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51.
Annette Eicker Maike Schumacher Jürgen Kusche Petra Döll Hannes Müller Schmied 《Surveys in Geophysics》2014,35(6):1285-1309
We introduce a new ensemble-based Kalman filter approach to assimilate GRACE satellite gravity data into the WaterGAP Global Hydrology Model. The approach (1) enables the use of the spatial resolution provided by GRACE by including the satellite observations as a gridded data product, (2) accounts for the complex spatial GRACE error correlation pattern by rigorous error propagation from the monthly GRACE solutions, and (3) allows us to integrate model parameter calibration and data assimilation within a unified framework. We investigate the formal contribution of GRACE observations to the Kalman filter update by analysis of the Kalman gain matrix. We then present first model runs, calibrated via data assimilation, for two different experiments: the first one assimilates GRACE basin averages of total water storage and the second one introduces gridded GRACE data at \(5^\circ\) resolution into the assimilation. We finally validate the assimilated model by running it in free mode (i.e., without adding any further GRACE information) for a period of 3 years following the assimilation phase and comparing the results to the GRACE observations available for this period. 相似文献
52.
Signal detectability in extreme precipitation changes assessed from twentieth century climate simulations 总被引:1,自引:0,他引:1
Seung-Ki Min Xuebin Zhang Francis W. Zwiers Petra Friederichs Andreas Hense 《Climate Dynamics》2009,32(1):95-111
This study assesses the detectability of external influences in changes of precipitation extremes in the twentieth century,
which is explored through a perfect model analysis with an ensemble of coupled global climate model (GCM) simulations. Three
indices of precipitation extremes are defined from the generalized extreme value (GEV) distribution: the 20-year return value
(P
20), the median (P
m), and the cumulative probability density as a probability-based index (PI). Time variations of area-averages of these three extreme indices are analyzed over different spatial domains from the globe
to continental regions. Treating all forcing simulations (ALL; natural plus anthropogenic) of the twentieth century as observations
and using a preindustrial control run (CTL) to estimate the internal variability, the amplitudes of response patterns to anthropogenic
(ANT), natural (NAT), greenhouse-gases (GHG), and sulfate aerosols (SUL) forcings are estimated using a Bayesian decision
method. Results show that there are decisively detectable ANT signals in global, hemispheric, and zonal band areas. When only land is considered, the global and hemispheric
detection results are unchanged, but detectable ANT signals in the zonal bands are limited to low latitudes. The ANT signals
are also detectable in the P
m and PI but not in P
20 at continental scales over Asia, South America, Africa, and Australia. This indicates that indices located near the center
of the GEV distribution (P
m and PI) may give better signal-to-noise ratio than indices representing the tail of the distribution (P
20). GHG and NAT signals are also detectable, but less robustly for more limited extreme indices and regions. These results
are largely insensitive when model data are masked to mimic the availability of the observed data. An imperfect model analysis
in which fingerprints are obtained from simulations with a different GCM suggests that ANT is robustly detectable only at
global and hemispheric scales, with high uncertainty in the zonal and continental results. 相似文献
53.
Observations collected between 2000 and 2008 at the Cabauw meteorological measurement platform in the Netherlands were conditionally
sampled to select nights with stably stratified atmospheric conditions, clear skies and weak horizontal wind speeds (<3 m s−1). For these conditions the eddy-correlation latent heat fluxes are found to be negligibly small, while the conditionally
sampled surface energy balance exhibits a maximum residual. However, inspection of the specific humidities for these conditions
reveals systematic drying trends that are a maximum at the lowest measurement level above the surface. These drying trends
occur for any prevailing wind direction. Latent heat fluxes are calculated from the humidity budget equation and from a Penman-Monteith
dewfall model, with the results suggesting that during clear, stable nights the observed latent heat fluxes as obtained from
the eddy-correlation technique are erroneously small. 相似文献
54.
Toshio Koike Petra Koudelova Patricia Ann Jaranilla-Sanchez Asif Mumtaz Bhatti Cho Thanda Nyunt Katsunori Tamagawa 《中国科学:地球科学(英文版)》2015,58(1):76-95
This paper introduces the process of development and practical use implementation of an advanced river management system for supporting integrated water resources management practices in Asian river basins under the framework of GEOSS Asia water cycle initiative (AWCI). The system is based on integration of data from earth observation satellites and in-situ networks with other types of data, including numerical weather prediction model outputs, climate model outputs, geographical information, and socio-economic data. The system builds on the water and energy budget distributed hydrological model (WEB-DHM) that was adapted for specific conditions of studied basins, in particular snow and glacier phenomena and equipped with other functions such as dam operation optimization scheme and a set of tools for climate change impact assessment to be able to generate relevant information for policy and decision makers. In situ data were archived for 18 selected basins at the data integration and analysis system of Japan (DIAS) and demonstration projects were carried out showing potential of the new system. It included climate change impact assessment on hydrological regimes, which is presently a critical step for sound management decisions. Results of such three case studies in Pakistan, Philippines, and Vietnam are provided here. 相似文献
55.
Impact of Climate Change and Variability on Irrigation Requirements: A Global Perspective 总被引:7,自引:1,他引:7
Petra Döll 《Climatic change》2002,54(3):269-293
Anthropogenic climate change does not only affect water resources but also water demand. Future water and food security will depend, among other factors, on the impact of climate change on water demand for irrigation. Using a recently developed global irrigation model, with a spatial resolution of 0.5° by 0.5°, we present the first global analysis of the impact of climate change and climate variability on irrigation water requirements. We compute how long-term average irrigation requirements might change under the climatic conditions of the 2020s and the 2070s, as provided by two climate models, and relate these changes to the variations in irrigation requirements caused by long-term and interannual climate variability in the 20th century. Two-thirds of the global area equipped for irrigation in 1995 will possibly suffer from increased water requirements, and on up to half of the total area (depending on the measure of variability), the negative impact of climate change is more significant than that of climate variability. 相似文献
56.
Does the Structural Quality of Running Waters Affect the Occurrence of Macrophytes? The morphological structure plays, besides e.g. nutrient concentration, an important role for the integrated assessment of running waters. This paper focuses on the relationship between structural quality and macrophyte vegetation. During summer 2000 structural quality according to LAWA, macrophyte vegetation, and selected habitat parameters were recorded in 135 mapping sections in running waters in Southern Germany. In streams of high structural diversity, generally higher species richness is expected than in rivers of low diversity of habitats. However, no significant differences in macrophyte species richness were detected between different classes of structural quality. In contrast, bryophytes alone showed a significant decrease in species richness with degradation of structural quality. The number of species of other macrophytes increased, respectively. The relationship between occurrence of macrophytes, structural quality, and other environmental variables was analysed using canonical correspondence analysis. Rivers of high structural quality mostly showed high flowing velocities and were heavily shaded. These environmental conditions, which characterize river types of mountainous regions, were predominantly tolerated by bryophytes. Vascular plants and charophytes generally prefer slowly flowing and unshaded habitats. River types exhibiting these environmental conditions often are more influenced by human activities and are more structurally degraded, respectively. With respect to these fundamental differences between river types, species richness of macrophytes and class of structural quality are not correlated when all types of rivers are taken into account. Type‐specific ecomorphological parameters, which conceal the differences in species richness caused by structural quality, are discussed. Structural degraded rivers can provide good environmental conditions for vascular plants and charophytes. To predict macrophyte species richness from structural quality, a differentiation of river types is essential. 相似文献
57.
Petra Bruckmann Niranjan D. Chatterjee Werner Rammensee Klaus Bielefeld 《Physics and Chemistry of Minerals》1993,20(5):362-368
Knudsen cell mass spectrometry has been applied to obtain activity (a
i) vs composition (X
i) data for 18 synthetic roedderites. (K, Na)2Mg5Si12O30, at temperatures between 900° and 1100° C. The samples were synthesized at 800° C and 1 kbar P
H
2O and characterized by X-ray powder diffractometry (XRD) and electron probe microanalysis (EPMA) prior to mass spectrometric activity measurement. The experimental a
i-X
i data have been smoothed, assuming for now the simplest possible model of a two-site K-Na mixing for this binary crystalline solution. Using the Margules formalism, and expressing the results in terms of one atom of K-Na mixing, the tentative equation of state is: W
G [J/mol] =-8704 -0.0067 · P, with P given in bar. The temperature-dependence of W
G could not be resolved due to its large uncertainty on the order of 2.8 kJ/mol. A more rigorous thermodynamic model for roedderites will have to be deferred until information on temperature-dependent K-Na disordering becomes available. Besides roedderites, single-phase eifelite-roedderite crystalline solutions have also been snythesized for the first time. They show a symmetric positive excess volume of mixing, with W
V [J/bar·mol]=0.1064±0.0021. 相似文献
58.
Estimating the Impact of Global Change on Flood and Drought Risks in Europe: A Continental, Integrated Analysis 总被引:11,自引:0,他引:11
Bernhard Lehner Petra Döll Joseph Alcamo Thomas Henrichs Frank Kaspar 《Climatic change》2006,75(3):273-299
Most studies on the impact of climate change on regional water resources focus on long-term average flows or mean water availability,
and they rarely take the effects of altered human water use into account. When analyzing extreme events such as floods and
droughts, the assessments are typically confined to smaller areas and case studies. At the same time it is acknowledged that
climate change may severely alter the risk of hydrological extremes over large regional scales, and that human water use will
put additional pressure on future water resources. In an attempt to bridge these various aspects, this paper presents a first-time
continental, integrated analysis of possible impacts of global change (here defined as climate and water use change) on future
flood and drought frequencies for the selected study area of Europe. The global integrated water model WaterGAP is evaluated
regarding its capability to simulate high and low-flow regimes and is then applied to calculate relative changes in flood
and drought frequencies. The results indicate large ‘critical regions’ for which significant changes in flood or drought risks
are expected under the proposed global change scenarios. The regions most prone to a rise in flood frequencies are northern
to northeastern Europe, while southern and southeastern Europe show significant increases in drought frequencies. In the critical
regions, events with an intensity of today's 100-year floods and droughts may recur every 10–50 years by the 2070s. Though
interim and preliminary, and despite the inherent uncertainties in the presented approach, the results underpin the importance
of developing mitigation and adaptation strategies for global change impacts on a continental scale. 相似文献
59.
The development of new and better methods for preventing and managing natural disasters requires a variety of different data
sets, covering the range from referenced data, e.g. topographic data and digital elevation models, to various kinds of thematic
data, e.g. data about soil, vegetation and land usage as well as monitoring data like precipitation and water levels. So a
well-organised data and information management and the implementation of a modern processing environment to acquire, store,
analyse and visualise data were decisive for the success of the German Research Network Natural Disasters (DFNK). An information
infrastructure was established to support data management and information flows inside the network. A web-based portal offers
general information to the public and internal documents, data and software tools to the project community. A catalog service
allows the overview of existing but distributed data scombined with flexible data retrieval. Based on internet technology
and global standards these concepts contribute to a superior information infrastructure and finally substantiate to the development
of Spatial Data Infrastructures (SDI). SDIs aim is to improve availability and usability of spatial data for the manifold
application areas. Disaster management is one field depending on a very high level on high-quality data equipment, and on
a working SDI. 相似文献
60.
The corporate purpose of Wismut GmbH is to decommission its former mining holdings and to rehabilitate the landscape and the environment. Sample taking and analysing the value of contaminants are necessary steps for the remediation of waste rock piles, the recycling of contaminated areas, controlled flooding of uranium mines. Main emphasis lies on the determination of heavy metals and radionuclides of natural decay chains of U‐238 and U‐235. Yearly about 60 000…70 000 determinations of radionuclides in waters were done. Facing this high output of determinations it is a permanent task for laboratory and quality management to ask: Are the results of different methods comparable to each other? Is there a preferred analytical technology? Which matrix influences exist? and What about the analytical costs? Answers to these important questions are given in this report. Summarizing our investigations done in the last few years it is possible to say that – by using different analytical methods the results of radionuclides in water samples (surface or groundwater) are comparable, – a not negligible influence of Ra‐223, Ra‐224 and Ra‐228 may exist by using the DIN 38404 C18 method to determine Ra‐226, – a preferred method cannot be defined, – the choice of the analytical method should include analytical questions (the sample matrix, the occurrence of other disturbing radionuclides, the necessary detection limit) and economical questions (costs, other parameters to be determined). 相似文献