Abstract
We present a new high‐resolution model of the Earth's global atmospheric electric circuit (GEC) represented by an equivalent electrical network. Contributions of clouds to the total resistance of the atmosphere and as current generators are treated more realistically than in previous GEC models. The model of cloud current generators is constructed on the basis of the ISCCP cloud data and the OTD/LIS lightning flash rates and TRMM rainfall data. The current generated and the electric resistance can be estimated with a spatial resolution of several degrees in latitude and longitude and 3 hour time resolution. The resistance of the atmosphere is calculated using an atmospheric conductivity model which is spatially dependent and sensitive to the level of solar activity. An equivalent circuit is constructed assuming the ionosphere and ground are ideal conductors. The circuit solution provides diurnal variations of the ionospheric potential and the GEC global current at the 3 hour time resolution as well as the global distributions and diurnal variations of the air‐Earth current density and electric field. The model confirms that the global atmospheric electric activity peaks daily at ∼21 UT. The diurnal variation of the ionospheric potential and the global current have a maximum at 12 and 21–24 UT in July and at 9 and 21 UT in December, and a global minimum at 3–6 UT independent of season. About 80% of the current is generated by thunderstorm convective clouds and 20% by mid‐level rain clouds.
Highlights
[2] The Engineering model of the Global ATmospheric Electric Circuit (EGATEC) was proposed to develop a novel engineering quasi‐3D model of the Earth’s DC global atmospheric electric circuit (GEC)
The majority of the models have been concerned with the flow of the electric current from thunderstorms, playing the role of the batteries driving the circuit through conduction currents and lightning, and the distribution of the electric potential in the vicinity of thunderstorms and mapping of the fields in the ionosphere
[66] In this paper we have presented a new, high‐resolution engineering model of the global electric circuit
Summary
[2] The Engineering model of the Global ATmospheric Electric Circuit (EGATEC) was proposed to develop a novel engineering quasi‐3D model of the Earth’s DC global atmospheric electric circuit (GEC). The rainfall estimates are gridded on at 3‐hour temporal resolution, similar to the ISCCP data, and 0.25° spatial resolution in a belt extending from 50°N to 50°S latitude (40°N to 40°S prior to February 2000, http://trmm.gsfc.nasa.gov/3b42.html) Both the lightning flash rate and the rainfall level is further used in the model to provide more information for an adequate division of the ISCCP clouds into current generator and non‐generator categories and to calculate equivalent DC current generators (Section 4). [34] In addition, for the non‐thunderstorm cloud generators we assume that they not produce any lightning and that their equivalent current source amplitudes are at 20% of that for thunderclouds (Mach et al [2010] obtained 25% from their analysis) This magnitude of the current sources produces electric fields inside and below the cloud of the order of 102–103 V/m, in agreement with values from [Imyanitov and Shifrin, 1962, Tables I and II and Figure 23d].
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