A climatological study of the Keetch/Byram drought index and fire activity in the Hawaiian Islands

The Hawaiian Islands experience damaging wildfires on a yearly basis. Soil moisture or lack thereof, influences the amount and flammability of vegetation. The Keetch and Byram drought index (KBDI) estimates the amount of soil moisture by tracking daily maximum temperatures and rainfall. For the first time, the relationship between the KBDI and fire activity on the Hawaiian Islands is examined using a number of different techniques. The KBDI is calculated daily for a 20-year period and then tested on a monthly time-scale on four major Hawaiian Islands against total area burned (TAB). The use of monthly TAB data for an individual island is a necessity when considering the relatively low frequency of fire activity and the small spatial scale of the islands. The relationship between the KBDI with TAB is explored with a number of rigorous statistical methods. A strong relationship between the KBDI and fire activity for the islands of Oahu, Maui, and Hawaii is found. At present a network of stations is used to operationally monitor fire danger on a daily basis.