# Wildfires in the Siberian Arctic
## 3 Results
### Seasonality of Wildfire  
Considered as a whole, the seasonal distribution of fire frequency was unimodal for the Siberian Arctic for the 2001-2021 period (Figure 2b). That pattern is typical at high latitudes [8]. However, for the severe 2019 fire year, the seasonal distribution was bimodal for the Siberian Arctic (Figure 2b).  
The duration of the wildfire season in the Siberian Arctic increased by about 12 days during the 2001-2021 period, although changes varied by geographic sector. In WS, the fire season duration increased by 36 days, with no significant change in ES sector. For FE, fire season duration decreased by ca. 20 days (Figure 2c; Table 1). Similarly, the date of fire season onset trended earlier in WS and later in the FE (Table 1). Fire season duration in the WS sector was positively correlated to summer air temperatures, while the decrease in duration for the FE was related to precipitation, ground cover moisture, and SPEI drought  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline  & **Whole Siberian** & **Western Siberia** & **Eastern Siberia** & **Far East Sector** \\ \cline{2-5}
**Variables** & **Arctic** & **Sector** & **Sector** & **Sector** \\ \cline{2-5}  & \multicolumn{5}{c}{**Annual Fire Frequency**} \\ \hline Air temperature (June–August) & _0.66 **_ & _0.41 *_ & _0.68 **_ & _0.39 *_ \\ Precipitations (June–August) & \(-\)_0.56 **_ & \(-\)_0.38 *_ & \(-\)_0.53 **_ & \(-\)_0.36 \\ Ground cover moisture & \(-\)_0.82 **_ & \(-\)_0.46 **_ & \(-\)_0.84 **_ & \(-\)_0.50 **_ \\ (May–September) & \(-\)_0.68 **_ & \(-\)_0.42 *_ & \(-\)_0.70 **_ & \(-\)_0.50 **_ \\ \hline \multicolumn{5}{c}{**Burnt area extent**} \\ \hline Air temperature (June–August) & _0.70 **_ & _0.43 *_ & _0.68 **_ & _0.27_ \\ Precipitations (June–August) & \(-\)0.49 **_ & \(-\)_0.27_ & \(-\)_0.44 **_ & \(-\)_0.15_ \\ Ground cover moisture & \(-\)_0.76 **_ & \(-\)_0.34_ & \(-\)_0.78 **_ & \(-\)_0.49 **_ \\ (May–September) & \(-\)_0.59 **_ & \(-\)_0.56 **_ & \(-\)_0.62 **_ & \(-\)_0.56 **_ \\ \hline \multicolumn{5}{c}{**Fire season duration**} \\ \hline Air temperature & 0.41 * & 0.72 ** & 0.19 & _0.28_ \\ Precipitations (June–August) & \(-\)0.47 ** & \(-\)0.22 & \(-\)0.32 & \(-\)_0.39 *_ \\ Ground cover moisture & \(-\)0.48 ** & \(-\)0.50 ** & \(-\)0.43 **_ & \(-\)_0.61 **_ \\ (May–September) & \(-\)0.09 & \(-\)0.10 & \(-\)0.25 & \(-\)_0.62 **_ \\ \hline \multicolumn{5}{c}{**Northern boundary**} \\ \hline Air temperature & 0.41 * & _0.65 **_ & 0.38 * & _0.18_ \\ (May–September) & \(-\)0.26 & \(-\)_0.25_ & \(-\)0.36 & \(-\)_0.37 *_ \\ \hline Ground cover moisture & \(-\)0.28 & \(-\)_0.42 **_ & \(-\)0.32 & \(-\)_0.33_ \\ (May–September) & \(-\)0.68 ** & \(-\)_0.27_ & \(-\)0.62 **_ & \(-\)_0.15_ \\ \hline \multicolumn{5}{c}{**Onset date**} \\ \hline Air temperature (May–June) & \(-\)0.41 * & \(-\)0.59 ** & \(-\)0.32 & \(-\)0.23 \\ \hline \multicolumn{5}{c}{**Final date**} \\ \hline Air temperature & 0.29 & 0.58 ** & _0.11_ & 0.09 \\ (August–September) & & & & \\ \hline \hline \end{tabular}  
* Values in the table are Pearson and Spearman (italic) correlation coefficients. Spearman statistic was used in cases of non-Gaussian distribution. Significance levels at \(p\) < 0.10 (*) and \(p\) < 0.05 (**) are marked. \({}^{\rm{B}}\) SPEI is Standardized Precipitation Evaportargiration Index. Median values were used in analysis. Note: SPEI increase corresponded to the drought decrease by definition.  
\end{table}
Table 2: Correlation of wildfire characteristics with climate in the Siberian Arctic (2001–2021) \({}^{\rm{A}}\).  
index (Table 2). In WS, higher air temperature was associated with an earlier onset and longer duration of the fire season (Table 1).