Assessing eddy heat flux and its parameterization: A wavenumber perspective from a 1/10° ocean simulation     

Alexa Griesel  Sarah T. Gille  Janet Sprintall  Julie L. McClean  Mathew E. Maltrud 《Ocean Modelling》2009,29(4):248-260

  相似文献   

Noble gas components in planetary atmospheres and interiors in relation to solar wind and meteorites     

K. Marti  K. J. Mathew 《Journal of Earth System Science》1998,107(4):425-431

We discuss observed xenon isotopic signatures in solar system reservoirs and possible relationships. The predominant trapped xenon component in ordinary chondrites (OC) is OC-Xe and its isotopic signature differs from Xe in ureilites, in carbonaceous chondrites, in the atmospheres of Earth and Mars, and in the solar wind. Additional minor Xe components were identified in type 3 chondrites and in the metal phase of chondrites. The OC-Xe and ureilite signatures are both consistent with varying mixtures of HL-Xe and slightly mass fractionated solar-type Xe. Xenon in the Martian atmosphere is found to be strongly mass fractionated by 37.7‰ per amu, relative to solar Xe, favoring the heavy isotopes. Xenon in SNC’s from the Martian mantle show admixture of solar-type Xe, which belongs to an elementally strongly fractionated component. The origin of the isotopic signatures of Ne and Xe in the terrestrial atmosphere are discussed in the light of evidence that the Xe isotopic fractionations in the Martian and terrestrial atmospheres are consistent. However, in the terrestrial atmospheric Xe component excesses are observed for¹³²Xe and also for^129,131Xe, relative to fractionated solar Xe. The suggested chemically fractionated fission Xe component (CFF-Xe) seems to closely match the above excesses. We discuss models of origin for planetary volatiles and possible processes driving their evolution to present day compositions.  相似文献   

Solar Photospheric and Chromospheric Observations using a Lithium Niobate Fabry-Perot Etalon     

C. Debi Prasad  Shibu K. Mathew  Arvind Bhatnagar  Ashok Ambastha 《Experimental Astronomy》1998,8(2):125-133

We have made a narrow band tunable filter for solar observations using a Lithium Niobate Fabry-Perot etalon. The 60 mm aperture etalon with a free spectral range of 4.22 Å and finesse of 26 at = 6122 Å has been procured from CSIRO, Australia. The wavelength tuning is achieved by applying high voltage to the etalon substrate at the rate of 0.45 Å per 1000 Volts. The filter is being used for imaging the sun in H line and obtaining Doppler- and Magnetogram in CaI 6122 Å line. In this paper, we present some initial observations carried out with this filter at Udaipur Solar Observatory.  相似文献   

Photogeologic mapping north of Khairwara,Udaipur district,Rajasthan     

Arupkumar Mitra  Supriya Brahma 《Journal of the Indian Society of Remote Sensing》1988,16(2):27-31

Photogeologic mapping of a sample area defined by latitudes 24° O to 6′N and longitudes 73° 30′ to 45′ E from a part of the Aravalli orogen, illustrates the advantages, as well as limitations, of photo-interpretation (PI) in terrains comprsing, highly deformed ancient rock formations. Discrimination between psammitic and pelitic metasediments is easy, using micro-relief and drainage parameters as PI elements; but that between pelites, ultra-basic schists and impure marbles is difficult and less reliable. Trends of foliations, several sets of joints and faults are distinct on the aerial photographs, but complete reconstruction of the superposed fold geometry is not possible. Within the area studied, dominantly pelitic, psammitic and a little clacareous metasediments, intruded by ultra-basics, exhibit a prominent and persistent NNE trend defined by lithologic contacts, bedding and foliations, with steep northwesterly dips. In its central part, bands of psammites within the pelites exhibit a hook shaped fold interference pattern (type 3 of Ramsay, 1967) with the later upright (Fleuty, 1964) fold axial trace trending northwesterly.  相似文献   

The Suburbanization of Food Insecurity: An Analysis of Projected Trends in the Atlanta Metropolitan Area     

Jerry Shannon  Mathew E. Hauer  Alexis Weaver  Sarah Shannon 《The Professional geographer》2018,70(1):84-93

Although general patterns of food insecurity in the United States are known, few studies have attempted to estimate small area food security or account for ongoing socioeconomic changes. Here we address these issues by producing small area estimates of food insecurity in the Atlanta metropolitan area using two methodologies: fixed effects modeling and demographic metabolism. In both cases, we use county-level data from the Current Population Survey to determine the association between food insecurity and demographic predictors. These associations are then applied to tract-level data from the 2009 to 2013 American Community Survey and projected data for 2020 to create small area estimates of food insecurity. We find broad consensus between our two methods. For both time periods, food insecurity is highest in southern sections of the city of Atlanta and its neighboring suburbs. Projections to 2020, however, show that food insecurity rates are projected to increase in outer-ring suburbs east and west of the city while decreasing in the urban core. These results highlight the need to further adapt antihunger efforts for often sprawling suburban communities, where poverty rates are increasing but spatial mismatch combined with poor transit access might hinder access to food assistance.  相似文献   

Mapping massacres: GIS and state terror in Guatemala     

Michael K. Steinberg  Carrie Height  Mathew Bampton 《Geoforum》2006,37(1):62-68

This paper employs GIS (geographic information systems) technology to visually display the locations of massacres associated with Guatemala’s civil war. While there have been other, more general maps published depicting the spatial dimensions of violence in Guatemala, few other maps depict this information at the department level, nor have they included information on indigenous populations and physical geography.These maps are part of the emerging field of human rights GIS. For example, over the past two decades, maps have become tools of empowerment in Central America and elsewhere, maps usually made with GIS technology. Indigenous groups in many countries in particular have embraced GIS technology and have begun to use maps as tools in their fight for land and marine resources, as well as greater political autonomy. In the case of massacres in Guatemala, displaying exactly where violent acts took place is one way to educate the Guatemalan public regarding the terrible violence of the recent past. Knowing the name of a specific town where a massacre took place is more concrete, potentially leading to perception of place and people, rather than simply being aware of violence in the countryside.  相似文献   

Tectonic Evolution of the Yangtze Passive Margin and Songpan Garze Fold Belt, China     

Mathew J.Harrowfield  et al 《地学前缘》2000,(Z1)

  相似文献   

Hydrological modelling in the anthroposphere: predicting local runoff in a heavily modified high-alpine catchment     

Johannes Wesemann  Mathew Herrnegger  Karsten Schulz 《山地科学学报》2018,15(5):921-938

Hydrological models within inflow forecasting systems for high-alpine hydropower reservoirs can provide valuable information as part of a decision support system for the improvement of hydropower production or flood retention. The information, especially concerning runoff, is however rarely available for the calibration of the hydrological models used. Therefore, a method is presented to derive local runoff from secondary information for the calibration of the model parameters of the rainfallrunoff model COSERO. Changes in water levels in reservoirs, reservoir outflows, discharge measurements at water intakes and in transport lines are thereby used to derive the local, “natural” flow for a given sub-catchment. The proposed method is applied within a research study for the ÖBB Infrastructure Railsystem division in the Stubache catchment in the central Austrian Alps. Here, the ÖBB operates the hydropower scheme “Kraftwerksgruppe Stubachtal”, which consists of 7 reservoirs and 4 hydropower stations. The hydrological model has been set up considering this human influences and the high natural heterogeneity in topography and land cover, including glaciers. Overall, the hydrological model performs mostly well for the catchment with highest NSE values of 0.78 for the calibration and 0.79 for the validation period, also considering the use of homogeneous parameter fields and the uncertainty of the derived local discharge values. The derived runoff data proved to be useful information for the model calibration. Further analysis, examining the water balance and its components as well as snow cover, showed satisfactory simulation results. In conclusion, a unique runoff dataset for a small scale high-alpine catchment has been created to establish a hydrological flow prediction model which in a further step can be used for improved and sustainable hydropower management.  相似文献   

The regional forcing of Northern hemisphere drought during recent warm tropical west Pacific Ocean La Niña events     

Andrew Hoell  Chris Funk  Mathew Barlow 《Climate Dynamics》2014,42(11-12):3289-3311

Northern Hemisphere circulations differ considerably between individual El Niño-Southern Oscillation events due to internal atmospheric variability and variation in the zonal location of sea surface temperature forcing over the tropical Pacific Ocean. This study examines the similarities between recent Northern Hemisphere droughts associated with La Niña events and anomalously warm tropical west Pacific sea surface temperatures during 1988–1989, 1998–2000, 2007–2008 and 2010–2011 in terms of the hemispheric-scale circulations and the regional forcing of precipitation over North America and Asia during the cold season of November through April. The continental precipitation reductions associated with recent central Pacific La Niña events were most severe over North America, eastern Africa, the Middle East and southwest Asia. High pressure dominated the entire Northern Hemisphere mid-latitudes and weakened and displaced storm tracks northward over North America into central Canada. Regionally over North America and Asia, the position of anomalous circulations within the zonal band of mid-latitude high pressure varied between each La Niña event. Over the northwestern and southeastern United States and southern Asia, the interactions of anomalous circulations resulted in consistent regional temperature advection, which was subsequently balanced by similar precipitation-modifying vertical motions. Over the central and northeastern United States, the spatial variation of anomalous circulations resulted in modest inter-seasonal temperature advection variations, which were balanced by varying vertical motion and precipitation patterns. Over the Middle East and eastern Africa, the divergence of moisture and the advection of dry air due to anomalous circulations enhanced each of the droughts.  相似文献   

La Niña diversity and Northwest Indian Ocean Rim teleconnections     

Andrew Hoell  Chris Funk  Mathew Barlow 《Climate Dynamics》2014,43(9-10):2707-2724

The differences in tropical Pacific sea surface temperature (SST) expressions of El Niño-Southern Oscillation (ENSO) events of the same phase have been linked with different global atmospheric circulation patterns. This study examines the dynamical forcing of precipitation during October–December (OND) and March–May (MAM) over East Africa and during December–March (DJFM) over Central-Southwest Asia for 1950–2010 associated with four tropical Pacific SST patterns characteristic of La Niña events, the cold phase of ENSO. The self-organizing map method along with a statistical distinguishability test was used to isolate La Niña events, and seasonal precipitation forcing was investigated in terms of the tropical overturning circulation and thermodynamic and moisture budgets. Recent La Niña events with strong opposing SST anomalies between the central and western Pacific Ocean (phases 3 and 4), force the strongest global circulation modifications and drought over the Northwest Indian Ocean Rim. Over East Africa during MAM and OND, subsidence is forced by an enhanced tropical overturning circulation and precipitation reductions are exacerbated by increases in moisture flux divergence. Over Central-Southwest Asia during DJFM, the thermodynamic forcing of subsidence is primarily responsible for precipitation reductions, with moisture flux divergence acting as a secondary mechanism to reduce precipitation. Eastern Pacific La Niña events in the absence of west Pacific SST anomalies (phases 1 and 2), are associated with weaker global teleconnections, particularly over the Indian Ocean Rim. The weak regional teleconnections result in statistically insignificant precipitation modifications over East Africa and Central-Southwest Asia.  相似文献