Analysis of the Diurnal Variation of the Global Electric Circuit Obtained From Different Numerical Models

Abstract

This work analyzes different current source and conductivity parameterizations and their influence on the diurnal variation of the global electric circuit (GEC). The diurnal variations of the current source parameterizations obtained using electric field and conductivity measurements from plane overflights combined with global Tropical Rainfall Measuring Mission satellite data give generally good agreement with measured diurnal variation 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 equation in 3‐D are used to calculate atmospheric resistance using yearly averaged conductivity obtained from the global circulation model Community Earth System Model (CESM). Then, using current source parameterization combining mean currents and global counts of electrified clouds, if the exponential conductivity is substituted by the conductivity from CESM, the peak to peak diurnal variation 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 diurnal variation of the electric field at Vostok is increased from 15% to 18% from the diurnal variation of the global current in the GEC if conductivity from CESM is used.

Toward a Realistic Representation of Global Electric Circuit Generators in Models of Atmospheric Dynamics

“…To summarize, neither of the existing attempts to simulate the diurnal variation of the GEC using a climate or weather forecasting model has succeeded in obtaining a realistic peak‐to‐peak amplitude (cf. Mareev & Volodin, , Figure 1a; Lucas et al, , Figure 7; Jánský et al, , Figure 3a). Our analysis has shown that when parameterizing the IP, it is important to take into account both convective activity (CAPE) and the area covered by electrified clouds (which can be inferred from the amount of precipitation), but neither of various reasonable alterations of our basic IP parameterization is able to significantly improve the agreement in magnitude between the simulated IP variation and the classical Carnegie curve.…”

“…Of these three parameters convective mass flux was found to provide the best characterization of the current distribution estimated from the TRMM (Tropical Rainfall Measuring Mission) satellite data. Jánský et al (2017) simulated the diurnal variation of GEC parameters (the IP, total current, fair-weather electric field at the Earth's surface) both by directly inferring GEC parameters from the CESM data (utilizing the parameterization developed by Kalb et al, 2016) or TRMM data and by calculating them in GEC models with the sources parameterized on the basis of these data. It is interesting that the graphs of the diurnal variation based on the TRMM data showed much better agreement with the classical Carnegie curve than those based on modeling with the CESM: The latter have smaller peak-to-peak amplitudes and reach their maxima about 5 hr earlier than the classical Carnegie curve.…”

Modeling Contributions of Continents and Oceans to the Diurnal Variation of the Global Electric Circuit

“…The focus on the IP makes it possible to analyze diurnal variations of contributions to the GEC from different land and ocean regions. There have been only few attempts to reproduce GEC variation in models of atmospheric dynamics (Jánský et al, 2017;Lucas et al, 2015;Mareev & Volodin, 2014); however, 10.1029/2019GL083166 previous modeling studies did not consistently address the problem of regional contributions, dealing with few regions bounded by large rectangles or even just by meridians; here we for the first time simulate and discuss regional contributions in detail, emphasizing the contrast of atmospheric dynamics above land and ocean.…”

“…Their sum, shown in Figure 2e, has the same shape as the classical Carnegie curve, known from electric field observations and shown in Figure 2f (after Harrison, 2013), although with maxima shifted by about 2 hr and with about 46% smaller peak-to-peak amplitude (18% of the mean against 34% of the mean). Since Figures 2c and 2d imply that contributions of land regions have larger relative peak-to-peak variation than those of oceans (54% and 7% of the respective means), it is likely that IP parameterizations based on convection overestimate ocean contributions, for Mareev and Volodin (2014) and Jánský et al (2017) obtained peak-to-peak amplitudes of the same order when using convection to parameterize GEC source currents in climate models. Note that our IP parameterization reproduces the shape of the classical Carnegie curve better than those used in previous studies in that it correctly predicts one minimum and two maxima within 1 or 2 hr of the real ones.…”

“…Investigating the diurnal cycle of atmospheric electricity facilitates understanding this relationship between the GEC and weather. Over the past few years, the interest in studying the diurnal variation of atmospheric electrical parameters has been increasing; recent progress in this direction is related to satellite and aircraft cloud observations (Liu et al, 2010;Mach et al, 2011;Peterson et al, 2017), analyzing the data of global lightning locating systems (Hutchins et al, 2014;Mezuman et al, 2014), and using weather and climate models to simulate DC GEC parameters (Jánský et al, 2017;Kalb et al, 2016;Mareev & Volodin, 2014) and distribution of lightning flashes (Romps et al, 2018).…”