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71.
72.
Rense Heath Kelsey Geoffrey I. Scott Dwayne E. Porter Thomas C. Siewicki Donald G. Edwards 《Estuaries and Coasts》2010,33(3):712-722
Currently, many states use precipitation information to regulate periodic closures of shellfish harvest areas based on a presumptive
relationship between rainfall and bacteria concentration. We evaluate this relationship in four South Carolina estuaries and
suggest new predictive models that integrate remote sensing precipitation data with additional environmental and climatic
data. Model comparisons using Akaike’s information criterion, tenfold cross-validation, and model r
2 values show substantial and consistent improvements using integrated precipitation, salinity, and water temperature data
as predictors. These models may be useful for shellfish area closure regulation support. The model development approaches
used here may also be useful in estimating bacteria concentration at beaches and can serve as the basis for developing near-real-time
estimates and forecast predictions of bacteria levels for closure decision-making tools. 相似文献
73.
The impact of the simulated large-scale atmospheric circulation on the regional climate is examined using the Weather Research and Forecasting (WRF) model as a regional climate model. The purpose is to understand the potential need for interior grid nudging for dynamical downscaling of global climate model (GCM) output for air quality applications under a changing climate. In this study we downscale the NCEP-Department of Energy Atmospheric Model Intercomparison Project (AMIP-II) Reanalysis using three continuous 20-year WRF simulations: one simulation without interior grid nudging and two using different interior grid nudging methods. The biases in 2-m temperature and precipitation for the simulation without interior grid nudging are unreasonably large with respect to the North American Regional Reanalysis (NARR) over the eastern half of the contiguous United States (CONUS) during the summer when air quality concerns are most relevant. This study examines how these differences arise from errors in predicting the large-scale atmospheric circulation. It is demonstrated that the Bermuda high, which strongly influences the regional climate for much of the eastern half of the CONUS during the summer, is poorly simulated without interior grid nudging. In particular, two summers when the Bermuda high was west (1993) and east (2003) of its climatological position are chosen to illustrate problems in the large-scale atmospheric circulation anomalies. For both summers, WRF without interior grid nudging fails to simulate the placement of the upper-level anticyclonic (1993) and cyclonic (2003) circulation anomalies. The displacement of the large-scale circulation impacts the lower atmosphere moisture transport and precipitable water, affecting the convective environment and precipitation. Using interior grid nudging improves the large-scale circulation aloft and moisture transport/precipitable water anomalies, thereby improving the simulated 2-m temperature and precipitation. The results demonstrate that constraining the RCM to the large-scale features in the driving fields improves the overall accuracy of the simulated regional climate, and suggest that in the absence of such a constraint, the RCM will likely misrepresent important large-scale shifts in the atmospheric circulation under a future climate. 相似文献
74.
Jared M. Maruskin Julie Bellerose Macken Wong Lara Mitchell David Richardson Douglas Mathews Tri Nguyen Usha Ganeshalingam Gina Ma 《Celestial Mechanics and Dynamical Astronomy》2013,115(3):281-298
In this paper, we discuss dust motion and investigate possible mass transfer of charged particles in a binary asteroid system, in which the asteroids are electrically charged due to solar radiation. The surface potential of the asteroids is assumed to be a piecewise function, with positive potential on the sunlit half and negative potential on the shadow half. We derive the nonautonomous equations of motion for charged particles and an analytic representation for their lofting conditions. Particle trajectories and temporary relative equilibria are examined in relation to their moving forbidden regions, a concept we define and discuss. Finally, we use a Monte Carlo simulation for a case study on mass transfer and loss rates between the asteroids. 相似文献
75.
Andrew N. O’Brien Miroslav D. Filipović Evan J. Crawford Nicholas F. H. Tothill Jordan D. Collier Ain Y. De Horta Graeme F. Wong Danica Drašković Jeff L. Payne Thomas G. Pannuti Jared P. Napier Stephen A. Griffith Wayne D. Staggs Srdjan Kotuš 《Astrophysics and Space Science》2013,347(1):159-168
A series of new radio-continuum (λ=20, 13, 6 and 3 cm) mosaic images focused on the NGC 55 galactic system were produced using archived observational data from the Australia Telescope Compact Array. These new images are both very sensitive (down to rms=33 μJy) and feature high angular resolution (down to <4″). Using these newly created images, 66 previously unidentified discrete sources are identified. Of these sources, 46 were classified as background sources, 11 as H?ii regions and 6 as supernova remnant candidates. This relatively low number of SNR candidates detected coupled with the low number of large H?ii regions is consistent with the estimated low star formation rate of the galaxy at 0.06 M ⊙?year?1. Our spectral index map shows that the core of galaxy appears to have a shallow spectral index between α=?0.2 and ?0.4. This indicates that the core of the galaxy is a region of high thermal radiation output. 相似文献
76.
Airborne LiDAR (Light Detection and Ranging) provides opportunities to generate high-quality digital elevation models (DEMs) even in wetland environments. Our project, performed over the Okefenokee Swamp in Georgia during the spring of 2010, shows that several, distinctive factors must be considered to ensure successful wetland LiDAR projects. Some of the challenges include selecting optimal flight times in accordance with weather variability and water levels, having effective and quality control protocols, applying and developing filtering and interpolation algorithms, breaklines in swamps and accounting for data striping and noise. While some of these issues are faced in any airborne LiDAR acquisition, many of these require special consideration in a low-slope wetland environment with water saturated soils, widespread shallow water, and sediments and extensive vegetation. An examination of these issues and how they were handled will help in ensuring the success of future LiDAR acquisitions and, in particular, will advance knowledge of producing quality DEMs in wetland environments. 相似文献
77.
78.
Michael J. Widener Neal C. Crago Jared Aldstadt 《International journal of geographical information science》2013,27(9):1707-1723
As geospatial researchers' access to high-performance computing clusters continues to increase alongside the availability of high-resolution spatial data, it is imperative that techniques are devised to exploit these clusters' ability to quickly process and analyze large amounts of information. This research concentrates on the parallel computation of A Multidirectional Optimal Ecotope-Based Algorithm (AMOEBA). AMOEBA is used to derive spatial weight matrices for spatial autoregressive models and as a method for identifying irregularly shaped spatial clusters. While improvements have been made to the original ‘exhaustive’ algorithm, the resulting ‘constructive’ algorithm can still take a significant amount of time to complete with large datasets. This article outlines a parallel implementation of AMOEBA (the P-AMOEBA) written in Java utilizing the message passing library MPJ Express. In order to account for differing types of spatial grid data, two decomposition methods are developed and tested. The benefits of using the new parallel algorithm are demonstrated on an example dataset. Results show that different decompositions of spatial data affect the computational load balance across multiple processors and that the parallel version of AMOEBA achieves substantially faster runtimes than those reported in related publications. 相似文献
79.
R. A. Heath 《新西兰海洋与淡水研究杂志》2013,47(1-2):148-177
The depths of reference surfaces for determining geostrophic currents in the Tasman and South‐western Pacific Basins and in the Hikurangi Trench are examined using Defant's method for the determination of the “layer of no motion”. These depths are then checked by comparing the directions of the resulting currents with the direction of flow deduced from hydrological evidence and, in the Hikurangi Trench, from an examination of the correlation between surface currents and the mass field. On this basis the reference surface was found to be at 2300 dbars in the Tasman Basin, 2000–2500 dbars in the Southwestern Pacific Basin and >1500 dbars in the head of the Hikurangi Trench. 相似文献
80.
R. A. Heath 《新西兰海洋与淡水研究杂志》2013,47(4):725-735
The frequent occurrence of swell in the entrance to Wellington, Lyttelton, and Akaroa Harbours, coupled with the small littoral drift of sediment on adjacent rocky coastlines, appears to promote development of larger entrances than those associated with tidal control in unconsolidated sediment. In contrast to these three harbours, tidally controlled entrances have either bars or banks that protect them from severe swell and act as bypasses to the littoral drift of sediment. The entrance to Paterson Inlet lies on a coast with little sediment transport and further protection from sediment influx is provided by islands located at its entrance. 相似文献