Comparison of three types of laser optical disdrometers under natural rainfall conditions     

Lisbeth Lolk Johannsen  Nives Zambon  Peter Strauss  Tomas Dostal  Martin Neumann  David Zumr 《水文科学杂志》2020,65(4):524-535

ABSTRACT

Optical disdrometers can be used to estimate rainfall erosivity; however, the relative accuracy of different disdrometers is unclear. This study compared three types of optical laser-based disdrometers to quantify differences in measured rainfall characteristics and to develop correction factors for kinetic energy (KE). Two identical PWS100 (Campbell Scientific), one Laser Precipitation Monitor (Thies Clima) and a first-generation Parsivel (OTT) were collocated with a weighing rain gauge (OTT Pluvio²) at a site in Austria. All disdrometers underestimated total rainfall compared to the rain gauge with relative biases from 2% to 29%. Differences in drop size distribution and velocity resulted in different KE estimates. By applying a linear regression to the KE–intensity relationship of each disdrometer, a correction factor for KE between the disdrometers was developed. This factor ranged from 1.15 to 1.36 and allowed comparison of KE between different disdrometer types despite differences in measured drop size and velocity.  相似文献   

Reaction of OH Radicals with Acetone: Determination of the Branching Ratio for the Abstraction Pathway at 298 K and 1 Torr     

Estelle Turpin  Christa Fittschen  Alexandre Tomas  Pascal Devolder 《Journal of Atmospheric Chemistry》2003,46(1):1-13

We have determined the 2-oxo-propyl CH₃C(O)CH₂ (sometimes called 1-methylvinoxy or acetonyl) radical yield for the reaction of acetone with OH radical relative to the 2-oxo-propyl yields for the reactions of F- and Cl atoms with acetone using the Discharge Flow technique. The 2-oxo-propyl radical has been monitored by Laser Induced Fluorescence LIF at short reaction times in the systems: OH + acetone (R1), F + acetone (R2), and Cl + acetone (R3). From these measurements we have deduced the branching ratio for the 2-oxo-propyl radical formation in the title reaction to be in the range 0.8 R 1.  相似文献   

The geology and Re–Os geochronology of the Palaeoproterozoic Vaikijaur Cu–Au–(Mo) porphyry-style deposit in the Jokkmokk granitoid, northern Sweden     

Christina Lundmark  Holly Stein  Pär Weihed 《Mineralium Deposita》2005,40(4):396-408

The Vaikijaur Cu–Au–(Mo) deposit is located in the ca. 1.88 Ga calc-alkaline Jokkmokk granitoid near the Archaean–Proterozoic palaeoboundary within the Fennoscandian shield of northern Sweden. The Skellefte VMS district lies immediately to the south and the northern Norrbotten Fe-oxide–Cu–Au deposits to the north. The Vaikijaur deposit occupies an area of 2×3 km within the Jokkmokk granitoid and includes stockwork quartz-sulphide veinlets and disseminated chalcopyrite, pyrite, gold, molybdenite, magnetite, and pyrrhotite. Porphyritic mafic dykes were emplaced along fractures in a ring dyke pattern. The Jokkmokk granitoid, dykes, and the mineralized area are foliated, indicating that mineralization predated the main regional deformation. The mineralized area is characterized by strong potassic alteration. Phyllic and propylitic alteration zones are also present. A pyrite-rich inner core is surrounded by a concentric zone with pyrite, chalcopyrite, and gold. Molybdenite is distributed irregularly throughout the chalcopyrite zone. Geophysical data indicate a strongly conductive central zone in the mineralized area bordered by conductive and high magnetic zones. Five high precision Re–Os age determinations for three molybdenite occurrences from outcrop and drill core samples constrain the age of porphyry-style Cu–Au–(Mo) mineralization to between 1889±10 and 1868±6 Ma. A younger molybdenite is associated with a much later metamorphic event at about 1750 Ma. These data suggest that primary porphyry-style mineralization was associated with calc-alkaline magmatism within the Archaean–Proterozoic boundary zone at ca. 1.89–1.87 Ga.  相似文献   

Economy, Politics and Institutions: From Adaptation to Adaptive Management in Climate Change     

Alexander Thompson  Paul Robbins  Brent Sohngen  Joseph Arvai  Tomas Koontz 《Climatic change》2006,78(1):1-5

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Egg production of the copepodAcartia tonsa in Florida Bay during summer. 1. The roles of food environment and diet     

G. S. Kleppel  Carol A. Burkart  Carmelo Tomas 《Estuaries and Coasts》1998,21(2):328-339

The diet and egg production rate ofAcartia tonsa were measured during the thermally stable period between June and October 1995 at four locations in inner and outer Florida Bay. We sought to characterize the role ofA. tonsa in the bay’s pelagic food web, which has been changing since 1987, when the dominant submerged vegetation began shifting from benthic seagrasses to planktonic algae. At Rankin Lake, a shallow basin on the north side of the inner bay, where extensive seagrass mortality and persistent cyanobacteria blooms have occurred, microplankton biomass was relatively high and dominated by heterotrophic protists and dinoflagellates. Nanoplankton at Rankin, Lake, while numerically abundant, usually contributed only a small portion of the biomass. The ingestion rate ofA. tonsa in Florida Bay varied independently of food concentration (i.e., total microplankton biomass), but rates were higher (mean±SD =3.88 ± 0.73 μg C copepod^?1 d^?1) on the north side of the bay than on the south side (0.78 ±0.11 μg C copepod^?1 d^?1). Microzooplankton and dinoflagellates were important dietary constituents, especially in the vicinity of Rankin Lake. Egg production in this region (mean ± SD = 14.2 ± 7.7 eggs female^?1 d^?1) was considerably high than the baywide mean (5.8±0.81 eggs female^?1d^?1), and principal components analysis revealed associations between egg production and both dietary microzooplankton and dinoflagellate biomass. However, although grazing rates were relatively high in the inner bay,A. tonsa removed only 1–6% of the primary production from the water column during the summer and its egg production rates were low relative to typical rates for the species.  相似文献   

Benefits from increased cooperation and energy trade under CO₂ commitments—The Nordic case     

Thomas Unger  Tomas Ekvall 《Climate Policy》2003,3(3):279-294

In this paper, benefits from increasing cross-border cooperation under future CO₂ commitments in the Nordic countries are examined and evaluated. Four cooperative strategies are analyzed and valued separately: cross-border electricity trade, cross-border emission-permit trade, the introduction of a trans-Nordic natural gas transmission grid, and, finally, utilization of all these three strategies simultaneously. The valuation is done under varying CO₂ commitments and under three different scenarios for future energy demand and technological development. In conducting this analysis, the energy-systems model-generator MARKAL (MARKet ALlocation) was used to model the Nordic energy system. It is shown that all cooperative strategies do lower the abatement costs considerably, especially if the strategy including full cooperation is utilized. In this case, additional costs from meeting CO₂ targets may be at least halved for commitments less than 10% reduction until 2050 based on emissions in 1995. No significant difference between low and high CO₂ commitments could be observed in the size of the benefits from cooperation, expressed in billions (10⁹) of Swedish crowns. Benefits from cooperation are generally larger for scenarios including relatively higher future energy demand.  相似文献   

Numerical studies on saltwater intrusion in a coastal aquifer in northwestern Germany   总被引：1，自引：2，他引：1  

Tomas Feseker 《Hydrogeology Journal》2007,15(2):267-279

Saltwater intrusion in coastal aquifers depends on the distribution of hydraulic properties, on the climate, and on human interference such as land reclamation. In order to analyze the key processes that control saltwater intrusion, a hypothetical steady-state salt distribution in a representative cross-section perpendicular to the coastline was calculated using a two-dimensional density-dependent solute transport model. The effects of changes in groundwater recharge, lowering of drainage levels, and a rising sea level on the shape and position of the freshwater/saltwater interface were modeled in separate simulations. The results show that the exchange of groundwater and surface water in the marsh areas is one of the key processes influencing saltwater intrusion. A rising sea level causes rapid progression of saltwater intrusion, whereas the drainage network compensates changes in groundwater recharge. The time scale of changes resulting from altered boundary conditions is on the order of decades and centuries, suggesting that the present-day salt distribution does not reflect a steady-state of equilibrium.  相似文献   

Towards a cross-domain interoperable framework for natural hazards and disaster risk reduction information     

Robert Tomas  Matthew Harrison  José I. Barredo  Florian Thomas  Miguel Llorente Isidro  Manuela Pfeiffer  Otakar Čerba 《Natural Hazards》2015,78(3):1545-1563

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Atmospheric impacts of Arctic sea-ice loss, 1979–2009: separating forced change from atmospheric internal variability     

James A. Screen  Clara Deser  Ian Simmonds  Robert Tomas 《Climate Dynamics》2014,43(1-2):333-344

The ongoing loss of Arctic sea-ice cover has implications for the wider climate system. The detection and importance of the atmospheric impacts of sea-ice loss depends, in part, on the relative magnitudes of the sea-ice forced change compared to natural atmospheric internal variability (AIV). This study analyses large ensembles of two independent atmospheric general circulation models in order to separate the forced response to historical Arctic sea-ice loss (1979–2009) from AIV, and to quantify signal-to-noise ratios. We also present results from a simulation with the sea-ice forcing roughly doubled in magnitude. In proximity to regions of sea-ice loss, we identify statistically significant near-surface atmospheric warming and precipitation increases, in autumn and winter in both models. In winter, both models exhibit a significant lowering of sea level pressure and geopotential height over the Arctic. All of these responses are broadly similar, but strengthened and/or more geographically extensive, when the sea-ice forcing is doubled in magnitude. Signal-to-noise ratios differ considerably between variables and locations. The temperature and precipitation responses are significantly easier to detect (higher signal-to-noise ratio) than the sea level pressure or geopotential height responses. Equally, the local response (i.e., in the vicinity of sea-ice loss) is easier to detect than the mid-latitude or upper-level responses. Based on our estimates of signal-to-noise, we conjecture that the local near-surface temperature and precipitation responses to past Arctic sea-ice loss exceed AIV and are detectable in observed records, but that the potential atmospheric circulation, upper-level and remote responses may be partially or wholly masked by AIV.  相似文献   

Weathering fluxes of arsenic from a small catchment in Slovak Republic   总被引：1，自引：1，他引：0  

Ahmed Melegy  Igor Slaninka  Tomas Pa?es  Stanislav Rapant 《Environmental Earth Sciences》2011,64(2):549-555

Inputs of As to a small catchment due to chemical weathering of bedrock, mechanical weathering of bedrock, and atmospheric precipitation were 71.53, 23.98 and 0.02 g ha⁻¹ year⁻¹, respectively. The output fluxes of As due to mechanical erosion of soil, biological uptake, stream discharge, and groundwater flow were 6.32, 4.77, 0.37 and 0.02 g ha⁻¹ year⁻¹, respectively. The results indicate that arsenic accumulates in soil and regolith with a very high rate. This is attributed to the selective weathering and erosion with respect to arsenic and fixation of arsenic in the secondary solids produced by weathering. The output fluxes of As in stream and groundwater in Vydrica catchment in Slovak Republic (0.39 g ha⁻¹ year⁻¹) based on muscovite–biotite granites and granodiorites were much lower compared to catchments in a gold district in the Czech Republic. These results may be ascribed to the low levels of arsenic pollution measured in Vydrica catchment. The arsenic fluxes were estimated by calculation of mechanical and chemical weathering rates of the bedrocks in Vydrica catchment from mass balance data on sodium and silica. The justification of the steady state of Na and Si is that neither of the elements is appreciably accumulated in plants and in exchangeable pool of ions in soil.  相似文献