Opened 2 years ago

Last modified 23 months ago

#836 new enhancement

New and old drivers don't have the same default for SPREAD_PREC

Reported by: aducharne Owned by: somebody
Priority: minor Milestone: ORCHIDEE 4.3
Component: Driver files Version: trunc
Keywords: Cc:

Description

The default values differs:

  • In the old driver, the default SPREAD_PREC is half the forcing time step if the latter is GE 3h, else it equals the forcing time step;
  • In the new driver, the default SPREAD_PREC is always half the forcing time step. There is also a possibility to "connect" the rainfall from two consecutive forcing time steps SPREAD_PREC_CONT, but the default is FALSE.

I think we should enforce a similar configuration of the two drivers as much as possible.

Personnally, I prefer the choices of the old drive, as intense rainfall rates reduce infiltration, SM and transpiration/photosynthesis. But I will follow the majority.

Change History (4)

comment:1 Changed 2 years ago by jpolcher

I chose to set SPREAD_PREC independent of the forcing time step. So have it as a fixes values in seconds. We now have hourly rainfall forcing. It would not be realistic to have 1/2h rain events throughout the year.

Many years ago I showed that in mid-latitudes the "conneted" rainfall events was quite realistic in particular in winter when rain events last many hours. The results were shown to the ORCHIDEE group.

comment:2 Changed 23 months ago by jgipsl

Decided at today's ORCH meeting : the trunk will change the default behaviour for SPRED_PREC according to what is done for the old driver.

comment:3 Changed 23 months ago by xnwang

Forcing_tools.f90 in the new driver in r7611 has the following functionality :
1) if SPREAD_PREC_SEC is defined by user in run.def: use this value for the simulation
2) if SPREAD_PREC_SEC is not defined by user in run.def: use the same default behavoir as in old driver. That is, precipitation is spread over a duration of half of the forcing time step if the latter GE 3h, otherwise the same duration as the forcing time step

This means a bit more flexibility to users about how to spread the precipitation, though it is different from the default behavoir in the old driver.

Last edited 23 months ago by jgipsl (previous) (diff)

comment:4 Changed 23 months ago by aducharne

Thanks a lot Xiaoni. Now, we have to ensure that SPREAD_PREC_SEC does not override the default behavior in the FGxnd configs, by commenting out this keyword.

In branch 2.2, this is done, but the code of forcing_tools.f90 does not include any equivalent of r7611 (and the default for SPREAD_PREC_SEC = 3600) => NEEDS TO BE CHANGED.

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