Km

• U=5m.s-1 • Total duration LES=3hours• The dynamic at the end of the first hour is used to fed FVM (u,v,w,theta). • Then emission is released for 2 two hours. Statistics are done over the last hour.

• Sv3=64% of 5x5km2 (LES-1)• Sv4=36% of 5x5km2(LES-2)• Sv5=25% of 5x5km2(LES-3)

• Sv6=16% of 5x5km2(LES-4)

Release of=0.1 ppb.m.s-1

FVM= 2 x 2 grid cells, 5 km resolution


Source size= 64% 5 km2 grid element


Source size= 16% 5 km2 grid element



16% surface emission64% surface emission A B

C D

A B

C

D

Results:concentration variance


Virtual monitoring stations


64%


16%


Conclusion

• A simple method to account for variability of emission

• Possibility to add error bars to model results

• Further steps: adding the information on the spatial variability


Results:mean concentration

A B

C D

A B

C

D




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A parameterization for sub-grid emission variability