FIRESEASONL calculation

[PTrascasaCastro]

Hi!

I am using the variable fire season length (FIRESEASONL) and don't understand how it's calculated: Units are days, but there is one value per month. I would expect one value per year, but I guess that the value shown is a cumulative sum or a running mean, could you please clarify? If it’s a running mean and I select for example May, would May be the central, the first or the last month?

Thanks in advance for your help,

Paloma

 

[erik]

This is something only available for clm4_0 in older versions of the model. It is in units of days per year. But, yes since history data is normally output monthly you will see it monthly. You will want to wait until the model has at least run for a full year to start thinking it reliable.

From my reading of the code it is reported all the time, and roughly corresponds to a running average. But, I recommend that you do some testing to make sure it behaves as you'd expect for that. After running for a year I'd expect it to vary fairly slowly, but monthly values could be different within a given year. And I recommend that you take a closer look at the code as well as the CLM4.0 Technical Note on the Thonicke et al. 2001 fire model (as well as looking up the Thonicke reference).

 

[PTrascasaCastro]

Hi Erik,

Thank you for your answer and sorry for taking so long to reply. I read the CLM4.0 technical note and it's indeed a running mean, it says:

"This time step translation is accomplished with minimal modification to the underlying logic of the original model, and consists mainly of re-interpreting the annual fractional area burned at each time step, as opposed to once per year, and using a running mean of the daily fire probability, with an e-folding time constant of one year, as opposed to a simple annual summation of daily fire probability. The result is that the fractional area burned for a given grid cell acquires a seasonal cycle that corresponds to the seasonal increases and decreases in daily fire probability as predicted by the original model".

Cheers,

Paloma