Analysis of the diurnal variation of the global electric circuit obtained from different numerical models

This work analyzes different current sourceand conductivity parameterizations and their influence on the diurnalvariation of the global electric circuit (GEC). The diurnalvariations of the current sourceparameterizations obtained using electric field and conductivity measurements from plane overflights combined with global TRMM satellite data give generally good agreement with measured diurnalvariation of the electric field at Vostok, Antarctica, where reference experimental measurements are performed. An approach employing 85-GHz passive microwave observations to infer currents within the GEC is compared and shows the best agreement in amplitude and phase with experimental measurements. To study the conductivity influence, GEC models solving the continuity equationin 3-D are used to calculate atmospheric resistance using yearly averaged conductivity obtained from the global circulation model CESM. Then, using current sourceparameterization combining mean currents and global counts of electrified clouds, if the exponential conductivity is substituted by the conductivity from CESM, the peak to peak diurnalvariation of the ionospheric potential of the GEC decreases from 24% to 20%. The main reason for the change is the presence of clouds while effects of 222Rn ionization, aerosols and topography are less pronounced. The simulated peak to peak diurnalvariation of the electric field at Vostok is increased from 15% to 18% from the diurnalvariation of the global current in the GEC if conductivity from CESM is used.