Influence of stratospheric ozone changes on long-term trends in the meso- and lower thermosphere   总被引：2，自引：2，他引：0  

J. Bremer  D. Peters 《Journal of Atmospheric and Solar》2008,70(11-12):1473-1481

As predicted by model calculations, long-term changes in the stratospheric ozone content should influence trends in the meso- and thermosphere also. These predictions have been tested by means of ionospheric reflection height data in the low-frequency (LF) range and critical frequency data series of the ionospheric E layer, foE, observed at different stations around the world. It was shown that an essential part of the derived trends in the mesosphere and in the lower thermosphere is correlated with long-term changes of the atmospheric ozone content. During the sub-interval with the strongest ozone decrease (1979–1995) the detected ionospheric trends are most pronounced. Additionally was also demonstrated that the longitudinally dependent ozone trends are related to similar variations in the foE trends.  相似文献   

Can crystallization of olivine tholeiite give rise to potassic rhyolites?—an experimental investigation   总被引：6，自引：0，他引：6  

Matthew L. Whitaker  Hanna Nekvasil  Donald H. Lindsley  Michael McCurry 《Bulletin of Volcanology》2008,70(3):417-434

Experiments were conducted to determine whether the rhyolites and basalts of the intraplate silica-saturated potassic suites could be genetically related through crystallization. Extreme crystallization (96–97%) of a high-MgO (10.62 wt%) olivine tholeiite from the Snake River Plain with an initial bulk water content of 0.4 wt% at a mid-crustal pressure of 4.3 kbar generated potassic rhyolitic liquids similar in major element chemistry to those found in the Quaternary rhyolite domes of the Snake River Plain and their plutonic equivalents in the Proterozoic Laramie Anorthosite Complex. Residual liquids comparable in composition to the bulk rock compositions of intermediate rocks found at the Craters of the Moon and Cedar Butte eruptive centers in the Snake River Plain are also generated along this crystallization path. This paper constitutes part of a special issue dedicated to Bill Bonnichsen on the petrogenesis and volcanology of anorogenic rhyolites.  相似文献   

Trends in the ionospheric E and F regions over Europe     

J. Bremer 《Annales Geophysicae》1998,16(8):986-996

Continuous observations in the ionospheric E and F regions have been regularly carried out since the fifties of this century at many ionosonde stations. Using these data from 31 European stations long-term trends have been derived for different parameters of the ionospheric E layer (h E, foE), F1 layer (foF1) and F2 layer (hmF2,foF2). The detected trends in the E and F1 layers (lowering of the E region height hE; increase of the peak electron densities of the E and F1 layers, foE and foF1) are in qualitative agreement with model predictions of an increasing atmospheric greenhouse effect. In the F2 region, however, the results are more complex. Whereas in the European region west of 30° E negative trends in hmF2 (peak height of the F2 layer) and in the peak electron density (foF2) have been found, in the eastern part of Europe (east of 30° E) positive trends dominate in both parameters. These marked longitudinal differences cannot be explained by an increasing greenhouse effect only, here probably dynamical effects in the F2 layer seem to play an essential role.  相似文献   

Representativeness of wind measurements on a mesoscale grid with station separations of 312 m to 10 km     

Steven R. Hanna  Joseph C. Chang 《Boundary-Layer Meteorology》1992,60(4):309-324

A field experiment was carried out in which wind speed and direction were measured over flat terrain at a height of 10 m using 13 identical instruments spaced logarithmically along two perpendicular 10 km lines. Station separations ranged from 312 m to 10 km. One-minute data from 11 sampling periods of duration 6 to 10 h were studied. p ]The statistics showed little dependence on whether the line of instruments was oriented along the wind or across the wind. The correlation coefficients between wind fluctuations at two stations separated by distance x were found to vary exponentially with x, with an integral distance scale on the order of 1 km. The integral time scale derived from the variation of the single station variances with averaging time was found to equal several minutes. At a station separation of 10 km, the correlation coefficients between the wind components at the two sites were calculated to be 0.24, 0.37, and 0.47 for averaging times of 1, 10, and 60 min, respectively. These values for the correlation coefficients correspond to root-mean-square differences in wind speed at the two stations of about 1.3, 1.0, and 0.7 m/s, respectively.Exponential formulas based on dimensional analysis are suggested for fitting these observations. It is found that the observations of spatial correlations are best fit if two independent integral distance scales are used — a boundary-layer distance scale of about 300 m that best applies to small station separations and a mesoscale distance scale of about 10 km that applies to larger station separations.  相似文献   

The effect of cr(iii) on the form and degradability of a polysaccharide produced by a bacterium isolated from a marine sediment     

P.J. Bremer  M.W. Loutit 《Marine environmental research》1986,20(4)

Polysaccharide was produced from a coryneformn bacterium isolated from sediment. The presence of Cr was shown to affect both the form and the yield of polysaccharide obtained from the bacterium. The binding of Cr to the polysaccharide decreased the rate at which sediment bacteria could degrade it.  相似文献   

Strength Anisotropy of Berea Sandstone: Results of X-Ray Computed Tomography,Compression Tests,and Discrete Modeling     

Kwang Yeom Kim  Li Zhuang  Hwayoung Yang  Hanna Kim  Ki-Bok Min 《Rock Mechanics and Rock Engineering》2016,49(4):1201-1210

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Modelling of the acid-base properties of two thermophilic bacteria at different growth times     

Hannah T.M. Heinrich  Phil J. Bremer  Christopher J. Daughney 《Geochimica et cosmochimica acta》2008,72(17):4185-4200

Acid-base titrations and electrophoretic mobility measurements were conducted on the thermophilic bacteria Anoxybacillus flavithermus and Geobacillus stearothermophilus at two different growth times corresponding to exponential and stationary/death phase. The data showed significant differences between the two investigated growth times for both bacterial species. In stationary/death phase samples, cells were disrupted and their buffering capacity was lower than that of exponential phase cells. For G. stearothermophilus the electrophoretic mobility profiles changed dramatically. Chemical equilibrium models were developed to simultaneously describe the data from the titrations and the electrophoretic mobility measurements. A simple approach was developed to determine confidence intervals for the overall variance between the model and the experimental data, in order to identify statistically significant changes in model fit and thereby select the simplest model that was able to adequately describe each data set. Exponential phase cells of the investigated thermophiles had a higher total site concentration than the average found for mesophilic bacteria (based on a previously published generalised model for the acid-base behaviour of mesophiles), whereas the opposite was true for cells in stationary/death phase. The results of this study indicate that growth phase is an important parameter that can affect ion binding by bacteria, that growth phase should be considered when developing or employing chemical models for bacteria-bearing systems.  相似文献   

Assessing the ambition of post-2020 climate targets: a comprehensive framework     

Niklas Höhne  Hanna Fekete  Michel G.J. den Elzen  Andries F. Hof  Takeshi Kuramochi 《Climate Policy》2018,18(4):425-441

One of the most fundamental questions surrounding the new Paris Agreement is whether countries’ proposals to reduce GHG emissions after 2020 are equally ambitious, considering differences in circumstances between countries. We review a variety of approaches to assess the ambition of the GHG emission reduction proposals by countries. The approaches are applied illustratively to the mitigation part of the post-2020 climate proposals (nationally determined contributions, or NDCs) by China, the EU, and the US. The analysis reveals several clear trends, even though the results differ per individual assessment approach. We recommend that such a comprehensive ambition assessment framework, employing a large variety of approaches, is used in the future to capture a wide spectrum of perspectives on ambition.

POLICY RELEVANCE

Assessing the ambition of the national climate proposals is particularly important as the Paris Agreement asks for regular reviews of national contributions, keeping in mind that countries raise their ambition over time. Such an assessment will be an important part of the regular global stocktake that will take place every five years, starting with a ‘light’ version in 2018. However, comprehensive methods to assess the proposals are lacking. This article provides such a comprehensive assessment framework.  相似文献   

Influence of ENSO and PDO on mountain glaciers in the outer tropics: case studies in Bolivia     

Bijeesh Kozhikkodan Veettil  Ulisses Franz Bremer  Sergio Florêncio de Souza  Éder Leandro Bayer Maier  Jefferson Cardia Simões 《Theoretical and Applied Climatology》2016,123(3-4):757-768

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Batch discovery of nine z∼ 1 clusters using X-ray and K or R, z' images     

S. Andreon  I. Valtchanov  L. R. Jones  B. Altieri  M. Bremer  J. Willis  M. Pierre  H. Quintana 《Monthly notices of the Royal Astronomical Society》2005,359(4):1250-1260

We present the results of an initial search for clusters of galaxies at z ∼ 1 and above, using data from 2.9 square degrees of XMM–Newton images. By selecting weak potentially extended X-ray sources with faint or no identifications in deep, ground-based optical imaging, we have constructed a starting sample of 19 high-redshift cluster candidates. Near-IR and R , z ' imaging of these fields identified nine of them as high-redshift systems. Six of these were confirmed spectroscopically, three at z ∼ 1.0 and the other three in the  0.8 < z < 0.92  range. The remaining three systems have solid photometric evidence to be at   z _phot∼ 0.8, 1.0  and 1.3. The present sample significantly increases the number of such clusters. The measured density of z ≳ 1 clusters, after discarding 'low'-redshift systems at z ≲ 0.92 is about 1.7 deg⁻² (with 68 per cent confidence interval equal to [1.0, 2.9]) for   f_X ≳ 2.5  10⁻¹⁵ erg cm⁻² s⁻¹  ([0.5–2] keV) and this is a lower limit, having screened not all potential z ∼ 1 candidate clusters. Coordinates, X-ray measures and evidence for nine X-ray-selected high-redshift clusters is given.  相似文献