Despite the importance of tropical ecosystems for climate regulation, biodiversity, water and nutrient cycles, only a few Critical Zone Observatories (CZOs) are located in the tropics. Among these, most are in humid climates, while very few data exist for semi-arid and sub-humid climates, due to the difficulty of estimating hydro-geochemical balances in catchments with ephemeral streams. We contribute to fill this gap by presenting a meteorological and hydro-geochemical dataset acquired at the Mule Hole catchment (4.1 km2), a pristine dry deciduous forest located in a biosphere reserve in south India. The dataset consists of time series of variables related to (i) meteorology, including rainfall, air temperature, relative humidity, wind speed and direction, and global radiation, (ii) hydrology, including water level and discharge at the catchment outlet, (iii) hydrogeology, including manual (monthly) and/or automated (from 15 min to hourly) groundwater levels in nine piezometers and (iv) geochemistry, including suspended sediment content in the stream and chemical composition of rainfall (event based), groundwater (monthly sampling) and stream water (storm events, 15 min to hourly frequency with an automatic sampler). The time series extend from 2003 to 2019. Measurement errors are minimized by frequent calibration of sensors and quality checks, both in the field and in the laboratory. Despite these precautions, several data gaps exist, due to occasional access restriction to the site and instrument destruction by wildlife. Results show that large seasonal and interannual variations of climatic conditions were reflected in the large variations of stream flow and groundwater recharge, as well as in water chemical composition. Notably, they reveal a long-term evolution of groundwater storage, suggesting hydrogeological cycles on a decadal scale. This dataset, alone or in combination with other data, has already allowed to better understand water and element cycling in tropical dry forests, and the role of forest diversity on biogeochemical cycles. As tropical ecosystems are underrepresented by Critical Zone Observatories, we expect this data note to be valuable for the global scientific community. 相似文献
We present the main findings of two recent studies using high-resolution MHD simulations of supersonic magnetized shear flow layers. First, a strong large-scale coalescence effect partially countered by small-scale reconnection events is shown to dominate the dynamics in a two-dimensional layer subject to Kelvin-Helmholtz (KH) instabilities. Second, an interaction mechanism between two different types of instabilities (KH and current-driven modes) is shown to occur in a cylindrical jet configuration embedded in an helical magnetic field. Finally, we discuss the implications of these results for astrophysical jets survival. 相似文献
Summary. Overlapping spreading centres (OSCs) represent a new type of plate boundary interaction in which en échelon rise segments overlap significantly and are not joined by a transform fault. A three-dimensional Fourier inversion of the magnetic field was performed on an overlapping spreading centre to remove the effects of topography and ridge orientation. A magnetic high exists at the tip of one of the two ridge segments. Forward modelling suggests that the anomalous magnetic field cannot be attributed to the effects of topography alone. The inversion reveals the existence of a magnetization high at the tip of the eastern spreading centre. Maximum magnetization values are consistent with ones obtained in other high amplitude zones in the Pacific as well as with the measured magnetization of samples dredged in the same areas. We suggest that the magnetization high over the eastern ridge tip of the 9°03'N OSC is associated with highly evolved basalts enriched in iron and titanium. Such enrichment may be caused by enhanced crystal fractionation within an axial magma chamber which is intermittent and occasionally freezes as the eastern spreading axis propagates into older lithosphere. 相似文献
Understanding the role of geological heterogeneity on the performance of managed aquifer recharge (MAR) in terms of effective groundwater storage is crucial to design MAR systems. Natural aquifers are affected by a variety of geologic strata and structures at different scales, which are responsible for wide ranging hydraulic properties. This study combines physical experiments and numerical modeling to investigate the effect of geologic structures commonly encountered in sedimentary environments, on MAR-induced groundwater flow patterns using injection wells. Models were conceptualized and parametrized based on the hydrogeological conditions of Tailan River basin in arid NW China, which hosts a typical, structurally complex, alluvial-fan aquifer system affected by sediment layering, clay lenses and anticline barriers, and is extensively studied for the strategic potential of MAR in addressing water shortages in the region. Results showed that, compared to a homogeneous scenario, high-permeability aquifer layers shortened groundwater ages, decreased the thickness of the artificially recharged water lenses (ARWLs), and shifted the stagnation points downstream. Clay lenses increased groundwater residence times but had little effect on spatial flow patterns due to their elongation parallel-to-flow direction. Overall groundwater ages, as well as the thickness of ARWLs created through injection on the upstream side of an anticline, increased, and this to a larger extent than through injection on the downstream side, which did not increase significantly compared to the homogeneous scenario. Results provide insights for MAR optimization in naturally heterogeneous aquifer systems, along with a benchmark tool for application to a wide range of typical geological conditions.
In coral islands, groundwater is a crucial freshwater resource for terrestrial life, including human water supply. Response of the freshwater lens to expected climate changes and subsequent vegetation alterations is quantified for Grande Glorieuse, a low-lying coral island in the Western Indian Ocean. Distributed models of recharge, evapotranspiration and saltwater phytotoxicity are integrated into a variable-density groundwater model to simulate the evolution of groundwater salinity. Model results are assessed against field observations including groundwater and geophysical measurements. Simulations show the major control currently exerted by the vegetation with regards to the lens morphology and the high sensitivity of the lens to climate alterations, impacting both quantity and salinity. Long-term changes in mean sea level and climatic conditions (rainfall and evapotranspiration) are predicted to be responsible for an average increase in salinity approaching 140 % (+8 kg m?3) when combined. In low-lying areas with high vegetation density, these changes top +300 % (+10 kg m?3). However, due to salinity increase and its phytotoxicity, it is shown that a corollary drop in vegetation activity can buffer the alteration of fresh groundwater. This illustrates the importance of accounting for vegetation dynamics to study groundwater in coral islands. 相似文献
Theoretical and Applied Climatology - In this study, we investigated the consequences of climate change on bioclimatic indices in vineyards along the edge of Lake Neuchatel in Switzerland. Like in... 相似文献
HI observations are reported for a new sample of 73 BCDGs candidates. HI emission has been detected from 53 of them. The distributions of HI parameters are given for detected objects.Published in Astrofizika, Vol. 38, No. 4, pp. 616–618, October–December, 1995. 相似文献