AN EVALUATION OF SEVERAL TURBULENCE SCHEMES FOR THE PREDICTION OF MEAN AND TURBULENT FIELDS IN COMPLEX TERRAIN

A prognostic three-dimensional mesoscale model has been developed andused in one- and two-dimensional modes to evaluate ten local turbulenceclosure schemes. The schemes ranged from first-order to the two-equationprognostic schemes. Predictions by the models were compared for aone-dimensional convective boundary layer using mixed layer scaling andmeasurements to interpret the results. Two-dimensional simulations were alsoperformed for a sea-breeze flow and for flow over a hill. The results showedthat for all of the models considered, minor differences were produced in themean meteorological fields and in the vertical scalar fluxes, but majordifferences were apparent in the velocity variances and dissipation rate.Predicted tracer concentrations were very sensitive to the turbulence modelformulation for dispersion from a point source in the convective boundarylayer, particularly for the prediction of maximum concentrations. Predictedtracer concentrations from a surface volume source for the two-dimensionalsimulations were similar for all models, although the degree of mixing in themorning growth period produced some differences. Generally, good results forthe mean meteorological fields can be obtained with first-order schemes, evenif they underpredict the magnitude of turbulence in the convective boundarylayer, and reasonable tracer concentrations can also be obtained with thesemodels provided near-source effects are not important. The two-equationprognostic models performed best for the prediction of turbulence in theconvective boundary layer.     

东印度洋水体输运的季节变化及相关盐度变化

利用20年（1992-2012年）的ECCO2模式模拟数据,主要研究了东印度洋（EIO）水体输运的季节变化.在EIO选取3个断面,分别为赤道、80°E和6°N.研究结果表明,跨赤道和80°E的季节输运主体部分大致相补偿.跨赤道的大部分水体输运局限在上层100 m,80°E的水体输运具有复杂结构,与显著的季风流、Wyrtki Jets（WJs）、赤道潜流（EUC）等有关.6°N上层水体净输运较小,但存在较强的边界流和相对较弱的内区流.纬向流的显著变化发生在80°E.在季风盛行季节,由于WJs减弱,赤道附近的水体输运以西向的梯度流为主,上层100 m的其余区域则主要受季风流控制.同样,由于EUC减弱,西向的梯度流与次表层东向的EUC之间也存在转换.在季风转换季节,季风流减弱,WJs与EUC分别在上层100 m和次表层占主导地位.此外,本研究还讨论了与季风流、WJs和EUC相关的盐水和暖水交换,有助于了解研究区域内温度和盐度的水平和垂直结构.     

On the Retrieval of Volcanic Sulfur Dioxide Emissions from GOME Backscatter Measurements

We focus on the retrieval of volcanic sulfur dioxide (SO₂) emissions from an analysis of atmospheric UV backscatter spectra obtained by the Global Ozone Monitoring Experiment (GOME) spectrometer on board the ESA European Remote Sensing Satellite (ERS-2). Here, the last major eruptions of Mt. Etna on Sicily (Italy) in July/August 2001 and October/November 2002 provided an excellent opportunity to study the retrieval of SO₂ columnar amounts from ground-based, LIDAR and satellite measurements. Our study shows that the bulk of emitted SO₂ was confined in the troposphere, mainly between 700 hPa and 400 hPa which is confirmed by trajectory analysis, by LIDAR observations and AVHRR observations. The area of influence of Mt. Etna eruptions ranges from the Western Saharan Desert to Greece and the near east states and even down to the basin of Tschad, Africa. Our analysis revealed that information about the plume height of volcanic eruptions and aerosol parameters is necessary for a reliable quantitative retrieval of SO₂ from space-borne sensor data at periods perturbed by volcanic eruptions.     

Cartographic Constructs: A Case Study of Nantucket Island Oral Histories

The widespread adoption of neoliberal reforms during the past quarter century has had profound implications for the livelihoods of those who live and work in cities throughout Latin America. This case study of Mérida, Mexico, builds directly on recent research about the changing nature of work and the role of informality as a livelihood strategy in Latin America and attempts to explain how place-specific patterns of informal work emerge from neoliberal reforms and concomitant urban economic restructuring. Drawing on field research and a large household survey, this article reveals that general patterns of informality coincide with previous findings from Latin America: high levels of informal work; increased heterogeneity of informality; and significant mobility, with a large share of workers “opting out” of the formal sector voluntarily. However, compared with previous research in Mexico, this study shows that informal work is significantly more pervasive, particularly among women; less likely to be voluntary; and pays considerably less. In light of gender considerations and significant discrepancies between local patterns of informality and national trends, this case study casts doubt on recent World Bank encyclicals affirming the resemblance between self-employment in Mexico and microentrepreneurship in more developed countries. Moreover, the article concludes that World Bank literature conveniently overlooks the gendered nature of informal work in Latin America and the profound divergence between the express purposes of neoliberalism and its actual implications. As a result, World Bank research on informality serves to justify the neoliberal model, rather than improve the livelihoods of those who live and work in cities throughout Latin America.     

The assessment of sediment sources: A field experiment

The possibility of using metals from mining activity as tracers for identifying stream sediment sources is explored. Sampling of monthly bed sediment yield and of the spatial and temporal variation in Pb concentration was undertaken in a 1·02 km² catchment, and estimates of the sediment contribution from different stream reaches are calculated. The method has considerable limitations, for metal concentrations are notably dependent on sediment size, season, source availability, and the chemical mobility of the metal used. In most natural streams these must preclude the use of pollutants for simple sediment source identification.     

A determination of the decay constant for spontaneous fission of natural uranium using fission track accumulation

The decay constant for spontaneous fission of natural uranium has been determined by accumulating fission fragment tracks in Lexan plastic held adjacent to uranium metal for one year. The value, 6.8 ± 0.6. 10⁻¹⁷ yr⁻¹, is consistent with values most commonly used in fission track dating.     

Raman spectrum of natural and synthetic stishovite

Raman spectra of natural and synthetic samples of stishovite have been measured with a micro-optical spectrometer system. These spectra have a pattern that is characteristic of rutile-structured oxides. The spectrum of synthetic stishovite is characterized by well-resolved bands at 231, 589, 753, and 967 cm^?1, which are assigned as theB _1g,E _g,A _1g, andB _2g fundamentals, respectively, of the first-order Raman spectrum of the ideal, ordered structure. Natural stishovite obtained from Meteor Crater, Arizona has a first-order Raman spectrum that is fully consistent with that of the synthetic material. The observed spectrum of the natural sample, however, is weaker and has bands in addition to those identified as fundamentals in the spectrum of the synthetic material. A broad band at ～475 cm^?1 may be indicative of glass or contaminants derived from the extraction procedure. Alternatively, this band may arise from multiphonon scattering that is enhanced by poor crystallinity or structural disorder in the natural shocked sample.