drag coefficient in wrf

[water]

When I do the ideal test to simulate a tropical cyclone, the roughness on land is a fixed value, but the drag coefficient is variable and can be up to = 0.1, is this normal?

 

[Ming Chen]

CD is a function of wind speed. This result is reasonable.

 

[water]

CD is a function of wind speed. This result is reasonable.

Thank you! Where can I find the formula for calculating CD

 

[Ming Chen]

It depends on the sfclay scheme. Which surface layer scheme did you use?

 

[water]

It depends on the sfclay scheme. Which surface layer scheme did you use?

I used Revised MM5.

 

[Ming Chen]

The calculation of surface exchange coefficient is conducted in phys/module_sf_sfclayrev.F, in which you can find the folloiwng piece of code:

        IF(PRESENT(ck) .and. PRESENT(cd) .and. PRESENT(cka) .and. PRESENT(cda)) THEN


           Ck(I)=(karman/psix10)*(karman/psiq10)


           Cd(I)=(karman/psix10)*(karman/psix10)


           Cka(I)=(karman/psix)*(karman/psiq)


           Cda(I)=(karman/psix)*(karman/psix)

        ENDIF

 

[water]

The calculation of surface exchange coefficient is conducted in phys/module_sf_sfclayrev.F, in which you can find the folloiwng piece of code:

        IF(PRESENT(ck) .and. PRESENT(cd) .and. PRESENT(cka) .and. PRESENT(cda)) THEN


           Ck(I)=(karman/psix10)*(karman/psiq10)


           Cd(I)=(karman/psix10)*(karman/psix10)


           Cka(I)=(karman/psix)*(karman/psiq)


           Cda(I)=(karman/psix)*(karman/psix)

        ENDIF

Thank you very much for your help. I would also like to ask how to modify soil moisture availability profiles.

 

[water]

Thank you very much for your help. I would also like to ask how to modify soil moisture availability profiles.

Q2:I used Noah LSM, what are the heights of layers 0-3 in the variable SMOIS?

 

[teddy]

Dear professor, why i can not find the calculation of surface exchange coefficient in phys/module_sf_sfclayrev.F? My WRF is v4.7.1. And I wonder the difference of the calculation of Cd when isftcflx=0,1, or 2 with sf_sfclay_physics=1.

The calculation of surface exchange coefficient is conducted in phys/module_sf_sfclayrev.F, in which you can find the folloiwng piece of code:

        IF(PRESENT(ck) .and. PRESENT(cd) .and. PRESENT(cka) .and. PRESENT(cda)) THEN


           Ck(I)=(karman/psix10)*(karman/psiq10)


           Cd(I)=(karman/psix10)*(karman/psix10)


           Cka(I)=(karman/psix)*(karman/psiq)


           Cda(I)=(karman/psix)*(karman/psix)

        ENDIF