A study on the interpolation of fire danger using radar precipitation estimates

In Canada, many fire management agencies interpolate indexes of the Fire We ather Index System to estimate the fire danger between weather stations. Di fficulties with interpolation arise because summer precipitation can be hig hly variable over short distances. This variability hinders the usefulness of interpolating precipitation, which is one of the inputs for the Fire Wea ther Index System. Precipitation estimates from the Canadian Atmospheric En vironment Service radar at Upsala, Ontario, were used to determine if this will enable a more accurate measure of the fire danger over the region. Thr ee methods of interpolation of the fire danger between weather stations wer e compared: first, the standard practice of interpolating fire weather inde xes from weather stations to any specified location; second, interpolating the weather variables, temperature, relative humidity, wind speed and preci pitation from the weather station to any specified site and then calculatin g the fire weather indexes; third, interpolating weather variables as in Me thod 2 above except using the precipitation estimate from the radar and the n calculating the fire weather indexes for any specified site. Overall, res ults indicate that the standard procedure of interpolating the fire weather indexes performs better than the other two methods. However, there are ind exes where the other methods perform best (e.g., the fine fuel moisture cod e is best determined by using the radar precipitation estimation method). F ire management agencies should continue to use the standard practice of int erpolating fire weather indexes to estimate fire danger between weather sta tions. Factors influencing the performance of the radar estimated precipita tion method of estimating fire danger are discussed along with potential ap plication of precipitation radar for fire management purposes.