Abstract Background To make strategic decisions about safety and resource allocation, managers must understand when prescribed burn windows of opportunity occur, how they vary throughout the year, and how to anticipate them. For two burn types—pile and broadcast—we characterize the temporal and spatial distributions of past “go-burn” days identified from a database of 15,468 burn permits from 2011 to 2024 in the Northern California Geographic Area Coordination Center’s region. We assess the mean temporal evolution of daily anomalies of local- and synoptic-scale environmental variables that occurred in the 2 weeks surrounding those ignitions. We then estimate the mean number of historical burn windows for both burn types in each month using a novel approach to define our prescription criteria. This approach defines the criteria based on ranges of environmental conditions present on past go-burn days. Results Broadcast burns exhibit a strong seasonal signal with the greatest number of ignitions in June and October. Pile burns were four times more numerous than broadcast burns and occurred most often in November–December. Ignition locations varied by month and burn type; e.g., piles ignited in the fall most often occurred in the Sierra while piles ignited in the spring most often occurred in the Foothills ecoregion. Composite local- and synoptic-scale variables indicated preferences for certain environmental conditions depending on the month. Conditions preceding February broadcast burns exhibited warming and drying near the surface and anomalous ridge patterns in the upper atmosphere. Pile burns in October were associated with cooler and wetter surface conditions and anomalous trough patterns aloft. The expected number of burn windows varied by month and burn type (e.g., broadcast burn windows were, on average, three times more likely than those of piles in October). Conclusions We found that ample opportunities exist in northern California for burning throughout the year, yet those opportunities heavily depend on burn type. Findings herein are useful for determining favorable environmental patterns that create burn windows and for identifying priority locations and times to implement broadcast and pile burns.
Worsnop et al. (Mon,) studied this question.