Evidence of geomagnetic storm effects in the lower atmosphere: A case study

Disturbances produced by geomagnetic storms in the higher regions of the Earth’s atmosphere, such as in the ionospheric F2 region and in the lower ionosphere, are relatively better known than those produced at lower altitudes, where the effects of geomagnetic storms have been little studied. During magnetically perturbed conditions, some changes in pressure and temperature at high latitudes have been observed, from the surface level to heights of around 30 km, but there are no morphological studies and/or patterns of behavior. Moreover, the physical mechanisms are still unknown and what exists is a matter of controversy. Thus, the aim of this paper is to contribute to the vertical profile of the effects of geomagnetic storms as observed in the lower sectors of the atmosphere. For that, we study the variations of two atmospheric parameters (temperature and wind speed) during an intense geomagnetic storm (minimum Dst = −300 nT), at heights between about 6 km and 20 km. The data used were obtained from weather balloon flights carried out at low, mid and mid-high latitudes in different longitudinal sectors of the northern hemisphere, which took place twice per day: 00:00 and 12:00 UT. Small, but statistically significant changes in temperature and in zonal component of the neutral winds are observed at mid-high latitudes, which can be linked to short-term geomagnetic forcing. However, the results show different atmospheric response to the geomagnetic storm in the different longitudinal sectors at tropospheric and stratospheric levels, which suggests a regional character of the geomagnetic storms effects at tropospheric levels.     

A case study of a dust storm weather situation in the Sudan in April 1973

Summary In connection with an invasion of cold air from the north over the Sudan in April 1973, a major dust storm or rather, a dust storm complex, passed over most of the Sudan.The weather development during this dust storm period is described and illustrated in detail with the aid of synoptic weather and visibility maps, as well as time sections based on SYNOP, METAR, and radiosonde reports from Sudanese meteorological stations.With the aid of the synoptic maps it has been possible to follow the development and movement of the dust storm complex and its relation to the cold fronts preceding the cold air invasion, to the intertropical front (ITF), and to thunderstorm highs which developed within the monsoon air south of the ITF during the initial stage. It was also possible to follow the latitudinal displacements of the ITF, which were caused by the weather systems and associated pressure changes in the harmattan and the monsoon air masses on both sides of it.At the beginning of the dust storm the cold fronts from the north were fairly distinct, but they gradually lost their frontal character. The cold air advection, however, gave rise to increased instability in the lower atmospheric layers, which facilitated the development of dust storms. Eventually the cold fronts merged with the ITF, which, on the other hand, constituted a sharp demarcation line between the harmattan and the monsoon air masses during the whole period, particularly with regard to the air borne dust. From the time sections and the synoptic maps it is evident that the discrepancy in concentration of air borne dust was very sharp along the ITF, particularly during the latter part of the dust storm period. When the ITF slowed down and eventually approached its southernmost position and, simultaneously, the cold air invasion ceased, the dust accumulated in part in the southeastern areas and was in part drained out of the Sudan to the southwest, passing the Central African Republic.     

电离层电场的半年变化对F2区峰值电子浓度的影响

利用一个电离层理论模式,模拟了太阳活动低年、地磁宁静情况下,中低纬和赤道地区电离层F2区峰值电子浓度(NmF2)的半年变化规律,重点讨论了电离层电场对NmF2半年变化的影响.模拟结果表明,当输入的电场没有周年和半年变化时,磁赤道地区电离层NmF2本身就具有一定的半年变化特征,而在稍高的纬度上,NmF2半年变化的强度较弱.当输入的电场具有一定的半年变化时,电离层NmF2的半年变化强度有明显的改变,且这种改变随地方时和地磁纬度不同有明显的差别.在地磁赤道附近的电离层赤道槽地区,从上午到午夜的时间内,具有半年变化的电场对电离层NmF2半年变化的强度是减弱的作用,在其他的时间内,电场对电离层NmF2半年变化强度是加强的作用.而在稍高纬度的电离层驼峰地区,情况明显不同.从上午一直到翌日日出前,具有半年变化的电场对电离层NmF2半年变化的幅度都是加强的作用.在其他的时间内,电场对电离层NmF2半年变化的幅度是减弱的作用.同时,研究表明电离层电场对NmF2半年变化的作用和“赤道喷泉”现象强烈相关.     

汶川M_S8.0地震对龙门山断裂带附近地应力环境影响初探——以北川、江油地区为例

为探讨汶川MS8.0地震对龙门山断裂带现今地应力环境的影响,2009年10—12月,在龙门山断裂带的北川、江油地区开展了3个200m深度钻孔水压致裂地应力测量,获得了汶川MS8.0地震发生1年多以后断裂带附近地壳浅表层地应力环境.根据研究区内的原地应力测量结果及汶川MS8.0地震引起的断层错动等资料,运用线弹性有限元数值模拟方法,计算得到了由断层错动位移所产生的附加应力,并推算了ZK02和ZK03位置震前应力分布特征.通过对比分析,揭示了断裂带附近地应力场的变化规律,探讨了汶川MS8.0地震对龙门山断裂带附近地应力环境的影响.     

On the strength of electric currents and zonal magnetic fields at the top of the Earth''s core: Methodology and preliminary estimates

A new method is described for estimating: (a) the meridional electric current density, j_θ, (b) the vertical growth rate of the zonal magnetic field, ∂B_φ/∂r, or its scale-height, B_φ/∂B_φ/∂r) and (c) the vertical growth rate of the vertical current density, ∂j_r/∂r, at a few isolated points on the top surface of the Earth's core from observations of the internal geomagnetic field at the Earth's surface. The theoretical technique rests on combining unaccelerated, gravitationally-driven Boussinesq fluid dynamics of the core with frozen-flux electromagnetism, the mantle being treated as a spherically symmetric insulator.

Insertion into this theory of main field models for epochs 1965, 1975 leads to preliminary values for these quantities of magnitude: (a) j_θ 1 A/m², (b) ∂B_φ/∂r 10⁻⁶ T/m or B_φ/(∂B_φ/∂r) 10 m, (c) ∂j_r/∂r 10⁻⁶ A/m³. Some geophysical implications of these estimates are discussed.     

The statistical and numerical study of the global distribution of coronal plasma and magnetic field near 2.5 Rs over a 10-year period

The basic characteristics of the global distribution for the corona plasma and magnetic field near 2.5 Rs are analyzed with the statistical and numerical methods for 136 Carrington Rotations (CRs) covering four different phases of solar activity. By using the observational data and the velocity distribution model in the corona, the statistical average distribution of the magnetic field, density and the coronal mass outputs are analyzed for the four different phases. Then, a numerical study of the global distribution near 2.5 Rs has been made by solving a self-consistent MHD system. Finally, the solar wind speed at 1 AU is given by mapping the speed at 2.5 Rs to that near 1 AU, and the comparison of the numerical results with the observational measurements and the simulation result of the Wang–Sheeley–Arge (WSA) model are made during more than 5 years. The numerical results indicate that the global distributions on the source surface of 2.5 Rs at different phases of solar activity could be used to predict the change of the solar wind in interplanetary space.     

The influence of storm characteristics and catchment conditions on extreme flood response : A case study based on the brue river basin,U.K.

Methods for estimating the magnitude of extreme floods are reviewed. A method which combines a probabilistic storm transposition technique with a physically-based distributed rainfallrunoff model is described. Synthetic storms with detailed spatial and temporal distributions are generated and applied to the calibrated model of the Brue river basin, U.K. (area 135 km²). The variability of catchment response due to storm characteristics (storm area, storm duration, storm movement, storm shape and within storm variation) and initial catchment wetness conditions is investigated. A probabilistic approach to estimating the return periods of extreme catchment responses is suggested.     

Estimation of the PM2.5 effective hygroscopic parameter and water content based on particle chemical composition: Methodology and case study

Particle hygroscopicity plays a key role in understanding the mechanisms of haze formation and particle optical properties. The present study developed a method for predicting the effective hygroscopic parameter k and the water content of PM_(2.5) on the basis of the k-K?hler theory and bulk chemical components of PM_(2.5). Our study demonstrated that the effective hygroscopic parameter can be estimated using the PM_(2.5) mass concentration, water-soluble ions, and total water-soluble carbon. By combining the estimated k and ambient relative humidity, the water content of PM_(2.5) can be further estimated. As an example, the k and water content of PM_(2.5) in Beijing were estimated utilizing the method proposed in this study. The annual average value of k of PM_(2.5) in Beijing was 0.25±0.09, the maximum k value 0.26±0.08 appeared in summer, and the seasonal variation is insignificant. The PM_(2.5) water content was determined by both the PM_(2.5) hygroscopicity and the ambient relative humidity(RH). The annual average mass ratio of water content and PM_(2.5) was 0.18±0.20, and the maximum value 0.31±0.25 appeared in summer. Based on the estimated water content of PM_(2.5) in Beijing, the relationship between the PM_(2.5) water content and RH was parameterized as: m(%)=0.03+(5.73×10~(-8)) ×RH~(3.72).This parametric formula helps to characterize the relationship between the PM_(2.5) mass concentration and atmospheric visibility.     

The potential of audiomagnetotellurics in the study of geothermal fields: A case study from the northern segment of the La Candelaria Range,northwestern Argentina

Despite its reduced penetration depth, audiomagnetotelluric (AMT) studies can be used to determine a broad range of features related to little studied geothermal fields. This technique requires a stepwise interpretation of results taking into consideration diverse information (e.g. topographic, hydrological, geological and/or structural data) to constrain the characteristics of the study area. In this work, an AMT study was performed at the hot springs in the northern segment of the La Candelaria Range in order to characterize the area at depth. Geometric aspects of the shallow subsurface were determined based on the dimensional and distortion analysis of the impedance tensors. Also, the correlation between structural features and regional strikes allowed us to define two geoelectric domains, useful to determine the controls on fluid circulation. The subsurface resistivity distribution was determined through 1D and 2D models. The patterns of the 1D models were compared with the morpho-structure of the range. Shallow and deep conductive zones were defined and a possible shallow geothermal system scheme proposed. A strong correlation was found between the AMT results and the geological framework of the region, showing the relevance of using AMT in geothermal areas during the early stages of subsurface prospecting.     

A comparison of neustonic plastic and zooplankton at different depths near the southern California shore

Previous studies of neustonic debris have been limited to surface sampling. Here we conducted two trawl surveys, one before and one shortly after a rain event, in which debris and zooplankton density were measured at three depths in Santa Monica Bay, California. Surface samples were collected with a manta trawl, mid-depth samples with a bongo net and bottom samples with an epibenthic sled, all having 333 micron nets. Density of debris was greatest near the bottom, least in midwater. Debris density increased after the storm, particularly at the sampling site closest to shore, reflecting inputs from land-based runoff and resuspended matter. The mass of plastic collected exceeded that of zooplankton, though when the comparison was limited to plastic debris similar to the size of most zooplankton, zooplankton mass was three times that of debris.     

Thermosphere–ionosphere response at middle and high latitudes during perturbed conditions: A case study

Neutral gas composition and ionospheric measurements taken by the Dynamic Explorer 2 satellite at F2-region heights (280–300 km) during an intense geomagnetic storm (peak Dst=−187 nT) were used to analyze the role of some possible physical mechanisms responsible for the changes of electron density at high and middle latitudes. The storm considered in this study occurred on 26 September 1982. The main features observed were increases of electron density during the initial stages of the storm at middle latitudes; followed by decreases of electron density at high and mid-high latitudes during the main phase of the storm and the first phase of the recovery. Delayed increases of electron density during the recovery phase have also been observed at mid-high latitudes (50–60°). Several mechanisms were discussed in explaining the features observed for the electron density variations.     

中近磁尾等离子体片统计特性研究

本文使用Cluster-C1卫星的CIS仪器和FGM仪器测量得到的质子通量数据和计算的β数据,判断Cluster卫星在地球磁尾不同位置位于等离子体片内的概率.使用2001-2004年7-11月的Cluster-C1数据,分别在行星际磁场南向和北向时,得出XRE区域内卫星位于等离子体片的概率在Y-Dz平面的分布图(Dz是卫星到中性片的距离).通过对比行星际磁场南向和北向时的卫星位于等离子体片的概率的分布图,我们发现等离子体片在行星际磁场南向时比在行星际磁场北向时要薄,并且这个效应在磁尾晨昏两侧比在午夜附近明显,同时我们还发现等离子体片在晨侧比在昏侧厚.     

Distribution of boulders at Miyara Bay of Ishigaki Island,Japan: A flow characteristic indicator of tsunami and storm waves

This study investigates the distribution of boulders at Miyara Bay of Ishigaki Island, Japan. These boulders were deposited on a reef flat extending approximately 400–1300 m in width. Most boulders were rectangular to ellipsoidal, without sharp broken edges. They are reef and coral rock fragments estimated as <335 m³ (<633 t). Locally in the bay, the relationship between the boulder weight and position shows that boulders of a given weight have a clear limit on seaward distribution on the reef flat. For example, more than 1, 10, and 100 tons of boulders were deposited, respectively, more than 500, 300, and 100 m from the reef edge. The line is consistent with the possible landward transport limit by maximum storm waves at the Ryukyu Islands, suggesting that the line was formed by the reworking of some boulders by maximally strong storm waves, although we can not exclude the possibility that the line was formed by tsunamis. Furthermore, 68% of boulders at the bay are deposited beyond this line. Therefore, the presence of these boulders at their present positions is difficult to explain solely by storm waves, implying the possible tsunami origin of these boulders. The boulders are characteristically concentrated along the high‐tide line, suggesting the drastic reduction of the tsunami hydraulic force along the line. Previous studies using radiocarbon age dating, as well as our study, imply that at least 69 boulders at Miyara Bay were probably deposited at their present positions by the 1771 Meiwa tsunami, although some of these boulders might have been emplaced and displaced on the reef flat by prior tsunami or storm surges.     

Wind erosion at the dry-up bottom of Aiby Lake-- A case study on the source of air dust

Clay-rich deposits are usually considered as hard materials to be eroded by wind.Data from both surface monitoring and field survey at the dry-up bottom of Aiby Lake present thatclay-rich lacustrine deposits are easily broken down and eroded away by wind in the seasonalalternation process under the natural arid environment, and are the significant source of air dust.The surface of the clay-rich deposits is broken and softened by the freezing-and-thawing action inwinter season and/or by salt and alkali action with precipitation. Impact of wind-input particles andplow of plant branches with wind force drive the clay-rich sediments moving. Wind picks up theclay pebbles and repeats the impaction further-ward onto the dry-up surface. Tremendous finematerials, including soft salts, are contributed to air dust, and transported in long distance.     

Seepage erosion and its implication to the formation of amphitheatre valley heads: A case study at Obara,Japan

Seepage erosion was investigated in an amphitheatre with a semicircular valley head, steep slopes, and a flat bottom developed in granodiorite hills at Obara, Aichi prefecture, Japan. A high sediment yield occurred where the measuring sites were located at the base of the landslide debris in the base of the convex slopes, whereas sediment outflows were small where the measuring sites were located at the base of the strong convex slopes. This implies that the seepage erosion was an effective agent for removal of debris deposited at the base of the slope. Small landslides can be found at the lower slopes within the area of the observed amphitheatre. The slope stability analysis and subsurface water observation of the lower slope suggest that the small landslides in this amphitheatre are due to over-steepened slopes, and relatively insensitive to subsurface water status. Colluvium in the flat valley bottom thinly covers the bedrock surface. Therefore the topography of the amphitheatre was found to be formed by parallel retreat of slopes by the repetition of basal seepage erosion and subsequent small landslides.     

Does upward seepage of river water and storm water runoff determine water quality of urban drainage systems in lowland areas? A case study for the Rhine–Meuse delta

The water quality of urban drainage ditches in lowlands in the Rhine‐Meuse delta was analysed with principal component analysis (PCA) during a dry period and a rain storm, and related to the seepage of polluted river water and effective impervious area (EIA). This was done in order to test the hypothesis that seepage of river water and storm water runoff from impervious areas strongly determine the water quality of urban drainage systems along large lowland rivers. Our analysis revealed that upward seepage of groundwater originating from rivers Rhine and Meuse was positively correlated with nitrate, potassium, sodium and chloride and negatively correlated with alkalinity, calcium, magnesium and iron. EIA was correlated with very few environmental variables (i.e. phosphate, pH and iron in the dry period and iron during the rain storm). Nickel and zinc concentrations generally exceeded the maximum allowable concentrations (MAC), while lead and phosphorus concentrations were just above the nutrient standards and MAC in a few locations during the rain storm. To optimize water quality in urban water systems, attention should be paid to all sources of pollution and not only to EIA. The impact of local groundwater seepage originating from large rivers in lowlands on the chemistry of urban water systems is often underestimated and should be taken into account when assessing water quality and improving water quality status. Copyright © 2009 John Wiley & Sons, Ltd.     

井-地与井间电位技术联合数值模拟研究剩余油分布(英文)

电法测井有很高的分辨率,但是它的探测半径仅限于井孔周围;井-地电位技术虽然可以探测到足够大的范围,但是它的分辨率却受到很大的限制,特别是对于油水分布或者结构复杂的储层。本文试图通过井-地电位技术和井间电位技术的联合来研究地下储层油水分布范围。具体方法是,采用井-地电位技术研究油水分布在在横向上的展布情况,利用井间电位技术研究油水储层在垂向上的分布,然后采用井间电位结果标定井地电位结果,两者结合提高纵向分辨率,从而确定剩余油的三维空间分布。研究中通过研究注水初期数值模拟结果与水淹期数值模拟结果之差,求取剩余油分布范围。有限差分方法数值模拟表明:井-地电位技术与井间电位技术联合方法可以有效地确定剩余油分布。     

A study on rainfall,runoff,and soil loss relations at different landuses-A case in Hilkot watershed in Pakistan

Reliable field data for all hydrologic parameters are often unavailable for watersheds even for those intensively monitored.In the absence of reliable such data,verified mathematical relations for an area can be used for other areas with same hydrologic and climatic regimes.The objectives of this research were:1) to assess the total runoff and sediment loss,and 2) to develop rainfall,runoff and soil loss relations for four prominent landuses(including degraded,pasture,forest and agriculture lands) in the Hilkot watershed(Pakistan).Four experimental natural runoff plots were established on the landuses (degraded,pasture,forest and agriculture land).The field study and data collection were conducted in the Hilkot watershed from 1999 to 2005.Regression analysis was conducted to establish relations among rainfall,runoff and soil loss for all landuses using.Regression analysis indicated good correlation with field data.