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اطلاعات انتشار: International Journal Of Environmental Research، هشتم،شماره۱، Winter ۲۰۱۴، سال ۰
تعداد صفحات: ۱۰
The scientific community agrees that climate change is one of the greatest challenges that our society will have to face this century. Indeed, the fourth report from the Intergovernmental Panel on Climate Change (IPPC) confirms the certitude of this phenomenon and its impacts, which can range from droughts to floods, health problems and food shortages. The principal objective of this paper is to assess the impact of climate change on flood events and its consequences on human. This point is necessary to define and evaluate different adaptation options. Even taking into account the medium greenhouse emission scenario, according to the results, it is expected that extreme precipitation will increase during the twenty century, although there is an uncertainty in the percentage due to the climatic models. It is expected an increase in peak discharge between 14±9 and 15±8 for 3 models and for the period 2001–2040 with a return period exceeding 40 years. For the period 2041–2080 there is more uncertainty, it is expected an increase between 12±8 and 19±10 for 2 models. According to the results, changes in flood event are expected with its associated uncertainty and new flood zones are detected with greater hazard to people.
اطلاعات انتشار: Journal Of Applied Fluid Mechanics، نهم،شماره۴، ۲۰۱۶، سال ۰
تعداد صفحات: ۱۳
Anumericalmodelisimplementedtodescribeﬂuiddynamicprocessesassociatedwithmid–latitude small–scale (10 km) upper ocean fronts by using modiﬁed state of the art computational ﬂuid dynamics tools. A periodic system was simulated using three different turbulent closures: 1) URANSReynolds Stress Model (RSM, seven equation turbulence model), 2) LES–Standard Smagorinsky (SS,algebraicmodel),and3)LES–ModiﬁedSmagorinsky,introducingacorrectionfornon–isotropic grids (MS). The results show the front developing instabilities and generating sub–mesoscale structures after four days of simulation. A strongly unstable shear ﬂow is found to be conﬁned within the mixed layer with a high Rossby number (Ro > 1) and high vertical velocity zones. The positive (negative) vertical velocity magnitude is found to be approximately O(10−3) m\s(O(10−2) m\s), one (two) order(s) of magnitude larger than the vertical velocity outside the sub–mesoscale structures, where the magnitude is stable at O(10−4) m\s. The latter value is consistent with previous numerical and experimental studies that use coarser grid sizes and therefore do not explicitly calculate the small scale structures. The nonlinear ﬂow introduced by the sub–mesoscale dynamics within the mixed layer and the non–isotropic grid used in the calculations generates a disparity between the predicted horizontal wave–number spectra computed using the RSM model with respect to the linear eddy viscosity model SS. The MS approach improves SS predictions. This improvement is more signiﬁcant below the mixed layer in the absence of ﬂow nonlinearities. The horizontal spectra predicted with the RSM model ﬁts a slope of−3 for large scale structures and a slope between−2 and−5\3 for turbulent structures smaller than 300 m. This work contributes to the investigation of thephysicalandmethodologicalaspectsforthedetailedmodellingandunderstandingofsmallscale structures in ocean turbulence.
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