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51.
Statistical downscaling of extremes of precipitation and temperature and construction of their future scenarios in an elevated and cold zone 总被引：5，自引：4，他引：1
Xiaoyan?Wang Tao?YangEmail author Quanxi?Shao Kumud?Acharya Weiguang?Wang Zhongbo?Yu 《Stochastic Environmental Research and Risk Assessment (SERRA)》2012,26(3):405-418
Reliable projections of extremes at finer spatial scales are important in assessing the potential impacts of climate change
on societal and natural systems, particularly for elevated and cold regions in the Tibetan Plateau. This paper presents future
projections of extremes of daily precipitation and temperature, under different future scenarios in the headwater catchment
of Yellow River basin over the 21st century, using the statistical downscaling model (SDSM). The results indicate that: (1)
although the mean temperature was simulated perfectly, followed by monthly pan evaporation, the skill scores in simulating
extreme indices of precipitation are inadequate; (2) The inter-annual variabilities for most extreme indices were underestimated,
although the model could reproduce the extreme temperatures well. In fact, the simulation of extreme indices for precipitation
and evaporation were not satisfactory in many cases. (3) In future period from 2011 to 2100, increases in the temperature
and evaporation indices are projected under a range of climate scenarios, although decreasing mean and maximum precipitation
are found in summer during 2020s. The findings of this work will contribute toward a better understanding of future climate
changes for this unique region. 相似文献
52.
华南局地锋生及对流系统发展的模拟分析研究 总被引：5，自引：1，他引：4
2009年3月28日一条东西向的锋面出现在华南25°N附近。伴随着锋面的活动,对流降水回波午后开始在广西的梧州附近发展,并在随后几小时向东移动,组织发展成为中尺度对流系统(MCS),为广东中西部及珠三角地区带来了雷暴、暴雨、冰雹等灾害天气。应用地面自动站、雷达回波、卫星云图以及NCEP-FNL再分析资料和WRF模式的模拟结果,对锋面暴雨形成的天气特征进行了诊断分析,考察了中尺度对流系统的发展演变过程及其与局地锋生的相互关系。结果表明,锋面对流系统形成发展于一个东西向水平尺度约200km的地面中尺度辐合线附近,对流起始发展于具有较大对流有效位能(CAPE)和较小对流抑制位能(CIN)的区域。伴随着对流的发展,锋面强度增强。锋生函数的计算发现,非绝热项和倾斜项分别在由对流引起的次级环流的上升运动支和下沉运动支起锋生作用,是引发中尺度锋生的主要影响因子。而相对来说,水平辐合项和形变项的作用却比较小。这与大尺度的锋生过程不同,中尺度锋生更主要的是由热力直接触发的非地转环流所驱动。涡度场的演变分析还发现,沿着850hPa锋区大的正涡度区与500hPa的强上升运动区对应良好,对流系统发展与中尺度锋生之间存在着类似于第二条件不稳定机制的相互作用,对流增强了锋生过程,锋面则对中尺度对流系统的发展起组织作用。中尺度锋生对对流组织发展的作用作为此类灾害天气形成的原因值得关注。 相似文献
53.
引入"概率包络"概念,从分析复杂多路径误差的概率分布入手,推导了两种非高斯分布的多路径误差概率分布模型,改进了两种基于污染正态分布的完好性阈值计算方法,并分别在伪距域和定位域对非高斯误差分布模型进行高斯概率包络分析,计算相应的均方差膨胀因子,从理论上体现了完好性阈值计算方法的严密性和有效性。仿真计算结果表明,两种改进的完好性阈值计算结果都能够对污染正态分布误差模型实现高斯概率包络,但第一种改进方法计算结果相对比较保守,第二种改进方法计算结果更加优化。 相似文献
54.
Transmutation of ancient settlements and environmental changes between 6000-2000 aBP in the Chaohu Lake Basin,East China 总被引：3，自引：3，他引：0
WU Li WANG Xinyuan ZHOU Kunshu MO Duowen ZHU Cheng GAO Chao ZHANG Guangsheng LI Lan LIU Li HAN Weiguang 《地理学报(英文版)》2010,(5)
Based on the temporal-spatial distribution features of ancient settlement sites from the middle and Iate Neolithic Age to the Han dynasty in the Chaohu Lake Basin of Anhui Province,East China.using the methods of GIS combined with the reconstructed paleoenvironment by the records of lake sediment since Holocene,the transmutation of ancient sottlements with response to environmental changes in this area has been discussed.Studies show that the main feature of transmutation of ancient settlements from the middle and Iate Neolithic Age to the Han Dynasty was that the distribution of settlements In this area changed from high altitudes to Iow ones and kept approaching the Chaohu Lake with the passage of time.These could be the response to the climate change from warm-moist to a relatively warm-dry condition during the middle Holocene.leading to the lake level fluctuations.The large area of exposed land provided enough space for human activities.These indicate that the above changes in geomorphologic evolution and hydrology influenced by climate cenditions affected the transmutation of ancient settlements greatly.The distribution pattern of settlement sites was that the number of sites in the west was more than in the east.This pattern may be related to the geomorphologic conditions such as frequent channel shifting of the Yangtze River as well as flood disasters during the Holocene optimum.Therefore,climate change was the inducement of the transmutation of ancient settlements in the Chaohu Lake Basin,which exerted great influence on the distribution,expansion and development of the ancient settlements. 相似文献
55.
56.
为完善变化环境下水库防洪调度方案,建立了集水文非一致性诊断、水文模型还现、设计洪水计算与水库调度规则优化于一体的水库适应性调控方法体系,并应用于沂沭泗水系仕阳水库.结果表明,仕阳水库入库洪水变异点发生在1975年;利用新安江模型对水文序列还现处理,得到满足一致性的设计洪水,其洪峰、最大24 h和最大72 h洪量均值,较原设计分别增大了 19.7%、14.5%和10.0%;建立了以防洪效益最大为目标函数的水库优化调度模型,采用动态规划进行求解.提出的适应性调度方案在20年、100年、1000年和5000年一遇设计洪水条件下,较水库现行设计方案最高洪水位分别降低了0.32、0.11、0.19和0.11 m. 相似文献
57.
为了探讨水文模型在不同水文数据同化方案下的径流模拟差异,本文采用集合卡尔曼滤波算法,以遥感蒸散发产品、实测径流为观测数据,构建了基于新安江模型的数据同化框架。基于此框架设计了4种不同同化方案(DA-ET、DAET(K)、DA-ET-Q、DA-ET-Q(K))以及1种对照方案OL,以赣江流域开展实例研究,评估了水文数据同化中遥感蒸散发产品的时间分辨率、模型蒸散发相关参数时变与否以及多源数据同化对径流模拟的影响。结果表明:在DA-ET方案下,同化两种不同时间分辨率的蒸散发产品均能提高模型整体的径流模拟精度,且时间分辨率更高的产品的同化效果更好;在DA-ET方案的基础上,考虑加入实测径流进行同化能够提升模型径流模拟精度,且DA-ET(K)与DA-ET-Q(K)方案所得径流相对误差的减幅均超过了20%,说明在蒸散发同化过程中同时考虑蒸散发参数动态变化的结果更优;相较于OL方案,4种同化方案均能不同程度地提高模型对径流高水部分的模拟能力,但DA-ET-Q(K)方案表现最差,而其余方案差异并不显著。本研究有助于进一步了解不同数据同化方案在径流模拟中的差异,从而为水资源高效利用与科学管理提供科学依据... 相似文献
58.
Canopy conductance (gc) is a crucial parameter in simulating evapotranspiration and modulating water exchange, but its variation mechanism has regional uncertainties and complex environmental co-controls. In addition, the effect of extreme rainfall on gc cannot be ignored under the changing climate. Here, we investigated the variation and environmental controls on gc and the effect of extreme rainfall events in a Cunninghamia lanceolata forest across the subtropical area of Southern China. In July 2020, an extreme rainstorm hit the source area of the Xin'an River, with the cumulative rainfall on July 7 and 8 reaching 216.6 mm. The thermal diffusion probe method was used to measure the density of sap flow, and the environmental factors such as air temperature (Ta), net solar radiation (Rn) and soil water content (SWC) were monitored during the growing seasons of 2020 and 2021. Ultimately, gc obtained by the Penman-Monteith equation was adopted since the result from the Köstner equation was overestimated. gc showed a unimodal curve on the diurnal scale, and this characteristic was more obvious after the extreme rainfall. Daily gc appeared a fluctuating pattern with a maximum in summer. gc was simultaneously affected by Ta, Rn, water vapour pressure difference (VPD), SWC, among which Ta was the most significant driving factor at both the diurnal and daily timescales. The regulation of Ta, VPD and SWC on gc had obvious thresholds, and the most definite response mode was VPD (2020: 1.25 kPa; 2021: 0.95 kPa). SWC and Ta were the dominant factors after the rainfall period, and the promotion effect of VPD on post-rainy days turned to inhibition effect on typical sunny days. These findings will further reveal the water exchange mechanism between atmosphere and vegetation and impacts of environmental factors in subtropical coniferous forests, especially after the extreme rainfall events. 相似文献
59.
珠江三角洲及其邻近海域第四纪地质与地震危险性 总被引：6，自引：2，他引：4
从第四纪地质研究的角度分析了珠江三角洲地区的地震危险性,认为北东,近东西和北西向三组断裂带把整个珠江三角洲断陷分割成７个次一级断块,并根据控制各次级断块的断裂第四纪活动性的强弱。 相似文献
60.