  We have developed a code that semi-analytically calculates the radio
footprint (intensity and polarization) of an extensive air shower subject to
atmospheric electric fields. This can be used to reconstruct the height
dependence of atmospheric electric field from the measured radio footprint. The
various parameterizations of the spatial extent of the induced currents are
based on the results of Monte-Carlo shower simulations. The calculated radio
footprints agree well with microscopic CoREAS simulations.
