The great interest of the concerned problem is explained by the influence of large forest fires on the ground level layer of the atmosphere, which causes medium temperature drop due to the area smoke screen and leads to the damage or delay of agricultural plant ripening and to various ecological disasters. Considering that, natural investigations of these problems are merely impossible and methods of mathematical modeling are urgent. This paper, inscribed in the context of the general mathematical model of forest fires, gives a new mathematical setting and a method of numerical solution of a problem of a large forest fire initiation. The objective of the present research is to define dimensions of the ignition zone and to study photochemical processes which are taking place.
