Responses of the Ionosphere to the Great Sumatra Earthquake and Volcanic Eruption of Pinatubo

A sudden ionospheric disturbance was detected by the Doppler shift sounding equipment at Beijing, about 25 min later after the outbreak of the Sumatra earthquake on 26 December 2004. This ionospheric disturbance appeared less than lOmin after the earthquake was first recorded at Beijing seismological station by the arrival of the seismic Rayleigh wave. The analysis shows that about 18rain is the time necessary for the seismic Rayleigh wave to propagate from the epicentre to Beijing and then about 5-10min for acoustic waves to propagate from the surface of the Beijing area to the altitude of the ionosphere. Also, a report was made as another example to show the ionospheric response of Doppler shift observation at Beijing area during the Mount Pinatubo eruption of 1991. These two examples show clear evidence of the lithosphere-atmosphere-ionosphere coupling. The former case is in the frequency domain of infrasonic waves of the Earth surface oscillation due to the Rayleigh waves caused by the earthquake, while the latter is in the acoustic-gravity wave category directly excited in the atmosphere by the mass and energy eruptions of Mount Pinatubo.

Simulating the Effects of the 1991 Mount Pinatubo Volcanic Eruption Using the ARPEGE Atmosphere General Circulation Model

The climate changes that occured following the volcanic eruption of Mount Pinatubo in the Phillippines on 15 June 1991 have been simulated using the ARPEGE atmosphere general circulation model （AGCM）. The model was forced by a reconstructed spatial-time distribution of stratospheric aerosols intended for use in long climate simulations. Four statistical ensembles of the AGCM simulations with and without volcanic aerosols over a period of 5 years following the eruption have been made, and the calculated fields have been compared to available observations. The model is able to reproduce some of the observed features after the eruption, such as the winter warming pattern that was observed over the Northern Hemisphere （NH） during the following winters. This pattern was caused by an enhanced Equator-to-pole temperature gradient in the stratosphere that developed due to aerosol heating of the tropics. This in turn led to a strengthening of the polar vortex, which tends to modulate the planetary wave field in such a way that an anomalously positive Arctic Oscillation pattern is produced in the troposphere and at the surface, favouring warm conditions over the NH. During the summer, the model produced a more uniform cooling over the NH.

Evidence of the 1991 Pinatubo volcanic eruption in South Polar snow

Traces of tephra and increased sulfate (SO42-) concentrations were identified in the1992-1994 snow layers in 2 firn cores from South Pole. The deposition of the Pinatubo SO42-aerosol was delayed due to the long transport to the high south latitudes and its initial existence at high altitudes in the Antarctic atmosphere. Electron microscopic analyses show that the element composition of the tephra is identical to that of volcanic ash found near the Pinatubo volcano in Philippines. Detailed stratigraphic snow sampling resolved the Pinatubo signal from that of Cerro Hudson eruption during August 1991 in Chile. The South Pole sulfate flux from Pinatubo is calculated to be (10.9 ±1.1) kg·km-2, while the Hudson sulfate flux is (3.2 ± 1.1) kg·km-2. This information will be useful to estimating the magnitudes of the past volcanic eruptions recorded in Antarctic ice core.

Variation characteristics of stratospheric aerosols due to the Pinatubo eruption by SAGE Ⅱ data

Both theoretical and observational studies reveal that the stratospheric volcanic aerosols have important impact on global climate change. The volcanic aerosols can also exert some influences on remote se(?)sing of the atmosphere-earth system . So it is necessary to monitor the aerosol variation in the stratosphere due to the volcanic eruption.

Mechanism of stratospheric decadal abrupt cooling in the Early 1990s as influenced by the Pinatubo eruption

Studies have suggested that one volcanic eruption can influence seasonal to inter-annual climate variations.This study indicates that the Pinatubo eruption in 1991 may have actually induced the stratospheric decadal cooling recorded in the early 1990s.Using the NCEP/NCAR reanalysis and TOMS/SBUV satellite data,a decadal abrupt cooling of stratospheric tropical air temperature was found to have occurred in the early 1990s during a long-term descending trend.We generated the spatio-temporal structures of the decadal abrupt changes(DACs) for the stratosphere,and explored the relationship between the Pinatubo volcano eruption in 1991 and stratospheric DACs in the early 1990s.Our results suggest that the eruption of Pinatubo prompted a decadal decrease of ozone by the activation of nitrate and sulfate volcanic aerosols on ClO free radicals.The stratospheric heat absorbed by ozone decreased over a decadal time scale.As a result,decadal abrupt cooling of stratospheric tropical air temperatures occurred in the early 1990s,and may be attributed to the Pinatubo eruption.The results therefore indicate that one strong volcanic eruption can induce stratospheric decadal climate variation.

皮纳图博火山云对1992年大范围气候的影响

１９９１年６月中旬，菲律宾的Ｐｉｎａｔｕｂｏ火山将近二千万吨含硫气溶胶喷入平流层高空，形成了本世纪最大的一次火山云事件。文章叙述了火山云在高空的扩散状况及其对１９９２年大范围气候的致冷影响。这表现为全球平均气温的明显下降；北半球１～１０月（尤其是夏秋季节）气候冷区明显增多，这种气候冷区有从低纬向高纬逐步移动的趋势；而且夏半年在我国也出现了一系列冷害现象。

Analysis of Temporal Signals of Climate

The dynamics of carbon dioxide in the atmosphere is analyzed and it is shown that the Pinatubo eruption in 1991 had a noticeable effect on these dynamics. The growth rate slowed down. Moreover, analyzing the year-on-year CO2 growth data, we can see an an-thropogenic footprint, possibly due to the burning of fossil fuels. On top of this anthropo-genic contribution is a natural contribution that is of similar magnitude, and that closely follows the ocean surface temperature (influenced by ENSO, El Ni&ntildeo Southern Oscilla-tion). This latter fact is consistent with the hypothesis of the correlation of global temper-atures and carbon-dioxide in the atmosphere being governed by Henry’s Law, in which carbon dioxide variations are the result of, rather than the cause of, temperature changes. This latter being the so-called “greenhouse effect”, sometimes mentioned as responsible for (anthropogenic) climate changes, and that cannot explain the observed phenomena described here. Similar conclusions are drawn on monthly data of carbon dioxide and temperature as well.

1991年皮纳图博火山灰沉降物对南海海洋环境及硅藻生长的影响

通过对菲律宾皮纳图博(Pinatubo)火山1991年6月爆发前后南海表层沉积物及沉降颗粒物中的硅藻丰度及群落组成进行分析,试图揭示皮纳图博火山爆发对南海硅藻生长的影响。研究发现,火山爆发后南海沉积物中硅藻相对丰度显著减少,原因主要在于皮纳图博火山喷发物大量沉积于南海深海,显著提高了南海沉积速率,同时稀释了沉积物中生源物质的含量。进一步对火山爆发前后同期南海中部深海沉降颗粒物开展研究发现,火山爆发次年同期沉降颗粒物总通量以及生物硅通量明显增加,而硅藻及其他硅质生物相对丰度和通量均显著降低,其中硅藻相对丰度从2.20×10^(8)枚·g^(-1)降到5.48×10^(7)枚·g^(-1),通量从2.90×10^(7)枚·m^(-2)·d^(-1)降到8.57×10^(6)枚·m^(-2)·d^(-1)。1年后的南海中部深海沉降颗粒物中仍然有大量火山玻璃的存在,可能是导致湿化学法测量生物硅含量明显增加的主要原因,而硅藻乃至所有硅质生物通量及丰度的显著降低可能与火山灰沉降的负面影响有关,也可能与1991年厄尔尼诺对南海海洋环境的影响有关。总之,1991年6月皮纳图博火山爆发后南海的沉积物硅藻及沉降颗粒物硅藻丰度都出现了显著降低,但具体的环境调控机制仍有待进一步深入研究。