The outer atmosphere of Tau -- II. Fluorescent lines     

A. D. McMurry  C. Jordan  K. G. Carpenter 《Monthly notices of the Royal Astronomical Society》1999,302(1):48-58

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The 16th Workshop on Antarctic Meteorology and Climate and 6th Year of Polar Prediction in the Southern Hemisphere Meeting     

David H.BROMWICH  Matthew A.LAZZARA  Arthur M.CAYETTE  Jordan G.POWERS  Kirstin WERNER  John J.CASSANO  Steven R.COLWELL  Scott CARPENTIER  Xun ZOU 《大气科学进展》2022,39(3):536-542

1. Overview In June 2021, the 16th Workshop on Antarctic Meteorology and Climate (WAMC) and the 6th Year of Polar Prediction in the Southern Hemisphere (YOPP-SH) Meeting (http://polarmet.osu.edu/WAMC;021/) were held online and hosted by the Polar Meteorology Group at Byrd Polar and Climate Research Center, The Ohio State University, Columbus,Ohio (Fig. 1).  相似文献   

A family-level macroinvertebrate biotic index for ecological assessment of lakes in Yunnan,China     

Li-Na Du  Yan-E Jiang  Xiao-Yong Chen  Jun-Xing Yang  David Aldridge 《Water Resources》2017,44(6):864-874

Persistent economic growth in Chinese southwestern Yunnan Province is setting aquatic ecosystems in its plateau lakes under enormous pressure. While several different systems have previously been used to study these lakes, no existing methodology adequately measures both the chemical and biotic parameters of these water bodies. Here, we present a novel Biotic Monitoring Yunnan Lakes (BMYL) index that provides a general assessment tool for ecological deterioration that is caused by organic pollution. Principal Component Analysis is used to analyze the occurrence of families of macroinvertebrates and chemical properties of the lakes. In brief, families of macroinvertebrates were given a score from 10 to 1 based on sensitivity to organic enrichment and eutrophication. Sampling at each lake yielded an Average Score per Lake (ASPL) which is calculated by dividing the total BMYL by the total number of scoring families. High ASPL values characterize a biologically intact lake containing relatively large numbers of high scoring taxa, while lower ASPL values denote a polluted lake that does not support many high scoring taxa. The results of the BMYL show a notably more accurate characterization of the long-term health of concerned aquatic ecosystems than studies that use abundance levels of species or a simple analysis of chemical parameter.  相似文献   

Strong slope-aspect control of regolith thickness by bedrock foliation     

Jordan D. Leone  W. Steven Holbrook  Clifford S. Riebe  Jon Chorover  Ty P.A. Ferré  Bradley J. Carr  Russell P. Callahan 《地球表面变化过程与地形》2020,45(12):2998-3010

The porous near-surface layer of the Earth's crust – the critical zone – constitutes a vital reservoir of water for ecosystems, provides baseflow to streams, guides recharge to deep aquifers, filters contaminants from groundwater, and regulates the long-term evolution of landscapes. Recent work suggests that the controls on regolith thickness include climate, tectonics, lithology, and vegetation. However, the relative paucity of observations of regolith structure and properties at landscape scales means that theoretical models of critical zone structure are incompletely tested. Here we present seismic refraction and electrical resistivity surveys that thoroughly characterize subsurface structure in a small catchment in the Santa Catalina Mountains, Arizona, USA, where slope-aspect effects on regolith structure are expected based on differences in vegetation. Our results show a stark contrast in physical properties and inferred regolith thickness on opposing slopes, but in the opposite sense of that expected from environmental models and observed vegetation patterns. Although vegetation (as expressed by normalized difference vegetation index [NDVI]) is denser on the north-facing slope, regolith on the south-facing slope is four times thicker (as indicated by lower seismic velocities and resistivities). This contrast cannot be explained by variations in topographic stress or conventional hillslope morphology models. Instead, regolith thickness appears to be controlled by metamorphic foliation: regolith is thicker where foliation dips into the topography, and thinner where foliation is nearly parallel to the surface. We hypothesize that, in this catchment, hydraulic conductivity and infiltration capacity control weathering: infiltration is hindered and regolith is thin where foliation is parallel to the surface topography, whereas water infiltrates deeper and regolith is thicker where foliation intersects topography at a substantial angle. These results suggest that bedrock foliation, and perhaps by extension sedimentary layering, can control regolith thickness and must be accounted for in models of critical zone development. © 2020 John Wiley & Sons, Ltd.  相似文献   

Investigating potential future changes in surface water flooding hazard and impact     

Alison C. Rudd  Alison L. Kay  Steven C. Wells  Timothy Aldridge  Steven J. Cole  Elizabeth J. Kendon  Elizabeth J. Stewart 《水文研究》2020,34(1):139-149

Surface water flooding (SWF) is a recurrent hazard that affects lives and livelihoods. Climate change is projected to change the frequency of extreme rainfall events that can lead to SWF. Increasingly, data from Regional Climate Models (RCMs) are being used to investigate the potential water-related impacts of climate change; such assessments often focus on broad-scale fluvial flooding and the use of coarse resolution (>12 km) RCMs. However, high-resolution (<4 km) convection-permitting RCMs are now becoming available that allow impact assessments of more localised SWF to be made. At the same time, there has been an increasing demand for more robust and timely real-time forecast and alert information on SWF. In the UK, a real-time SWF Hazard Impact Model framework has been developed. The system uses 1-km gridded surface runoff estimates from a hydrological model to simulate the SWF hazard. These are linked to detailed inundation model outputs through an Impact Library to assess impacts on property, people, transport, and infrastructure for four severity levels. Here, a set of high-resolution (1.5 km and 12 km) RCM data has been used as input to a grid-based hydrological model over southern Britain to simulate Current (1996–2009) and Future (~2100s; RCP8.5) surface runoff. Counts of threshold-exceedance for surface runoff and precipitation (at 1-, 3- and 6-hr durations) are analysed. Results show that the percentage increases in surface runoff extremes, are less than those of precipitation extremes. The higher-resolution RCM simulates the largest percentage increases, which occur in winter, and the winter exceedance counts are greater than summer exceedance counts. For property impacts, the largest percentage increases are also in winter; however, it is the 12-km RCM output that leads to the largest percentage increase in impacts. The added-value of high-resolution climate model data for hydrological modelling is from capturing the more intense convective storms in surface runoff estimates.  相似文献   

Relationship between Age and Oxygen along Line W in the Northwest Atlantic Ocean     

Jordan L. Thomas  Darryn W. Waugh  Anand Gnanadesikan 《Ocean Science Journal》2020,55(2):203-217

The relationship between age and oxygen is one that is often assumed in oceanography to be relatively simple. Because oxygen utilization rates are difficul  相似文献   

Effects of forestry on summertime low flows and physical fish habitat in snowmelt‐dominant headwater catchments of the Pacific Northwest     

Stefan Gronsdahl  R. Dan Moore  Jordan Rosenfeld  Rich McCleary  Rita Winkler 《水文研究》2019,33(25):3152-3168

Periods of summertime low flows are often critical for fish. This study quantified the impacts of forest clear‐cutting on summertime low flows and fish habitat and how they evolved through time in two snowmelt‐dominant headwater catchments in the southern interior of British Columbia, Canada. A paired‐catchment analysis was applied to July–September water yield, the number of days each year with flow less than 10% of mean annual discharge, and daily streamflow for each calendar day. The postharvest time series were divided into treatment periods of approximately 6–10 years, which were analysed independently to evaluate how the effects of forestry changed through time. An instream flow assessment using a physical habitat simulation‐style approach was used to relate streamflow to the availability of physical habitat for resident rainbow trout. About two decades after the onset of logging and as the extent of logging increased to approximately 50% of the catchments, reductions in daily summertime low flows became more significant for the July–September yield (43%) and for the analysis by calendar day (11–68%). Reductions in summertime low flows were most pronounced in the catchment with the longest postharvest time series. On the basis of the temporal patterns of response, we hypothesize that the delayed reductions in late‐summer flow represent the combined effects of a persistent advance in snowmelt timing in combination with at least a partial recovery of transpiration and interception loss from the regenerating forests. These results indicate that asymptotic hydrological recovery as time progresses following logging is not suitable for understanding the impacts of forest harvesting on summertime low flows. Additionally, these reductions in streamflow corresponded to persistent decreases in modelled fish habitat availability that typically ranged from 20% to 50% during the summer low‐flow period in one of the catchments, suggesting that forest harvest may have substantial delayed effects on rearing salmonids in headwater streams.  相似文献   

Indicators of the Anthropocene: is there a case for conservation?     

Hannah Jordan  Colin Prosser 《Geology Today》2014,30(2):61-66

The Earth's atmosphere, biosphere and lithosphere are increasingly being modified by human activity. Given this anthropogenic influence on the natural environment, the case for recognizing an Anthropocene Epoch has recently been made and there is ongoing debate as to whether, and how, to formally characterize and define such an epoch. As a contribution to this debate, this article explores whether or not the landscapes, deposits, landforms and key marker horizons that may be used to characterize and define an Anthropocene Epoch could, and should, be identified and conserved in the same manner as other parts of the geological succession. Anthropogenic features pose a conservation challenge, however, as they often cross cut existing conservation frameworks which tend to focus on the natural, historic or cultural environment. Developing a coherent approach to the conservation of the indicators of an Anthropocene Epoch would, therefore, require an integrated system of describing, auditing and designating features for conservation. A major benefit of such an approach would be the opportunities for interdisciplinary collaboration between the wide range of researchers interested or involved in studying and conserving the record of anthropogenic activity.  相似文献   

Isoprene and Its Oxidation Products Methyl Vinyl Ketone, Methacrolein, and Isoprene Related Peroxides Measured Online over the Tropical Rain Forest of Surinam in March 1998   总被引：2，自引：0，他引：2  

C. Warneke  R. Holzinger  A. Hansel  A. Jordan  W. Lindinger  U. Pöschl  J. Williams  P. Hoor  H. Fischer  P. J. Crutzen  H. A. Scheeren  J. Lelieveld 《Journal of Atmospheric Chemistry》2001,38(2):167-185

Airborne measurements of volatile organic compounds (VOC) were performed overthe tropical rainforest in Surinam (0–12 km altitude,2°–7° N, 54°–58° W) using the proton transferreaction mass spectrometry (PTR-MS) technique, which allows online monitoringof compounds like isoprene, its oxidation products methyl vinyl ketone,methacrolein, tentatively identified hydroxy-isoprene-hydroperoxides, andseveral other organic compounds. Isoprene volume mixing ratios (VMR) variedfrom below the detection limit at the highest altitudes to about 7 nmol/molin the planetary boundary layer shortly before sunset. Correlations betweenisoprene and its product compounds were made for different times of day andaltitudes, with the isoprene-hydroperoxides showing the highest correlation.Model calculated mixing ratios of the isoprene oxidation products using adetailed hydrocarbon oxidation mechanism, as well as the intercomparisonmeasurement with air samples collected during the flights in canisters andlater analysed with a GC-FID, showed good agreement with the PTR-MSmeasurements, in particular at the higher mixing ratios.Low OH concentrations in the range of 1–3 × 10⁵molecules cm^-3 averaged over 24 hours were calculated due to lossof OH and HO₂ in the isoprene oxidation chain, thereby stronglyenhancing the lifetime of gases in the forest boundary layer.  相似文献   

Nutrient flux in a landscape: Effects of coastal land use and terrestrial community mosaic on nutrient transport to coastal waters   总被引：1，自引：0，他引：1  

David L. Correll  Thomas E. Jordan  Donald E. Weller 《Estuaries and Coasts》1992,15(4):431-442

Long-term interdisciplinary studies of the Rhode River estuary and its watershed in the mid-Atlantic coastal plain of North America have measured fluxes of nitrogen and phosphorus fractions through the hydrologically-linked ecosystems of this landscape. These ecosystems are upland forest, cropland, and pasture; streamside riparian forests; floodplain swamps; tidal brackish marshes and mudflats; and an estuarine embayment. Croplands discharged far more nitrogen per hectare in runoff than did forests and pastures. However, riparian deciduous hardwood forest bordering the cropland removed over 80 percent of the nitrate and total phosphorus in overland flows and about 85 percent of the nitrate in shallow groundwater drainage from cropland. Nevertheless, nutrient discharges from riparian forests downslope from croplands still exceeded discharges from pastures and other forests. The atomic ratio of nitrogen to phosphorus discharged from the watersheds into the estuary was about 9 for total nutrients and 6 for inorganic nutrient fractions. Such a low N:P ratio would promote nitrogen rather than phosphorus limitation of phytoplankton growth in the estuary. Estuarine tidal marshes trapped particulate nutrients and released dissolved nutrients. Subtidal mudflats in the upper estuary trapped particulate P, released dissolved phosphate, and consumed nitrate. This resulted in a decrease in the ratio of dissolved inorganic N:P in the estuary. However, the upper estuary was a major sink for total phosphorus due to sediment accretion in the subtidal area. Bulk precipitation accounted for 31 percent of the total nongaseous nitrogen influx to the landscape, while farming accounted for 69 percent. Forty-six percent of the total non-gaseous nitrogen influx was removed as farm products, 53 percent either accumulated in the watershed or was lost in gaseous forms, and 1 percent entered the Rhode River. Of the total phosphorus influx to the landscape, 7 percent was from bulk precipitation and 93 percent was from farming. Forty-five percent of the total phosphorus influx was removed as farm products, 48 percent accumulated in the watershed, and 7 percent entered the Rhode River. These nitrogen and phosphorus discharges into the Rhode River, although a small fraction of total loadings to the watershed, were large enough to cause seriously overenriched conditions in the upper estuary.  相似文献