utility of DIURNAL_INPUT_SRFLX option in PISCES

biogeochemistry
1

Hi,
I would like to know what is the purpose of the option DIURNAL_INPUT_SRFLX avaliable in cppdefs.h when running PISCES. I get it is something related to the shortwave radiation at the surface, but what does it change activating it? Can anybody help me? Thank you.

2

For what I understand, this option is undefined when using PISCES as it would lead to an overestimation of surface radiation, and thus productivity. Please contact Vincent Echevin (IRD) for more details in this topic.

3

Hi, in fact, this is to deal with a diurnal cycle, if any, in the solar short-wave radiation imposed in the forcing files (variable radsw in frc/blk files). Short-wave radiation is used to derive the photosynthetic available radiation (PAR) for phytoplankton growth. Since PISCES do not accept PAR=radsw=0 (see PISCES equations), this key must be activated if there is a diurnal cycle in radsw. In that case, another variable (radswbio) is read in the forcing files instead of radsw.
The variable radswbio is the solar short-wave radiation without diurnal cycle, and this must be specifically pre-processed and included in the forcing files, for example by running “Aforc_CFSR/add_radswbio_CFSR.m” for CFSR data.
Good luck !

4

Thanks a lot for your explanation, Pedro!

5

Thanks Andrés, I’ll take that in consideration.