Potential MJO Impacts on Global Wildfires

The Madden-Julian Oscillation (MJO) influences weather events globally. Because of its effects on variables such as temperature, precipitation, and lightning, the MJO has the potential to affect wildfires in the extratropics as well as the tropics. Wildfires are closely related to meteorology and climatology, but also influenced by the biosphere and human activities. To identify an MJO signal in wildfire data, MJO events were identified using the Real-time Multivariate MJO (RMM) index. Preliminary investigation utilized data from the SPITFIRE model. This model is able to reproduce satellite observations of wildfire climatology, and is thus a useful reference point to search for MJO effects on wildfires. Global composites of model data were made to locate areas that showed strong signals. These areas were then analyzed individually in detail to discern the MJO's impact on the local scale, as well as to rule out small-scale effects in the observed signal. The four variables from the model used in the analysis were the Nesterov Index (NI), which incorporates surface temperature and humidity; the Fire Danger Index (FDI), which adds the availability of fire fuel to the NI for a more robust estimate of fire threat; burn area, and fire number within a grid box. It is found that these variables fluctuate through the life cycle of the MJO, although their pattern varies over different regions. The results confirm the MJO impact on wildfires in many regions of the world and point to the direction of further studies to understand the physical mechanisms for this impact.