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Synoptic weather typing and regression-based downscaling approaches have become popular in evaluating the impacts of climate change on a variety of environmental problems, particularly those involving extreme impacts. One of the reasons for the popularity of these approaches is their ability to categorize a complex set of meteorological variables into a coherent index, facilitating the projection of changes in frequency and intensity of future daily extreme weather events and/or their impacts. This paper illustrated the capability of the synoptic weather typing and regression methods to analyze climatic change impacts on a number of extreme weather events and environmental problems for south–central Canada, such as freezing rain, heavy rainfall, high-/low-streamflow events, air pollution, and human health. These statistical approaches are helpful in analyzing extreme events and projecting their impacts into the future through three major steps or analysis procedures: (1) historical simulation modeling to identify extreme weather events or their impacts, (2) statistical downscaling to provide station-scale future hourly/daily climate data, and (3) projecting changes in the frequency and intensity of future extreme weather events and their impacts under a changing climate. To realize these steps, it is first necessary to conceptualize the modeling of the meteorology, hydrology and impacts model variables of significance and to apply a number of linear/nonlinear regression techniques. Because the climate/weather validation process is critical, a formal model result verification process has been built into each of these three steps. With carefully chosen physically consistent and relevant variables, the results of the verification, based on historical observations of the outcome variables simulated by the models, show a very good agreement in all applications and extremes tested to date. Overall, the modeled results from climate change studies indicate that the frequency and intensity of future extreme weather events and their impacts are generally projected to significantly increase late this century over south–central Canada under a changing climate. The implications of these increases need be taken into consideration and integrated into policies and planning for adaptation strategies, including measures to incorporate climate change into engineering infrastructure design standards and disaster risk reduction measures. This paper briefly summarized these climate change research projects, focusing on the modeling methodologies and results, and attempted to use plain language to make the results more accessible and interesting to the broader informed audience. These research projects have been used to support decision-makers in south–central Canada when dealing with future extreme weather events under climate change. 相似文献
75.
Daniel F. Nadeau Eric R. Pardyjak Chad W. Higgins Harinda Joseph S. Fernando Marc B. Parlange 《Boundary-Layer Meteorology》2011,141(2):301-324
A simple model to study the decay of turbulent kinetic energy (TKE) in the convective surface layer is presented. In this
model, the TKE is dependent upon two terms, the turbulent dissipation rate and the surface buoyancy fluctuations. The time
evolution of the surface sensible heat flux is modelled based on fitting functions of actual measurements from the LITFASS-2003
field campaign. These fitting functions carry an amplitude and a time scale. With this approach, the sensible heat flux can
be estimated without having to solve the entire surface energy balance. The period of interest covers two characteristic transition
sub-periods involved in the decay of convective boundary-layer turbulence. The first sub-period is the afternoon transition,
when the sensible heat flux starts to decrease in response to the reduction in solar radiation. It is typically associated
with a decay rate of TKE of approximately t
−2 (t is time following the start of the decay) after several convective eddy turnover times. The early evening transition is the
second sub-period, typically just before sunset when the surface sensible heat flux becomes negative. This sub-period is characterized
by an abrupt decay in TKE associated with the rapid collapse of turbulence. Overall, the results presented show a significant
improvement of the modelled TKE decay when compared to the often applied assumption of a sensible heat flux decreasing instantaneously
or with a very short forcing time scale. In addition, for atmospheric modelling studies, it is suggested that the afternoon
and early evening decay of sensible heat flux be modelled as a complementary error function. 相似文献
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Geographic Polarization,Partisan Voting,And The Battle Over Same‐Sex Marriage Within The Culture War
Geographic polarization arises when partisan, or like‐minded, voters live in enclaves separate from voters of differing partisan behavior. Research studies at multiple scales of analysis suggest that geographic polarization most typically occurs regarding partisan voting behavior; however, few studies have analyzed polarization with a focus on policy preferences. This research examines same‐sex marriage policy through two statewide issues that shared the presidential election ballot in 2004. The results of that presidential election and these two ballot initiatives are examined in Cincinnati, Ohio, and counties in its surrounding Metropolitan Statistical Area (MSA) in both Ohio and Kentucky. A geographically polarized relationship was found between partisan results and same‐sex marriage results. In addition, the findings suggest that despite a close link between partisan voting and issue voting on same‐sex marriage, spatial clustering (geographic polarization) was identified of those who voted differently from their fellow partisans. 相似文献
78.
Emily L. Kara Chad Heimerl Tess Killpack Matthew C. Van de Bogert Hiroko Yoshida Stephen R. Carpenter 《Aquatic Sciences - Research Across Boundaries》2012,74(2):241-253
A phosphorus (P) budget was estimated for the watershed of Lake Mendota, Wisconsin, to assess the effects of nutrient management
on P accumulation in the watershed soils. We estimated how nutrient management programs and legislation have affected the
budget by comparing the budget for 2007 to a budget calculated for 1995, prior to implementation of the programs. Since 1995,
inputs decreased from 1,310,000 to 853,000 kg P/yr (35% reduction) and accumulation decreased from 575,000 to 279,000 kg P/yr
(51% reduction). Changes in P input and accumulation were attributed primarily to enhanced agricultural nutrient management,
reduction in dairy cattle feed supplements and an urban P fertilizer ban. Four scenarios were investigated to determine potential
impacts of additional nutrient management tactics on the watershed P budget and P loading to Lake Mendota. Elimination of
chemical P fertilizer input has the greatest potential to reduce watershed P accumulation and establishment of riparian buffers
has the greatest potential to prevent P loading to Lake Mendota. 相似文献
79.
A short-term predictive system for surface currents from a rapidly deployed coastal HF radar network
Donald Barrick Vicente Fernandez Maria I. Ferrer Chad Whelan Øyvind Breivik 《Ocean Dynamics》2012,62(5):725-740
In order to address the need for surface trajectory forecasts following deployment of coastal HF radar systems during emergency-response situations (e.g., search and rescue, oil spill), a short-term predictive system (STPS) based on only a few hours data background is presented. First, open-modal analysis (OMA) coefficients are fitted to 1-D surface currents from all available radar stations at each time interval. OMA has the effect of applying a spatial low-pass filter to the data, fills gaps, and can extend coverage to areas where radial vectors are available from a single radar only. Then, a set of temporal modes is fitted to the time series of OMA coefficients, typically over a short 12-h trailing period. These modes include tidal and inertial harmonics, as well as constant and linear trends. This temporal model is the STPS basis for producing up to a 12-h current vector forecast from which a trajectory forecast can be derived. We show results of this method applied to data gathered during the September 2010 rapid-response demonstration in northern Norway. Forecasted coefficients, currents, and trajectories are compared with the same measured quantities, and statistics of skill are assessed employing 16 24-h data sets. Forecasted and measured kinetic variances of the OMA coefficients typically agreed to within 10–15%. In one case where errors were larger, strong wind changes are suspected and examined as the cause. Sudden wind variability is not included properly within the STPS attack we presently employ and will be a subject for future improvement. 相似文献
80.
Flow over Hills: A Large-Eddy Simulation of the Bolund Case 总被引:6,自引:6,他引:0
Marc Diebold Chad Higgins Jiannong Fang Andreas Bechmann Marc B. Parlange 《Boundary-Layer Meteorology》2013,148(1):177-194
Simulation of local atmospheric flows around complex topography is important for several applications in wind energy (short-term wind forecasting and turbine siting and control), local weather prediction in mountainous regions and avalanche risk assessment. However, atmospheric simulation around steep mountain topography remains challenging, and a number of different approaches are used to represent such topography in numerical models. The immersed boundary method (IBM) is particularly well-suited for efficient and numerically stable simulation of flow around steep terrain. It uses a homogenous grid and permits a fast meshing of the topography. Here, we use the IBM in conjunction with a large-eddy simulation (LES) and test it against two unique datasets. In the first comparison, the LES is used to reproduce experimental results from a wind-tunnel study of a smooth three-dimensional hill. In the second comparison, we simulate the wind field around the Bolund Hill, Denmark, and make direct comparisons with field measurements. Both cases show good agreement between the simulation results and the experimental data, with the largest disagreement observed near the surface. The source of error is investigated by performing additional simulations with a variety of spatial resolutions and surface roughness properties. 相似文献