Lagrangian predictability assessed in the East China Sea     

Helga S. Huntley  B.L. Lipphardt  A.D. Kirwan 《Ocean Modelling》2011,36(1-2):163-178

A group of 30 surface drifters, launched over a 4 day period as part of a US Navy exercise in early October 2007, are used to assess the predictability of trajectories in a confined geographic region at the northwestern edge of the Kuroshio north of Taiwan. Model trajectories were computed from archives of hourly hindcast velocities from the US Navy East Asian Seas (EAS16) model with 1/16° horizontal resolution. Three metrics are defined for comparing observed and modeled trajectories. All three metrics indicated that model trajectories separated from observations by roughly 15 km after the first 24 h on average. Because of the unique launch strategy for these drifters, with six repetitions of launches from four locations, the dependence of predictability on both launch time and launch location could be assessed separately. Predictive skill displayed only modest dependence on launch time, likely influenced by the passage of a typhoon near the experiment area a few days prior to the first drifter launch. Launch location was a much more reliable indicator of predictive skill, with trajectories for launches closest to the edge of the Kuroshio typically hardest to predict, and those for launches on the shelf, where currents tended to be weaker, predicted more accurately. Comparisons of skill metric statistics for modeled trajectories from hindcasts with and without tides suggested that tidal currents have only a small impact on predictive skill. The influence of archive time and space resolution was also studied using sets of model trajectories computed from hindcast archives that were systematically subsampled separately in space and time. Coarsening by up to a factor of eight in either space or time had little impact on predictive skill. Further coarsening degraded trajectory predictions, particularly when coarsening in time leads to an archive time step too large to adequately resolve the tides. While accurate trajectory predictions remain challenging for ocean models, skill assessments like the one presented here are important for developing error estimates for users of trajectory forecasts and for gaining new insight into potential sources of model errors.  相似文献   

PSV-wave propagation in a medium with local heterogeneities: a hybrid formulation and its application   总被引：1，自引：0，他引：1  

Helga Emmerich 《Geophysical Journal International》1992,109(1):54-64

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Globalizing urban resilience     

Helga Leitner  Eric Sheppard  Sophie Webber  Emma Colven 《Urban geography》2018,39(8):1276-1284

Urban resilience, a new urban development and governance agenda, is being rolled out from the top down by a network of public, private, non-profit sector actors forming a global urban resilience complex: producing norms that circulate globally, creating assessment tools rendering urban resilience technical and managerial, and commodifying urban resilience such that private sector involvement becomes integral to urban development planning and governance. The Rockefeller Foundation's 100 Resilience Cities Program is at the center of this complex, working with the World Bank, global consultants, NGOs, and private sector service providers to enroll cities, develop and circulate urban resilience assessment tools, and create a market catalyzed by the notion of a resilience dividend. Notwithstanding the claim of this program being open and inclusive, aspects of its initial operationalization in Jakarta suggest that urban resilience assessment tools preempt alternative understandings of urban resilience and marginalizing voices of the city's most vulnerable populations.  相似文献   

Variscan potassic dyke magmatism of durbachitic affinity at the southern end of the Bohemian Massif (Lower Austria)     

Helga Zeitlhofer  Bernhard Grasemann  Konstantin Petrakakis 《International Journal of Earth Sciences》2016,105(4):1175-1197

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Model ALADIN as regional climate model for Central and Eastern Europe   总被引：4，自引：0，他引：4  

Aleš Farda  Michel Déué  Samuel Somot  András Horányi  Valery Spiridonov  Helga Tóth 《Studia Geophysica et Geodaetica》2010,54(2):313-332

Results obtained with two versions of the Limited Area Model (LAM) ALADIN over differently sized integration domains (large, intermediate and small) in the European area are presented in order to investigate both the general model performance and the influence of domain choice on the quality of obtained results. The aim is also to illustrate the issues related to the strategy of selection of the optimal integration domain. Each of these studies has been performed with two versions of the ALADIN model: the first one is ALADIN-CLIMATE developed at CNRM/Météo-France, the second one is ALADIN-CLIMATE/CZ prepared at the Czech Hydrometeorological Institute (CHMI). This leaves us with total of six experiments forced by the European Centre for Medium-Range Weather Forecasts (ECMWF) ERA-40 reanalysis data. The west Balkan domain covering Bulgaria is used as an evaluation region for investigation of the temporal and spatial properties of simulated precipitation and temperature fields. This region has been selected for its challenging orography making the results obtained here a valuable source for studies leading to further developments in climate modeling. It was found that size of the domain strongly affects the quality of obtained results. We have found that the largest domain reproduces the spatial characteristics of climate (such as bias) very well, but its use results in a poor representation of temporal aspects, which are however captured very well in experiments over both smaller domains. Our findings suggest that there is no optimal choice of domain size, securing the best results for both spatial and temporal evaluation.  相似文献   

A record of ductile syn-intrusional fabrics to post solidification cataclasis: Magnetic fabric analysis of neoproterozoic Mirpur and Mt. Abu Granitoids,NW India     

Helga de Wall  Stefan Schöbel  Manoj K. Pandit  Kamal K. Sharma  J. Just 《Journal of the Geological Society of India》2010,75(1):239-253

The Mirpur granite body represents a relatively small (10 km²) pluton intruded along the northern margin of the adjacent Mt. Abu batholith (∼125 km²) in NW India. It is a visibly undeformed alkali feldspar rich pink granite; in contrast, the Mt. Abu is a composite granitoid body and variably deformed. Both are intruded by rhyolitic dykes and the terminal magmatic events in both the cases are mafic dykes. The AMS (Anisotropy of Magnetic Susceptibility) data identify the Mt. Abu with SE-dipping foliations and subvertical lineations as a single structural domain while the Mirpur granite body shows two domains characterized by predominantly E — W trend of magnetic foliation in the eastern part (domain I) and N — S orientations in the western part (domain II). The domain I shows magmatic fabrics, typical for the peraluminous granites of Malani Igneous Suite (MIS). Change in fabric orientation in the domain II has resulted from cataclasis wherein the samples show destruction of the original E — W fabric and complete transposition by N — S trends. The foliations in the Mt. Abu granites have been related to SE orientation of maximum horizontal stress. The same maximum stress direction can be inferred from dyke orientation in the Mirpur granite, which is interpreted as continuation of the tectonic imprint in this region during emplacement of both the granites. Age of the cataclastic overprint with a predominant N — S orientation is not yet constrained but corresponds with the trend of the nearby Sindreth basin within the Malani Igneous Suite. The Neoproterozoic tectonic scenario for the region has been interpreted in terms of an ongoing crustal convergence and granitic magma emplacement against the back stop offered by the rigid Delhi Fold Belt.  相似文献