Category:Fire Weather

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Fire Weather - Collectively, those weather parameters that influence fire occurrence and subsequent fire behaviour (e.g. dry-bulb temperature, relative humidity, wind speed and direction, precipitation, atmospheric stability, winds aloft).

(CIFFC Glossary of Forest Fire Management Terms)










Contents

Fire Weather Data Collection

Established Weather Stations

Alberta Environment and Sustainable Resource Development Forestry Division operates a network of close to 200 weather stations across Alberta

This network is made up of various data collection sources including lookout tower personnel, ranger stations, remote automated weather stations, contract observers and Environment Canada stations. Each of these data sources has different data collection schedules and outputs and some may be more applicable or useful for the research project. The Remote Automated Weather Stations (46 in Alberta) produces hourly weather data outputs. When using weather data from any of these sources, it is critical to assess how accurately the the weather station represents the conditions at the research area with respect to general weather (precipitation and prevailing winds), elevation and aspect. PM weather readings from most weather stations will include calculated FWI values for the station. Alberta SRD staff with access to the FIRES program can download weather data(current and historical) for these weather stations.

The British Colubia Wildfire Management Branch weather station network is comprised of 260 hourly weather stations which supply data inputs to the Canadian Forest Fire Danger Rating System and weather forecasting models. Hourly weather data can be made accessible to researchers through ministry personnel.

Environment Canada (need input)

On Site Automated Weather Station (AWS)

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Complex research programs will require more site specific weather data and will often erect an on site automated weather station. Often, the automated weather station will be placed at the burn site in the early spring to establish a reliable foundation of weather data and cumulative FWI values. Prescribed burn planners should place the on site automated weather station in a representative site as close to the prescribed burn as possible.

Automated weather stations should be located in a large, open area away from obstructions and sources of dust and surface moisture. Consider security (from animals and human vandalism) when selecting a site.


The following are guidelines for a typical fire management operation:

1. Locate the AWS in large, open area with environmental conditions representative of the area under study. Consider the following when choosing a AWS deployment site:

  • vegetation cover type
  • weather patterns - prevailing winds, precipation, temperature
  • topography - slope and aspect
  • elevation

2. The AWS should be located away from sources of dust (roads) and surface moisture (lakes, rivers).

3. Avoid microclimates such as paved areas or large reflective objects that will impact weather data.

4. Consider security from vandalism or disturbance from animals.

5. On larger or more complex burns, deployment of a second AWS may be worthwhile to record worst case conditions on the burn.

Interagency Wildland Fire Weather Station Standards and Guidelines. PMS 426-3. National Wildfire Coordinating Group.

Lawson and Armitage 2008 (page 23) discusses the benefits of automated weather stations and describes accuracy standards for the essential components these systems.

Weather data via hand-held radios

Alberta SRD radios have the capability to receive weather observations from the closest weather station (RAWS? or automated weather station).

Digital Weather Meters

The USDA Forest Service Tech Tip publication Evaluating Digital Meters for Fire Weather Observations describes various digital weather meters available at the time (2000) and the accuracies associated with each meter.

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KestrelTM meters are one of the most widely used hand held weather observation tools used in fire management operations.


Adherence to recommended operating proceduresand calibrationof the meter will ensure accurate weather data readings.

The KestrelTM 4500 with built in data logging and bluetooth capability has been used as a portable weather station and linked remotely with a laptop computer to download weather data in field studies by Vandermeer et al. (2011, p.3)

Fireline Belt Weather Kit

The sling psychrometer is essential for measuring relative humidity and is an integral component of the fireline belt weather kit. Detailed instructions for sling psychrometer use can be found in How to use the Fireline Belt Weather Kit. When determining relative humidity with the sling psycrometer, it is necessary to input the wet bulb temperature and the dry bulb temperature in a psychrometric table that is appropriate to the elevation of the readings. These tables can be found in Tables for the Canadian Forest Fire Weather Index System (page 41)

More elaborate models including the BacharachTM sling psychrometer are available. This model has a built in slide rule mechanism which will determine relative humidity from the wet bulb and dry bulb temperatures taken from with this sling psychrometer.

A fireline belt weather kit may include an anemometer however the Beaufort Wind Scale can be used to make reliable estimations without a wind measuring device. Appendix 4 (pg. 54) in the Field Guide to the Canadian Forest FBP System (Taylor 1997) provides environmental descriptors that can be used for estimating 10-meter open wind speeds.

Weather Observation Data sheet

Weather data should be recorded hourly (as a minimum) or every half hour (on more dynamic burns) and any sudden changes in weather (temperature, relative humidity, wind shifts or gusts, cloud cover, precipitation, etc.) should be recorded.

References

Canadian Forestry Service. 1984. Tables for the Canadian Forest Fire Weather Index System. Environ. Can., Can. For. Serv., For. Tech. Rep 25 (4th ed.).

Hirsch, K.G. 1996. Canadian forest Fire Behavior Prediction (FBP) System: user's guide. Nat. Resour. Can., Can. For. Serv., Northewest Reg., North. For. Cent., Edmonton, Alberta. Spec. Rep.7.

Interagency Wildland Fire Weather Station Standards and Guidelines. PMS 426-3. National Wildfire Coordinating Group.

Lawson, B.D.; Armitage, O.B. 2008. Weather guide for the Canadian Forest Fire Danger Rating System. Nat. Resour. Can., Can. For. Serv., North. For. Cent., Edmonton, AB.

Lemon, G., Mangan, D. 2000 Evaluating Digital Meters for Fire Weather Observations. USDA Forest Service. Technology and Development Program.

Taylor,S.W.; Pike R.G.; Alexander,M.E. 1997. Field guide to the Canadian Forest Fire Behavkor Prediction (FBP) System. Nat. Resour. Can., Can. For. Serv., North. For. Cent., edmonton, alberta. Spec. Rep.11

Turner, J.A. and Lawson, B.D. 1978. Weather in the Canadian forest fire fanger rating system. A user guide to national standards and practices. Fisheries and Environment Canada, Canadian Forest Service, Pacific Forest Research Centre, Victoria, BC. Information Report BC-X-177. 40 p.

Vandermeer,S.; Ault,R.; Hvenegaard,S. 2011. An evaluation of handheld infrared cameras for ground initial attack crew use during wildfire mop-up operationsFPInnovations Wildland Fire Operations Research Group

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