HR: 08:20h
AN: AE41A-02    [PDF]
TI: Lightning Behaviour in the Northwest Territories, Canada
AU: * Kochtubajda, B
EM: bob.kochtubajda@ec.gc.ca
AF: Environment Canada, Meteorological Service of Canada, Room 200, 4999 98th Avenue, Edmonton, AB T6B 2X3 Canada
AU: Flannigan, M D
AF: Canadian Forest Service, Great Lakes Forest Research Centre, 1219 Queen Street East, Sault Ste Marie, ON P6A 2E5 Canada
AU: Gyakum, J R
AF: McGill University, Dept. Atmospheric and Oceanic Sciences, 805 Sherbrooke Street West, Montreal, QC H3A 2K6 Canada
AU: Stewart, R E
AF: McGill University, Dept. Atmospheric and Oceanic Sciences, 805 Sherbrooke Street West, Montreal, QC H3A 2K6 Canada
AU: Way, A
AF: McGill University, Dept. Atmospheric and Oceanic Sciences, 805 Sherbrooke Street West, Montreal, QC H3A 2K6 Canada
AB: Thunderstorms play an important role in the cycling of water and energy over the boreal ecosystem of the Northwest Territories (NWT) of Canada during the warm season. Associated lightning activity can also initiate forest fires. Global distributions of lightning derived from satellite observations indicate that this region experiences a relatively large amount of lightning, given its high latitude location. However, no previous work has been directly applied to the NWT. A variety of data sets have been used to study lightning activity, cloud and convective processes in the water cycle and their impacts on the forests of the NWT for the 1994-1999 fire seasons. These include the archived strike data from the lightning detection network operating in the NWT, fire data from the Canadian Forest Service's national Large Fire Database, surface and upper-air station data, and historical gridded data from the Environment Canada and the National Centers for Environmental Prediction (NCEP) digital archives. Lightning activity over the NWT is linked with its geographic alignment, large scale flows, and diurnal heating cycle. The convective storm season and resultant lightning activity is characterized as short but intense with a strong peak in cloud-to-ground lightning during June and July. The maximum area of lightning activity varies in space and in time and is influenced by local moisture sources (such as wetland areas and small lakes) and by topography. The diurnal distribution of strikes indicates that most of the lightning is linked with daytime-heating initiated thunderstorms. There was a relatively low amount of lightning activity during the 1994-95 seasons but an unusually high fraction of positive lightning strikes during 1995. The positive ground strikes may have been influenced by the presence of smoke from fires. Lightning-initiated fire occurrence peaks during July, while much of the burned area occurs in June. Events with an especially large number of lightning strikes (more than 2000) are characterized by the eastward progression from the Gulf of Alaska toward the Mackenzie Basin of an anomalously strong 500-hPa trough, and the associated breakdown of a strong 500-hPa ridge over the NWT.
DE: 3304 Atmospheric electricity
DE: 3314 Convective processes
DE: 3324 Lightning
DE: 3364 Synoptic-scale meteorology
SC: Atmospheric and Space Electricity [AE]
MN: 2003 Fall Meeting