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131.
Md. Rashed Chowdhury P.-S. Chu Thomas A. Schroeder Xin Zhao 《Journal of Coastal Conservation》2008,12(2):93-104
The objective of this study is to provide an improved climatology of sea level extremes on seasonal and long-term time scales for Hawaii and the U.S-Trust islands. Observations revealed that the Hawaiian and U.S.-Trust islands, by and large, display a strong annual cycle. For estimating the statistics of return period, the three-parameter generalized extreme value (GEV) distribution is fitted using the method of L-moments. In the context of extremes (20- to 100-year return periods), the deviations in most of the Hawaiian Islands (except at Nawiliwili and Hilo) displayed a moderate sea-level rise (i.e., close to 200 mm), but the deviations in the U.S.-Trust islands displayed a considerably higher rise (i.e., more than 300 mm) in some seasons due to typhoon-related storm surges. This rise may cause damage to roads, harbors, and unstable sandy beaches. Correlations between the El Niño-Southern Oscillation (ENSO) climate cycle and the variability of seasonal sea level have been investigated. Results show that correlation for the station located west of the International Date Line (DL) is strong, but it is moderate or even weaker for stations east of the DL. The skill of SST-based Canonical Correlation Analyses (CCA) forecasts was found to be weak to moderate (0.4–0.6 for Honolulu, Kahului, Hilo, and Wake, and 0.3 or below for Kahului, Mokuoloe, and Johnston). Finally, these findings are synthesized for evaluating the potential implications of sea level variability in these islands. 相似文献
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133.
This paper aims at analyzing the feasibility of a waste heat recovery power generation plant based on parametric optimization and performance analysis using different organic Rankine cycle configurations and heat source temperature conditions with working fluid R-12, R-123, R-134a, and R-717. A parametric optimization of turbine inlet temperature(TIT) was performed to obtain the irreversibility rate, system efficiency, availability ratio, turbine work output, system mass flow rate, second-law efficiency, and turbine outlet quality, along the saturated vapor line and also on superheating at an inlet pressure of 2.50 MP in basic as well as regenerative organic Rankine cycle. The calculated results reveal that selection of a basic organic Rankine cycle using R-123 as working fluid gives the maximum system efficiency, turbine work output, second-law efficiency, availability ratio with minimum system irreversibility rate and system mass flow rate up to a TIT of 150°C and appears to be a choice system for generation of power by utilizing the flue gas waste heat of thermal power plants and above 150°C the regenerative superheat organic Rankine cycle configuration using R 123 as working fluid gives the same results. 相似文献
134.
湖北省2008年初低温雨雪冰冻过程气候特征分析 总被引:1,自引:0,他引:1
2008年初,湖北省出现了严重的低温雨雪冰冻灾害,直接经济损失高达110亿元以上,有必要对灾害期间的气候特征进行系统、科学的分析和总结。对湖北省76个气象站2008年1月12日~2月3日气温、降水(雪)、日照以及低温持续日数等要素进行时空间差异分析及历史与同期比较,并选取10个代表站历史上所有低温雨雪天气过程,对其过程持续低温日数、最长连续雨雪日数、过程极端低温进行比较分析。结果表明:(1)此次过程的平均气温异常偏低,该省大部为-1~-2℃,比常年同期偏低4~6℃,为各站历史同期最低,其中主要是最高气温异常偏低所致,但极端低温并不低;(2)降雪过程频繁,雨雪量异常偏多;(3)低温冰冻持续时间长,该省大部在16~22 d,位于历史第一;(4)日照异常偏少。持续而稳定的大气环流异常形势是湖北省大范围低温雨雪天气的直接原因。 相似文献
135.
Hossein Tabari Patrick Willems 《Journal of the American Water Resources Association》2016,52(2):541-559
This study focuses on the empirical statistical analysis of the anomalies in daily precipitation extremes by applying the quantile perturbation method (QPM) to data from 31 Iranian weather stations during the period between 1961 and 2005. The possible causes behind the anomalies in precipitation extremes are identified by analyzing their relationship with the anomalies in eight atmospheric indices (i.e., NAO, SOI, PDO, AMO, NCP, DMI, WeMO, SSN). In terms of decadal oscillations, the country was generally wet in the 1960s and 1970s with most stations exhibiting periods of higher quantile perturbations, whereas lower quantile perturbations were dominant in the 1980s and 1990s. The highest perturbation in extreme precipitation quantiles prevails in Central Iran during the early 1980s, in which the quantiles are about 50% higher than the ones based on the full time series. The frequency of significant precipitation anomalies for winter season was greater than that for spring and autumn seasons. For the summer season, the humid region in North Iran demonstrates strong positive anomalies. The results highlight the noticeable role of large‐scale climatic factors in the anomalous behavior of precipitation extremes in Iran. The atmospheric drivers of the quantile anomalies in extreme precipitation were found to differ from one season to another. 相似文献
136.
在气候变化背景下,区域降水变化波动较大。湖北地处亚热带,位于典型的季风区内,旱涝灾害比较突出,特别是水患,历来是威胁湖北的一大灾害,因此对降水时空变化进行分析研究,有很现实的意义。利用1961年以来全省65站逐日降水观测资料为基础,根据气候特征和行政区划将湖北省进行区域划分,利用多种统计分析方法,以揭示在全球气候变暖背景下湖北省各区域的降水变化事实。结果表明:湖北省平均年降水量鄂西北最少,鄂东南最多,秋季降水量的减少和冬季降水量的增加最为显著;极端降水事件的变化中,鄂西北发生站次最多,江汉平原其次,鄂西南和鄂东南最少。该结论为湖北各区域的旱涝变化趋势预估、为水资源管理和防汛抗旱工作提供科学的参考 相似文献
137.
138.
目的 研究某高超声速导弹飞行过程中的振动状态,获得导弹在给定压力载荷下的振动响应特性。方法结合有限元分析、随机振动理论,利用三维软件构建导弹有限元模型,并在Ansys Workbench平台对其进行模态分析及谐响应分析。基于模态分析结果,对导弹进行随机振动响应试验,探究导弹在频域及力学上的振动响应特征。结果 计算得出导弹前六阶固有频率和振型,获得导弹上一检测点在给定振动激励载荷下的加速度响应曲线,并得到导弹整体结构的应力分布云图。结论 导弹模型强度符合要求,导弹在振动激励载荷下的加速度响应峰值均出现在380~400Hz,应力极值出现在导弹尾部区域,在此区域内,导弹更易产生结构性损伤。在飞行器地面环境模拟试验中,应着重考虑此频域及位置的振动条件。 相似文献
139.
三江源地区极端气候事件演变事实及其成因探究 总被引:8,自引:0,他引:8
利用三江源地区14个气象台站1962-2005年逐日气温、降水资料分析了该地区冷暖干湿极端气候事件的演变规律,探讨了其变化成因。研究表明:近44a来三江源地区气温等级由冷向暖转变,极端高温事件频繁发生,而极端低温事件则逐年减少,致使气温不断向着更高的均值状态持续增暖;尽管降水量干湿变化不甚显著,但降水的极端状况即严重干旱或暴雨事件均呈减少趋势,降水量的变化趋于稳定,降水变率减小;地形对极端气温、降水事件频次变幅的空间分布均有着较为显著的影响,且对后者的影响更为显著;高原季风、厄尔尼诺事件及高原积雪等因子的年际振荡是三江源地区极端气候事件发生频次波动的主要原因。 相似文献
140.
Spatial pattern of impervious surfaces and their impacts on land surface temperature in Beijing, China 总被引:8,自引:0,他引:8
XIAO Rong-bo OUYANG Zhi-yun ZHENG Hu Wei-feng SCHIENKE Erich W WANG Xiao-ke 《环境科学学报(英文版)》2007,19(2):250-256
Land surface temperature (LST), which is heavily influenced by urban surface structures, is a significant parameter in urban environmental analysis. This study examined the effect impervious surfaces (IS) spatial patterns have on LST in Beijing, China. A classification and regression tree model (CART) was adopted to estimate IS as a continuous variable using Landsat images from two seasons combined with QuickBird. LST was retrieved from the Landsat Thematic Mapper (TM) image to examine the relationships between IS and LST. The results revealed that CART was capable of consistently predicting LST with acceptable accuracy (correlation coefficient of 0.94 and the average error of 8.59%). Spatial patterns of IS exhibited changing gradients across the various urban-rural transects, with LST values showing a concentric shape that increased as you moved from the outskirts towards the downtown areas. Transect analysis also indicated that the changes in both IS and LST patterns were similar at various resolution levels, which suggests a distinct linear relationship between them. Results of correlation analysis further showed that IS tended to be positively correlated with LST, and that the correlation coefficients increased from 0.807 to 0.925 with increases in IS pixel size. The findings identified in this study provide a theoretical basis for improving urban planning efforts to lessen urban temperatures and thus dampen urban heat island effects. 相似文献