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941.
Michael R. Line E.J. Mierkiewicz R.J. Oliversen J.K. Wilson L.M. Haffner F.L. Roesler 《Icarus》2012,219(2):609-617
The lunar sodium tail extends long distances due to radiation pressure on sodium atoms in the lunar exosphere. Our earlier observations measured the average radial velocity of sodium atoms moving down the lunar tail beyond Earth (i.e., near the anti-lunar point) to be ~12.5 km/s. Here we use the Wisconsin H-alpha Mapper to obtain the first kinematically resolved maps of the intensity and velocity distribution of this emission over a 15° × 15 ° region on the sky near the anti-lunar point. We present both spatially and spectrally resolved observations obtained over four nights bracketing new Moon in October 2007. The spatial distribution of the sodium atoms is elongated along the ecliptic with the location of the peak intensity drifting 3° east along the ecliptic per night. Preliminary modeling results suggest the spatial and velocity distributions in the sodium exotail are sensitive to the near surface lunar sodium velocity distribution. Future observations of this sort along with detailed modeling offer new opportunities to describe the time history of lunar surface sputtering over several days. 相似文献
942.
Recent retrievals of zonal thermal winds obtained in a cyclostrophic regime on Venus are generally consistent with cloud tracking measurements at mid-latitudes, but become unphysical in polar regions where the values obtained above the clouds are often less than or close to zero. Using a global atmospheric model, we show that the main source of errors that appear in the polar regions when retrieving the zonal thermal winds is most likely due to uncertainties in the zonal wind intensity in the choice of the lower boundary condition.Here we suggest a new and robust method to better estimate the lower boundary condition for high latitudes, thereby improving the retrieved zonal thermal winds throughout the high latitudes middle atmosphere. This new method is applied to temperature fields derived from Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) data on board the Venus Express spacecraft. We obtain a zonal thermal wind field that is in better agreement with other, more direct methods based on either retrieving the zonal winds from cloud tracking or from direct measurements of the meridional slope of pressure surfaces. 相似文献
943.
Richard C. Ghail Colin Wilson Marina Galand David Hall Chris Cochrane Philippa Mason Joern Helbert Franck MontMessin Sanjay Limaye Manish Patel Neil Bowles Daphne Stam Jan-Erik Wahlund Fabio Rocca David Waltham Tamsin A. Mather Juliet Biggs Matthew Genge Philippe Paillou Karl Mitchell Lionel Wilson Upendra N. Singh 《Experimental Astronomy》2012,33(2-3):337-363
944.
945.
Edwin Sumargo Hilary McMillan Rachel Weihs Carolyn J. Ellis Anna M. Wilson F. Martin Ralph 《水文研究》2021,35(1):e13998
Soil moisture is a key modifier of runoff generation from rainfall excess, including during extreme precipitation events associated with Atmospheric Rivers (ARs). This paper presents a new, publicly available dataset from a soil moisture monitoring network in Northern California's Russian River Basin, designed to assess soil moisture controls on runoff generation under AR conditions. The observations consist of 2-min volumetric soil moisture at 19 sites and 6 depths (5, 10, 15, 20, 50, and 100 cm), starting in summer 2017. The goals of this monitoring network are to aid the development of research applications and situational awareness tools for Forecast-Informed Reservoir Operations at Lake Mendocino. We present short analyses of these data to demonstrate their capability to characterize soil moisture responses to precipitation across sites and depths, including time series analysis, correlation analysis, and identification of soil saturation thresholds that induce runoff. Our results show strong inter-site Pearson's correlations (>0.8) at the seasonal timescale. Correlations are strong (>0.8) during events with high antecedent soil moisture and during drydown periods, and weak (<0.5) otherwise. High event runoff ratios are observed when antecedent soil moisture thresholds are exceeded, and when antecedent runoff is high. Although local heterogeneity in soil moisture can limit the utility of point source data in some hydrologic model applications, our analyses indicate three ways in which soil moisture data are valuable for model design: (1) sensors installed at 6 depths per location enable us to identify the soil depth below which evapotranspiration and saturation dynamics change, and therefore choose model soil layer depths, (2) time series analysis indicates the role of soil moisture processes in controlling runoff ratio during precipitation, which hydrologic models should replicate, and (3) spatial correlation analysis of the soil moisture fluctuations helps identify when and where distributed hydrologic modelling may be beneficial. 相似文献
946.
Melanie Shaw Miles J. Furnas Katharina Fabricius David Haynes Steve Carter Jochen F. Mueller 《Marine pollution bulletin》2010,60(1):113-122
Pesticide runoff from agriculture poses a threat to water quality in the world heritage listed Great Barrier Reef (GBR) and sensitive monitoring tools are needed to detect these pollutants. This study investigated the utility of passive samplers in this role through deployment during a wet and dry season at river mouths, two near-shore regions and an offshore region. The nearshore marine environment was shown to be contaminated with pesticides in both the dry and wet seasons (average water concentrations of 1.3-3.8 ng L−1 and 2.2-6.4 ng L−1, respectively), while no pesticides were detected further offshore. Continuous monitoring of two rivers over 13 months showed waters flowing to the GBR were contaminated with herbicides (diuron, atrazine, hexazinone) year round, with highest average concentrations present during summer (350 ng L−1). The use of passive samplers has enabled identification of insecticides in GBR waters which have not been reported in the literature previously. 相似文献
947.
Bruce F. Houghton Rebecca J. Carey Katharine V. Cashman Colin J.N. Wilson Barbara J. Hobden Julia E. Hammer 《Journal of Volcanology and Geothermal Research》2010
The 22 km3 (DRE) 1.8 ka Taupo eruption ejected chemically uniform rhyolite in a wide range of eruptive styles and intensities. The 7 eruptive units include the ‘type examples’ of phreatoplinian (units 3 and 4) and ultraplinian fall (unit 5) deposits, and low-aspect-ratio ignimbrite (unit 6). Contrasts in bulk vesicularity, vesicle (and microlite) number densities and the size distributions of bubbles (and crystals) in the Taupo ejecta can be linked to the influence of shallow conduit processes on volatile exsolution and gas escape, before and during eruption, rather than changes in pre-eruptive chemistry. Existing work has modeled the individual phases of this complex eruption but not fully explained the abrupt shifts in style/intensity that occur between phases. We link these rapid transitions to changes in vent position, which permitted contrasts in storage, conduit geometry, and magma ascent history. 相似文献
948.
949.
Kuei-Yuan Chan Panos Y. Papalambros Steve J. Skerlos 《Stochastic Environmental Research and Risk Assessment (SERRA)》2010,24(1):101-116
We develop methodologies to enable applications of reliability-based design optimization (RBDO) to environmental policy setting
problems. RBDO considers uncertainty as random variables and parameters in an optimization framework with probabilistic constraints.
Three challenges in environmental decision-making problems not addressed by current RBDO methods are efficient methods in
handling: (1) non-normally distributed random parameters, (2) discrete random parameters, and (3) joint reliability constraints
(e.g., meeting constraints simultaneously with a single reliability). We propose a modified sequential quadratic programming
algorithm to address these challenges. An active set strategy is combined with a reliability contour formulation to solve
problems with multiple non-normal random parameters. The reliability contour formulation can also handle discrete random parameters
by converting them to equivalent continuous ones. Joint reliability constraints are estimated by their theoretical upper bounds
using reliability indexes and angles of normal vectors between active constraints. To demonstrate the methods, we consider
a simplified airshed example where CO and NOx standards are violated and are brought into compliance by reducing the speed
limits of two nearby highways. This analytical example is based on the CALINE4 model. Results show the potential of this approach
to handle complex large-scale environmental regulation problems. 相似文献
950.
An IRSL age of 17.0 ± 2.2 ka (and a “mean age” of ca. 19 ka) reported by Grapes et al. [Grapes, R., Rieser, U., Wang, N. Optical luminescence dating of a loess section containing a critical tephra marker horizon, SW North Island of New Zealand. Quaternary Geochronology 5(2-3), 164–169.] for the Kawakawa/Oruanui tephra, and other ages associated with a loess section in New Zealand are untenable: age data presented are inconsistent, no formal statistical treatments or error determinations were undertaken in age analysis, and the ages proposed are seriously at odds with multiple radiocarbon age determinations on tephra sequences bracketing the Kawakawa/Oruanui tephra and with palaeoenvironmental evidence elsewhere for the time period concerned. We suggest that the bulk polymineral IRSL ages on the tephra and encapsulating loess deposits were underestimated in part because of contamination of the loess by the integration of younger materials during slow deposition and continuous modification by upbuilding pedogenesis. Single-grain luminescence assays may reveal such contamination. A 14C-based age of ca. 27 ± 1 ka cal BP (2σ), reported in 2008, currently remains the best estimate for the age of eruption of the Kawakawa/Oruanui tephra. 相似文献