2.8 KiB
2.24.4. Peat fires¶
The burned area due to peat fires is given as \({A}_{b}\):
(2.24.37)¶\[A_{b} = c \ f_{cli,p} f_{peat} (1 - f_{sat} ) A_{g}\]
where \(c\) (s-1) is a constant; \(f_{cli,p}\) represents the effect of climate on the burned area; \(f_{peat}\) is the fractional coverage of peatland in the grid cell; and \(f_{sat}\) is the fraction of the grid cell with a water table at the surface or higher. \(c\) = 0.17 \(\times\) 10 -3 hr-1 for tropical peat fires and \(c\) = 0.9 \(\times\) 10 -5 hr -1 for boreal peat fires are derived using an inverse method, by matching simulations to earlier studies: about 2.4 Mha peatland was burned over Indonesia in 1997 (Page et al. 2002) and the average burned area of peat fires in Western Canada was 0.2 Mha yr -1 for 1980-1999 (Turetsky et al. 2004).
For tropical peat fires, \(f_{cli,p}\) is set as a function of long-term precipitation \(P_{60d}\) :
(2.24.38)¶\[f_{cli,p} = \ max \left[0,\min \left(1,\frac{4-P_{60d} }{4} \right)\right]^{2} .\]
For boreal peat fires, \(f_{cli,p}\) is set to
(2.24.39)¶\[f_{cli,p} = \exp (-\pi \frac{\theta _{17cm} }{0.3} )\cdot \max [0,\min (1,\frac{T_{17cm} -T_{f} }{10} )]\]
where \(\theta _{17cm}\) is the wetness of the top 17 cm of soil.
Peat fires lead to peat burning and the combustion and mortality of vegetation over peatlands. For tropical peat fires, based on Page et al. (2002), about 6% of the peat carbon loss from stored carbon is caused by 33.9% of the peatland burned. Carbon emissions due to peat burning (g C m-2 s-1) are therefore set as the product of 6%/33.9%, burned area fraction of peat fire (s-1), and soil organic carbon (g C m-2). For boreal peat fires, the carbon emissions due to peat burning are set as 2.2 kg C m-2 peat fire area (Turetsky et al. 2002). Biomass combustion and vegetation mortality in post-fire peatlands are set the same as section 2.24.1.3 for non-crop PFTs and as section 2.24.2 for crops PFTs.