Evaluating uncertainties in regional climate simulations over South America at the seasonal scale

This work focuses on the evaluation of different sources of uncertainty affecting regional climate simulations over South America at the seasonal scale, using the MM5 model. The simulations cover a 3-month period for the austral spring season. Several four-member ensembles were performed in order to quantify the uncertainty due to: the internal variability; the definition of the regional model domain; the choice of physical parameterizations and the selection of physical parameters within a particular cumulus scheme. The uncertainty was measured by means of the spread among individual members of each ensemble during the integration period. Results show that the internal variability, triggered by differences in the initial conditions, represents the lowest level of uncertainty for every variable analyzed. The geographic distribution of the spread among ensemble members depends on the variable: for precipitation and temperature the largest spread is found over tropical South America while for the mean sea level pressure the largest spread is located over the southeastern Atlantic Ocean, where large synoptic-scale activity occurs. Using nudging techniques to ingest the boundary conditions reduces dramatically the internal variability. The uncertainty due to the domain choice displays a similar spatial pattern compared with the internal variability, except for the mean sea level pressure field, though its magnitude is larger all over the model domain for every variable. The largest spread among ensemble members is found for the ensemble in which different combinations of physical parameterizations are selected. The perturbed physics ensemble produces a level of uncertainty slightly larger than the internal variability. This study suggests that no matter what the source of uncertainty is, the geographical distribution of the spread among members of the ensembles is invariant, particularly for precipitation and temperature.     

地磁数据分析的一些思考

通过若干实例,本文讨论了地磁数据分析中的一些方法.这些方法包括时间序列的多项式拟合,相关性分析,频谱分析和小波分析等.在Matlab和AutoSignal软件下实现了以上方法,并基于这些方法研究了地磁场形态和地磁现象的频谱特征.我们分析了Surlari观测台（余纬45.3°,经度26.3°）的地磁时间序列,并与Ottawa（余纬44.6°,〖JP2〗经度284.5°）,Canberra（余纬125.3°,经度149.3°）, Kakioka（余纬53.8°,经度140.2°）,Vernadsky〖JP〗（余纬155.3°,经度295.7°）等台站的结果进行了对比分析,讨论了Fourier变换时间窗和小波基函数选取的影响,有限长时间序列引起的边缘效应,以及小波尺度和Fourier频率的关系等问题.我们采用谱分析和小波分析处理了2007年两个台站的地磁数据,研究了地磁场形态和地磁现象的频谱特征,并讨论了Fourier变换和小波变换的优缺点.     

Influence of the atmospheric conditions on PM<Subscript>10</Subscript> concentrations in Poznań, Poland

This study investigates atmospheric conditions’ influence on the mean and extreme characteristics of PM₁₀ concentrations in Poznań during the period 2006–2013. A correlation analysis was carried out to identify the most important meteorological variables influencing the seasonal dynamics of PM₁₀ concentrations. The highest absolute correlation values were obtained for planetary boundary layer height (r = ?0.57), thermal (daily minimum air temperature: r = ?0.51), anemological (average daily wind speed: r = ?0.37), and pluvial (precipitation occurrence: r = ?0.36) conditions, however the highest correlations were observed for temporal autocorrelations (1 day lag: r = 0.70). As regulated by law, extreme events were identified on the basis of daily threshold value i.e. 50 μg m^?3. On average, annually there are approximately 71.3 days anywhere in the city when the threshold value is exceeded, 46.6 % of those occur in winter. Additionally, 83.7 % of these cases have been found to be continuous episodes of a few days, with the longest one persisting for 22 days. The analysis of the macro-scale circulation patterns led to the identification of an easy-to-perceive seasonal relations between atmospheric fields that favour the occurrence of high PM₁₀ concentration, as well as synoptic situations contributing to the rapid air quality improvement. The highest PM₁₀ concentrations are a clear reaction to a decrease in air temperature by over 3 °C, with simultaneous lowering of PBL height, mean wind speed (by around 1 m s^?1) and changing dominant wind directions from western to eastern sectors. In most cases, such a situation is related to the expansion of a high pressure system over eastern Europe and weakening of the Icelandic Low. Usually, air quality conditions improve along with an intensification of westerlies associated with the occurrence of low pressure systems over western and central Europe. Opposite relations are distinguishable in summer, when air quality deterioration is related to the inflow of tropical air masses originating over the Sahara desert.     

Transgressive dunefield landforms and vegetation associations,Doña Juana,Veracruz, Mexico

Transgressive dune fields often comprise a multiplicity of landforms where vegetation processes largely affect landform dynamics, which in turn, also affect vegetation processes. These associations have seldom been studied in detail. This paper examines four separate landform types in a complex coastal transgressive dunefield located in the central Gulf of Mexico, in order to assess the relationships between dunefield habitat, local environmental factors, vegetation associations and landform evolution. Topographic surveys using tape and clinometer were conducted in conjunction with vegetation survey transects at four locations across the Doña Juana dunefield. Vegetation surveys allowed the estimation of relative plant cover of each plant species found along the transects. A large variety of landforms were found at the Doña Juana Dunefield: deflation plains, gegenwalle (counter) ridges, transverse dune trailing ridges, blowouts and parabolic dunes, aklé (fish‐scale shaped) dunefields and precipitation ridges, with plant species associations developing on these different landforms equally variable. Flood tolerant species were located in the lower parts (deflation plain and gegenwalle ridges) whereas the older and dryer parts were covered by coastal matorral shrubs. Burial‐tolerant species were dominant in the most mobile areas (blowouts and aklé dunefield and margin). The dune trailing ridge, with relatively milder conditions, showed the highest richness, with no dominant species. A dual interaction was found such that colonizing species both create and affect topography, and in turn, topography determines vegetation association and succession patterns. In coastal dunes, the vegetation and abiotic environment (namely the different landforms and the inherent micronevironmental variability) interact tightly and generate a complex and highly dynamic biogeomorphic system where substrate mobility and colonization processes reinforce one another in positive feedback. Copyright © 2010 John Wiley & Sons, Ltd.     

Mobilization of metals from riverine suspended matter in seawater

Suspended matter from rivers in the Russian Far East was leached by seawater to assess the extent of Zn, Cd, Pb, and Cu release from the land-derived solids to estuarine and coastal waters. The concentration of solids in the leaching experiments was 0.25 g/l. The suspended matter used varied in metal content from background levels to heavily contaminated.The concentration of Zn, Cd, Pb, and Cu in the leaching solution after 1, 4, 24, 48, and 96 h was determined by anodic stripping voltammetry. Measurable Cd was transferred from river suspended matter to seawater with both background and elevated Cd concentrations, though the amount of Cd released was different. The increase in Zn and Pb in solution was observed only at the enriched concentration of metals in the suspended solids. The Cu transfer into solution was more pronounced from material with elevated Cu concentration, but the amount of degradable organic matter in the solid phase was more important.The losses of metals from the riverine solids varied from 60% to 80% of total concentration for Cd to negligible for Pb, independent of contamination. The Zn loss depended on the initial concentration in the solids and decreased from 11–16% for the heavily contaminated suspended matter to 3–8% for the moderately enriched ones and to negligible for the pristine solids. Cu loss varied from 1% to 30% of total content, with no clear dependence on concentration in the suspended matter.The significance of additional input of dissolved metals to estuarine and coastal waters from remobilization was assessed by comparison with the initial concentration of dissolved metals in river water. Such experiments could be used to assess the water quality impact of atmospheric fallout of contaminated solids and storm drainage from the urbanized areas, in addition to river suspended matter studies.     

Influence of atmospheric circulation on precipitation in Altai Mountains

We analyzed the changes in precipitation regime in the Altai Mountains for 1959-2014 and estimate the influence of atmospheric circulations on these changes. Our study showed that during last 56 years the changes in the precipitation regime had a positive trend for the warm seasons(April-October),but weakly positive or negative trends for the cold seasons(November-March). It was found that these changes correspond to the decreasing contribution of “Northern meridional and Stationary anticyclone(Nm-Sa)” and “Northern meridional and East zonal(Nm-Ez)” circulation groups and to the increasing contribution of “West zonal and Southern meridional(Wz-Sm)” circulation groups,accordingly to the Dzerdzeevskii classification. In addition,it was found that the variation of precipitation has a step change point in 1980. For the warm seasons,the precipitation change at this point is associated with the reduced influence of “West zonal(Wz)”,“Northern meridional and Stationary anticyclone(Nm-Sa)” and “Northern meridional and Southern meridional(Nm-Sm)” circulation groups. For the cold seasons,a substantialincrease of “Wz-Sm” and a decrease of “Nm-Sa”,“Nm-Ez” circulation groups are responsible for the precipitation change in the two time periods(1959-1980 and 1981-2014).     

Coastal cooling/heating events: Laboratory experiments

We report the results of laboratory experiments on water heating/cooling, performed in 5 m long water channel with a slope. About 63 series of photos were analyzed: for 3 locations, for 3 bottom slopes (3.7, 6.7 and 12 degrees) and for different Ra numbers. It was pointed out that there exist two types of mixing characterizing different circulations in the presence of slope: gravity current and undersurface jet; the thermal bar is the region where one type of mixing is replaced by another; the highest speed and flowrate are at the break point; the flow is three-dimensional.     

Country-Specific Market Impacts of Climate Change

We develop a new climate-impact model, theGlobal Impact Model (GIM), which combines futurescenarios, detailed spatial simulations by generalcirculation models (GCMs), sectoral features,climate-response functions, and adaptation to generatecountry-specific impacts by market sector. Estimatesare made for three future scenarios, two GCMs, andtwo climate-response functions – a reduced-form modeland a cross-sectional model. Combining empiricallybased response functions, sectoral data by country,and careful climate forecasts gives analysts a morepowerful tool for estimating market impacts. GIMpredicts that country specific results vary, implyingthat research in this area is likely to bepolicy-relevant.     

U-Pb ID-TIMS age of the Tiksheozero carbonatite: expression of 2.0 Ga alkaline magmatism in Karelia, Russia

The Tiksheozero carbonatite in northern Russian Karelia is a transitional type between alkaline ultramafic — carbonatitic and alkaline gabbroic suites. The complex is dominated by pyroxenite with a variety of subordinate mafic and ultramafic phases and nepheline syenite. Carbonatite occurs in a main central body and in veins. In this study we have obtained a reliable age for the complex by single grain ID-TIMS U-Pb analyses of zircon and baddeleyite. The age of 1999 ± 5 Ma is important because it places the emplacement of the alkaline complexes in the context of craton-wide extension and break-up events which preceded the initiation of a major Paleoproterozoic orogenic cycle. The Paleoproterozoic age also emphasizes the fact that not all members of the Kola alkaline province are of Paleozoic age.