22
faults and the ionosphere were suggested as GEC generators in addition to thun‑
derstorms in order to account for the observed variations of the ionospheric total
electron content.
In [27] the relations were analysed between distributed GEC models and
simplified equivalent-circuit models, where different parts of the atmosphere are
replaced by equivalent resistors and capacitors; the limitations of such models
were established. The influence of conductivity inhomogeneities on the iono‑
spheric potential was also studied; it was shown that the account of conductivity
reduction inside a thunderstorm generator may lead to substantial increase in its
contribution to the GEC. The mechanisms whereby conductivity perturbations
in the atmosphere have an impact on the ionospheric potential dynamics were
also discussed in [25].
One of the main reasons for the increasing interest in
the GEC during the last
few years is the close connection between electrical processes in the atmosphere
and the climate dynamics. In [28] the dynamics of the ionospheric potential on
different time scales was studied using a general circulation model. A parame‑
terization was suggested for the contribution to the ionospheric potential from
convection regions, associated with electrified clouds, i. e. with GEC generators.
The calculated diurnal and seasonal ionospheric potential variations turned out
to agree with the experimental data; also, the decrease in the ionospheric poten‑
tial by about 10% over the 21st century was predicted.
In [29] the principal criteria were formulated for the formation and mainte‑
nance of a GEC in the atmospheres of the Solar System planets. Having estimat‑
ed the vertical conductivity profile in the atmosphere of Mars, the authors con‑
cluded that there is no stationary GEC on Mars, but the current still can flow in
the circuit, if a high-power and extensive generator, presumably related to the
electrification
during the dust storms, is working.
3. Electrical processes in clouds and their simulation
The problem of generation and evolution of the intense convective systems
is one of the most topical and complicated problems of the atmospheric physics.
Investigation of electrical processes in convective systems is necessary for
self‑consistent analysis of the atmospheric dynamics and for increasing the pre‑
cision of weather forecasts. During the period 2010–2015 in Russian Federation
a number of attempts were made to include the main electrical processes in hy‑
drodynamic numerical models of the atmosphere [30–33]. Numerical non-sta‑
tionary three-dimensional model of a convective cloud with parameterized de‑
scription of microphysical processes allowing for the electrification was
developed by a scientific group from RosHydroMet Voeikov Main Geophysical
Observatory. The spatio-temporal distribution of the main cloud characteristics,
E. A. Mareev, V. N. Stasenko, A. A. Bulatov, S. O. Dementyeva, A. A. Evtushenko, N. V. Ilin, ...
23
Atmospheric
Electricity
including the volume charge density and the electric field, were estimated. The
calculations showed that the electric structure of the cloud is different at various
stages of its life, i. e., it varies from unipolar to dipolar and then to tripolar. These
results are in a fair agreement with the field studies [30,31]. Numerical calcula‑
tions of the convective cloud formation during unstable atmospheric stratification
and in the presence of background wind were performed by means of the
three-dimensional non-stationary model developed in RosHydroMet High
Mountain Geophysical Institute with detailed description of hydrodynamic, ther‑
modynamic, microphysical, and electric processes. The formation of the positive
and negative volume electric charges was studied, and the electric field at various
stages of cloud development was calculated with the help of this model. It was
found that the precipitation particle growth time in an intense convective cloud
decreases by 30% due to electric coagulation [32, 33]. A hazardous meteorolog‑
ical phenomenon, bora in Novorossiysk, was studied using the results of numer‑
ical modelling based on the WRF-ARW mesoscale atmospheric model, the
SWAN model of wind waves and the observational data obtained during expe‑
ditions [34]. The WRF model proved to simulate bora qualitatively well; this fact
shows that mesoscale atmospheric models could successfully reproduce such
events.
Predicting lightning activity is important for different applications and fun‑
damental research. Nowadays in most cases indirect nonelectrical indices are
used for such forecasts. However, this method, which considers thermodynamic
and microphysical features of the convective cloud evolution, but does not in‑
clude non‑local interaction of
electrical charged particles, is not capable to pre‑
dict lightning activity with high accuracy. Forecasts based on indirect indices
depending on the parameterization of microphysical processes in the WRF mod‑
el were studied in papers [35, 36]. A new algorithm of predicting lightning ac‑
tivity was proposed on the basis of direct calculation of the electric potential and
the electric field in thunderclouds with the help of the WRF model data [35–38].
The results yielded by this model were shown to be in accordance with the ex‑
perimental data concerning the electrical characteristics of thunderclouds. The
simulation of real thunderstorms in Nizhny Novgorod region showed good cor‑
relation with the radar data.
Owing to an important role of lightning discharges in local and global electric
phenomena in the Earth’s atmosphere, simulation of the fields and currents dur‑
ing a lightning
discharge is a topical problem, important for both direct and in‑
verse electrodynamics problems. Researchers from the IAP RAS proposed a
numerical model of large‑scale electrodynamics of
a lightning discharge based
on the complete set of Maxwell’s equations, which makes it possible to describe
both the quasistatic and fast transient electric fields and currents in the atmos‑
phere [39–41]. The proposed model of the electromagnetic response of the