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排序方式: 共有49条查询结果,搜索用时 875 毫秒
1.
2.
Wang Zonghao Mao Jianping Huang Jihong Arnold Gruber Albert Thomasell Tan Sun Chen 《Acta Meteorologica Sinica》1992,6(4):421-432
This paper is to examine the impact of satellite data on the systematic error of operational B-model in China.Em-phasis is put on the study of the impact of satellite sounding data on forecasts of the sea level pressure field and 500 hPaheight.The major findings are as follows.(1)The B-model usually underforecasts the strength of features in the sea level pressure(SLP)field,i.e.pressuresare too low near high pressure systems and too high near low pressure systems.(2)The nature of the systematic errors found in the 500 hPa height forecasts is not as clear cut as that of the SLPforecasts,but most often the same type of pattern is seen,i.e.,the heights in troughs are not low enough and those inridges are not high enough.(3)The use of satellite data in the B-model analysis/forecast system is found to have an impact upon the model'sforecast of SLP and 500 hPa height.Systematic errors in the vicinity of surface lows/500 hPa troughs over the oceansare usually found to be significantly reduced.A less conclusive mix of positive and negative impacts was found for allother types of features. 相似文献
3.
Zusammenfassung Es wird gezeigt, daß durch Weglassung des Relais bzw. durch Wegnahme der Relaisspannung von der Kontaktbahn ihr Isolationszustand (Feuchtigkeit, Verunreinigungen) ohne Einfluß auf den Temperaturmeßkreis bleibt. Zur Feuchtigkeitsmessung wird das Feuchtigkeitselement dem Temperaturelement parallel geschaltet. Dadurch ergibt sich außerdem eine Erweiterung des Feuchtemeßbereichs. Die Temperatur-registrierung wird damit auch zur Ausgangslinie für die Registrierung mit weiteren Meßelementen.
Mit 4 Textabbildungen 相似文献
Summary It is shown that, by eliminating the relay and, therefore, the relay voltage from the commutator the state of the latter with respect to isolation (humidity, contamination) does no longer affect the temperature measuring circuit. In the modified radiosonde, the humidity element is connected in parallel to the temperature element. This results in an extension of the humidity measuring range down to about 15%. The temperature recording trace becomes the base-line for the humidity or other additional traces.
Résumé En supprimant le relais ou la tension de relais sur le cercle de contact, l'état d'isolation de la sonde (humidité, impuretés) est sans effet sur le circuit de mesure de la température. Pour mesurer l'humidité, l'élément sensible est connecté en parallèle sur l'élément thermique, ce qui accroît le domaine de mesure de l'humidité. L'enregistrement de température sert alors de ligne de base pour l'enregistrement avec d'autres éléments de mesure.
Mit 4 Textabbildungen 相似文献
4.
Jürgen M. Reitner Wilfried Gruber Alexander Römer Rainer Morawetz 《Swiss Journal of Geoscience》2010,103(3):385-405
We present a study of the inneralpine basin of Hopfgarten focused on the analysis of basin fill in order to reveal its formation
in relation to paleo-ice flow and tectonics. The study is based on geological mapping as well as seismic (reflection and refraction)
and geoelectrical surveys. The oldest sequence in the basin, identified by seismic stratigraphy at 400 m below surface, consists
of coarse grained sediments of supposedly Oligocene to Miocene age, which subsided along faults linked to the Inn fault. Three
superimposed sequences, each displaying baselaps in contact with a subglacially formed unconformity and sigmoid foresets,
show pleniglacial conditions followed by a glaciolacustrine environment. The uppermost of these three sequences lies on top
of last glacial maximum till (LGM; Würmian Pleniglacial; MIS 2) and represents Termination I. The middle sequence is classified
as Termination II following the Rissian Pleniglacial (MIS 6). The oldest glacial sequence cannot be constrained chronostratigraphically
but might correlate with Termination V following the major glaciation of MIS 12. Limited glacial erosion during the LGM occurred
only during the ice build-up phase. Further overdeepening was impeded due to topographic barrier and mutual blockades of glaciers
within this highly dissected landscape. The occurrence and relative timing of the impediment was controlled by the onset of
transfluences and thus by the altitude of coles. The higher amount of overdeepening during older glacial periods is explained
by longer phases of free ice advance in the ice build up phase due to higher transfluences routes at that time. Thus, the
preservation of older Pleistocene sequences within the basin may be the result of the lowering of watersheds from one glaciation
to the next. Our model of an inverse relationship between glacial shaping of the surface and the subsurface may apply to similar
Alpine landscapes as well. 相似文献
5.
A New Sensitivity Analysis and Solution Method for Scintillometer Measurements of Area-Averaged Turbulent Fluxes 总被引:1,自引:1,他引:0
Scintillometer measurements of the turbulence inner-scale length $l_\mathrm{o }$ l o and refractive index structure function $C_n^2$ C n 2 allow for the retrieval of large-scale area-averaged turbulent fluxes in the atmospheric surface layer. This retrieval involves the solution of the non-linear set of equations defined by the Monin–Obukhov similarity hypothesis. A new method that uses an analytic solution to the set of equations is presented, which leads to a stable and efficient numerical method of computation that has the potential of eliminating computational error. Mathematical expressions are derived that map out the sensitivity of the turbulent flux measurements to uncertainties in source measurements such as $l_\mathrm{o }$ l o . These sensitivity functions differ from results in the previous literature; the reasons for the differences are explored. 相似文献
6.
Christian Kofler Volkmar Mair Stephan Gruber Maria Cristina Todisco Ian Nettleton Stefan Steger Marc Zebisch Stefan Schneiderbauer Francesco Comiti 《地球表面变化过程与地形》2021,46(7):1311-1327
The fronts of two rock glaciers located in South Tyrol (Italian Alps) failed on 13 August 2014, initiating debris flows in their downslope channels. A multimethod approach including climate, meteorological, and ground temperature data analysis, aerial image correlation, as well as geotechnical testing and modeling, led to the reconstruction of the two events. An integrated investigation of static predisposing factors, slowly changing preparatory factors, and potential triggering events shed light on the most likely reasons for such failures. Our results suggest that the occurrence of front destabilization at the two rock glaciers can only partly be explained by the occurrence of heavy rainfall events. Indeed, antecedent hydrological and thermal ground conditions were characterized by a saturated active layer favored by a snow-rich winter and extensive precipitation in late spring and summer. Also, the rising trend of air temperature during spring and summer months since 1950s might explain the concurrent marked displacement of the two rock glaciers. Indeed, geotechnical investigations have provided strong indications that one of the investigated rock glacier fronts was at a marginally stable state prior to 2014. As rainfall events more intense than the one that occurred in August 2014 were previously recorded in the same area without resulting failures at the studied rock glaciers, we propose that both predisposing and preparatory destabilizing factors have played a key role in the 2014 rock glacier front failures. 相似文献
7.
Mechanisms linking active rock glaciers and impounded surface water formation in high‐mountain areas
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Nicola Colombo Luigi Sambuelli Cesare Comina Chiara Colombero Marco Giardino Stephan Gruber Gaetano Viviano Livia Vittori Antisari Franco Salerno 《地球表面变化过程与地形》2018,43(2):417-431
Rock glaciers are slowly flowing mixtures of debris and ice occurring in mountains. They can represent a reservoir of water, and melting ice inside them can affect surface water hydrochemistry. Investigating the interactions between rock glaciers and water bodies is therefore necessary to better understand these mechanisms. With this goal, we elucidate the hydrology and structural setting of a rock glacier–marginal pond system, providing new insights into the mechanisms linking active rock glaciers and impounded surface waters. This was achieved through the integration of waterborne geophysical techniques (ground penetrating radar, electrical resistivity tomography and self‐potentials) and heat tracing. Results of these surveys showed that rock glacier advance has progressively filled the valley depression where the pond is located, creating a dam that could have modified the level of impounded water. A sub‐surface hydrological window connecting the rock glacier to the pond was also detected, where an inflow of cold and mineralised underground waters from the rock glacier was observed. Here, greater water contribution from the rock glacier occurred following intense precipitation events during the ice‐free season, with concomitant increasing electrical conductivity values. The outflowing dynamic of the pond is dominated by a sub‐surface seepage where a minor fault zone in bedrock was found, characterised by altered and highly‐fractured rocks. The applied approach is evaluated here as a suitable technique for investigating logistically‐complex hydrological settings which could be possibly transferred to wider scales of investigation. Copyright © 2017 John Wiley & Sons, Ltd. 相似文献
8.
V. Paoletti S. Gruber N. Varley M. D’Antonio R. Supper K. Motschka 《Surveys in Geophysics》2016,37(3):601-623
The island of Socorro is located in the eastern Pacific Ocean, 650 km off the coast of Mexico. It is a rare example of an oceanic volcanic island whose above sea level volume is made up mostly of peralkaline trachytes and rhyolites, with subordinate mafic rocks. Subaerial volcanism started several hundred thousand years ago and continues until recent times. We present an investigation of surface and subsurface geology of the island, based on the first detailed extensive geophysical survey on the island. Acquired airborne magnetic and gamma-ray data were compared to existing geological information and supplemented with field investigations and satellite imagery. Magnetic data show a wide minimum in the central part of the island, possibly connected to a high-temperature zone in the deeper central portion of the volcano, likely to be due to a still hot magma body. The data also depict two parallel edges possibly suggesting the existence of a nested caldera. Analysis on upward continued magnetic data by recent imaging techniques highlighted two deep sources located around 5 km b.s.l., interpreted as feeding structures that are now filled with crystalline rocks. Gamma-ray data have been interpreted through integration with the geological survey results. Several previously known volcanic deposits have been identified based on radioelement distribution, and others have been redefined based on field evidence. A new succession of volcanic members is proposed, to be verified through more detailed geological mapping, geochemical analyses of rock samples and radiometric dating. 相似文献
9.
A gravity field model is computed from the four accurate gravitational gradient components of GOCE (Gravity field and steady-state Ocean Circulation Explorer), combined with the analysis of the kinematic orbits, and some moderate constraint (or stabilization) in the polar areas where no observation from GOCE is available due to the orbit geometry. The normal matrix of each component is computed individually in order to study its contribution to the combined solution. The results show that the contribution of Vzz is the largest, with an average value of 32.74% of the total solution; the second and the third largest are Vzz and Vyy, with average values of 28.04% and 26.08%, respectively; the component Vxz contributes 11.81%. Validation with external data shows that each component has its characteristic value and that the information content of the component Vxz is not negligible and should be included for gravity field recovery. The orbit part as derived from high-low satellite-to-satellite tracking (SST-hl) to the GPS contributes mostly to the coefficients below degree and order (d/o) 20, and to non-zonal coefficients from d/o 20 to 80. The mean value of the contribution of the polar stabilization is the smallest with a value of 0.22%, nevertheless it is important. In addition to the contribution analysis in terms of the normal matrices, each individual component of the gradiometer has been combined with SST and polar stabilization, to give a set of single component gravity field models. These partially combined solutions are compared to the fully combined solution in terms of geoid differences. They show that the partially combined solution with Vzz is closest to the complete solution. Even closer is a combination with Vxx and Vyy. In addition to the GOCE-only solution, a GOCE-GRACE (Gravity Recovery And Climate Experiment) combined gravity field model is derived and the information content of GOCE and an available set of normal equations of GRACE are investigated. Results show that, as expected, GRACE dominates the solution below degree 90 and GOCE above degree 140. 相似文献
10.
Evaluation of the first GOCE static gravity field models using terrestrial gravity,vertical deflections and EGM2008 quasigeoid heights 总被引:1,自引:1,他引:0
Recently, four global geopotential models (GGMs) were computed and released based on the first 2 months of data collected
by the Gravity field and steady-state Ocean Circulation Explorer (GOCE) dedicated satellite gravity field mission. Given that
GOCE is a technologically complex mission and different processing strategies were applied to real space-collected GOCE data
for the first time, evaluation of the new models is an important aspect. As a first assessment strategy, we use terrestrial
gravity data over Switzerland and Australia and astrogeodetic vertical deflections over Europe and Australia as ground-truth
data sets for GOCE model evaluation. We apply a spectral enhancement method (SEM) to the truncated GOCE GGMs to make their
spectral content more comparable with the terrestrial data. The SEM utilises the high-degree bands of EGM2008 and residual
terrain model data as a data source to widely bridge the spectral gap between the satellite and terrestrial data. Analysis
of root mean square (RMS) errors is carried out as a function of (i) the GOCE GGM expansion degree and (ii) the four different
GOCE GGMs. The RMS curves are also compared against those from EGM2008 and GRACE-based GGMs. As a second assessment strategy,
we compare global grids of GOCE GGM and EGM2008 quasigeoid heights. In connection with EGM2008 error estimates, this allows
location of regions where GOCE is likely to deliver improved knowledge on the Earth’s gravity field. Our ground truth data
sets, together with the EGM2008 quasigeoid comparisons, signal clear improvements in the spectral band ~160–165 to ~180–185
in terms of spherical harmonic degrees for the GOCE-based GGMs, fairly independently of the individual GOCE model used. The
results from both assessments together provide strong evidence that the first 2 months of GOCE observations improve the knowledge
of the Earth’s static gravity field at spatial scales between ~125 and ~110 km, particularly over parts of Asia, Africa, South
America and Antarctica, in comparison with the pre-GOCE-era. 相似文献