EISCAT measurements of the solar wind     

A. R. Breen  W. A. Coles  R. R. Grail  M. T. Klinglesmith  J. Markkanen  P. J. Moran  B. Tegid  P. J. S. Williams 《Annales Geophysicae》1997,14(12):1235-1245

EISCAT observations of interplanetary scintillation have been used to measure the velocity of the solar wind at distances between 15 and 130R (solar radii) from the Sun. The results show that the solar wind consists of two distinct components, a fast stream with a velocity of 800 km s^–1 and a slow stream at 400 kms^–1. The fast stream appears to reach its final velocity much closer to the Sun than expected. The results presented here suggest that this is also true for the slow solar wind. Away from interaction regions the flow vector of the solar wind is purely radial to the Sun. Observations have been made of fast wind/slow wind interactions which show enhanced levels of scintillation in compression regions.  相似文献   

Exploring a New Regionalism-Based Approach to Managing Drinking Water Systems in Rural Regions     

Sarah-Patricia Breen 《社会与自然资源》2018,31(6):698-716

Rural regions face many challenges when managing drinking water systems. Current management approaches lack the ability to deal with the complexity that surrounds these infrastructure systems and the critical service they provide, in particular, the links between these systems and the economy and environment. This research explores the potential for an alternative approach. The proposed new regionalism-based approach recognizes and accounts for the myriad of influencing factors, using different mechanisms to support and encourage drinking water systems in fulfilling their potential role in supporting regional resilience. Using a case study approach, data collected from semistructured interviews indicate that elements of the proposed approach are already in use within the Kootenay Development Region of British Columbia, Canada. Results indicate that while the need for an alternate management approach is recognized, and elements of the proposed approach are increasingly applied, substantive barriers remain, such as the existing institutional and jurisdictional structure.  相似文献   

Developing Governance Principles for Public Natural Resources     

Darragh Hare  Ann B. Forstchen  Christian A. Smith  Daniel J. Decker 《社会与自然资源》2018,31(3):382-388

Wildlife governance principles (WGPs) identify desirable governance characteristics for wildlife conservation in the United States (US). The types of institutional, ecological, and socio-cultural challenges that WGPs are designed to address also affect governance of public natural resources other than wildlife and in places other than the US. This raises the possibility that a similar set of governance principles might help natural resource professionals working in other resource contexts address the particular challenges they face. We describe the process by which we developed WGPs and offer seven practically oriented questions to help natural resource professionals ascertain whether a similar set of principles could improve governance in their context. In some contexts, minor modification of WGPs might be appropriate; in others, the process by which we developed WGPs could serve as a blueprint for formulating appropriate principles.  相似文献   

Eye on the Ionosphere     

Jo Ann Joselyn 《GPS Solutions》1999,3(1):79-81

  相似文献   

Shallow Circulations: Relevance and Strategies for Satellite Observation     

Gilles Bellon  Oliver Reitebuch  Ann Kristin Naumann 《Surveys in Geophysics》2017,38(6):1509-1528

Shallow circulations are central to many tropical cloud systems. We investigate the potential of existing and upcoming data to document these circulations. Different methods to observe or constrain atmospheric circulations rely on satellite-borne instruments. Direct observations of the wind are currently possible at the ocean surface or using tracer patterns. Satellite-borne wind lidar will soon be available, with a much better coverage and accuracy. Meanwhile, circulations can be constrained using satellite observations of atmospheric diabatic heating. We evaluate the commonalities and discrepancies of these estimates together with reanalysis in systems that include shallow circulations. It appears that existing datasets are in qualitative agreement, but that they still differ too much to provide robust evaluation criteria for general circulation models. This state of affairs highlights the potential of satellite-borne wind lidar and of further work on current satellite retrievals.  相似文献   

Thresholds for post-wildfire debris flows: Insights from the Pinal Fire,Arizona, USA     

Carissa A. Raymond  Luke A. McGuire  Ann M. Youberg  Dennis M. Staley  Jason W. Kean 《地球表面变化过程与地形》2020,45(6):1349-1360

Wildfire significantly alters the hydrologic properties of a burned area, leading to increases in overland flow, erosion, and the potential for runoff-generated debris flows. The initiation of debris flows in recently burned areas is well characterized by rainfall intensity-duration (ID) thresholds. However, there is currently a paucity of data quantifying the rainfall intensities required to trigger post-wildfire debris flows, which limits our understanding of how and why rainfall ID thresholds vary in different climatic and geologic settings. In this study, we monitored debris-flow activity following the Pinal Fire in central Arizona, which differs from both a climatic and hydrogeomorphic perspective from other regions in the western United States where ID thresholds for post-wildfire debris flows are well established, namely the Transverse Ranges of southern California. Since the peak rainfall intensity within a rainstorm may exceed the rainfall intensity required to trigger a debris flow, the development of robust rainfall ID thresholds requires knowledge of the timing of debris flows within rainstorms. Existing post-wildfire debris-flow studies in Arizona only constrain the peak rainfall intensity within debris-flow-producing storms, which may far exceed the intensity that actually triggered the observed debris flow. In this study, we used pressure transducers within five burned drainage basins to constrain the timing of debris flows within rainstorms. Rainfall ID thresholds derived here from triggering rainfall intensities are, on average, 22 mm h⁻¹ lower than ID thresholds derived under the assumption that the triggering intensity is equal to the maximum rainfall intensity recorded during a rainstorm. We then use a hydrologic model to demonstrate that the magnitude of the 15-min rainfall ID threshold at the Pinal Fire site is associated with the rainfall intensity required to exceed a recently proposed dimensionless discharge threshold for debris-flow initiation. Model results further suggest that previously observed differences in regional ID thresholds between Arizona and the San Gabriel Mountains of southern California may be attributed, in large part, to differences in the hydraulic properties of burned soils. © 2019 John Wiley & Sons, Ltd.  相似文献   

沉水植物氧化塘对污水厂尾水深度净化效果与机制的小试研究   总被引：4，自引：0，他引：4  

赵安娜  冯慕华  郭萧  柯凡  潘继征  李文朝 《湖泊科学》2010,22(4):538-544

室外采用玻璃缸装置研究了抚仙湖常见的9种沉水植物氧化塘对澄江县污水厂尾水营养盐的去除效果及机制.结果表明:氧化塘中沉水植物的光合作用导致水体较高的DO和pH值,从而提高氧化塘总氮和总磷的去除率,但沉水植物叶片的腐烂分解则提高了水体氮磷的含量.沉水植物氧化塘对总氮和总磷的去除率分别介于19.44%-64.71%和28.13%-98.33%.沉水植物的直接吸收对总氮和总磷量去除的贡献比较低,占氧化塘总氮和总磷量的0.26%-1.54%和0.47%-1.77%.沉水植物氧化塘内DO、pH变化,促进了氮的降解及氧化还原分解,使其对氮的去除占氧化塘总氮量的30.71%-65.25%,而磷的去除则主要通过化学沉淀及基质吸附,占氧化塘总磷量的73.37%-93.34%.最终,选出蓖齿眼子菜、苦草、黑藻、金鱼藻和光叶眼子菜对氧化塘中氮磷具有较高的去除率.  相似文献   

Reconstructing a prehistoric topography using legacy point data in a depositional environment          下载免费PDF全文

Julian A. M. Vermeer  Peter A. Finke  Ann Zwertvaegher  Vanessa Gelorini  Machteld Bats  Marc Antrop  Jacques Verniers  Philippe Crombé 《地球表面变化过程与地形》2014,39(5):632-645

  相似文献   

Spatial and temporal influences of in-stream factors on the chemistry and epilithic biomasses of upland stream metal deposits     

Katrina Ann Macintosh  David Griffiths 《Aquatic Sciences - Research Across Boundaries》2014,76(3):331-338

The density and composition of stream bed metal deposits are affected by physical, chemical and biological processes. In this paper we investigate the importance of these processes and their relation to algal and non-photosynthetic detrital (NPD) biomass in a set of upland streams in Northern Ireland. Deposit density and Fe, Mn, Al and P concentrations varied with stream pH across sites but not seasonally. No effects of stream bed erosion or photoreduction were detected on deposit densities. Seasonal variation in stream water metal concentrations was correlated with rainfall. NPD biomass was a significant predictor of both spatial and seasonal variation in deposit concentrations. There were strong, non-linear, relations between NPD biomass and deposit metal concentrations, with Fe and Mn becoming relatively more important and algal biomass declining above threshold deposit/NPD densities. The results suggest that NPD biomass influences deposit density and reduces the biomass of photosynthetic autotrophs above a threshold deposit density.  相似文献   

An investigation of the SO₂ content of the venusian mesosphere using SPICAV-UV in nadir mode     

Emmanuel Marcq  Denis Belyaev  Anna Fedorova  Ann Carine Vandaele 《Icarus》2011,211(1):58-69

Using the SPICAV-UV spectrometer aboard Venus Express in nadir mode, we were able to derive spectral radiance factors in the middle atmosphere of Venus in the 170-320 nm range at a spectral resolution of R ? 200 during 2006 and 2007 in the northern hemisphere. By comparison with a radiative transfer model of the upper atmosphere of Venus, we could derive column abundance above the visible cloud top for SO₂ using its spectral absorption bands near 280 and 220 nm. SO₂ column densities show large temporal and spatial variations on a horizontal scale of a few hundred kilometers. Typical SO₂ column densities at low latitudes (up to 50°N) were found between 5 and 50 μm-atm, whereas in the northern polar region SO₂ content was usually below 5 μm-atm. The observed latitudinal variations follow closely the cloud top altitude derived by SPICAV-IR and are thought to be of dynamical origin. Also, a sudden increase of SO₂ column density in the whole northern hemisphere has been observed in early 2007, possibly related to a convective episode advecting some deep SO₂ into the upper atmosphere.  相似文献