| 其他摘要 | Is the sun driving the sub-orbital time-scale, decadal to centennial, climate change? Although there are thousands of observations from current climatology, and the historical climate record, and the paleoclimate proxies from the geology record such as the ice core, tree rings, which suggest the relationship between the solar activity and the climate change, the critics argue that the statistic analysis is not significant enough to support the opinion because the internal driver of the climate such as ocean-atmosphere system oscillation can produce the same time-scale climate change according to the statistic work. The key point to making break through is to set up the mechanism of the relation between solar activity and lower atmosphere. Three theories have been established:1) the total solar energy variation theory (herein TSI theory) , the solar energy varying with the solar activity and causing the climate change; 2) the ultra-violet variation theory (herein UV theory), the ultra-violet energy varying due to the solar activity taking 32% of the total solar energy change which can significantly affect the middle atmosphere and change the planet wave to transport the energy to lower atmosphere and to change the climate; 3) spaceweather theory (herein SW theory), the particle flux in the upper atmosphere changing due to the solar activity, which can affect the global cloud coverage and then influence the climate. Satellite observations prove that the variation of the total solar energy output between solar maximum and solar minimum reaches only 0.1% ( about 1W/s at the top of the atmosphere), which is too small to drive the climate according current climatology theory. The lack of long term observation for the UV theory reduced its progress. SW theory is made up of two sub－theories: 1) the ion mediate nuclei theory (IMN); 2) the spaceweather-global circuit-cloud microphysics theory (herein SGC). IMN theory was used to explain the relationship between variation of galactic cosmic ray (GCR) flux and global cloud coverage. However, with progress of the research on the variation of global cloud coverage during the solar cycle, the latitudinal difference for change of the cloud coverage was found. Then it is hard to explain the cloud coverage variation by the IMN theory. The SGC theory then seems to be a more efficient candidate. The SGC theory is developed by a series of statistic research on the meteorologic affair and solar activity, which is independent of other internal drivers such as the ocean-atmosphere system. The SGC theory can not only explain the effect of solar activity affairs such as the solar proton affair, the variation of GCR, the variation of the flux of the electron precipitation on the meteorology and the cloud cover, but also can explain the latitudinal difference of the response of the low atmosphere to the solar activity. The theoretical framework of the SGC theory has been established. However there are still lots of numerical work which is necessary to complete the theory. This work is the initial effort to complete the numerical simulation for the SGC theory. There are three models involved: 1) the updated global circuit model; 2) the initial model for the charges in the layer cloud; 3) the electric cloud microphysical model with the treatment of the wider range of the particle size, the new flow, the weight and inertia of the particle and the superposition and with the comparison of the image charge method to the conducting sphere method.
1. The global circuit model
This new global electric circuit model has improved accuracy for the galactic cosmic ray ion-pair production, the near surface ion production by radioactivity, and the concentrations and size distribution of aerosols. The effect on the global circuit parameters of the variabilities with solar activity, volcanic activity, and seasonal changes has been evaluated.
A treatment has been introduced for a layer of ultrafine aerosol particles in the high latitude, high altitude stratosphere, following large, explosive volcanic eruptions. This has the capability of providing a regional stratospheric column resistance comparable with the tropospheric value, so that the total column resistance and the ionosphere-earth current density Jz become sensitive to ionization by energetic particle fluxes that only penetrated to mid-stratospheric levels. While ionization from the influx of relativistic electrons from the radiation belts would cancel this volcanic stratospheric column resistance most of the time, observations indicate that in periods of low solar wind velocity near heliospheric current sheet crossings the influx is reduced sufficiently so that cancellation no longer occurs.
2. The initial model for the charge in the layer cloud
The variable flow of ionosphere-earth current density Jz generates variable amounts of space charge near the upper and lower boundaries of clouds. We modeled the production of space charge and its partitioning between droplets, aerosol particles, and atmospheric ions, for a range of relevant atmospheric variables. The results give average charges on droplets of 50 to 100 elementary charges; positive at cloud top and negative at cloud base, which supports the recent measurements of Beard et al. (2004). The effects of moderate downdrafts at cloud top and updrafts at cloud base may be necessary to provide a narrow enough boundary layer together with a more concentrated current density, to generate the observed charges.
When taken with models of electrical effects on cloud microphysics, the results are consistent with observations of meteorological responses to processes affecting Jz, and suggest that the accumulation of space charge in layer clouds may affect cloud microphysics sufficiently to cause measurable effects on weather and climate.
3. The cloud electric mircohpysics
The charges on the droplets and the aerosol particles, including the ice forming nuclei (IFN) and the cloud condensation nuclei (CCN), have an effect on the scavenging rates that is a complicated function of droplet size, particle size, particle density, and amounts of charge on each. Since there is a long-range Coulomb-type force that is repulsive for particles having charges of the same sign (and attractive for opposite sign) and a short-range image force that is always attractive, trajectory calculations show electrically-induced decreases as well as increases in scavenging rates (and in particle-particle and droplet-droplet coagulation rates).
Depending on the results of the model, the electrical effects on scavenging are likely to be an increase in scavenging rates for the larger particles being scavenged by the larger droplets, with a decrease below the scavenging rates for the smaller particles in the presence of smaller droplets. The increase of the scavenging rate for the larger particles promotes the close of the “Greenfield Gap”.
The comparison of the image charge method and conducting sphere method shows that the greatest difference of the results appears in the “Greenfield Gap”. In “Greenfield Gap”, conducting sphere method gives larger collision efficient than the image charge method. The increase of the radius ratio between droplet and particle causes less difference between two methods.
4. The SGC theory and the climate
Depended on three models above, it is clear that the low cloud is more sensitive to the solar activity, which is fit for the results from lots of statistic results such as Svensmark et al.(2000), Kniveton et al.(2004).
With the ultrafine aerosol in the middle and upper stratosphere, the cloud in the high latitude and polar region will more sensitive to the solar activity. And the difference response to the solar activity between low latitude and high latitude increase. The different response causes different direct of variation of the cloud coverage. The low latitude and tropical region will become warmer and the high and polar region will be cooler. The warmer tropical can increase the magnitude of the thunderstorm and produce larger upward current It. The enhancement of the upward current increases the downward current density at the polar region. The temperature difference increases. Then this forms the new feedback system to increase the solar activity effect. It can be used to explain the beginning of the “Little Ice Age”.
For the longer orbital time scale climate change——Milankovich period，the variation of upward current due to the variation of the temperature will affect the climate besides the irradiance variation effect. |
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