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151.
Measures of Parameter Uncertainty in Geostatistical Estimation and Geostatistical Optimal Design 总被引:4,自引:2,他引:2
Wolfgang Nowak 《Mathematical Geosciences》2010,42(2):199-221
Studies of site exploration, data assimilation, or geostatistical inversion measure parameter uncertainty in order to assess
the optimality of a suggested scheme. This study reviews and discusses measures for parameter uncertainty in spatial estimation.
Most measures originate from alphabetic criteria in optimal design and were transferred to geostatistical estimation. Further
rather intuitive measures can be found in the geostatistical literature, and some new measures will be suggested in this study.
It is shown how these measures relate to the optimality alphabet and to relative entropy. Issues of physical and statistical
significance are addressed whenever they arise. Computational feasibility and efficient ways to evaluate the above measures
are discussed in this paper, and an illustrative synthetic case study is provided. A major conclusion is that the mean estimation
variance and the averaged conditional integral scale are a powerful duo for characterizing conditional parameter uncertainty,
with direct correspondence to the well-understood optimality alphabet. This study is based on cokriging generalized to uncertain
mean and trends because it is the most general representative of linear spatial estimation within the Bayesian framework.
Generalization to kriging and quasi-linear schemes is straightforward. Options for application to non-Gaussian and non-linear
problems are discussed. 相似文献
152.
Turbulent flux observations and modelling over a shallow lake and a wet grassland in the Nam Co basin,Tibetan Plateau 总被引:2,自引:1,他引:1
Tobias?BiermannEmail author Wolfgang?Babel Weiqiang?Ma Xuelong?Chen Elisabeth?Thiem Yaoming?Ma Thomas?Foken 《Theoretical and Applied Climatology》2014,116(1-2):301-316
The Tibetan Plateau plays an important role in the global water cycle and is strongly influenced by climate change. While energy and matter fluxes have been more intensely studied over land surfaces, a large proportion of lakes have either been neglected or parameterised with simple bulk approaches. Therefore, turbulent fluxes were measured over wet grassland and a shallow lake with a single eddy-covariance complex at the shoreline in the Nam Co basin in summer 2009. Footprint analysis was used to split observations according to the underlying surface, and two sophisticated surface models were utilised to derive gap-free time series. Results were then compared with observations and simulations from a nearby eddy-covariance station over dry grassland, yielding pronounced differences. Observations and footprint integrated simulations compared well, even for situations with flux contributions including grassland and lake. The accessibility problem for EC measurements on lakes can be overcome by combining standard meteorological measurements at the shoreline with model simulations, only requiring representative estimates of lake surface temperature. 相似文献
153.
Cindy Mora-Stock Martin Thorwart Tina Wunderlich Stefan Bredemeyer Thor H. Hansteen Wolfgang Rabbel 《International Journal of Earth Sciences》2014,103(7):2015-2028
Llaima and Villarrica are two of the most active volcanoes in the Chilean Southern Volcanic Zone and presently show contrasting types of activity. Llaima is a closed vent edifice with fumarolic activity, while Villarrica has an open vent with a lava lake, continuous degassing and tremor activity. This study is focused on characterizing the relationships between volcanic and seismic activity in the months before and after the 2010 M8.8 Maule earthquake, which was located in NNW direction from the volcanoes. Time series for tremors, long-period and volcano-tectonic events were obtained from the catalogue of the Volcanic Observatory of the Southern Andes (OVDAS) and from the SFB 574 temporary volcanic network. An increase in the amount of tremor activity, long-period events and degassing rates was observed at Villarrica weeks before the mainshock and continued at a high level also after it. This increase in activity is interpreted to be caused by enhanced magma influx at depth and may be unrelated to the Maule event. In Llaima, an increase in the volcano-tectonic activity was observed directly after the earthquake. The simultaneous post-earthquake activity at both volcanoes is consistent with a structural adjustment response. Since this enhanced activity lasted for more than a year, we suggest that it is related to a medium-term change in the static stress. Thus, the Maule earthquake may have affected both volcanoes, but did not trigger eruptions, from which we assume that none of the volcanoes were in a critical state. 相似文献
154.
A microwave technique for the measurement of ocean wave spectra has been compared with wave gauge output during extensive field testing. The method is based on the dual-frequency technique for detecting long ocean waves by matching the modulation of short waves with the beat wavelength between two transmitted microwave frequencies. The new method, however, utilizes three microwave frequencies in order to reduce mean backscatter not related to short-wave modulation. Two prototype scatterometers have been built using three frequencies at L -band and at K u-band. Wave spectra have been measured by both radar systems which, when properly normalized, agree well with simultaneous in situ measurements taken by conventional wave gauges at the pier site. Thirteen sets of spectra have been computed, five of which correspond to a situation in which a local wind sea was generated and then decayed. The present experiment does not demonstrate the directionality of this new technique 相似文献
155.
A. H. Treiman G. A. McKay D. D. Bogard D. W. Mittlefehldt M.-S. Wang L. Keller M. E. Lipschutz M. M. Lindstrom D. Garrison 《Meteoritics & planetary science》1994,29(5):581-592
Abstract By mineral and bulk compositions, the Lewis Cliff (LEW) 88516 meteorite is quite similar to the ALHA77005 martian meteorite. These two meteorites are not paired because their mineral compositions are distinct, they were found 500 km apart in ice fields with different sources for meteorites, and their terrestrial residence ages are different. Minerals in LEW88516 include: olivine, pyroxenes (low- and high-Ca), and maskelynite (after plagioclase); and the minor minerals chromite, whitlockite, ilmenite, and pyrrhotite. Mineral grains in LEW88516 range up to a few mm. Texturally, the meteorite is complex, with regions of olivine and chromite poikilitically enclosed in pyroxene, regions of interstitial basaltic texture, and glass-rich (shock) veinlets. Olivine compositions range from Fo64 to Fo70, (avg. Fo67), more ferroan and with more variation than in ALHA77005 (Fo69 to Fo73). Pyroxene compositions fall between En77Wo4 and En65Wo15 and in clusters near En63Wo9 and En53Wo33, on average more magnesian and with more variation than in ALHA77005. Shock features in LEW88516 range from weak deformation through complete melting. Bulk chemical analyses by modal recombination of electron microprobe analyses, instrumental neutron activation, and radiochemical neutron activation confirm that LEW88516 is more closely related to ALHA77005 than to other known martian meteorites. Key element abundance ratios are typical of martian meteorites, as is its non-chondritic rare earth pattern. Differences between the chemical compositions of LEW88516 and ALHA77005 are consistent with slight differences in the proportions of their constituent minerals and not from fundamental petrogenetic differences. Noble gas abundances in LEW88516, like those in ALHA77005, show modest excesses of 40Ar and 129Xe from trapped (shock-implanted) gas. As with other ALHA77005 and the shergottite martian meteorites (except EETA79001), noble gas isotope abundances in LEW88516 are consistent with exposure to cosmic rays for 2.5–3 Ma. The absence of substantial effects of shielding from cosmic rays suggest LEW88516 spent this time as an object no larger than a few cm in diameter. 相似文献
156.
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158.
David A. Yuen Melissa A. Scruggs Frank J. Spera Yingcai Zheng Hao Hu Stephen R. McNutt Glenn Thompson Kyle Mandli Barry R. Keller Songqiao Shawn Wei Zhigang Peng Zili Zhou Francesco Mulargia Yuichiro Tanioka 《地震研究进展(英文)》2022,2(3):100134
We present a narrative of the eruptive events culminating in the cataclysmic January 15, 2022 eruption of Hunga Tonga-Hunga Ha'apai Volcano by synthesizing diverse preliminary seismic, volcanological, sound wave, and lightning data available within the first few weeks after the eruption occurred. The first hour of eruptive activity produced fast-propagating tsunami waves, long-period seismic waves, loud audible sound waves, infrasonic waves, exceptionally intense volcanic lightning and an unsteady volcanic plume that transiently reached—at 58 ?km—the Earth's mesosphere. Energetic seismic signals were recorded worldwide and the globally stacked seismogram showed episodic seismic events within the most intense periods of phreatoplinian activity, and they correlated well with the infrasound pressure waveform recorded in Fiji. Gravity wave signals were strong enough to be observed over the entire planet in just the first few hours, with some circling the Earth multiple times subsequently. These large-amplitude, long-wavelength atmospheric disturbances come from the Earth's atmosphere being forced by the magmatic mixture of tephra, melt and gasses emitted by the unsteady but quasi-continuous eruption from 0402±1–1800 UTC on January 15, 2022. Atmospheric forcing lasted much longer than rupturing from large earthquakes recorded on modern instruments, producing a type of shock wave that originated from the interaction between compressed air and ambient (wavy) sea surface. This scenario differs from conventional ideas of earthquake slip, landslides, or caldera collapse-generated tsunami waves because of the enormous (~1000x) volumetric change due to the supercritical nature of volatiles associated with the hot, volatile-rich phreatoplinian plume. The time series of plume altitude can be translated to volumetric discharge and mass flow rate. For an eruption duration of ~12 ?h, the eruptive volume and mass are estimated at 1.9 ?km3 and ~2 900 ?Tg, respectively, corresponding to a VEI of 5–6 for this event. The high frequency and intensity of lightning was enhanced by the production of fine ash due to magma—seawater interaction with concomitant high charge per unit mass and the high pre-eruptive concentration of dissolved volatiles. Analysis of lightning flash frequencies provides a rapid metric for plume activity and eruption magnitude. Many aspects of this eruption await further investigation by multidisciplinary teams. It represents a unique opportunity for fundamental research regarding the complex, non-linear behavior of high energetic volcanic eruptions and attendant phenomena, with critical implications for hazard mitigation, volcano forecasting, and first-response efforts in future disasters. 相似文献
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