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Full Citation: Lutz, James A.; van Wagtendonk, Jan W.; Thode, Andrea E.; Miller, Jay D.; Franklin, Jerry F. 2009. Climate, lightning ignitions, and fire severity in Yosemite National Park, California, USA. International Journal of Wildland Fire 18(7):765-774.
External Identifier(s): 10.1071/WF08117 Digital Object Identifier
Location: Yosemite National Park, California, U.S.
Ecosystem types: Lower montane, upper montane, and subalpine vegetation
Southwest FireCLIME Keywords: None
FRAMES Keywords: burn severity, NBR - Normalized Burn Ratio, Sierra Nevada, Yosemite National Park, climate change, climate variability, snowpack, fire regime attributes, landscape flammability, patch complexity, snow water equivalent, Abies concolor, Abies magnifica, coniferous forests, elevation, fire frequency, fire intensity, fire management, fire regimes, fire size, forest management, ignition, Juniperus occidentalis, lightning, lightning caused fires, mosaic, national parks, Pinus albicaulis, Pinus contorta, Pinus jeffreyi, Pinus lambertiana, Pinus monticola, Pinus ponderosa, ponderosa pine, Populus tremuloides, precipitation, Pseudotsuga menziesii, Douglas-fir, Quercus kelloggii, rate of spread, Sequoiadendron giganteum , remote sensing, Tsuga mertensiana, water, wildfires

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Climate, lightning ignitions, and fire severity in Yosemite National Park, California, USA

James A. Lutz, Jan W. van Wagtendonk, Andrea E. Thode, Jay D. Miller, Jerry F. Franklin
Summary - what did the authors do and why?

The authors examined fire-climate relationships between snowpack accumulation and fire ignition, size, and severity of lightning-ignited fires from 1984 to 2005.
Publication findings:

The authors found that the 1 April snow water equivalent (SWE) is correlated with the number of lightning-ignited fires and area burned. High levels of persistent snowpack later into the year decreases the possibility of lightning-ignited fires during the fire season. Conversely, low levels lead to an increase in fire activity earlier in the fire season. The type and duration of winter precipitation greatly affects the fuel moisture conditions of the early fire season, and to a lesser extent, the late fire season as fuels are typically dry regardless of the previous winter’s precipitation. However, the relationship between SWE and area burned was weaker as bottom-up controls were stronger predictors of fire behavior on the landscape. However, they found that fire season length is not directly related to fire severity in that a longer fire season does not necessarily result in more severe fire across the landscape, especially in more drought tolerant ecosystems. Convective instability associated with high temperatures may also lead to increased lightning occurrence and thus increased ignition rates. Should spring SWE decrease, landscape flammability may increase and become more variable.

Climate and Fire Linkages

How do fire season length and ERC relate to fire severity?

The authors found that the 1 April snow water equivalent (SWE) is correlated with the number of lightning-ignited fires and area burned. High levels of persistent snowpack later into the year decreases the possibility of lightning-ignited fires during the fire season. Conversely, low levels lead to an increase in fire activity earlier in the fire season. The type and duration of winter precipitation greatly affects the fuel moisture conditions of the early fire season, and to a lesser extent, the late fire season as fuels are typically dry regardless of the previous winter’s precipitation. However, the relationship between SWE and area burned was weaker as bottom-up controls were stronger predictors of fire behavior on the landscape. However, they found that fire season length is not directly related to fire severity in that a longer fire season does not necessarily result in more severe fire across the landscape, especially in more drought tolerant ecosystems.

How do temperature, relative humidity and vapor pressure deficit relate to annual area burned and fire size?

Convective instability associated with high temperatures may also lead to increased lightning occurrence and thus increased ignition rates.

How do snowpack and precipitation (snow/rain) relate to annual area burned and fire size?

The authors found that the 1 April snow water equivalent (SWE) is correlated with the number of lightning-ignited fires and area burned. High levels of persistent snowpack later into the year decreases the possibility of lightning-ignited fires during the fire season. Conversely, low levels lead to an increase in fire activity earlier in the fire season. The type and duration of winter precipitation greatly affects the fuel moisture conditions of the early fire season, and to a lesser extent, the late fire season as fuels are typically dry regardless of the previous winter’s precipitation. However, the relationship between SWE and area burned was weaker as bottom-up controls were stronger predictors of fire behavior on the landscape. However, they found that fire season length is not directly related to fire severity in that a longer fire season does not necessarily result in more severe fire across the landscape, especially in more drought tolerant ecosystems. Convective instability associated with high temperatures may also lead to increased lightning occurrence and thus increased ignition rates. Should spring SWE decrease, landscape flammability may increase and become more variable.