Lightning and Fires in the Northwest Territories and Responses to Future Climate Change
Dates
Year
2006
Citation
Kochtubajda, B., Flannigan, M. D., Gyakum, J. R., Stewart, R. E., Logan, K. A., and Nguyen, T. V., 2006, Lightning and Fires in the Northwest Territories and Responses to Future Climate Change: Arctic, v. 59, no. 2, p. 211-221.
Summary
ABSTRACT. Lightning and fire characteristics within the Northwest Territories (NWT) jurisdiction of the Mackenzie Basin between 1994 and 1999 are examined using data from the lightning detection network operating in the NWT and from the national Large Fire Database maintained by the Canadian Forest Service. The convective storm season with associated lightning activity over this region is short hut intense, with a strong peak in cloud-to-ground lightning during July. The maximum area of lightning activity is influenced by local moisture sources and by topography. The diurnal distribution of cloud-to-ground flashes indicates that most of the lightning was linked to thunderstorms initiated by daytime heating. The lightning-initiated [...]
Summary
ABSTRACT. Lightning and fire characteristics within the Northwest Territories (NWT) jurisdiction of the Mackenzie Basin between 1994 and 1999 are examined using data from the lightning detection network operating in the NWT and from the national Large Fire Database maintained by the Canadian Forest Service. The convective storm season with associated lightning activity over this region is short hut intense, with a strong peak in cloud-to-ground lightning during July. The maximum area of lightning activity is influenced by local moisture sources and by topography. The diurnal distribution of cloud-to-ground flashes indicates that most of the lightning was linked to thunderstorms initiated by daytime heating. The lightning-initiated fire occurrences peaked during July, while much of the burned area was produced in June. The longer, warmer, and drier summer seasons projected to result from climate change are expected to increase the frequency and intensity of forest fires by the end of the 21st century. Their considerable consequences for forests and wildlife make these changes a concern for northern communities, forest managers, and wildlife biologists. The fire regime of the NWT can he described by the intensity, frequency, seasonality, size, type, and severity of the fires (Weber and [Flannigan], 1997). The fire season typically starts in late May and usually ends by early September (Forster, 1995). Cloud-to-ground lightning flashes associated with summer thunderstorms typically start approximately 80% of the forest fires in the NWT (Epp and Lanoville, 1996). Over the past 30 years, on average, 320 fires have occurred each year in the NWT, and these fires have consumed approximately 675 000 ha (Ward and Mawdsley, 2000). The number of fires and the area burned are highly variable from year to year (Fig. 5). The lowest number of fires in any year occurred during the 1997 fire season when only 105 fires were started, whereas the highest number of fires (627) occurred in 1994 (National Forestry Database). The spatial distribution of fires (Fig. 6) shows that most of the territory has experienced fires at some time. Figure 8 shows the ratio of 3 × CO2 to 1 × CO2 mean seasonal severity rating as predicted by the CCCma and Hadley models. Although both models suggest significant increases in SSR (CCCma: 1.19: Hadley: 1.44) averaged over the Mackenzie Basin, they differ in the details. The CCCma model suggests little change in SSR over the southern Mackenzie region of the NWT. but significant increases in northwestern NWT. The Hadley model, on the other hand, suggests significant increases in the southern NWT and northern Alberta and British Columbia, but decreasing SSR over northwestern NWT. This shows that there is a great deal of regional variation in the response to climate change. Some of these differences arise because the models differ in their large-scale scenario patterns. In addition, the coarse spatial resolution of the GCM (ca. 400 km) lowers confidence in its results over complex, mountainous terrain in part of our study region. In such areas, it is better to use a regional climate model (RCM) with finer spatial resolution (ca. 40 km: Caya and Laprise, 1999) that can better resolve the terrain.
