A new approach to calculate electric fields and charge density distribution when lightning strikes a tall object

•This paper for the first time derives electric field expressions in the monopole technique.•Derive charge density expressions along the tall object and lightning channel.•Very-close range electric fields are calculated based on this new method and compared with the results of traditional dipole technique.•Provide an alternative explanation to the inverse of polarity of the vertical electric field at very close range from the tall object base.