BYRAM DERIVATION OF THE ENERGY CRITERION FOR FOREST AND WILDLAND FIRES

G.M. Byram's energy criterion for forest and wildland fires consists o f two equations: one for computing the rate of flow of kinetic energy in the atmosphere due to the wind field (P(w)), and one for estimating the rate of conversion of thermal energy to kinetic energy in the con vection column (P(f)). The derivation of the equations has remained un published since their introduction in 1959. Byram considered the dimen sionless ratio of P(f) to P(w) an indicator of the vertical structure of convection over a fire and referred to the ratio as the convection number, N(c). In view of past and current interest in the behavior of large fires, Byram's derivation of the equations for P(w) and P(f) is presented along with a sketch and some additional wording for purposes of clarification. The assumptions and possible limitations in Byram's analysis are discussed.