Abstract
Wildland fire behavior is highly dependent upon local meteorological conditions. While topography and the state of available fuels also influence fire behavior and spread, near-surface atmospheric conditions in proximity to wildland fires are the most dynamic determining variables for wildfire evolution. Recent episodes of drought across the southern High Plains have contributed to unprecedented wildfire activity in the region’s grasslands, including within the Texas Tech University West Texas Mesonet (WTM) domain. The juxtaposition of this meso-network with the occurrence of numerous wind-driven wildfires has provided a unique dataset of proximity meteorological observations useful in analyzing fire start environments. This study presents statistical analyses of WTM 2-m relative humidity and 6-m wind speed, parameters utilized in local Red Flag fire weather warning criteria, along with 2-m temperature in temporal and spatial proximity to 99 wind-driven grassland wildfire starts which occurred between January 2006 and May 2010. Since the state of vegetative fuels also influences fire behavior, but is dependent upon local weather, the proximity observations are used to calculate fine dead-fuel moisture and to examine pre-conditioning potential per the preceding humidity recoveries for each documented fire start. A comparison of the meteorological observations to local Red Flag warning criteria, which was met or exceeded for critical values of relative humidity and wind speed in 64% of the surveyed fire starts, also is included. Furthermore, seasonal and diurnal tendencies for local wind-driven wildfire activity are noted.
Highlights
Episodes of long-term drought, interrupted by brief reprieves of periodic heavy rainfall, have characterized the climatology of the southern High Plains in recent years
National Weather Service (NWS) policy defines critical values for these meteorological parameters that serve as explicit criteria for local Red Flag warnings (RFWs)
Remotely-sensed start times and locations were found using the initial detection of either biomass debris lofted within smoke plumes via radar reflectivity or infrared satellite “hot spots” detected in 4 km 11–3.9 μm channel imagery (Fig. 1) for each of the 99 winddriven wildfire starts documented within the West Texas Mesonet (WTM) domain (Huang et al 2007 and Jones and Christopher 2010)
Summary
Episodes of long-term drought, interrupted by brief reprieves of periodic heavy rainfall, have characterized the climatology of the southern High Plains in recent years An artifact of this climatic variability has been an enhanced cycle of vegetative growth and curing of abundant grassland biofuels that has contributed to increased levels of wildland fire activity (Van Speybroeck et al 2007). This study presents analyses of observed meteorological WTM data obtained in spatial and temporal proximity to 99 wind-driven grassland wildfire starts The presentation of these proximity observations and analyses is preceded by a discussion of seasonal and diurnal trends for local wildfire activity evident in the dataset. The observations are differentiated by the eventual fire size for each start to further illustrate how specific combinations of RH and wind speed may influence potential for fire growth
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