应用GPS可降水量分析河北省一次回流降雪天气

利用地基GPS反演的可降水量资料、地面加密自动站和常规天气资料,对2011年2月发生在河北省的一次回流降雪天气过程进行了分析.结果表明:①降雪过程前期,GPS可降水量由西南向东北逐渐增大,后期自北向南减小,与西南暖湿气流的输送和地面冷高压的南压对应.②第1阶段降雪的主要影响系统为高空槽,GPS可降水量不断增加,对应的实际降水也是先增后减;第2阶段的降雪主要表现为回流降雪,降雪前期GPS可降水量迅速增长,实际降水出现在GPS可降水量峰值及下降阶段.随着地面冷高压逐渐南压,GPS可降水量逐渐下降,实际降水也逐渐减弱至停止.③在探空层结曲线上,高湿层位于地面附近和700 hPa附近,而二者之间的近地层存在着低湿层.     

MARCO POLO: near earth object sample return mission

MARCO POLO is a joint European–Japanese sample return mission to a Near-Earth Object. This Euro-Asian mission will go to a primitive Near-Earth Object (NEO), which we anticipate will contain primitive materials without any known meteorite analogue, scientifically characterize it at multiple scales, and bring samples back to Earth for detailed scientific investigation. Small bodies, as primitive leftover building blocks of the Solar System formation process, offer important clues to the chemical mixture from which the planets formed some 4.6 billion years ago. Current exobiological scenarios for the origin of Life invoke an exogenous delivery of organic matter to the early Earth: it has been proposed that primitive bodies could have brought these complex organic molecules capable of triggering the pre-biotic synthesis of biochemical compounds. Moreover, collisions of NEOs with the Earth pose a finite hazard to life. For all these reasons, the exploration of such objects is particularly interesting and urgent. The scientific objectives of MARCO POLO will therefore contribute to a better understanding of the origin and evolution of the Solar System, the Earth, and possibly Life itself. Moreover, MARCO POLO provides important information on the volatile-rich (e.g. water) nature of primitive NEOs, which may be particularly important for future space resource utilization as well as providing critical information for the security of Earth. MARCO POLO is a proposal offering several options, leading to great flexibility in the actual implementation. The baseline mission scenario is based on a launch with a Soyuz-type launcher and consists of a Mother Spacecraft (MSC) carrying a possible Lander named SIFNOS, small hoppers, sampling devices, a re-entry capsule and scientific payloads. The MSC leaves Earth orbit, cruises toward the target with ion engines, rendezvous with the target, conducts a global characterization of the target to select a sampling site, and delivers small hoppers (MINERVA type, JAXA) and SIFNOS. The latter, if added, will perform a soft landing, anchor to the target surface, and make various in situ measurements of surface/subsurface materials near the sampling site. Two surface samples will be collected by the MSC using “touch and go” manoeuvres. Two complementary sample collection devices will be used in this phase: one developed by ESA and another provided by JAXA, mounted on a retractable extension arm. After the completion of the sampling and ascent of the MSC, the arm will be retracted to transfer the sample containers into the MSC. The MSC will then make its journey back to Earth and release the re-entry capsule into the Earth’s atmosphere.     

FLUCTUATION OF AGROCLIMATIC ZONES AND ITS IMPACT ON AGRICULTURAL PRODUCTION IN CHINA

Accumulated temperature above 100℃ (Σ t) and minimum annual temperature (Tm) are the major indexes for demarcating agroclimatic thermal zones. The paper calculated the return period (τ) of Σ t and Tm, and the shift ofΣ t-and Tm-isopleths with T. The results show: (1) According to the magnitude of shift of Σ t-and Tm-isopleths, in Northeast China, Inner Mongolia and northern Xinjiang the fluctuation of thermal resources in growing season from year to year is the greatest and strongly impacts the yield of annual thermophilous crops, but in the Changjiang River basin the fluctuation of the low temperature in winter is the greatest and seriously injures the perennial subtropical tree crops. ( 2) In the anomalous cool summer year with t = 30, the northern boundaries of the southern subtropical, northern subtropical and warm temperate zones and the southern boundary of the frigid temperate zone in China could be expected to shift southward 150, 220, 250 and 300 km from their normal positions, respective     

Seismic hazard evaluation at Algiers using Benouar's earthquake catalogue

This paper presents the evaluation of seismic hazard at the site of Algiers (capital of Algeria). In order to implement earthquake-resistant design codes, it is usually necessary to know the maximum dynamic load which a particular structure might experience during its economic life, or alternatively, the most probable return period of a specified design load. The evaluation of the seismic hazard at the site, based on peak ground motion acceleration and using Cornell's method and Benouar's earthquake Maghreb catalogue, in terms of return period, probability of exceedance of PGA, design ground motion and a response spectrum, is carried out for the City of Algiers and its surroundings. The response spectrum for Algiers presented in this paper is the first one realized in Algeria using revised Algerian data.     

渤海重现期波高的数值计算

利用RAMS大气模式给出的20年风场资料,利用SWAN近海波浪模式对渤海海域的波浪进行了20 a数值计算.通过与一般过程和大风过程的实测资料的对比后发现.波浪模拟值与实潮值符合地较好,SWAN模式适合渤海海域波浪的计算。通过分析发现.辽东湾常浪向为SSW。强浪向为SSW;渤海中部常浪向为S,强浪向为NE;渤海海峡常浪向为NNW,强浪向为NNW;莱州湾常浪向为S,强浪向为NNE;渤海湾常浪向为S.强浪向为NE。渤中偏东南海域(38°～39°N,119.5°～120.5°E)多年一遇有效波高最大.其中百年一遇有效波高最大值达到6.7m。     

Adapting earthquake actions in Eurocode 8 for performance‐based seismic design

Performance‐based seismic design (PBSD) can be considered as the coupling of expected levels of ground motion with desired levels of structural performance, with the objective of achieving greater control over earthquake‐induced losses. Eurocode 8 (EC8) already envisages two design levels of motion, for no collapse and damage limitation performance targets, anchored to recommended return periods of 475 and 95 years, respectively. For PBSD the earthquake actions need to be presented in ways that are appropriate to the estimation of inelastic displacements, since these provide an effective control on damage at different limit states. The adequacy of current earthquake actions in EC8 are reviewed from this perspective and areas requiring additional development are identified. The implications of these representations of the seismic loads, in terms of mapping and zonation, are discussed. The current practice of defining the loading levels on the basis of the pre‐selected return periods is challenged, and ideas are discussed for calibrating the loading‐performance levels for design on the basis of quantitative earthquake loss estimation. Copyright © 2005 John Wiley & Sons, Ltd.     

Unusual sedimentary deposits on the SE side of Stromboli volcano, Italy: products of a tsunami caused by the ca. 5000 years BP Sciara del Fuoco collapse?

The role of sector collapse in the generation of catastrophic volcanigenic tsunami has become well understood only recently, in part because of the problems in the preservation and recognition of tsunami deposits. Tinti et al. [Tinti, S., Bortolucci, E., Romagnoli, C., 2000. Computer simulations of tsunamis due to sector collapse at Stromboli, Italy. J. Volcanol. Geotherm. Res. 96, 103–128] modeled a tsunami produced by the c. 5,000 years BP collapse of the Sciara del Fuoco on the island volcano Stromboli. Although deposits associated with this event are generally lacking on the island, volcaniclastic breccias on the SE side of the island extending to an elevation above 120 m a.s.l. may have been generated by this tsunami. Deposits above 100 m are dominated by coarse breccias comprising disorganized, poorly sorted, nonbedded, angular to subangular lava blocks in a matrix of finer pyroclastic debris. These breccias are interpreted as a water-induced mass flow, possibly a noncohesive debris flow, generated as colluvial material on steep slopes was remobilized by the return flow of the tsunami wave, the run-up of which reached an elevation exceeding 120 m a.s.l. Finer breccias of subrounded to rounded lava blocks cropping out at 15 m a.s.l. are similar to modern high-energy beach deposits and are interpreted as beach material redeposited by the advancing tsunami wave. The location of these deposits matches the predicted location of the maximum tsunami wave amplitude as calculated by modeling studies of Tinti et al. [Tinti, S., Bortolucci, E., Romagnoli, C., 2000. Computer simulations of tsunamis due to sector collapse at Stromboli, Italy. J. Volcanol. Geotherm. Res. 96, 103–128]. Whereas the identification and modeling of paleo-tsunami events is typically based on the observation of the sedimentary deposits of the tsunami run-up, return flow may be equally or more important in controlling patterns of sedimentation.     

陕西黄土高原区降雨缺水风险分析

在黄土高原区,连续数月干旱缺水频繁发生,影响农业灌溉。通过降雨缺水的风险理论分析,评价了陕西省黄土高原区降雨缺水风险以及在一定时段内发生连续数月干旱缺水的风险概率和重现期。     

多年持续干旱历时的概率分布与重现期确定方法的研究

用直接方法（解析法）和间接方法（模拟法）对多年持续干旱历时的概率分布进行了分析，提出了一种确定多年持续干旱历时重现期的方法－全历时重现期法。该方法概念明确，便于实用。     

Numerical experiment with modelled return echo of a satellite altimeter from a rough ocean surface and a simple iterative algorithm for the estimation of significant wave height

We have simulated the return echo of a satellite altimeter from a rough ocean surface using an analytical formula and have studied its sensitivity with respect to various oceanic and altimeter parameters. Our numerical experiment shows that for normally observed significant wave heights (SWH) the effect of off-nadir angle (ONA) up to 0.5° on the leading edge is not severe. Also, small surface roughness skewness seems to have little effect on the overall shape of the echo. Newton’s iterative scheme has been used to retrieve SWH from the mean return waveform without noise and with additive Gaussian noise typical of Seasat and Geosat altimeters. It has been observed that SWH can be retrieved in the presence of noise with an accuracy of ±0.6 m for ONA less than 0.5°. For higher ONA, accurate retrieval requires the use of precomputed look-up table along with our scheme.