Why the transfer rate is a linearly decreasing function of time ?

[Xueli Huo]

Hi,

I am reading the chapter of Vegetation Phenology and Turnover in the CLM Technical Note. 2.20. Vegetation Phenology and Turnover — ctsm CTSM master documentation
Everything is clear until I read the description of the transfer rate in equation 2.20.13

"tonset (s) is the number of seconds remaining in the current phenology onset growth period. The form of Eq. (2.20.13) produces a flux from the transfer pool which declines linearly over the onset growth period, approaching zero flux in the final timestep."

tonset is linearly decreased which should result the transfer rate reversely increases. Why the transfer rate will be 0 when tonset is 0 ?

Any clarification or explanation provided will be appreciated.

Thanks.

 

[oleson]

I think the corresponding piece of code is in CNPhenology:

! only calculate these fluxes during onset period
if (onset_flag(p) == 1._r8) then

! The transfer rate is a linearly decreasing function of time,
! going to zero on the last timestep of the onset period

if (abs(onset_counter(p) - dt) <= dt/2._r8) then
t1 = 1.0_r8 / dt
else
t1 = 2.0_r8 / (onset_counter(p))
end if

I think the case where tsonset=0 is probably handled by the onset_flag which is set to zero once onset_counter is zero, so that that section of code is not executed.