The Southwest Monsoon and the relation to fire occurrence

In southeastern Arizona, a decline in climatological fire starts occurs in early July. The decline coincides with the arrival of the Southwest Monsoon, a seasonal climate phenomenon impacting southeastern Arizona. Corresponding changes in atmospheric elements such as relative humidity and dew point in conjunction with the monsoon could be some of the mitigating factors. Determining the extent of the monsoon's role in fire occurrence has not been well quantified or documented in either the climate or fire communities. The problem becomes quite complex given the interannual spatial and temporal variability in both the monsoon and fire occurrence. The changes in atmospheric conditions stemming from the monsoon result in both fire producing and fire mitigating effects.; This study examines the applicability of two existing definitions of the monsoon onset to fire occurrence and quantitatively assesses fire and atmospheric moisture elements occurring within the monsoon season. Historical fire occurrence data and weather data from Remote Automatic Weather Stations in southeastern Arizona are analyzed in an effort to improve understanding of this fire-monsoon relationship.