Hi, all: For the setting of the wind drag coefficient (see attached), i’m confused about the meaning of “1000*Evap transfer coeff, <0 use wind drag”. For example, if i set this value to be 1.5, what does that mean? Does it means the wind drag coefficient to be 1.5? Any help will be appreciated. Thanks! Bin Attached files

In EFDC_DSI, "1000*Evap transfer coeff, <0 use wind drag" is used to calculate the wind function CLEVAP for the evaporation calculations. In the subroutine CALTSXY.f90, CLEVAP is first initialized as CLEVAP (L) = 0.001 * ABS(REVC) Then a condition is checked if REVC is less than zero or not. *

! *** EVAPORATION WIND FUNCTION (FW)ABS(REVC)

IF( ISTOPT(2) == 1 .OR. IEVAP == 2 )THEN

IF(REVC < 0.)THEN

CLEVAPTMP=0.001

DO L=LF,LL

CLEVAP(L)=1.E-3*(0.8+0.065*WINDST(L))

CLEVAP(L)=MAX(CLEVAP(L),CLEVAPTMP)

ENDDO

ENDIF

ENDIF

So, if REVC is smaller than zero, then the evaporation function will be calculated using the formula CLEVAP(L) = 1.E-3

*(0.8 + 0.065*WINDST(L)) and the maximum of them will be used.

I hope it helps. Let me know if you have any confusion.

Best,

Janesh

Hi, Janesh

Thank you for your reply.

I still have a little confusion. What if i don’t need to calculate the evaporation since i have observed evaporation? For the “Atmospheric Parameters” settings, if i choose “False” for the “Internally compute Evaporation”, will the “1000*Evap Transfer Coeff, <0 use WSP Drag" still work? Or could i set any value and the value will not affect the results? Also, if "1000*Evap Transfer Coeff, <0 use WSP Drag” is used for evaporation calculation, then I’m still confused about where to set the “wind drag coefficient”? Since i see some literatures referring to the Calibration with adjusting the wind drag coefficient in EFDC.

Thanks again! Any suggestion will be appreciated.

Bin