light units for ec_Fobar

[jklinck]

What are the units for the light values (ec_Fobar) in mod_eclight?

I am trying to compare this model to the one in Gregg and Carder (1990) where Ho in that paper has units of W/m2/nanometer.

These value differ by about 10. Are these values in micromole photons/m2/s? Converting these units don't give corresponding values.

Thanks,

John

[arango]

I don't know what are the units. This is used in the downwelling spectral irradiance routine ana_specir.h. This was adapted from a routine provided by Paul Bissett for the EcoSim model. That routine says that it is based on Gregg and Carder (1990) model and few units were provided. It is used to compute SpecIr (quanta/m2/s):

Code: Select all

!
!  Convert from W/cm/um to micromole quanta/m2/s.
!
              SpecIr(i,j,iband)=Ed(iband)*10.0_r8*qlam(iband)

So it is possible that there is a bug about the units in this routine. However, notice that the above statement is multiplied by 10. We would need to check backwards this routine and figure out what are the units. The ec_Fobar is used to compute:

Code: Select all

!
!  Correct solar constant for Earth-Sun distance.
!
      cff=(1.0_r8+0.0167_r8*COS(2.0_r8*pi*(yday-3.0_r8)/365.0_r8))**2
      DO iband=1,NBands
        Fo(iband)=ec_Fobar(iband)*cff
      END DO