Here we do not take account of this effect. The IP is determined as the sum over all the sources existing simultaneously over the globe. It turned out that the IP value is close to the observable values when this coefficient equals 0. A pronounced characteristic of the Earth's electric field is its diurnal variation as found originally in analysis of electric field measurements on board the Carnegie ship [i. In a model experiment the calculation of IP between and has been carried out. It was found that the calculated IP diurnal variation averaged over all the days corresponds rather well to the measured values.
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This shift of the model maximum to earlier time can be explained by the fact that in the climate models convection occurs at once when the static stability is disturbed, while the real convection develops during 1—3 h. Another test is the study of the seasonal annual variation. Note that the reanalysis of all available measurements of the IP [ Markson , ] shows a consistent result for the annual variation, with a maximum in Northern hemisphere summer.
The annual variation of the global circuit with a Northern hemisphere summer maximum is attributable to the asymmetry in land mass between the Northern and Southern hemispheres and the global variation in air temperature that accompanies that asymmetry [ Williams , ; Reddell et al. Over the ocean in the areas of intensive convection the amount of these events is as big as 0. We note only that IP data available up to date are very restricted; in the literature so far the main attention was given to the study of lightning activity variation on the ENSO time scale [ Hamid et al.
The main features of the modern distribution of lightning over the globe are reproduced by the model INMCM4. Therefore, positive correlation of the IP with temperature for a certain time scale does not imply positive correlation of lightning activity with temperature on the spatial scale of the globe. It was noted already that using the sounding series conducted so far, it is difficult to reveal any reliable trends connected with certain physical parameter changes, except for the pronounced IP increase in the early s [ Markson , ]. The global warming is about 2.
This is understandable because the temperature increase leads to the increase of the difference between the dry adiabatic lapse rate and the moist adiabatic lapse rate see also the discussion below. As was explained above, sufficiently strong power law dependence of LFR on convection height over land may lead to positive correlation of global lightning activity with temperature while IP demonstrates the negative correlation with temperature.
Physically, it may be explained by assuming that a warmer climate leads to fewer thunderstorms, while those that are to develop are more intense [ Del Genio et al. It is well recognized by now that the GEC and global lightning activity form a natural framework for investigating climate issues [ Williams , , ]. Moreover, the IP and the mean global flash rate can serve as global indices relating the state of the GEC to the planetary climate. It is important, however, that the GEC forms due to continuous operation of ionization sources, along with meteorological factors. Many results of simulations are consistent with measurements and the general understanding of the global circuit, including the Carnegie curve and seasonal variations.
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On the other hand, using a GCM allows us to study the influence of different factors on the GEC state, first of all, the impact of convection intensity and its trends in a warmer climate. So far there is no clear manifestation of such a trend [ Markson , ]. An expanded discussion of the observational claims for a decline in the GEC, in particular, the twentieth century secular decrease in the atmospheric potential gradient [ Harrison , ], can be found in Williams [ ]. One of the most important aspects of our approach is an account for all the electrified clouds—both thunderstorms and ESCs—because all of them are represented by the electric current in the IP parameterization.
Thévenin's Theorem - Circuit with Two Independent Sources
Note that the existence of ESCs, with an electrical polarity appropriate for contributing to the ionospheric potential, has recently been verified in aircraft overflights of cumulonimbus clouds by NASA Marshall Space flight Center [ Mach et al. According to Mach et al. But a closer fit to the Carnegie curve is possible if the contributions from ESCs are increased by a factor of 3 or 4. Further observations and modeling are needed to resolve a problem of ESC contribution to the global circuit. In general, it is related to the fact that the temperature increase leads to the increase of the difference between the dry adiabatic lapse rate and the moist adiabatic lapse rate.
All the GCMs more or less follow the moist adiabat in the tropics [e. The models show [ IPCC , ] that the greatest warming due to increasing greenhouse gases will occur not at the surface, but in the equatorial upper troposphere, which in the mean decreases the atmospheric lapse rate, tending to inhibit convection. Del Genio et al.
Our model needs to be further studied in terms of the trend in convective available potential energy in the considered scenario and, respectively, the concrete mechanism connecting the temperature change with the GEC response [ Williams , ]. We did not take into account potentially important contributors into the IP—Austausch convective generator operating in the fair weather regions [i. Both of them need to be studied better to be taken into account in the IP parameterization.
A drawback of our model so far is also the simplified treatment of the conductivity profile in the atmosphere and the current density in electrified clouds. These limitations impede a direct comparison of the modeling results with the available record of IP. Further development of the model implies allowing for conductivity perturbations inside and outside the clouds, following the approaches developed in Zhou and Tinsley [ ], Baumgaertner et al.
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It should be noted that Baumgaertner et al. One of necessary directions of further modeling should be the study of the influence of aerosols on the conductivity both outside and inside the clouds.
It is consistent with previous climate model simulations which have shown that lightning activity will increase in a warmer climate [ Price and Rind , ; Shindell et al. The computed diurnal and seasonal variability of the GEC corresponds well to the observational data. The authors thank I. Mokhov and the reviewers of the paper for their valuable comments.source site
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This work was supported by a grant from the RF Government contract The Editor thanks Colin Price and an anonymous reviewer for their assistance in evaluating this paper. Volume Issue. If you do not receive an email within 10 minutes, your email address may not be registered, and you may need to create a new Wiley Online Library account. If the address matches an existing account you will receive an email with instructions to retrieve your username. Open access. What delights may its practioner expect as his reward? First is the sheer joy of making things. As the child delights in his mud pie, so the adult enjoys building things, especially things of his own design.
I think this delight must be an image of God's delight in making things, a delight shown in the distinctiveness of each leaf and each snowflake. Second is the pleasure of making things that are useful to other people. Deep within, we want others to use our work and to find it helpful. In this respect the programming system is not essentially different from the child's first clay pencil holder "for Daddy's office. The programmed computer has all the fascination of the pinball machine or the jukebox mechanism, carried to the ultimate.
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Fourth is the joy of always learning, which springs from the nonrepeating nature of the task. In one way or another the problem is ever new, and its solver learns something: sometimes practical, sometimes theoretical, and sometimes both. Finally, there is the delight of working in such a tractable medium. The programmer, like the poet, works only slightly removed from pure thought-stuff.
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He builds his castles in the air, from air, creating by exertion of the imagination. Few media of creation are so flexible, so easy to polish and rework, so readily capable of realizing grand conceptual structures. As we shall see later, this tractability has its own problems. Yet the program construct, unlike the poet's words, is real in the sense that it moves and works, producing visible outputs separately from the construct itself.
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