A Study on the Interpolation of Fire Danger Using Radar Precipitation Estimates

In Canada, many fire management agencies interpolate indexes of the Fire Weather Index System to estimate the fire danger between weather stations. Difficulties with interpolation arise because summer precipitation can be highly variable over short distances. This variability hinders the usefulness of interpolating precipitation, which is one of the inputs for the Fire Weather Index System. Precipitation estimates from the Canadian Atmospheric Environment Service radar at Upsala, Ontario, were used to determine if this will enable a more accurate measure of the fire danger over the region. Three methods of interpolation of the fire danger between weather stations were compared: first, the standard practice of interpolating fire weather indexes from weather stations to any specified location; second, interpolating the weather variables, temperature, relative humidity, wind speed and precipitation from the weather station to any specified site and then calculating the fire weather indexes; third, interpolating weather variables as in Method 2 above except using the precipitation estimate from the radar and then calculating the fire weather indexes for any specified site. Overall, results indicate that the standard procedure of interpolating the fire weather indexes performs better than the other two methods. However, there are indexes where the other methods perform best (e.g., the fine fuel moisture code is best determined by using the radar precipitation estimation method). Fire management agencies should continue to use the standard practice of interpolating fire weather indexes to estimate fire danger between weather stations. Factors influencing the performance of the radar estimated precipitation method of estimating fire danger are discussed along with potential application of precipitation radar for fire management purposes.