Dynamic downscaling of 22-year CFS winter seasonal hindcasts with the UCLA-ETA regional climate model over the United States     

Fernando De Sales  Yongkang Xue 《Climate Dynamics》2013,41(2):255-275

This study evaluates the UCLA-ETA regional model’s dynamic downscaling ability to improve the National Center for Environmental Prediction Climate Forecast System (NCEP CFS), winter season predictions over the contiguous United States (US). Spatial distributions and temporal variations of seasonal and monthly precipitation are the main focus. A multi-member ensemble means of 22 winters from 1982 through 2004 are included in the study. CFS over-predicts the precipitation in eastern and western US by as much as 45 and 90 % on average compared to observations, respectively. Dynamic downscaling improves the precipitation hindcasts across the domain, except in the southern States, by substantially reducing the excessive precipitation produced by the CFS. Average precipitation root-mean-square error for CFS and UCLA-ETA are 1.5 and 0.9 mm day^?1, respectively. In addition, downscaling improves the simulation of spatial distribution of snow water equivalent and land surface heat fluxes. Despite these large improvements, the UCLA-ETA’s ability to improve the inter-annual and intra-seasonal precipitation variability is not clear, probably because of the imposed CFS’ lateral boundary conditions. Preliminary analysis of the cause for the large precipitation differences between the models reveals that the CFS appears to underestimate the moisture flux convergence despite producing excessive precipitation amounts. Additionally, the comparison of modeled monthly surface sensible and latent heat fluxes with Global Land Data Assimilation System land data set shows that the CFS incorrectly partitioned most of surface energy into evaporation, unlike the UCLA-ETA. These findings suggest that the downscaling improvements are mostly due to a better representation of land-surface processes by the UCLA-ETA. Sensitivity tests also reveal that higher-resolution topography only played a secondary role in the dynamic downscaling improvement.  相似文献   

History of Paleoseismic Activity Along the Hohhot Segment of Daqingshan Piedmont Fault in the Late Quaternary   总被引：1，自引：0，他引：1  

Ran Yongkang  Zhang Peizhen  Hu Bo  Guo Wensheng 《中国地震研究》2001,15(2):190-204

INTRODUCTIONTheDaqingshanpledmont扭nit Is an irllt,oltant active normal tsult In the active fault－depressionzone——Hetao ault－depression zone In the northern part of Ordos Block,North China．It lies in ENEdirection long the southern pledmont of Daqingshan Mountain,dips to south,and extends for 200 kmor。。The fault was formed In the Eocene and strongly activated In the Cenozolc．Its verticaldlspl。ement exceeds 2400 m since the Quaternary(Rese。h Group on Ordos Block,State…  相似文献   

Paleoseismic study of the east Kalpintage fault in southwest Tianshan based on deformation of alluvial fans and 10Be dating     

An Li  Yongkang Ran  Liangxin Xu  Huaguo Liu 《Natural Hazards》2013,68(2):1075-1087

Multiple earthquakes produced by thrusting deformation have been recorded over the last century in the Tianshan area. Paleoseismic studies are very important in the exploration of the active quaternary tectonics and the risk assessment of great earthquakes in the Tianshan orogenic region. However, in this area, paleoseismic research is still lacking because of the lack of samples dated by ¹⁴C or optically stimulated luminescence (OSL) methods. We determined the ages of the alluvial fans by ¹⁰Be terrestrial cosmogenic nuclide (TCN) dating, measured the surface deformation of the fault scarp in a GPS survey, and evaluated the vertical displacements of the events in trenches in the east Kalpintage fault in the southwest Tianshan region. We estimated the displacement and recurrence intervals of the paleoseismic events and constrained the errors of the ¹⁰Be ages and slip rates using a Monte Carlo simulation method. Our study suggests that each paleoseismic event shows a similar displacement of ~1.5 m with a recurrence interval of ~5 kyr in the east Kalpintage fault. The calculated slip rate is 0.31(+0.21/?0.18) mm/yr. In such arid regions with large areas of coarse gravel that lack ¹⁴C or OSL samples, the integration of TCN dating, geomorphic deformation survey, and trenching methods is a reliable alternative for studying the active regional tectonics.  相似文献   

南天山低角度逆断层古地震破裂变形模式     

李安  杨晓平  冉勇康  黄伟亮  张玲  徐良鑫  刘华国  李胜强 《震灾防御技术》2016,11(2):173-185

近年来逆冲型破坏性地震频发,这对于逆冲型破裂的古地震研究方法提出了新的要求。由于逆断层角度的变化,在地震中可能表现出截然不同的破裂样式。通过对南天山大量古地震探槽开挖和古地震事件分析研究中发现,低角度逆断层的古地震具有一些常见的破裂类型。本文中挑选了位于南天山三个重要山前逆断裂褶皱带:西段柯坪推覆系、中段库车坳陷的秋里塔格褶皱带和东段焉耆盆地北缘和静逆断裂褶皱带的7个典型探槽剖面,对这类低角度逆断层的古地震进行变形模式、事件识别和位移量计算的总结归纳。低角度逆断层古地震破裂具有以下几种样式并具有各自识别古地震事件和计算位移量的方法:1一条断面对应一次事件的破裂形式,利用断面上断点位置识别古地震事件并判断事件的先后顺序。每个断面各自的位移量正好代表一次事件的位移量。2单条断面多次破裂的样式可以通过上下不同地层的位错量差异判断古地震事件,各个相邻地层之间的位错量差值代表古地震事件的位移量。3多条断面同时破裂的情况表现为多条断面被相同一套地层覆盖,事件位移量为多条断面的位错量之和。4挠曲变形和"推土机"作用是低角度逆断层古地震破裂常见的变形方式,这部分变形量不能忽略,可以通过线平衡和面平衡方法获得断层水平缩短量。  相似文献   

新乡市地质灾害现状特征及防治措施     

杨涛  王让  张磊  罗学贵 《地质灾害与环境保护》2009,20(2):8-12

新乡市是地质灾害易发区,主要发育有崩塌、滑坡、泥石流、地面塌陷、地裂缝等地质灾害。笔者在新乡市地质灾害现状调查的基础上,分析了地质灾害的分布特点和成因,并对全市的地质灾害防治提出具体措施。  相似文献   

蒙城数字地震台记录面波震级的初步对比     

周琼  曹志磊  胡莲芝  汪继林  薛志明  周永康 《地震地磁观测与研究》2008,29(5):32-35

选用蒙城地震台2001年1月到2007年12月的456个地震,与中国地震台网中心提供的《中国地震大震速报目录》进行面波震级的对比,得出蒙城地震台的台基校正值、标准误差,并进一步分析了两者之间的相关性、一致性,对蒙城地震台单台面波震级的准确测定提供了重要的参考依据。  相似文献   

利用SAWYER-ELIASSEN次级方程对两支雨带的诊断   总被引：1，自引：1，他引：0  

周顺武  丁治英  陈永康 《南京气象学院学报》1999,22(3):326-330

利用中尺度模式（ Ｍ Ｍ４）模拟的 １９８１ 年 ６ 月 ２７ 日江淮地区梅雨锋暴雨过程的高分辨率资料,使用 Ｓａｗ ｙｅｒ Ｅｌｉａｓｓｅｎ 次级方程,对与雨带相联系的中尺度结构进行了诊断分析。通过模式输出资料进行数值求解,揭示了急流锋生在两支雨带形成和维持中的特殊贡献。分析表明,高、低空急流耦合产生急流锋生环流,锋生环流有利于两支雨带的形成。  相似文献   

Ecological thresholds of phytoplankton community across environmental gradients in the harmful algal blooms-frequently-occurring,subtropical coastal waters,East China Sea     

Ran Ye  Chunying Ge  Qiong Wang  Qing Xu  Guofeng Xu  Yongkang Yan  Mingli Qin  Yanhong Cai  Yuejun Fei 《海洋学报(英文版)》2021,40(6):100-110

Phytoplankton communities can response immediately and directly to environmental changes,and thus have been applied as reliable biotic indicators in aquatic systems.This study provided insights into the relationships concerning ecological thresholds of phytoplankton communities and individual taxon in response to environmental changes in coastal waters of northern Zhejiang Province,East China Sea.Results demonstrated that there existed seasonal variations of phytoplankton community ecological thresholds of which spring being higher than those in summer.As for individual species,Prorocentrum donghaiense and Noctiluca scintillans were identified as the most tolerant and sensitive indicator species in spring and summer,respectively.They exhibited strong indications in response to environmental changes.These findings highlighted that phytoplankton community structure in this region was stable when environmental gradients were below the thresholds of sensitive species,whereas potential harmful algal blooms may occur when environmental gradients exceeded the thresholds of tolerant species.  相似文献   

岩溶地下河在SWAT中的概化方法——以毕节倒天河流域为例     

张程鹏  张凤娥  耿新新  冀俊杰  陈永康 《中国岩溶》2020,39(5):665-672

岩溶地下河的存在严重影响了土壤和水评估工具（SWAT）在岩溶地区的普遍适用性。针对岩溶地下河在SWAT中的概化问题,提出基于数字高程模型（DEM）预处理结合SWAT流域自动识别功能的方法,将岩溶地下河暴露于地表,把岩溶区复杂的地表－地下二元结构简化为地表一元结构,并以贵州毕节地下河发育的倒天河流域为例进行应用。结果表明:① 对比未经概化地下河建立的模型,概化地下河建立的模型识别流域面积增大30.73%,子流域个数增加29.27%,水文响应单元（HRU）个数增加43.82%;② 参数取最大物理意义范围时,未经概化地下河建立的模型p因子=0.64,不满足建模条件,物理模型本身存在问题;③ 概化地下河建立的模型月步长模拟结果:校准期R2=0.96,NS=0.96,验证期R2=0.94,NS=0.93,月尺度模拟效果非常好。岩溶地下河概化方法使SWAT在流域划分方面更加合理,搭建的模型模拟更加合理。该研究拓展了SWAT模型在岩溶区的应用。   相似文献   

河北矾山盆地北缘断层八营段的古地震重复模型   总被引：13，自引：1，他引：12  

冉勇康  方仲景 《中国地震》1998,14(1):47-58

通过实测断错地貌面,开挖在探槽以及系统的地层年代采样,推断和揭露出矾出盆地北缘断层八营段９万年来总移量量为３４ｍ。经７．５万年来共发生过９次古位移事件。其中大探槽揭露的４次事件分别发生在距今：Ａ,２．８万年;Ｂ．１．４万年;Ｃ,０．７５万年和Ｄ,６５６年（？）左右。该段落古地震地重复模型分为两个阶段：９￣１．４万年间符合“时间可推测模型”;１．４万年来以来则为“位称衰减模型”。  相似文献