Have volcanoes already passed their zenith influencing the ozone layer?

Earth's ozone layer is only a very small part of the atmosphere, but its intact abundance is most important to the vitality of human beings. Observations have shown that especially after the plinian eruption of Pinatubo volcano in 1991 the ozone layer showed a dramatic depletion. Could a similar hypothetic eruption in the future cause an equal effective destruction of ozone while considering the increasing reduction of man-made halogens in the stratosphere after the Montreal protocol in 1987?     

The role and performance of ground-based networks in tracking the evolution of the ozone layer

In the 1980s, ground-based monitoring of the ozone layer played a key role in the discovery of the Antarctic Ozone Hole as well as in the first documentation of significant winter and spring long-term downward trends in the populated mid-latitude regions. The article summarizes the close-to-hundred-year-long history of ground-based measurements of stratospheric ozone, and more recent observations of constituents that influence its equilibrium. Ozone observations began long before the recognition of the impact of increasing emissions of manmade ozone-depleting substances on ozone and therefore on UV levels, human health, ecosystems and the Earth climate. The historical ozone observations prior to 1980s are used as a reference for the assessments of the state of the ozone layer linked to the enforcement of the Montreal Protocol. In this paper, we describe the worldwide monitoring networks and their ozone observations used to determine long-term trends with an accuracy of a few percent per decade. Since 1989, the ground-based monitoring activities have provided support for the amendments of the Montreal Protocol (MP). They include monitoring of (a) the ozone total column and the vertical distribution at global scale, (b) the ozone-depleting substances (ODS) related to the MP such as chlorofluorocarbons (CFCs), and their decomposition products in the stratosphere, and (c) the atmospheric species playing a role in ozone depletion, e.g., nitrogen oxides, water vapor, aerosols, polar stratospheric clouds. We highlight important accomplishments in the atmospheric monitoring performed by the Global Atmosphere Watch program (GAW) run under the auspices of the World Meteorological Organization (WMO) and by the Network for the Detection of Atmospheric Composition Change (NDACC). We also address the complementary roles of ground-based networks and satellite instruments. High-quality ground-based measurements have been used to evaluate ozone variabilities and long-term trends, assess chemistry climate models, and check the long-term stability of satellite data, including more recently the merged satellite time-series developed for the detection of ozone recovery at global scale, which might be further modified by climate change.     

Single hidden layer artificial neural network models versus multiple linear regression model in forecasting the time series of total ozone

Present paper endeavors to develop predictive artificial neural network model for forecasting the mean monthly total ozone concentration over Arosa, Switzerland. Single hidden layer neural network models with variable number of nodes have been developed and their performances have been evaluated using the method of least squares and error estimation. Their performances have been compared with multiple linear regression model. Ultimately, single-hidden-layer model with 8 hidden nodes have been identified as the best predictive model.     

河套干旱地区夏季边界层结构特征观测分析

利用2013年夏季7月爱尔达K/LLX802J型机动式边界层风廓线雷达获取的三维风场资料和银川站高空气象探测资料,对河套干旱地区夏季边界层日变化特征进行了分析.结果表明:爱尔达K/LLX802J型机动式风廓线雷达能较好的反映并分辨出夏季河套干旱地区边界层内大气湍流和风场的演变过程.夏季7月河套干旱地区边界层高度白天平均为2127.2 m,夜间平均为1760.7 m,白天边界层高度比夜间平均高366.5 m.河套干旱区夏季地表非绝热加热对边界层的影响主要集中在800 m以下,800~2000 m高度边界层则主要受昼夜交替和大尺度天气系统的影响.夏季7月河套干旱地区边界层风速在300 m以下随高度增加而增大,离地500 m以下边界层易在北京时间07:00-11:00和18:00-21:00时段发生风速切变;300 m以下边界层白天盛行西南偏南风、夜间盛行南风,300~2000 m高度边界层白天和夜间均盛行东南风;离地300 m以下边界层易在夜间21:00-23:00时出现风向切变.夏季7月白天河套干旱地区边界层大气垂直速度在300 m高度以下随高度增加而增大,由0.3 m·s^-1增大到0.6 m·s^-1,夜间边界层大气垂直速度在200 m高度以下随高度增大而增大;300 m高度以上边界层大气垂直速度无论昼夜随高度变化均较小.     

冻融条件下浅层黄土中温度与水分的空间变化相关性

黄土高原是西北典型的季节性冻土区,在黄土斜坡冻结和融解过程中土体内的温度、水分变化显著,导致土体中含水量及地下水位发生相应的变化,诱发一系列的滑坡、崩塌等地质环境问题。选择甘肃永靖县黑方台黄土斜坡为研究区,原位监测冻结至融解过程中黄土的温度和含水量,研究冻融条件下黄土斜(边)坡冻结层温度和水分及变化特征及其关系。结果表明,本次监测点黄土冻结深度为52cm,黄土剖面温度表现为3个特征带:温度稳定传递带、温度变动带、温度交替显著带。温度在黄土斜(边)坡冻融过程中对水分具有控制性作用,含水量随温度变化划分为3个阶段:1小于2℃,含水量随温度呈现非线性递增趋势;22~6℃,含水量随温度呈现波动性下降;3大于6℃,水分由小幅增加直至稳定,温度影响权重减小。随着冻结土层完全融解,被冻结水分融解后向下运移,最终导致剖面含水量急剧增加,因此,冻结至融解过程中含水量发生急剧增加,是导致浅层黄土滑塌的重要因素。     

Oxygen and ozone in the early Earth's atmosphere

The precise amount of O₂ and O₃ in the Earth's prebiological paleoatmosphere has been a topic of considerable discussion in the past. Since the photolysis of H₂O and CO₂, the prebiological mechanisms to produce O₂, depends on the ultraviolet (UV) flux from the Sun, a reliable quantification of the problem requires detailed knowledge of such flux. Using the most recent astronomical observation of young stars from the International Ultraviolet Explorer, as well as a detailed photochemical model of the paleoatmosphere, we find that the amount of O₂ in the prebiological paleoatmosphere may have been as much as 10⁶ times greater than previously estimated.Some of the implications of this new value are discussed.     

青藏公路沿线多年冻土区活动层起始冻融时间的时空变化特征和影响因素

多年冻土区活动层冻融格局对气候系统、能量平衡、水文过程和生态系统有重要的影响,地表冻融时间是反映冻融格局时空变化的重要指标。为了探明多年冻土区活动层起始冻融时间的影响因素和机制,通过对青藏公路沿线8个典型活动层观测场地表起始融化时间（OOT）和起始冻结时间（OOF）进行研究,分析了不同观测场起始冻融时间的时空差异及其影响因素。结果表明：（1）青藏高原多年冻土区活动层起始融化主要发生在4月中下旬,起始冻结主要发生在10月中下旬。OOT的年际变化幅度远大于OOF,每年起始冻结的发生较起始融化更为准时。（2）起始融化发生时的气温普遍比起始冻结发生时高1~4℃。气温对OOT的影响要比对OOF大,其中OOT的变化主要与春季气温有关,冬季气温对其影响不大。（3）植被和土壤水分对OOT和OOF有重要调节作用,土壤含水率越高,植被状况越好,起始融化和冻结的发生时间往往越迟。（4）在起始融化和冻结阶段,厚度较大和持续时间较长的积雪对地温变化有明显的抑制作用,对OOT和OOF有延迟作用。     

Impacts of ozone on trees and crops

In this review article, we explore how surface-level ozone affects trees and crops with special emphasis on consequences for productivity and carbon sequestration. Vegetation exposure to ozone reduces photosynthesis, growth, and other plant functions. Ozone formation in the atmosphere is a product of NO_x, which are also a source of nitrogen deposition. Reduced carbon sequestration of temperate forests resulting from ozone is likely offset by increased carbon sequestration from nitrogen fertilization. However, since fertilized croplands are generally not nitrogen-limited, capping ozone-polluting substances in the USA, Europe, and China can reduce future crop yield loss substantially.     

Future ozone in a changing climate

The stratospheric ozone layer is expected to recover as a result of the regulations of the Montreal Protocol on chlorine and bromine containing ozone-depleting substances (ODSs). Model simulations project a return of global annually averaged total column ozone to 1980 levels before the middle of the 21^st century, well before the ODSs will return to 1980 levels. This earlier ozone return date is due to the effects of rising greenhouse gas (GHG) concentrations. GHGs influence ozone directly by chemical reactions, but also indirectly by changing stratospheric temperature and the Brewer–Dobson circulation. Based on projections of chemistry–climate models, this article summarizes the effects of GHGs on stratospheric and total column ozone in the mid-latitude upper stratosphere, Arctic and Antarctic spring, and the tropics. The sensitivity of future ozone change to the GHG scenario is discussed, as well as the specific role of a future increase in nitrous oxide and methane.     

Possible ozone influence on the quasi-biennial oscillation in the equatorial stratosphere

Doklady Earth Sciences -     

On the indentation of a poroelastic layer

The paper examines the axisymmetric contact problem related to the indentation of a fluid saturated poroelastic layer by a smooth rigid punch. The layer rests in bonded contact with a rigid impermeable base and the surface of the layer is considered to be either permeable or impermeable. The paper develops the integral equations governing the problem for the generalized case where the pore fluid exhibits compressibility. The numerical results presented in the paper illustrate the influence of the relative layer thickness, drainage conditions and the compressibility of the pore fluid on the degree of consolidation settlement of the indenting punch.     

空间实体的拓扑构建

空间实体的拓扑关系是地理信息系统进行空间分析、决策支持的基础.拓扑关系的关键点在于拓扑结构的构建.首先介绍了点集拓扑理论, 归纳了有实际应用价值的各种拓扑关系, 分析了拓扑模型中的最基本拓扑元素和空间实体的关系; 然后提出了一种要素类的拓扑构建方法, 其算法以MAPGIS7.0空间实体的结构为依据, 主要体现要素分裂的思想.实践证明, 这些方法能够有效的构建空间实体的拓扑关系.      

Low level of stratospheric ozone near the Jharia coal field in India

The Indian reserve of coking coal is mainly located in the Jharia coal field in Jharkhand. Although air pollution due to oxides and dioxides of carbon, nitrogen and sulphur is reported to have increased in this area due to large-scale opencast mining and coal fires, no significant study on the possible impact of coal fires on the stratospheric ozone concentration has been reported so far. The possible impact of coal fires, which have been burning for more than 90 years on the current stratospheric ozone concentration has been investigated using satellite based data obtained from Upper Atmospheric Research Satellite (UARS MLS), Earth Observing System Microwave Limb Sounder (EOS MLS) and Ozone Monitoring Instrument (OMI) in this paper. The stratospheric ozone values for the years 1992–2007, in the 28–36 km altitude range near Jharia and places to its north are found to be consistently lower than those of places lying to its south (up to a radius of 1000 km around Jharia) by 4.0–20%. This low stratospheric ozone level around Jharia is being observed and reported for the first time. However, due to lack of systematic ground-based measurements of tropospheric ozone and vertical ozone profiles at Jharia and other far off places in different directions, it is difficult to conclude strongly on the existence of a relationship between pollution from coal fires and stratospheric ozone depletion.     

Rocket measurements of ozone concentrations in the stratosphere and mesosphere over Thumba

A rocket-borne solar middle ultraviolet photometer has been developed at the Physical Research Laboratory, Ahmedabad for the measurement of ozone concentrations at stratospheric and mesospheric heights. The instrument has now been flown successfully several times from thumba and ozone concentrations determined over an altitude range of 15 to 80 km. This paper describes the instrumentation, data analysis technique as well as the laboratory calibration procedures. Also presented are the results from four successful rocket experiments conducted during equinoctial months under an Indo-USSR collaborative programme for strato-mesospheric studies. The results show that at Thumba peak ozone concentrations vary between 2·2 and 3·1×10¹² molecules per cc and the peak altitude varies from 25 to 29 km from flight to flight. In the altitude region above about 40 km the ozone concentrations over Thumba are lower than the standard mid-latitude model values, by a factor lying between 1·5 and 2·5.     

On the modeling of electrical boundary layer (electrode layer) and derivation of atmospheric electrical profiles,eddy diffusion coefficient and scales of electrode layer

Electrode layer or electrical boundary layer is one of the charge generators in the global atmospheric electric circuit. In spite of this we find very few model studies and few measurements of it in the literature. Using a new technique it is shown that in this layer, the space charge density varies exponentially in vertical. A new experimental method based on the surface measurements is discussed to determine all the characteristic scales and an average electrical and meteorological state of an electrode layer. The results obtained are in good agreement with the previous studies. So, it is suggested that an exponential space charge density profile will no longer be an assumption in the case of electrode layer studies. The profiles of atmospheric electric field and electrical conductivity are also derived and a new term named as electrode layer constant is introduced.     

Context of the suboxic layer in the Arabian Sea

The setting of the Arabian Sea is reviewed in order to examine which of the circumstances causing large oxygen depletion in the ocean are responsible for the suboxic layer (concentrations < 0.1 ml 1⁻¹) in the northern thermocline there. The wind field forces circulations that restrict but do not exclude exchange with the south, and a recent box-model interpretation of trichlorofluoromethane measurements indicates a modest throughflow for the layer of about 5 × 10⁶m^{3s −1}.The associated oxygen-flux divergence is roughly consistent with biochemical determinations of local oxygen-consumption rates, both approaches giving values (3–6 pl 1⁻¹ s^τ-1) that are modest in comparison with estimates elsewhere in the world ocean. Despite the high mean-annual surface productivity in the region (nearly 1gCm⁻² day⁻¹), it seems plausible that too little of this particulate matter is consumed at thermocline depths to cause an inflated oxygen demand there. Since the layer is neither an isolated pool, nor a sluggish backwater, nor a conspicuous oxygen sink, the suboxic concentrations must be due (as earlier proposed) to the low concentration in the water entering the layer from the south. That depletion in turn seems due to moderate consumption as the water travels the very long trajectories from its zone of sea-surface renewal (Lats. 40–50°S). Although large seasonal variations are expected in both throughflow volume transport and surface productivity (suggesting comparable changes in consumption rate), the volume of the suboxic layer seems big enough to buffer the oxygen levels there against any very noticeable overall variability.