Progress in Studies of the Precipitation Diurnal Variation over Contiguous China          下载免费PDF全文

YU Rucong  LI Jian  CHEN Haoming  YUAN Weihua 《Acta Meteorologica Sinica》2014,28(5):877-902

This paper summarizes the recent progress in studies of the diurnal variation of precipitation over con- tiguous China. The main results are as follows. （1） The rainfall diurnal variation over contiguous China presents distinct regional features. In summer, precipitation peaks in the late afternoon over the south- ern inland China and northeastern China, while it peaks around midnight over southwestern China. In the upper and middle reaches of Yangtze River valley, precipitation occurs mostly in the early morning. Summer precipitation over the central eastern China （most regions of the Tibetan Plateau） has two diurnal peaks, i.e., one in the early morning （midnight） and the other in the late afternoon. （2） The rainfall diurnal variation experiences obvious seasonal and sub-seasonal evolutions. In cold seasons, the regional contrast of rainfall diurnal peaks decreases, with an early morning maximum over most of the southern China. Over the central eastern China, diurnal monsoon rainfall shows sub-seasonal variations with the movement of summer monsoon systems. The rainfall peak mainly occurs in the early morning （late afternoon） during the active （break） monsoon period. （3） Cloud properties and occurrence time of rainfall diurnal peaks are different for long- and short-duration rainfall events. Long-duration rainfall events are dominated by strat- iform precipitation, with the maximum surface rain rate and the highest profile occurring in the late night to early morning, while short-duration rainfall events are more related to convective precipitation, with the maximum surface rain rate and the highest profile occurring between the late afternoon and early night. （4） The rainfall diurnal variation is influenced by multi-scale mountain-valley and land-sea breezes as well as large-scale atmospheric circulation, and involves complicated formation and evolution of cloud and rainfall systems. The diurnal cycle of winds in the lower troposphere also contributes to the regional differences  相似文献   

An Overview of Nowcasting Development, Applications, and Services in the Hong Kong Observatory          下载免费PDF全文

LI Ping-Wah  WONG Wai-Kin  CHEUNG Ping  YEUNG Hon-Yin 《Acta Meteorologica Sinica》2014,28(5):859-876

The Hong Kong Observatory （HKO） has been developing a suite of nowcasting systems to support op- erations of the forecasting center and to provide a variety of nowcasting services for the general public and specialized users. The core system is named the Short-range Warnings of Intense Rainstorm of Localized Systems （SWIRLS）, which is a radar-based nowcasting system mainly for the automatic tracking of the movement of radar echoes and the short-range Quantitative Precipitation Forecast （QPF）. The differential, integral （or variational）, and object-oriented tracking algorithms were developed and integrated into the nowcasting suite. In order to predict severe weather associated with intense thunderstorms, such as high gust, hail, and lightning, SWIRLS was enhanced to SWIRLS-II by introduction of a number of physical models, especially the icing physics as well as the thermodynamics of the atmosphere. SWIRLS-Ⅱ was further enhanced with non-hydrostatic, high resolution numerical models for extending the forecast range up to 6h ahead. Meanwhile, SWIRLS was also modified for providing nowcasting services for aviation community and specialized users. To take into account the rapid development of lightning events, ensemble nowcasting techniques such as time-lagged and weighted average ensemble approaches were also adopted in the nowcasting system. Apart from operational uses in Hong Kong, SWIRLS/SWIRLS-Ⅱ was also exported to other places to participate in several international events such as the WMO/WWRP Forecast Demon- stration Project （FDP） during the Beijing 2008 Olympics Games and the Shanghai Expo 2010. Meanwhile, SWIRLS has also been transferred to various regional meteorological organizations for establishing their nowcasting infrastructure. This paper summarizes the history and the technologies of SWIRLS/SWIRLS-Ⅱ and its variants and the associated nowcasting applications and services provided by the HKO since the mid 1990s.  相似文献   

Improvement of the semi-Lagrangian advection scheme in the GRAPES model: Theoretical analysis and idealized tests   总被引：2，自引：0，他引：2  

HUANG Bo  CHEN Dehui  LI Xingliang  LI Chao 《大气科学进展》2014,31(3):693-704

ABSTRACT The Global/Regional Assimilation and PrEdiction System （GRAPES） is the newgeneration numerical weather predic- tion （NWP） system developed by the China Meteorological Administration. It is a fully compressible non-hydrostatical global/regional unified model that uses a traditional semi-Lagrangian advection scheme with cubic Lagrangian interpola tion （referred to as the SL_CL scheme）. The SL_CL scheme has been used in many operational NWP models, but there are still some deficiencies, such as the damping effects due to the interpolation and the relatively low accuracy. Based on Reich＇s semi-Lagrangian advection scheme （referred to as the R2007 scheme）, the Re_R2007 scheme that uses the low- and high-order B-spline function for interpolation at the departure point, is developed in this paper. One- and two-dimensional idealized tests in the rectangular coordinate system with uniform grid cells were conducted to compare the Re..R2007 scheme and the SL_CL scheme. The numerical results showed that： （1） the damping effects were remarkably reduced with the Re_R2007 scheme; and （2） the normalized errors of the Re_R2007 scheme were about 7.5 and 3 times smaller than those of the SL_CL scheme in one- and two-dimensional tests, respectively, indicating the higher accuracy of the Re..R2007 scheme. Furthermore, two solid-body rotation tests were conducted in the latitude-longitude spherical coordinate system with non uniform grid cells, which also verified the Re_R2007 scheme＇s advantages. Finally, in comparison with other global advection schemes, the Re_R2007 scheme was competitive in terms of accuracy and flow independence. An encouraging possibility for the application of the Re_R2007 scheme to the GRAPES model is provided.  相似文献   

Land use changes and sea level rise may induce a “coastal squeeze” on the coasts of Veracruz,Mexico     

《Global Environmental Change》2014

“Coastal squeeze” refers to the process in which coastal ecosystems are threatened by the combination of sea level rise (SLR) and the presence of a physical barrier, such as human infrastructure. This situation prevents the landward migration of ecosystems and species, as the coastline moves inland, and they are thus exposed to local extinction. Our objective was to explore coastal squeeze in the state of Veracruz, Mexico, through the study of urban expansion on the coast, an analysis of coastline geodynamics, and a projection of the potential effect of SLR on the distribution of two focal plant species which are endemic to the coastal dunes of Mexico. Urbanization of the coast, parallel to the shoreline, has been taking place increasingly rapidly, displacing ecosystems, both natural (mangroves, beaches and coastal dunes) and transformed (cultivated fields and pastures). Taking into consideration the geodynamic trends of the coastline and an analysis of its historical evolution, it can be seen that the coastal strip is eroding at rates that vary from slow to very rapid. Finally, the results of ecological niche modeling indicate that, under scenarios of SLR, the potential distribution of the two focal species would diminish: Chamaecrista chamaecristoides by 6–28%, and Palafoxia lindenii by 2–15%. These results indicate that “coastal squeeze” is likely in the study area, and that measures to limit or mitigate this process are required. Such measures could include urbanization programs which limit development to appropriate zones, the restoration and rehabilitation of deteriorated ecosystems and the conservation of those ecosystems which are still healthy.  相似文献   

基于空间变异修正普通克里金的矿区复杂地形高精度建模     

于广婷  刘同文  王琦  潘懋  李涛  宋冠涵  刘善伟 《测绘通报》2022,(11):106-111

普通克里金法是构建矿区三维地形模型并揭示地表沉陷形变场动态变化规律的有效方法。但普通克里金法存在平滑效应的问题,导致估计值的空间变异程度小于实际,无法真实反映矿区复杂地表形态的空间变化特征。本文结合矿区实际地形采样数据,提出了一种空间变异修正的普通克里金法,并将其应用于矿区复杂地形的高精度建模,并与已有方法在建模精度和空间变异性复现方面进行了对比分析。研究结果表明,空间变异修正的普通克里金法能够很好地处理平滑效应对建模的影响,具有更高的建模精度和空间变异性复现能力,在矿区复杂地形高精度建模应用中具有较强的适用性,可以作为一种可靠的建模工具用于矿区复杂地形沉陷形变场动态变化规律分析。  相似文献   

降雨条件下北川斜坡破坏的数值模拟     

王淑云  叶天力  鲁晓兵  聂雪媛 《中国地质灾害与防治学报》2014,(2):43-48

本文采用FLAC的两相流模式和修正的Mohr—Coulomb模型,对北川地区震后土在降雨条件下的位移和速度矢量进行了数值模拟和分析,同时在室内进行了降雨条件下斜坡破坏的模型实验。分析结果表明：土体在沿坡面的最大水平位移发生在坡脚处,土体水平位移是衡量斜坡破坏的首要指标,可采用坡面特征点的位移突变作为斜坡破坏的判别标准;数值模拟得到的斜坡破坏与降雨历时关系与室内模型实验结果吻合较好。  相似文献   

中坝隧道地下分水岭演化的数值模拟分析     

廖晓超  许模  蒋莉  赵瑞  苟敬 《地下水》2014,(1):48-49,52

由于铁路隧道的施工,地下水进入隧道,形成了新的排泄基准面,对区域地下水环境产生较大影响,故对该类问题进行深入研究具有重要的工程实践意义。以中坝岩溶隧道为例,采用Visual modflow对中坝隧道进行三维数值模拟,模拟中坝隧道开挖建设后,地下分水岭的演化过程,以此来探讨分析其对地下水环境的影响。  相似文献   

水源热泵井群布置方案对地下水流场影响分析     

韦婷  车巧慧  韩玉杰 《地下水》2014,(3):31-33

以某地下水源热泵系统工程为例,依据工程场地实际抽水-回灌试验数据,建立研究区地下水流数值模拟模型,分析该地区适宜的井群布置方案,并定量研究不同井群布置方案对地下水流场的影响范围与程度,为确定合理的井群布置方案提供技术支撑。研究表明：对于同一含水层回灌,随着抽水-回灌时间的延长,就有利于抽水-回灌能力及尽量减小对周边地下水开采的影响而言,抽水井、回灌井交叉布置,部分回灌井集中布置的方案较为合理。  相似文献   

芦山地震的发生对周围断层影响的数值模拟   总被引：4，自引：0，他引：4  

李玉江  陈连旺  刘少峰  杨树新  荆燕 《地球学报》2014,35(5):627-634

芦山地震发生后,地震的发生造成周围断层应力变化值得关注。本文基于川滇地区的三维非线性有限元模型,利用芦山地震同震静态滑移量结果,分析地震的发生对川滇地区主要断裂的同震加卸载效应。初步结果表明,芦山地震的发生造成龙门山断裂中南段、岷江断裂、马尔康断裂、鲜水河断裂北西段、大凉山断裂南段、小江断裂南段不同程度的应力增加。其中龙门山断裂中南段增加最为显著,最大库仑应力增加量达0.035 MPa;岷江断裂次之,最大达0.0075 MPa;马尔康断裂增加量达0.0031 MPa;鲜水河断裂北西段达0.0008 MPa。而从断裂带同震应变积累与释放方面分析的结果同样表明上述四条断裂地震危险性增强。该结果可以为川滇地区地震危险性分析提供一定的参考依据。  相似文献   

The mechanism of post-rift fault activities in Baiyun sag,Pearl River Mouth basin     

《Journal of Asian Earth Sciences》2014

Post-rift fault activities were often observed in deepwater basins, which have great contributions to oil and gas migration and accumulation. The main causes for post-rift fault activities include tectonic events, mud or salt diapirs, and gravitational collapse. In the South China Sea continental margin, post-rift fault activities are widely distributed, especially in Baiyun sag, one of the largest deepwater sag with its main body located beneath present continental slope. During the post-rift stage, large population of faults kept active for a long time from 32 Ma (T70) till 5.5 Ma (T10). Seismic interpretation, fault analysis and analogue modeling experiments indicate that the post-rift fault activities in Baiyun sag between 32 Ma (T70) and 13.8 Ma (T30) was mainly controlled by gravity pointing to the Main Baiyun sag, which caused the faults extensive on the side facing Main Baiyun sag and the back side compressive. Around 32 Ma (T70), the breakup of the continental margin and the spreading of the South China Sea shed a combined effect of weak compression toward Baiyun sag. The gravity during post-rift stage might be caused by discrepant subsidence and sedimentation between strongly thinned sag center and wing areas. This is supported by positive relationship between sedimentation rate and fault growth index. After 13.8 Ma (T30), fault activity shows negative relationship with sedimentation rate. Compressive uplift and erosion in seismic profiles as well as negative tectonic subsiding rates suggest that the fault activity from 13.8 Ma (T30) to 5.5 Ma (T10) might be controlled by the subductive compression from the Philippine plate in the east.  相似文献