Geomagnetic activity and the North Atlantic Oscillation

The North Atlantic Oscillation (NAO) is the prominent pattern of winter climate variability that has a strong effect on weather in the North Atlantic region and the adjacent continents. At present, uncertainty prevails as to the mechanisms controlling the variability of the NAO. It is also difficult to explain why the positive phase of the NAO has prevailed over the past 37 years (1972–2008). We found high positive correlation coefficients between geomagnetic activity (used as a measure of solar wind intensity) and the NAO indices that equal 0.76 for 1962–1994 and 0.63 for 1961–2011. Positive correlations of the distribution of surface air temperature with the NAO and similarly with geomagnetic activity occur in the Northern Hemisphere. These results encourage our search for possible causes controlling the NAO. We have found that at times of high geomagnetic activity the NAO index is positive and magnetic reconnection may enable the solar wind to initiate downward winds in the magnetosphere. Wind anomalies originate at the edge of the stratospheric polar vortex and propagate downward through the troposphere taking part in the intensification of the vortex and of the westerlies. Stronger northerly winds over Greenland carry cold air southward and, together with the enhanced westerlies, advect the warm air from the Atlantic along the deep Icelandic low into Eurasia increasing temperatures there. On the other hand, at times of low geomagnetic activity, the NAO index is negative and the stratospheric polar vortex is weak. Warm air from the subtropics is carried into the Arctic and a rapid amplification of planetary waves propagating upward may cause displacement or even splitting of the weak vortex and sudden stratospheric warming. During this negative NAO phase the weakened westerlies allow more cold air to build up over North America and Eurasia.     

Changes in geomagnetic activity and global temperature during the past 40 years

The purpose of this study is to investigate the effect of geomagnetic activity (used as a measure of solar wind parameters) on the variability of large-scale climate patterns and on changes in the global temperature. We show that positive statistically significant correlations between global temperature and the distribution of surface temperature over Eurasia, the East and Equatorial Pacific and over the North Atlantic for the period 1966?C2009 correspond to large-scale climate patterns defined by climate indices. We found very similar positive correlations between geomagnetic activity and the distribution of surface temperature in the mentioned regions. As an effect of geomagnetic storms, energetic particles penetrate from the magnetosphere into the region of the stratospheric polar vortex. The increase of temperature and pressure can be observed over northern Canada. The vortex shifts towards Europe, rotates counter-clockwise and the wind blows from the polar region over Greenland southwards. It diverts the warm flow proceeding northward over the Atlantic, eastward along the deep Icelandic low extending as far as the Barents Sea and takes part in warming Eurasia. The strengthened zonal flow from Siberia cools the western Pacific with the impact on the warming of the equatorial and eastern Pacific when also a distinct 1976?C78 climate shift occurred. Processes in the Atlantic and Pacific play a significant role and a time delay (wind forcing over the previous 1?C4 yr) appears to be the most important for the relocation of the oceanic gyres. Results showing statistically significant relations between time series for geomagnetic activity, for the sum of climate indices and for the global temperature help to verify findings concerning the chain of processes from the magnetosphere to the troposphere.     

Geomagnetic activity and wind velocity during the Maunder minimum

Following a given classification of geomagnetic activity, we obtained aa index values for the Maunder minimum (1645–1715). It is found that the recurrent and fluctuating activities were not appreciable and that the shock activity levels were very low. The aa index level was due almost entirely to the quiet days. Calculated average solar-wind velocities were 194.3 km s^–1 from 1657 to 1700 and 218.7 km s^–1 from 1700 onwards. Also, the coronal magnetic field magnitude and southward interplanetary magnetic field component Bz were lower. It is concluded that the nearly absent levels of geomagnetic activity during this period were due to lower coronal and Bz magnetic field magnitudes as well as to the continuous impinging on the Earth of a slow wind.     

Multi-resolution analysis of global surface air temperature and solar activity relationship

In this work the surface temperature anomaly (dTG) and sunspot number (R_z) time series in the period 1880–2000 are studied with wavelet multi-resolution analysis. We found a very low correlation of 0.11 between dTG and R_z in the 11-yr-solar cycle band. A higher correlation of 0.66 is found in the ～22-yr-band with zero lag correlation coefficient between dTG and R_z. Furthermore, the long-term trend is markedly different between dTG and R_z. This might occurs because of the long-term warming on the last century, which is attributed mainly to anthropogenic effects.     

Geomagnetic activity dependence of O in transit from the ionosphere

Energetic O⁺ ions have important dynamic effects on the ring current. Insights into the effects of O⁺ on ring current dynamics have come primarily from models, not observations. Here, we discuss observations of O⁺ populations escaping from the ionosphere and their access to the plasma sheet and ring current. We review data establishing that a significant flux of O⁺ escapes the ionosphere during geomagnetically quiet intervals. We then estimate the relative magnitude of the O⁺ population in transit between the ionosphere and ring current during quiet intervals before geomagnetic storms. Our analysis suggests that dynamic reconfigurations of the magnetosphere during geomagnetic storms significantly alter the O⁺ transport paths from the ionosphere to the ring current. During these reconfigurations some of the pre-existing, quiet time, in-transit O⁺ populations are captured on magnetic field lines leading to the ring current. The prompt appearance of this O⁺ population in the ring current could modify the evolution of the ring current in the storm growth phase. Our analysis suggests that the consequences of an activity-dependent O⁺ transport path to the ring current should be systematically investigated.     

高纬日侧电离层离子上行的地磁活动依赖性研究

本文对比分析了太阳活动高、低年期间高纬日侧顶部电离层离子上行随地磁活动水平的变化特征.按地磁活动水平, 将DMSP卫星在太阳活动高年(2000-2002年, F13和F15)及太阳活动低年(2007-2009年, F13;2007-2010年, F15)期间的SSIES离子漂移速度观测数据分为三组:地磁平静期(Kp < 3), 中等地磁扰动期(3 ≤ Kp < 5)和强地磁活动期(Kp ≥ 5), 分别统计分析了高纬日侧顶部电离层离子上行特征的时空分布.对比分析发现:(1)太阳活动低年期间, 高纬日侧电离层离子上行发生率以及上行速度峰值均是太阳活动高年的2倍多, 而离子上行通量峰值只有高年的1/6-1/4;(2)在相同太阳活动条件下, 地磁活动水平对日侧电离层离子上行发生率峰值的影响并不明显, 但对离子上行发生率的空间分布有着显著的控制作用:电离层离子上行高发区随地磁活动向低纬度扩展, 并在强地磁活动期间呈现饱和的趋势; (3)日侧顶部电离层等离子体似乎存在两个效率相当的上行区域, 一个位于极尖/极隙区纬度附近, 离子可沿开放磁力线上行进入磁尾; 另一个位于晨侧亚极光区附近, 离子沿闭合磁力线上行, 有可能进入日侧等离子体层边界层.

     

地磁房湿度对地磁观测的影响及解决方案

地磁房湿度变化较快或过大都易引起地磁数据的异常变化,且室内湿度不易控制,地磁房、磁通门磁力仪探头湿度智能在线分析监控系统,可以实时显示监控地磁房、磁通门磁力仪探头湿度的变化,超过湿度阈值则发出报警信号,进而可以采用科学的方法控制探头观测环境的湿度,提高观测数据的稳定性、可靠性。本文介绍了该系统的设计思路和主要功能。     

Hindcasting global temperature by evolutionary computation

Interpretation of changes of global temperature is important for our understanding of the climate system and for our confidence in projections for the future. Massive efforts have been devoted to improve the accuracy of reproducing the global temperature by the available climate models, but the hindcasts are still inaccurate. Notwithstanding the need to further advance climate models, one may consider data-driven approaches, providing practically useful results in a simpler and faster way. Without assuming any prior knowledge about physics and without imposing a model structure that encapsulates the existing knowledge about the underlying processes, we hindcast global temperature by automatically identified evolutionary computation models. We use 60 years of records of global temperature and climate drivers, with training and testing periods being 1950–1999 and 2000–2009, respectively. This paper demonstrates that the global temperature observed in the past is mimicked with reasonably good accuracy. Evolutionary computation holds promise for modeling the global climate system, which looks hopelessly complex in classical perspective.     

Relationship between global mean sea-level and global mean temperature in a climate simulation of the past millennium

The possibility of using global mean near-surface temperature, its rate of change or the global mean ocean heat-flux as predictors to statistically estimate the change of global mean sea-level is explored in the context of a long climate simulation of the past millennium with the climate model ECHO-G. Such relationships have recently been proposed to by-pass the difficulty of estimating future sea-level changes based on simulations with coarse-resolution climate models. It is found that, in this simulation, a simple linear relationship between mean temperature and the rate of change of sea level does not exist. A regression parameter linking both variables, and estimated in sliding 120-year windows, varies widely along the simulation and, in some periods, even attains negative values. The ocean heat-flux and the rate-of-change of mean temperature seem to better capture the rate-of-change of sea level due to thermal expansion.     

Air temperature feedback and its contribution to global warming

Air temperature feedback results from the thermal-radiative coupling between the atmosphere and the surface and plays an important role in surface energy balance. This paper reveals the contribution of air temperature feedback to the global warming from 1980 to 2000. The air temperature feedback kernel, evaluated using the ERA-Interim reanalysis data, is used to discuss the physical mechanism for air temperature feedback, the dependency of the strength of air temperature feedback on the climatological spatial distributions of air temperature, water vapor and cloud content, and the contributions of air temperature feedback to rapid global warming. The coupling between temperature feedback and each of the external forcings and individual feedback processes will amplify the anomaly of direct energy flux convergence at the surface induced by the external forcings and individual processes. The air temperature feedback amplifies the initial surface warming due to the increase in CO₂ concentration, ice and snow melting, increase in water vapor, and change in ocean heat storage. It also amplifies the surface warming due to the longwave radiaitve forcing associated with the increase in cloud cover, which acts to suppress the cooling of the shortwave effect of cloud forcing. Overall, temperature feedback plays an important role in the global warming from 1980 to 2000, as the net positive contribution to the perturbation of global mean energy flux at the surface from the air temperature feedback is larger than the net negative contribution from external forcing and all non-temperature feedbacks.     

<地磁测量与地磁台站工作指南>简介

地磁场的急剧变化,无疑会对我们周围的物理环境产生影响。地磁学家们基于地磁观测台站的普遍重要性,经国际地磁和高空物理协会（ＩＡＧＡ）秘书长Ｊ．Ａ．Ｊｏｓｅｌｙｎ博士批准,中国地震局监测预报司组织国内地磁界著名的专家、学者将由ＩＡＧＡ编纂出版、两位地磁观测方面的国际权威人士Ｓａｎｋｏｗｓｋｉ（波兰）和Ｓｕｃｋｓｄｏｒｆｆ（芬兰）博士撰写的《地磁测量与地磁台站工作指南》一书译成中文,并由地震出版社出版,北京向导书刊有限公司发行。该书是当代地磁台站观测技术的最新著作。它简明扼要地叙述了地磁台的现代化仪器…     

国际地磁参考场在我国地磁基础研究中的应用

国际地磁参考场资料在我国得到广泛应用。利用国际地磁参考场资料，我国学者研究了高斯分析、地球磁场模型及其源场可能位置、重磁关系、核幔耦合、地磁场能量、地球非偶极子磁场西向漂移等。在绘制中国地磁等值图中也利用了某些国际地磁参考场资料。     

全球巨大地震活动性分析

通过分析全球巨大地震活动周期、活跃时段和活动空间分布特征,探讨未来全球发生巨大地震的活跃时段和主体区域.结果表明:①全球地震活动存在着置信度远超过95％的50年左右显著活动周期,此外还存在80-100年左右显著性不强的活动周期;②通过对全球地震Ms≥8.3时间序列图和Ms≥8.0应变能时间序列图分析,得到活跃期10-14年,平静期39-41年,2004年后又进入了巨大地震的强活跃期,可能会一直持续到2018年;③强活跃时段内发生的Ms≥8.5巨大地震存在着一定的相关性,太平洋板块北边界(美国阿拉斯加附近区域—阿留申群岛—千岛群岛)是发生8.5级以上地震最关注的地区,其次是太平洋板块的南美洲边界(尤其是秘鲁及其周边区域),应对这两个地区进行重点关注和监测.本文从地震活动性角度研究巨大地震的强活跃期问题,并推测全球发生8.5级以上地震的活跃时段和主体地区,而对于其机理问题值得进一步深入研究.     

Spatiotemporal modes of global sea surface temperature variability

This study identifies the salient global modes of sea surface temperature variability based on 145 years of HadlSST data.Unlike the traditional mode identification by EOF analysis,a combination of wavelet and EOF analysis is used to extract the leading modes at distinct time scales.The spatial patterns of some well-known regional modes are recovered,with the global connection and frequency content of these modes being revealed.Our analysis indicates that,in terms of global influence,the Pacific Ocean is the major player,and the tropical Pacific is the center of action on various time scales.The Atlantic Ocean has its own outstanding modes,but their global impacts are not as strong as those from the Pacific.The Indian Ocean generally shows a passive response to the Pacific,with a basin-wide pattern in the tropics.Despite some preliminary theoretical attempts,how to elucidate the dynamics underlying the global modes of sea surface temperature variability is still an open question.     

The importance of ocean temperature to global biogeochemistry

Variations in the mean temperature of the ocean, on time scales from millennial to millions of years, in the past and projected for the future, are large enough to impact the geochemistry of the carbon, oxygen, and methane geochemical systems. In each system, the time scale of the temperature perturbation is key. On time frames of 1-100 ky, atmospheric CO₂ is controlled by the ocean. CO₂ temperature-dependent solubility and greenhouse forcing combine to create an amplifying feedback with ocean temperature; the CaCO₃ cycle increases this effect somewhat on time scales longer than ∼5-10 ky. The CO₂/T feedback can be seen in the climate record from Vostok, and a model including the temperature feedback predicts that 10% of the fossil fuel CO₂ will reside in the atmosphere for longer than 100 ky. Timing is important for oxygen, as well; the atmosphere controls the ocean on short time scales, but ocean anoxia controls atmospheric pO₂ on million-year time scales and longer. Warming the ocean to Cretaceous temperatures might eventually increase pO₂ by approximately 25%, in the absence of other perturbations. The response of methane clathrate to climate change in the coming century will probably be small, but on longer time scales of 1-10 ky, there may be a positive feedback with ocean temperature, amplifying the long-term climate impact of anthropogenic CO₂ release.     

关于数字地磁台站观测系统的发展与观测资料应用的一点思考

针对地球科学和国家建设对地磁观测与研究的需求，结合“九五”地磁台站观测技术数字化改造，对地磁台站观测系统的发展及数字观测资料的应用提出了一些见解。     

Geomagnetic and sunspot activity associations and ionospheric effects of lightning phenomena at Trivandrum near dip equator

From a study of thunder/lightning observations in Trivandrum (near dip equator) for selected years between 1853 and 2005, we could find an inverse relation of the same with sunspot activity and associations with enhancements in diurnal range of local geomagnetic declination. The results seem to suggest lightning-associated modulation of E-region dynamo currents in the equatorial ionosphere and the thunderstorm activity near dip equator probably acts as a moderator to regulate electric potential gradient changes in the global electric circuit due to solar activity changes.     

地磁测量卫星

地磁测量卫星是地磁测量的重要工具,它相对于一般地磁测量仪器具有覆盖面广、精度高、实时采集和处理等特点.本文按照发射时间,介绍了早期的POGO、Magsat等磁测卫星,并重点介绍了现仍在使用的Oersted卫星和CHAMP卫星,以及2012年将要发射的Swarm卫星.同时阐述了这些卫星的结构、工作原理和主要的磁测仪器,最后介绍了卫星资料在各领域的应用.     

Geomagnetic disturbances and earthquakes in the Vrancea zone

Based on the example of the Vrancea zone of concentrated seismicity, it is shown how the stress-strain state of the medium responds to a disturbance of the geomagnetic field. Geomagnetic conditions are examined in relation to earthquakes in the Vrancea zone in the period 1988–1996. It is established that the seismic energy release in the Vrancea zone is associated with differences (“gradients”) in the H component of the geomagnetic field. Such a gradient preceding earthquakes is shown to be the midnight polar substorm and the degree of its mid-latitude effect. The time interval from the maximum of the substorm development to a shock (τ, h) is directly related to the focal depth. The seismic characteristics K _en and h (km) are demonstrated to be related to morphological features of the substorm development, namely, its duration T (min), intensity, and background. Differences in the duration of polar substorms before crustal (shallow) and deep earthquakes are revealed. Morphological features of the spectrum of geomagnetic variations preceding the seismic energy release are established.