三维4参数模型实现地图到CGCS2000的转换

讨论了参心系下的地形图转换到2000国家大地坐标系(CGCS2000)下的方法。用全国大致有代表性的区域进行实验,证明所采用的方法完全能满足国家基本比例尺地形图的精度要求。     

几种移去恢复法的比较分析

小区域的工程建设中,为充分利用GPS测得的大地高成果,通常采用几何拟合法和移去恢复法计算当地的大地水准面模型,通过具体算例对常用的拟合模型和几种移去恢复法进行分析比较,提出基于CQG2000的移去恢复法,试验表明该法较其它方法精度有明显提高。     

Major-ion bulk deposition around an active volcano (Mt. Etna, Italy)

Bulk atmospheric deposition of major cations (Na, K, Ca, Mg) and anions (Cl, F, SO₄) were measured at 15 sites around an active volcano, Mount Etna, from 2001 to 2003. Their composition indicates several natural sources, among which deposition of plume-derived volcanogenic gas compounds is prevalent for F, Cl and S. Plume-derived acidic compounds are also responsible for the prevailing acidic composition of the samples collected on the summit of the volcano (pH in the 2.45–5.57 range). Cation species have complex origin, including deposition of plume volcanogenic ash and aerosols and soil-dust wind re-suspension of either volcanic or carbonate sedimentary rocks. Variation of the deposition rates during the March 2001–March 2003 period, coupled with previous measurements from 1997 to 2000 (Appl Geochem 16:985–1000, 2001), were compared with the variation of SO₂ flux, volcanic activity and rainfall. The deposition rate was mainly controlled by rainfall. Commonly, about 0.1–0.9% of HF, HCl and SO₂ emitted by the summit crater's plume were deposited around the volcano. We estimate that ∼2 Gg of volcanogenic sulphur were deposited over the Etnean area during the 2002–2003 flank eruption, at an average rate of ∼24 Mg day⁻¹ which is two orders of magnitude higher than that typical of quiescent degassing phases.     

天文经纬度归心实用算式推证

文中分析天文经纬度归心公式中各变量的特点,推导基于2000国家大地坐标系统简单实用的归心计算公式,进一步给出由已确定变量推求归心元素测量精度的数学关系式。验证实用公式计算的归心改正数满足专用工程天文经纬度的计算精度需求。     

在EBEX-2000实验资料中湍流耗散率、长度尺度和结构参数特征

采用2000年8月在美国加州棉花地两个高度上应用超声三分量仪、快速响应温度和湿度仪进行的EBEX-2000 (International Energy Balance Experiment, 2000, 简称EBEX-2000) 风速三分量、温度和湿度湍流实验观测数据, 计算分析了在不同稳定度下的湍流能量和热量耗散率和湍流结构参数特征.并与Kansas和长白山原始森林湍流实验得到的结果进行了比较, 得到了一些湍流特征量在不同下垫面情况下的一些有意义的特征.     

Equilibrium trading of climate and weather risk and numerical simulation in a Markovian framework

We consider financial markets with agents exposed to external sources of risk caused, for example, by short-term climate events such as the South Pacific sea surface temperature anomalies widely known by the name El Nino. Since such risks cannot be hedged through investments on the capital market alone, we face a typical example of an incomplete financial market. In order to make this risk tradable, we use a financial market model in which an additional insurance asset provides another possibility of investment besides the usual capital market. Given one of the many possible market prices of risk, each agent can maximize his individual exponential utility from his income obtained from trading in the capital market, the additional security, and his risk-exposure function. Under the equilibrium market-clearing condition for the insurance security the market price of risk is uniquely determined by a backward stochastic differential equation. We translate these stochastic equations via the Feynman–Kac formalism into semi-linear parabolic partial differential equations. Numerical schemes are available by which these semilinear pde can be simulated. We choose two simple qualitatively interesting models to describe sea surface temperature, and with an ENSO risk exposed fisher and farmer and a climate risk neutral bank three model agents with simple risk exposure functions. By simulating the expected appreciation price of risk trading, the optimal utility of the agents as a function of temperature, and their optimal investment into the risk trading security we obtain first insight into the dynamics of such a market in simple situations.

省级基础地理信息数据坐标转换软件设计与实现

介绍了数字线划图、数字高程模型、数字正射影像图、数字栅格地图由1980西安坐标系向2000国家大地坐标系的转换关键技术,阐述了省级基础地理信息数据坐标转换软件的设计原则、总体架构、主要功能及实现方法,对高效、快速将1980西安坐标系下的成果转到2000国家大地坐标系具有一定的指导作用。     

Seismic microzonation of Dehradun City using geophysical and geotechnical characteristics in the upper 30 m of soil column

The understanding of geotechnical characteristics of near-surface material is of fundamental interest in seismic microzonation. Shear wave velocity (Vs), one of the most important soil properties for soil response modeling, has been evaluated through seismic profiling using the multichannel analysis of surface waves in the city of Dehradun situated along the foothills of northwest Himalaya. Fifty sites in the city have been investigated with survey lines between 72 and 96 m in length. Multiple 1-D and interpolated 2-D profiles have been generated up to a depth of 30–40 m. The Vs were used in the SHAKE2000 software in combination with seismic input motion of the recent Chamoli earthquake to obtain site response and amplification spectra. The estimated Vs are higher in the northern part of the study area (i.e., 200–700 m/s from the surface to a depth of about 30 m) as compared to the south and southwestern parts of the city (i.e., 180–400 m/s for the same depth range). The response spectra suggest that spectral acceleration values for two-story structures are three to eight times higher than peak ground acceleration at bedrock. The analysis also suggests peak amplification at 3–4, 2–2.5, and 1–1.5 Hz in the northern, central, and south-southwestern parts of the city, respectively. The spatial distributions of Vs and spectral accelerations provide valuable information for the seismic microzonation in different parts of the urban area of Dehradun.     

The caldera-forming eruption of Volcán Ceboruco, Mexico

3 of magma erupted, ∼95% of which was deposited as fall layers. During most of the deposition of P1, eruptive intensity (mass flux) was almost constant at 4–8×10⁷ kg s⁻¹, producing a Plinian column 25–30 km in height. Size grading at the top of P1 indicates, however, that mass flux waned dramatically, and possibly that there was a brief pause in the eruption. During the post-P1 phase of the eruption, a much smaller volume of magma erupted, although mass flux varied by more than an order of magnitude. We suggest that caldera collapse began at the end of the P1 phase of the eruption, because along with the large differences in mass flux behavior between P1 and post-P1 layers, there were also dramatic changes in lithic content (P1 contains ∼8% lithics; post-P1 layers contain 30–60%) and magma composition (P1 is 98% rhyodacite; post-P1 layers are 60–90% rhyodacite). However, the total volume of magma erupted during the Jala pumice event is close to that estimated for the caldera. These observations appear to conflict with models which envision that, after an eruption is initiated by overpressure in the magma chamber, caldera collapse begins when the reservoir becomes underpressurized as a result of the removal of magma. The conflict arises because firstly, the P1 layer makes up too large a proportion (∼75%) of the total volume erupted to correspond to an overpressurized phase, and secondly, the caldera volume exceeds the post-P1 volume of magma by at least a factor of three. The mismatches between model and observations could be reconciled if collapse began near the beginning of the eruption, but no record of such early collapse is evident in the tephra sequence. The apparent inability to place the Jala pumice eruptive sequence into existing models of caldera collapse, which were constructed to explain the formation of calderas much greater in volume than that at Ceboruco, may indicate that differences in caldera mechanics exist that depend on size or that a more general model for caldera formation is needed. Received: 18 November 1998 / Accepted: 23 October 1999     

Hekla 1947, 1845, 1510 and 1158 tephra in Finland: challenges of tracing tephra from moderate eruptions

Several cryptotephra layers that originate from Icelandic volcanic eruptions with a volcanic explosivity index (VEI) of ≤ 4 and tephra volumes of < 1 km³ have previously been identified in Northern Europe, albeit within a restricted geographical area. One of these is the Hekla 1947 tephra that formed a visible fall-out in southern Finland. We searched for the Hekla 1947 tephra from peat archives within the previously inferred fall-out zone but found no evidence of its presence. Instead, we report the first identification of Hekla 1845 and Hekla 1510 cryptotephra layers outside of Iceland, the Faroe Islands, Ireland and the UK. Additionally, Hekla 1158 tephra was found in Finland for the first time. Our results confirm that Icelandic eruptions of moderate size can form cryptotephra deposits that are extensive enough to be used in inter-regional correlations of environmental archives and carry a great potential for refining regional tephrochronological frameworks. Our results also reveal that Icelandic tephra has been dispersed into Finnish airspace at least seven times during the past millennium and in addition to a direct eastward route the ash clouds can travel either via a northerly or a southerly transport pathway.