POWELL without SPITZ CPP option

[fdufois]

Hi all,

I'm using the POWELL model, and I've got the feeling that there is a bug in the light limitation function f(I) (right term of eq. 7 in Powell et al., 2003).

If the SPITZ CPP option is turned on, we end up with f(I)=alpha*I/sqrt(Vm^2+alpha^2*I^2). This is coherent with eq.7 and f(I) is dimensionless ; all good (BTW, alpha is in d-1.m2/W not in m2/W as stated in npzd_Powell.in).

But without the SPITZ CPP key, it looks like f(I)=I, with dimension W/m2. This is rather weird.

I might however have done a mistake or forgotten a line while reading npzd_Powell.h . Could you confirm that this is a bug?
I reckon the SPITZ CPP option should be used at any time, but I couldn't find any mention to it anywhere.

Cheers,

Francois

[spitz]

Francois

You are right. The light coding without the Spitz formulation turned on is wrong. And the Spitz formulation is not really due to Spitz but to our great friend Fasham.

Y. Spitz