The next layer: Towards open pedagogy in geospatial education     

David Ray Abernathy 《Transactions in GIS》2023,27(5):1467-1478

Open-source software and open data are becoming increasingly popular in the teaching and learning of geographic information science. The cost savings that are derived from using free software over proprietary software are one driving factor, yet the move from “closed” to “open” represents much more than financial austerity—it signifies a broader shift in educational philosophy. This article documents the gradual transition of an introductory undergraduate course in geographic information systems from an entirely closed course to one that has become increasingly open. Having completely adopted the first three layers of open—software, data, and educational resources—the course is now turning toward the next layer: embracing the philosophy of open pedagogy.  相似文献   

A Velocity Dealiasing Scheme for C-band Weather Radar Systems简     

LI Gang  HE Guangxin  Xiaolei ZOU  Peter Sawin RAY 《大气科学进展》2014,31(1):17-26

A dealiasing algorithm for radar radial velocity observed by C-band Doppler radars is presented as an extension of an existing S-band dealiasing algorithm. This has operational significance in that many portable and many commercial broadcast radars, as well as approximately one half of the Chinese weather radar network （CINRAD）, are C-band radars. With a wavelength of about 5 cm, the Nyquist interval of C-band radars is just about one half that of S-band radars （wavelength of about 10 cm） and thus has more velocity folding. The proposed algorithm includes seven modules to remove noisy data, find the starting radials, dealias velocities, and apply least squares error checking in both the radial and azimuth directions. The proposed velocity dealiasing method was applied to one widespread rain case and three strong convective cases from radars operating in China. It was found that, on average, 92.95% of the aliased radial velocity data could be correctly de-aliased by the algorithm, resulting in 96.65% of the data being valid.  相似文献   

Recent past and future patterns of the Etesian winds based on regional scale climate model simulations   总被引：1，自引：0，他引：1  

Christina Anagnostopoulou  Prodromos Zanis  Eleni Katragkou  Ioannis Tegoulias  Konstantia Tolika 《Climate Dynamics》2014,42(7-8):1819-1836

The aim of this work is to investigate the recent past and future patterns of the Etesian winds, one of the most persistent localized wind systems in the world, which dominates the wind regime during warm period over the Aegean Sea and eastern Mediterranean. An objective classification method, the Two Step Cluster Analysis (TSCA), is applied on daily data from regional climate model simulations carried out with RegCM3 for the recent past (1961–1990) and future periods (2021–2050 and 2071–2100) constrained at lateral boundaries either by ERA-40 reanalysis fields or the global circulation model (GCM) ECHAM5. Three distinct Etesian patterns are identified by TSCA with the location and strength of the anticyclonic action center dominating the differences among the patterns. In case of the first Etesian pattern there is a ridge located over western and central Europe while for the other two Etesian patterns the location of the ridge moves eastward indicating a strong anticyclonic center over the Balkans. The horizontal and vertical spatial structure of geopotential height and the vertical velocity indicates that in all three Etesian patterns the anticyclonic action center over central Europe or Balkan Peninsula cannot be considered as an extension of the Azores high. The future projections for the late 21st century under SRES A1B scenario indicate a strengthening of the Etesian winds associated with the strengthening of the anticyclonic action center, and the deepening of Asian thermal Low over eastern Mediterranean. Furthermore the future projections indicate a weakening of the subsidence over eastern Mediterranean which is rather controlled by the deepening of the south Asian thermal Low in line with the projected in future weakening of South Asian monsoon and Hadley cell circulations.  相似文献   

Oceanic origin of southeast tropical Atlantic biases     

Zhao Xu  Mingkui Li  Christina M. Patricola  Ping Chang 《Climate Dynamics》2014,43(11):2915-2930

Most coupled general circulation models suffer from a prominent warm sea surface temperature bias in the southeast tropical Atlantic Ocean off the coast of Africa. The origin of the bias is not understood and remains highly controversial. Previous studies suggest that the origin of the bias stems from systematic errors of atmospheric models in simulating surface heat flux and coastal wind, or poorly simulated coastal upwelling. In this study, we show, using different reanalysis and observational data sets combined with a set of eddy-resolving regional ocean model simulations, that systematic errors in ocean models also make a significant contribution to the bias problem. In particular (1) the strong warm bias at the Angola-Benguela front that is maintained by the local wind and the convergence of Angola and Benguela Currents is caused by an overshooting of the Angola Current in ocean models and (2) the alongshore warm bias to the south of the front is caused by ocean model deficiencies in simulating the sharp thermocline along the Angola coast, which is linked to biases in the equatorial thermocline, and the complex circulation system within the Benguela upwelling zone.  相似文献   

Hydrochemistry and hydrogen sulfide generating processes in the Malm aquifer,Bavarian Molasse Basin,Germany     

Christina Mayrhofer  Reinhard Niessner  Thomas Baumann 《Hydrogeology Journal》2014,22(1):151-162

Knowledge about the hydrochemical conditions of deep groundwater is crucial for the design and operation of geothermal facilities. In this study, the hydrochemical heterogeneity of the groundwaters in the Malm aquifer, Germany, is assessed, and reasons for the extraordinarily high H₂S concentrations in the central part of the Bavarian Molasse Basin are proposed. Samples were taken at 16 sites, for a total of 37 individual wells, to analyze cations, anions, gas loading and composition. The hydrochemical characteristics of the Malm groundwater in the center of the Molasse Basin are rather heterogeneous. Although the groundwater in the central basin is dominated by meteoric waters, there is a significant infiltration of saline water from higher strata. Care has to be taken in the interpretation of data from geothermal sites, as effects of chemical stimulation of the boreholes may not be fully removed before the final analyses. The distribution of H₂S in the gas phase is correlated to the gas loading of the water which increases in the central basin. Temperatures, isotopic data and the sulfur mass balance indicate that H₂S in the central basin is related to thermochemical sulfate reduction (south of Munich) and bacterial sulfate reduction (north of Munich).  相似文献   

Estimation of specific yields of individual litho-units in a terrain with multiple litho-units: A water balance approach   总被引：1，自引：0，他引：1  

Ranjan Kumar Ray  Arunangshu Mukherjee  Rumi Mukherjee 《Journal of the Geological Society of India》2014,84(2):221-226

In a terrain with more than one litho-unit, the traditional water balance approach provides a single spatially averaged specific yield. A methodology is proposed here, which can be applied to estimate specific yields of individual litho-units in such terrains. This approach is demonstrated here considering two watersheds, which are covered partly by limestone and partly by sandstone. Watershed wise specific yields were estimated using a traditional water balance method. The specific yields thus obtained are the volume-weighted averages of the specific yields of the individual litho-units in the watersheds. Based on the volumes of aquifers desaturated and the watershed wise specific yield values, a set of two linear equations in two variables was formulated. These linear equations were solved to get the specific yields of the individual litho-units. Specific yields of sandstone (Chandarpur Group) and limestone (Charmuria Formation) units in the study area were thus estimated to be 0.004 and 0.037 respectively.  相似文献   

Re–Os isotope and platinum-group element geochemistry of the Pobei Ni–Cu sulfide-bearing mafic–ultramafic complex in the northeastern part of the Tarim Craton     

Sheng-Hong Yang  Mei-Fu Zhou  Peter C. Lightfoot  Ji-Feng Xu  Christina Yan Wang  Chang-Yi Jiang  Wen-Jun Qu 《Mineralium Deposita》2014,49(3):381-397

A number of mafic–ultramafic intrusions that host Ni–Cu sulfide mineralization occur in the northeastern Tarim Craton and the eastern Tianshan Orogenic Belt (NW China). The sulfide-mineralized Pobei mafic–ultramafic complex is located in the northeastern part of the Tarim Craton. The complex is composed of gabbro and olivine gabbro, cut by dunite, wehrlite, and melatroctolite of the Poyi and Poshi intrusions. Disseminated Ni–Cu sulfide mineralization is present towards the base of the ultramafic bodies. The sulfide mineralization is typically low grade (<0.5 wt.% Ni and <2 wt.% S) with low platinum-group element (PGE) concentrations (<24.5 ppb Pt and <69 ppb Pd); the abundance of Cu in 100 % sulfide is 1–8 wt.%, and Ni abundance in 100 % sulfide is typically >4 wt.%. Samples from the Pobei complex have εNd (at 280 Ma) values up to +8.1, consistent with the derivation of the magma from an asthenospheric mantle source. Fo 89.5 mol.% olivine from the ultramafic bodies is consistent with a primitive parental magma. Sulfide-bearing dunite and wehrlite have high Cu/Pd ratios ranging from 24,000 to 218,000, indicating a magma that evolved under conditions of sulfide saturation. The grades of Ni, Cu, and PGE in 100 % sulfide show a strong positive correlation. A model for these variations is proposed where the mantle source of the Pobei magma retained ~0.033 wt.% sulfide during the production of a PGE-depleted parental magma. The parental magma migrated from the mantle to the crust and underwent further S saturation to generate the observed mineralization along with its high Cu/Pd ratio at an R-factor varying from 100 to 1,200. The mineralization at Poshi and Poyi has very high γOs (at 280 Ma) values (+30 to +292) that are negatively correlated with the abundance of Os in 100 % sulfide (5.81–271 ppb) and positively correlated with the Re/Os ratios; this indicates that sulfide saturation was triggered by the assimilation of crustal sulfide with both high γOs and Re/Os ratios. When compared to other Permian mafic–ultramafic intrusions with sulfide mineralization in the East Tianshan, the Poyi and Poshi ultramafic bodies were formed from more primitive magmas, and this helps to explain why the sulfide mineralization has high Ni tenor.  相似文献   

Disseminated sulphides in basalts from the northern Central Indian Ridge: implications on late-stage hydrothermal activity     

Ranadip Banerjee  Dwijesh Ray 《Geo-Marine Letters》2015,35(2):91-103

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New insights on petrography and geochemistry of impactites from the Lonar crater,India          下载免费PDF全文

Dwijesh Ray  Dewashish Upadhyay  Saumitra Misra  Horton E. Newsom  Sambhunath Ghosh 《Meteoritics & planetary science》2017,52(8):1577-1599

The Lonar impact crater, India, is one of the few known terrestrial impact craters excavated in continental basaltic target rocks (Deccan Traps, ~65 Ma). The impactites reported from the crater to date mainly include centimeter‐ to decimeter‐sized impact‐melt bombs, and aerodynamically shaped millimeter‐ and submillimeter‐sized impact spherules. They occur in situ within the ejecta around the crater rim and show schlieren structure. In contrast, non–in situ glassy objects, loosely strewn around the crater lake and in the ejecta around the crater rim do not show any schlieren structure. These non–in situ fragments appear to be similar to ancient bricks from the Daityasudan temple in the Lonar village. Synthesis of existing and new major and trace element data on the Lonar impact spherules show that (1) the target Lonar basalts incorporated into the spherules had undergone minimal preimpact alteration. Also, the paleosol layer as preserved between the top‐most target basalt flow and the ejecta blanket, even after the impact, was not a source component for the Lonar impactites, (2) the Archean basement below the Deccan traps were unlikely to have contributed material to the impactite parental melts, and (3) the impactor asteroid components (Cr, Co, Ni) were concentrated only within the submillimeter‐sized spherules. Two component mixing calculations using major oxides and Cr, Co, and Ni suggest that the Lonar impactor was a EH‐type chondrite with the submillimeter‐sized spherules containing ~6 wt% impactor components.  相似文献   

On the possible origin of troilite‐metal nodules in the Katol chondrite (L6‐7)          下载免费PDF全文

Dwijesh Ray  S. Ghosh  S.V.S. Murty 《Meteoritics & planetary science》2017,52(1):72-88

Microtextural study of a single troilite‐metal nodule (TMN) from the Katol L6‐7 chondrite, a recent fall (May, 2012) in India suggests that the TMN is primarily an aggregate of submicron‐scale intergrowth of troilite and kamacite (mean Ni: 6.18 wt%) juxtaposed with intensely fractured silicates, mainly olivine (Fa: 25 mole%), low‐Ca pyroxene (Fs: 21.2 mole%), and a large volume of maskelynite. Evidence of shock textures in the TMN indicates a high degree of shock metamorphism that involves plagioclase‐maskelynite and olivine‐wadsleyite/ringwoodite transformations and formation of quenched metal‐sulfide melt textures due to localized shear‐induced frictional melting. It is inferred that the TMN formation is an independent, localized event by a high energy impact and its subsequent incorporation in the ejected chondritic fragment of the parent body. Katol chondrite has been calibrated with a peak shock pressure of S5 (~45 GPa) after Stöffler et al. (1991), whereas peak shock pressure within the TMN exceeds the shock facies S6 (>45 GPa) following Bennett and McSween (1996) and Stöffler et al. (1991). Overall, the shock‐thermal history of the Katol TMN is dissimilar as compared to the host chondrite.  相似文献