Selection of the data time interval for the prediction of maximum ozone concentrations

This paper highlights the problem of step-length selection for the one-step-ahead prediction of ozone called the data time interval. This is done using a case study-based comparison of two approaches for predicting the maximum daily values of tropospheric ozone. The first approach is the 1-day-ahead prediction and the second is the prediction of the maximum values based on a multi-step-ahead iteration of 1-h predictions. Gaussian process modelling is utilised for this comparison. In particular, evolving Gaussian-process models are used that update on-line with the incoming measurement data. These sorts of models have been successfully used in the past for the prediction of ozone pollution. This paper contributes an assessment of the way that the maximum ozone values are predicted. A comparison of the daily maximum ozone values forecasted by a model based on 1-day-ahead predictions with those obtained by iterated 1-h-ahead predictions of the ozone with predictions at predetermined hours of the day is given. The forecast results are in favour of the on-line model based on hourly predictions when approaching closer to the real maximum values of ozone, and in favour of the daily predictions when they are made on a daily basis.     

Climate change scenarios of heat waves in Central Europe and their uncertainties

The study examines climate change scenarios of Central European heat waves with a focus on related uncertainties in a large ensemble of regional climate model (RCM) simulations from the EURO-CORDEX and ENSEMBLES projects. Historical runs (1970–1999) driven by global climate models (GCMs) are evaluated against the E-OBS gridded data set in the first step. Although the RCMs are found to reproduce the frequency of heat waves quite well, those RCMs with the coarser grid (25 and 50 km) considerably overestimate the frequency of severe heat waves. This deficiency is improved in higher-resolution (12.5 km) EURO-CORDEX RCMs. In the near future (2020–2049), heat waves are projected to be nearly twice as frequent in comparison to the modelled historical period, and the increase is even larger for severe heat waves. Uncertainty originates mainly from the selection of RCMs and GCMs because the increase is similar for all concentration scenarios. For the late twenty-first century (2070–2099), a substantial increase in heat wave frequencies is projected, the magnitude of which depends mainly upon concentration scenario. Three to four heat waves per summer are projected in this period (compared to less than one in the recent climate), and severe heat waves are likely to become a regular phenomenon. This increment is primarily driven by a positive shift of temperature distribution, but changes in its scale and enhanced temporal autocorrelation of temperature also contribute to the projected increase in heat wave frequencies.     

青藏工程走廊热融湖湖底热状态

热融湖塘对寒区环境可产生较大影响, 其侧向热侵蚀会诱发冻土工程病害.选取青藏工程走廊热融湖塘分布密集的楚玛尔河、五道梁、北麓河3个亚区, 于2009—2010年通过HOBO水位传感器对4个固定湖塘的连续监测和大量湖塘的随机观测, 探讨了不同季节、不同水深湖底的热状态.在结冰期的1月中旬, 楚玛尔河90%以上的湖塘湖底温度都在0 ℃以下, 主要与湖塘较浅和湖水高矿化度有关.五道梁和北麓河湖底温度相对较高, 只有约20%的湖底温度低于0 ℃, 这些湖水深小于最大冻结冰层厚度; 最高温度高于4 ℃, 主要与湖较深有关.但3个亚区湖底温度均随着水深增加而增加.在6~9月融冰期, 湖底温度普遍增加, 最高达到18 ℃以上, 浅湖增温快于深湖, 湖底温度随着水深增加而递减.湖底温度年际变化近似为正弦曲线, 在1~2月, 湖底温度最低, 之后逐渐升高, 到7~8月, 湖底温度达到最高.      

多尺度突变现象的扫描式t检验方法及其相干性分析

阐明了将检测两子样本平均值之差的学生氏t检验推广到对多尺度突变现象进行扫描式检测的计算方法;对于t检验要求序列独立的限制,引用了初步的订正方法;还给出了检测两个序列间多尺度突变相干性的计算公式.扫描式t检验不仅具有相当于子波变换检测多尺度突变现象的功能,而且解决了子波变换检测突变时缺少临界值的问题.由于t统计量包含有二阶矩均方差,它不能像子波变换那样作为分解工具,但检测的尺度参数也就不必局限于2的整数幂,因而可以进行扫描式检测.应用于尼罗河年最高与最低水位历史序列(AD622—1470),能较客观和精确地检测出两序列在某些尺度上的相干性(同步或反位相)变化;并由此重新划分了该流域几十年至百余年时间尺度的相对干湿期.结果与目前查阅到的埃及灾荒历史记载相吻合.     

折射波地震记录叠加成像方法研究

多次覆盖折射波地震勘探是用来追踪反射波成像质量较差地区的地质构造或用于追踪深层基底形态及研究基岩面的一种勘探方法.基于折射波理论,用折射地震记录中的折射波对地下折射界面进行成像,应用共深度折射面元叠加成像理论方法,给出用共深度折射面元叠加成像技术对地下折射界面进行成像的速度分析与动校正计算方法,提出一种适用于折射波发育探区的共深度折射点叠加成像方法,最后以模型和实际例子说明方法的正确性和实用性.     

Classification of and recent research involving radiative shocks

Radiative shocks (RS) occur in astrophysical systems and in high-energy density laboratory experiments. Aided by three dimensionless parameters, we propose a classification of RS into four types, integrating previous work that has focused independently on optical depth and on Mach number. Specific terms, such as a cooling function, a radiative flux, or radiative energy and pressure must be added to the Euler equations in order to model these various kinds of shocks. We examine how these terms correspond to the radiative classification regimes. In astrophysics, observed RS arise generally in optically thin material. Thus, radiation escapes without interaction with the surrounding gas, except perhaps to ionize it, and the energy loss in such shocks can be modeled by a cooling function Λ. In this case only the post-shock region is structured by the radiation cooling. We found the analytical solution for hydrodynamic equations including Λ∝ ρ ^ε P ^ζ x ^θ for arbitrary values of ε, ζ, θ. This is a completely new result. An application of this calculation for the accretion shock in cataclysmic variables of polar type is given in astrophysical terms. We also draw a parallel between RS experiments performed using the LULI2000 laser facility, in France and the Omega laser Facility, in USA. RS developed in these laboratories are more or less optically thick. These high-Mach number RS present a radiative precursor.     

Experimental results to study astrophysical plasma jets using Intense Lasers

We present experimental results of plasma jet, interacted with an ambient medium, using intense lasers to investigate the complex features of astrophysical jets. This experiment was performed in France at the LULI facility, Ecole Polytechnique, using one long pulse laser to generate the jet and a short pulse laser to probe it by proton radiography. A foam filled cone target was used to generate high velocity plasma jet, and a gas jet nozzle produced the well known ambient medium. Using visible pyrometry and interferometry, we were able to measure the jet velocity and electronic density. We get a panel of measurements at various gas density and time delay. From these measurements, we could underline the growth of a perturbed shape of the jet interaction with the ambient medium. The reason of this last observation is still in debate and will be presented in the article.     

On the integral inversion of satellite-to-satellite velocity differences for local gravity field recovery: a theoretical study

The gravity field can be recovered locally from the satellite-to-satellite velocity differences (VDs) between twin-satellites moving in the same orbit. To do so, three different integral formulae are derived in this paper to recover geoid height, radial component of gravity anomaly and gravity disturbance at sea level. Their kernel functions contain the product of two Legendre polynomials with different arguments. Such kernels are relatively complicated and it may be impossible to find their closed-forms. However, we could find the one related to recovering the geoid height from the VD data. The use of spectral forms of the kernels is possible and one does not have to generate them to very high degrees. The kernel functions are well-behaving meaning that they reduce the contribution of far-zone data and for example a cap margin of \(7^{\circ }\) is enough for recovering gravity anomalies. This means that the inversion area should be larger by \(7^{\circ }\) from all directions than the desired area to reduce the effect of spatial truncation error of the integral formula. Numerical studies using simulated data over Fennoscandia showed that when the distance between the twin-satellites is small, higher frequencies of the anomalies can be recovered from the VD data. In the ideal case of having short distance between the satellites flying at 250 km level, recovering radial component of gravity anomaly with an accuracy of 7 mGal is possible over Fennoscandia, if the VD data is contaminated only with the spatial truncation error, which is an ideal assumption. However, the problem is that the power of VD signal is very low when the satellites are close and it is very difficult to recognise the signal amongst the noise of the VD data. We also show that for a successful determination of gravity anomalies at sea level from an altitude of 250 km mean VDs with better accuracy than 0.01 mm/s are required. When coloured noise at this level is used for the VDs at 250 km with separation of 300 km, the accuracy of recovery will be about 11 mGal over Fennoscandia. In the case of using the real velocities of the satellites, the main problems are downward/upward continuation of the VDs on the mean orbital sphere and taking the azimuthal integration of them.     

Underground mining hazard map including building site categories in an area affected by underground mining activities

The objective of the paper is generation of an underground mining hazard map. The method applied to create the map is based on five categories of areas with different characters of underground mining influence making use of the so-called building site categories. The individual areas with different groups represent various suitability or unsuitability for founding new structures in such influenced territories. They will also reflect a higher or lower degree of influence on already existing structures. Areas affected by underground mining of category V are suitable without any significant restrictions. Areas of the medium category represent influence of building site categories III and IV with economically acceptable measures for founding engineering purposes. The last type is areas with high influence in the category I and II and they are clearly unsuitable for new development. Structures may be founded there in exceptional cases only. This methodology was applied on four map sheets in 1:10,000 scale in a coal mining region in the town of Karviná and its environs in the direction to the City of Ostrava (Czech Republic). Extensive changes caused by underground mining have been identified in the study area and the implementation of the suggested maps may help to deal with the issue in terms of land development by means of land use planning.     

Petrology and geochemistry of the 2014–2015 Holuhraun eruption,central Iceland: compositional and mineralogical characteristics,temporal variability and magma storage

The 2014–2015 Holuhraun fissure eruption provided a rare opportunity to study in detail the magmatic processes and magma plumbing system dynamics during a 6-month-long, moderate- to large-volume basaltic fissure eruption. In this contribution, we present a comprehensive dataset, including major and trace elements of whole-rock and glassy tephra samples, mineral chemistry, and radiogenic and oxygen isotope analyses from an extensive set of samples (n?=?62) that were collected systematically in several field campaigns throughout the entire eruptive period. We also present the first detailed chemical and isotopic characterization of magmatic sulfides from Iceland. In conjunction with a unique set of geophysical data, our approach provides a detailed temporal and spatial resolution of magmatic processes before and during this eruption. The 2014–2015 Holuhraun magma is compositionally indistinguishable from recent basalts erupted from the Bárðarbunga volcanic system, consistent with seismic observations for magma ascent close to the Bárðarbunga central volcano, followed by dyke propagation to the Holuhraun eruption site. Whole-rock elemental and isotopic compositions are remarkably constant throughout the eruption. Moreover, the inferred depth of the magma reservoir tapped during the eruption is consistently 8?±?5 km, in agreement with geodetic observations and melt inclusion entrapment pressures, but inconsistent with vertically extensive multi-tiered magma storage prior to eruption. The near constancy in the chemical and isotopic composition of the lava is consistent with the efficient homogenization of mantle-derived compositional variability. In contrast, occurrence of different mineral populations, including sulfide globules, which display significant compositional variability, requires a more complex earlier magmatic history. This may include sampling of heterogeneous mantle melts that mixed, crystallized and finally homogenized at mid- to lower-crustal conditions.