Revisiting Pyroclimographs

Benjamin Hatchett 

Wildland fire activity often demonstrates distinct seasonality. Multiple peaks of activity may occur throughout the year with varying magnitudes and durations due to climatologically conducive conditions for wildfire activity or intentional burning. However, anomalous fire environment conditions may favor out-of-season wildfires. Characterization of conditions that increase fire ignition probabilities, extreme fire behavior, and beneficial fire potential enhances our understanding of fire history and past fire behavior while providing insight into how forecast conditions may influence subsequent wildland fires. Here, we apply a commonly-utilized approach to display a region’s temperature and precipitation climatology--the climograph--to visually communicate the seasonal cycle, interannual variability, and individual wildland fire events at daily resolution. We use period-of-record satellite observations from the Moderate Resolution Imaging Spectroradiometer and the Visible Infrared Imaging Radiometer Suite. Counts of detections and cumulative fire radiative power provide first-order indicators of elevated or reduced fire activity, either typically (i.e., wildfire season or prescribed burning season) or anomalously (i.e., out-of-season wildfire). Using a case study of Southern California, we show how pyroclimograph results vary as the region of interest shifts and how their interpretation can be complemented with additional fire environment data.