Meteorological impact on MODIS observed boreal fire counts: the role of lightning

Meteorological impacts on the variability of wildfires in boreal North America including Alaska and Canada are investigated using six years of the MODIS fire counts, the meteorological data from North American Regional Reanalysis (NARR), and the lightning data collected by the Canadian Lightning Detection Network (CLDN) and the Bureau of Land Management's Alaska Lightning Detection Network (ALDN). An algorithm is created to integrate and match the fire, lightning, and NARR data to the 32 km NARR grid. This unique dataset allows for the derivation of dry and wet lightning strikes across the entirety of northern North America. Using six regional domains defined to specifically include the core of the North American boreal forest, a detailed spatial and temporal analysis is performed to discern the seasonal and interannual variability of dry and wet lighting strikes. In addition, the meteorological variables contributing to these lightning events and to the number of observed fire counts are analyzed. It is reveled that the combination of low-level instability and anomalously high 500 hPa geopotential heights result in a greater number of dry lightning strikes and MODIS fire counts. A closer investigation shows a complex relationship between the variables resulting in increased dry lightning activity and the variables resulting favorable fire conditions. Dry lightning strikes account for only 20% of the total lightning strikes however; they are related to 40% of the fire accounts that are associated with lightning activity. Furthermore, a new approach is taken to understand the role of moisture. Results highlight the importance of long stretches of consecutive dry days rather than precipitation amount to the number of observed fire counts.