Analysis is based on a following set of simple assumptions. A thundercloud is represented by a vertical dipole of positive polarity. Electrical conductivity of the atmosphere increases exponentially with height, and not altered by presence of thundercloud. Electromotive force in thundercloud is represented by a constant current generator. It is taken that an electric field consists of three parts. The first is field due to charge in each pole which increases at a rate depending on electrical conductivity of the air at a height of pole; the second, due to space charge which grows with charges in poles; the third, due to free decaying space charge which is released after a lightning discharge. Characteristic dissimilarity of the form of field recovery curve, observed after a near discharge to that of distant discharge, is well interpreted by this analysis.