A review of Titan’s atmospheric phenomena

Saturn’s satellite Titan is a particularly interesting body in our solar system. It is the only satellite with a dense atmosphere, which is primarily made of nitrogen and methane. It harbours an intricate photochemistry, that populates the atmosphere with aerosols, but that should deplete irreversibly the methane. The observation that methane is not depleted led to the study of Titan’s methane cycle, starting with its atmospheric part. The features that inhabit Titan’s atmosphere can last for timescales varying from year to day. For instance, the reversal of the north–south asymmetry is linked to the 16-year seasonal cycle. Diurnal phenomena have also been observed, like a stratospheric haze enhancement or a possible tropospheric drizzle. Furthermore, clouds have been reported on Titan since 1993. From these first detections and up to now, with the recent inputs from the Cassini–Huygens mission, clouds have displayed a large range of shapes, altitudes, and natures, from the flocky tropospheric clouds at the south pole to the stratiform ones in the northern stratosphere. It is still difficult to compose a clear picture of the physical processes governing these phenomena, even though of lot of different means of observation (spectroscopy, imaging) are available now. We propose here an overview of the phenomena reported between 1993 and 2008 in the low atmosphere of Titan, with indications on the location, altitude, and their characteristics in order to give a perspective of our up-to-date understanding of Titan’s meteorological manifestations. We shall focus mainly on direct imaging observations, from both space- and ground-based facilities. All of these observations, published in more than 30 different refereed papers to date, allow us to build a precise chronology of Titan’s atmospheric changes (including the north–south asymmetry, diurnal and seasonal effects, etc). Since the interpretation is at an early stage, we only briefly mention some of the current theories regarding the features’ nature.     

Salt Marsh and Fringing Oyster Reef Transgression in a Shallow Temperate Estuary: Implications for Restoration,Conservation and Blue Carbon

The importance of intertidal estuarine habitats, like salt marsh and oyster reef, has been well established, as has their ubiquitous loss along our coasts with resultant forfeiture of the ecosystem services they provide. Furthering our understanding of how these habitats are evolving in the face of anthropogenic and climate driven changes will help improve management strategies. Previous work has shown that the growth and productivity of both oyster reefs and salt marshes are strongly linked to elevation in the intertidal zone (duration of aerial exposure). We build on that research by examining the growth of marsh-fringing oyster reefs at yearly to decadal time scales and examine movement of the boundary between oyster reef and salt marsh at decadal to centennial time scales. We show that the growth of marsh-fringing reefs is strongly associated to the duration of aerial exposure, with little growth occurring below mean low water and above mean sea level. Marsh-shoreline movement, in the presence or absence of fringing oyster reefs, was reconstructed using transects of sediment cores. Carbonaceous marsh sediments sampled below the modern fringing oyster reefs indicate that marsh shorelines within Back Sound, North Carolina are predominantly in a state of transgression (landward retreat), and modern oyster-reef locations were previously occupied by salt marsh within the past two centuries. Cores fronting transgressive marsh shorelines absent fringing reefs sampled thinner and less extensive carbonaceous marsh sediment than at sites with fringing reefs. This indicates that fringing reefs are preserving carbonaceous marsh sediment from total erosion as they transgress and colonize the exposed marsh shoreline making marsh sediments more resistant to erosion. The amount of marsh sediment preservation underneath the reef scales with the reef’s relief, as reefs with the greatest relief were level with the marsh platform, preserving a maximum amount of carbonaceous sediments during transgression by buffering the marsh from erosional processes. Thus, fringing oyster reefs not only have the capacity to shelter shorelines but, if located at the ideal tidal elevation, they also keep up with accelerating sea-level rise and cap carbonaceous sediments, protecting them from erosion, as reefs develop along the marsh.     

秘鲁南部阿雷基帕段海岸岩基带找矿方向探讨

通过详细的岩相学和锆石U-Pb年龄的研究,秘鲁海岸岩基带阿雷基帕段的填图工作得到了补充,该岩基带岩浆活动可分为7个阶段和4个旋回,各阶段都显示出不同的岩浆容量,其地貌主要表现为岩基和岩脉。旋回Ⅰ和旋回Ⅱ代表侏罗纪岩浆活动阶段（201~145Ma）,岩浆分异为辉长岩到花岗岩;旋回Ⅲ和旋回Ⅳ代表白垩纪岩浆,岩浆分异为英云闪长岩-二长花岗岩、闪长岩与花岗闪长岩及英云闪长岩-花岗闪长岩。对角闪石和黑云母矿物晶体的数量关系研究表明,旋回Ⅰ的侵入岩有大量辉石和角闪石结晶,并伴随金-铁成矿作用;旋回Ⅱ有大量的群集角闪石晶体和呈定向排列或群集的六边形黑云母,且伴随铜-金-铁成矿作用;旋回Ⅲ侵入岩内发育角闪石和黑云母,伴随着金-铜和铁成矿作用;旋回Ⅳ发育大量角闪石和六边形黑云母,岩石更偏长英质,并伴随铜-锌-金-银-铁和铜-金-钼成矿作用。     

Salt mapping in the Lower Macquarie area,Australia, using airborne electromagnetic data

An airborne electromagnetic survey was flown over 13 000 km² in the Lower Macquarie Valley in central New South Wales, Australia. Whilst bulk conductivity values from the survey provide useful insights into the regional hydrogeology of the area, mapping salinity and salinity hazards requires the derivation of salt store values from the survey data. This paper describes the methodology of deriving salt stores from conductivity data and accompanying physical measurements. A post-flight sampling programme involving physical, chemical, electromagnetic and geological examination of cores from eight drill holes provides field-based measurements through which the bulk conductivity data can be related to salt stores. Linear models were generated to understand the relationship between salt stores, conductivity and other parameters, and to produce an optimum salt store map from the data. A strong relationship was evident between observed salt stores and drill hole-derived observations, which include parameters such as conductivity, lithology, stratigraphy, lithostratigraphy/weathering and depth. The main predictor for salt stores was observed conductivity with only a minor influence due to lithology. Significant salt stores are predicted at depth in the northern part of the survey. Superficial salt stores are generally low (<4 kg/m³) in the Lower Macquarie and should not pose a threat to native vegetation or agricultural activities.     

Identifying sources and distributions of sediment contaminants at two US Virgin Islands marinas

Differences in sediment contaminant concentrations within two marinas and adjacent to the marinas in St. Thomas, US Virgin Islands were compared to calculate the portion of those contaminants due to marina activities. In marina 1 (containing no vessel maintenance areas, but with a fuel dock) 88% of observed PAHs and 0% of metals were attributed to marina activities. In the marina/boatyard complex, 46% of PAHs and 89% of metals were attributed to marina sources. The distance from storm drain discharges, and sediment characteristics play a greater role in the distribution and fate of pollutants than do activities associated with a given marina station. The data also provided some evidence that the protection marinas offer to vessels from wind, currents, and waves may concentrate contaminants.     

Evaluation of climatic change through harmonic analysis

In the present work, a precipitation and temperature series from Barcelona (Spain) are analysed in order to detect the possible existence of climatic changes or cycles. The analysis is carried out both from the temporal and spectral standpoints. The techniques used range from the classical periodogram and Blackman-Tukey method through to the Maximum Entropy method. The results do not show the existence of climatic cycles, though they do show a clear tendency toward increased precipitation and decreased temperature, since the last years of series.     

An overview of the external magnetic field with regard to magnetic surveys

Surveys in Geophysics -     

Regional modeling of climate change impacts on smallholder agriculture and ecosystems in Central America

Climate change will have serious repercussions for agriculture, ecosystems, and farmer livelihoods in Central America. Smallholder farmers are particularly vulnerable due to their reliance on agriculture and ecosystem services for their livelihoods. There is an urgent need to develop national and local adaptation responses to reduce these impacts, yet evidence from historical climate change is fragmentary. Modeling efforts help bridge this gap. Here, we review the past decade of research on agricultural and ecological climate change impact models for Central America. The results of this review provide insights into the expected impacts of climate change and suggest policy actions that can help minimize these impacts. Modeling indicates future climate-driven changes, often declines, in suitability for Central American crops. Declines in suitability for coffee, a central crop in the regional economy, are noteworthy. Ecosystem models suggest that climate-driven changes are likely at low- and high-elevation montane forest transitions. Modeling of vulnerability suggests that smallholders in many parts of the region have one or more vulnerability factors that put them at risk. Initial adaptation policies can be guided by these existing modeling results. At the same time, improved modeling is being developed that will allow policy action specifically targeted to vulnerable groups, crops, and locations. We suggest that more robust modeling of ecological responses to climate change, improved representation of the region in climate models, and simulation of climate influences on crop yields and diseases (especially coffee leaf rust) are key priorities for future research.     

Foreign minorities from developing countries in Madrid

Spain, which has always been a land of emigrants, is currently a centre of attraction for immigrants, as are other countries in Mediterranean Europe. The proportion is not as high as in other countries with a longer tradition of immigration. In this survey we selected the six nationalities which provide the highest numbers of immigrants from the developing world, and which have the greatest racial or cultural contrast to the native population. We analyse their structural features, whether or not immigrants from the same country are collect in the Madrid Metropolitan Area, the recent mobility of the immigrant population, and the evolution of immigration since the Administration carried out a regularization process, as well as Spaniards' opinion of foreign immigrants.