浅析现浇板裂缝产生原因及治理方法     

李功保 《安徽地质》2005,15(3):225-226

近年来,随着现浇结构使用越来越广泛,但建设物现浇板板角出现裂缝的现象越来越多,笔者就板角裂缝的形成原因,进行了简要分析,并提出了其预防措施.  相似文献   

高空西北气流下铜仁东部特大暴雨的预报分析及思考          下载免费PDF全文

徐大红  胡萍  杨群  李习瑾 《中低纬山地气象》2022,46(2):9-17

利用贵州省预报业务常规、地面自动站加密观测资料、NCEP/FNL1°×1°再分析资料、业务数值预报模式,分析2020年6月29日铜仁市东部高空西北气流影响下的特大暴雨环境场特征、地面中小尺度场特征以及3家数值预报模式检验,初步分析产生此次特大暴雨的可能成因是在副高东南退、东北冷涡槽后高空西北气流维持、低层冷平流下传西输、地面辐合维持增强为涡旋、地面东路弱冷空气侵入、能量锋区斜压性增强;短临监测发现雷达回波有列车效应、低层辐合高层辐散的共轭配置、中层气旋式辐合;初步得出了西北气流影响下弱天气尺度环境场的铜仁市东部暴雨的预报着眼点。  相似文献   

A Case Study of the Initiation of Parallel Convective Lines Back-Building from the South Side of a Mei-yu Front over Complex Terrain     

Qiwei WANG  Yi ZHANG  Kefeng ZHU  Zhemin TAN  Ming XUE 《大气科学进展》2021,38(5):717-736

Parallel back-building convective lines are often observed extending to the southwest of some mesoscale convective systems(MCSs)embedded in the mei-yu front in China.The convective lines with echo training behavior can quickly develop into a stronger convective group of echoes,resulting in locally heavy rainfall within the mei-yu front rainband.The initiation mechanism of the back-building convective lines is still unclear and is studied based on high-resolution numerical simulation of a case that occurred during 27?28 June 2013.In the present case,the new convection along the convective lines was found to be forced by nonuniform interaction between the cold outflow associated with the mei-yu front MCSs and the warm southerly airflow on the south side of the mei-yu front,which both are modified by local terrain.The mei-yu front MCSs evolved from the western to the eastern side of a basin surrounded by several mesoscale mountains and induced cold outflow centered over the eastern part of the basin.The strong southwest airflow ahead of the mei-yu front passed the Nanling Mountains and impacted the cold outflow within the basin.The nonuniform interaction led to the first stage of parallel convective line formation,in which the low mountains along the boundary of the two airflows enhanced the heterogeneity of their interaction.Subsequently,the convective group quickly developed from the first stage convective lines resulted in apparent precipitation cooling that enhanced the cold outflow and made the cold outflow a sharp southward windshift.The enhanced cold outflow pushed the warm southerly airflow southward and impacted the mountains on the southeast side of the basin,where the roughly parallel mountain valleys or gaps play a controlling role in a second stage formation of parallel convective lines.  相似文献   

The political ecology playbook for ecosystem restoration: Principles for effective,equitable, and transformative landscapes     

《Global Environmental Change》2021

The urgency of restoring ecosystems to improve human wellbeing and mitigate climate and biodiversity crises is attracting global attention. The UN Decade on Ecosystem Restoration (2021–2030) is a global call to action to support the restoration of degraded ecosystems. And yet, many forest restoration efforts, for instance, have failed to meet restoration goals; indeed, they worsened social precarities and ecological conditions. By merely focusing on symptoms of forest loss and degradation, these interventions have neglected the underlying issues of equity and justice driving forest decline. To address these root causes, thus creating socially just and sustainable solutions, we develop the Political Ecology Playbook for Ecosystem Restoration. We outline a set of ten principles for achieving long-lasting, resilient, and equitable ecosystem restoration. These principles are guided by political ecology, a framework that addresses environmental concerns from a broadly political economic perspective, attending to power, politics, and equity within specific geographic and historical contexts. Drawing on the chain of explanation, this multi-scale, cross-landscapes Playbook aims to produce healthy relationships between people and nature that are ecologically, socially, and economically just – and thus sustainable and resilient – while recognizing the political nature of such relationships. We argue that the Political Ecology Playbook should guide ecosystem restoration worldwide.  相似文献   

天山南坡暖季暴雨过程的水汽来源及输送特征     

庄晓翠  李博渊  赵江伟  李建刚  张林梅 《干旱气象》2022,(1)

利用1981—2020年5—9月天山南坡16个气象站逐日降水资料和NCEP/NCAR GDAS再分析资料,分析天山南坡暖季暴雨过程的环流形势,并采用HYSPLIT模式,模拟追踪水汽源地及输送特征。结果表明:天山南坡暖季暴雨主要发生在南亚高压双体型、500 hPa以上西南急流(气流)、700 hPa切变辐合以及天山地形辐合抬升的重叠区域。水汽主要源自中亚、大西洋及其沿岸、地中海和黑海及其附近,经TKAP(塔吉克斯坦、吉尔吉斯坦、阿富汗东北部、巴基斯坦北部和印度西北部)、南疆、北疆关键区,分别从偏西、偏南、偏北通道输入暴雨区,700 hPa以上偏西通道、以下偏北通道占主导地位,且贡献最大的是南疆关键区。源自中亚的水汽主要输送至暴雨区700 hPa及以下,对暴雨的贡献较大,且沿途损失较大;源自大西洋及其沿岸、地中海和黑海及其附近的水汽主要输送至暴雨区700 hPa以上,对暴雨的贡献较小。另外,中低层还存在源自北疆、南疆、北美洲东部、蒙古的水汽。基于上述特征,建立了天山南坡暖季暴雨过程水汽三维精细化结构模型。  相似文献   

天山南坡暖季暴雨过程的水汽来源及输送特征     

庄晓翠  李博渊  赵江伟  李建刚  张林梅 《干旱气象》2022,(1)

利用1981—2020年5—9月天山南坡16个气象站逐日降水资料和NCEP/NCAR GDAS再分析资料,分析天山南坡暖季暴雨过程的环流形势,并采用HYSPLIT模式,模拟追踪水汽源地及输送特征。结果表明:天山南坡暖季暴雨主要发生在南亚高压双体型、500 hPa以上西南急流(气流)、700 hPa切变辐合以及天山地形辐合抬升的重叠区域。水汽主要源自中亚、大西洋及其沿岸、地中海和黑海及其附近,经TKAP(塔吉克斯坦、吉尔吉斯坦、阿富汗东北部、巴基斯坦北部和印度西北部)、南疆、北疆关键区,分别从偏西、偏南、偏北通道输入暴雨区,700 hPa以上偏西通道、以下偏北通道占主导地位,且贡献最大的是南疆关键区。源自中亚的水汽主要输送至暴雨区700 hPa及以下,对暴雨的贡献较大,且沿途损失较大;源自大西洋及其沿岸、地中海和黑海及其附近的水汽主要输送至暴雨区700 hPa以上,对暴雨的贡献较小。另外,中低层还存在源自北疆、南疆、北美洲东部、蒙古的水汽。基于上述特征,建立了天山南坡暖季暴雨过程水汽三维精细化结构模型。  相似文献   

Climatology of Shear Line and Related Rainstorm over the Southern Yangtze River Valley Based on an Improved Intelligent Identification Method     

刘金卿  陈鹤  徐靖宇 《热带气象学报(英文版)》2022,28(4):413-424

Based on four reanalysis datasets including CMA-RA, ERA5, ERA-Interim, and FNL, this paper proposes an improved intelligent method for shear line identification by introducing a second-order zonal-wind shear. Climatic characteristics of shear lines and related rainstorms over the Southern Yangtze River Valley (SYRV) during the summers (June-August) from 2008 to 2018 are then analyzed by using two types of unsupervised machine learning algorithm, namely the t-distributed stochastic neighbor embedding method (t-SNE) and the k-means clustering method. The results are as follows: (1) The reproducibility of the 850 hPa wind fields over the SYRV using China’s reanalysis product CMA-RA is superior to that of European and American products including ERA5, ERA-Interim, and FNL. (2) Theory and observations indicate that the introduction of a second-order zonal-wind shear criterion can effectively eliminate the continuous cyclonic curvature of the wind field and identify shear lines with significant discontinuities. (3) The occurrence frequency of shear lines appearing in the daytime and nighttime is almost equal, but the intensity and the accompanying rainstorm have a clear diurnal variation: they are significantly stronger during daytime than those at nighttime. (4) Half (47%) of the shear lines can cause short-duration rainstorms (≥20 mm (3h)-1 ), and shear line rainstorms account for one-sixth (16%) of the total summer short-duration rainstorms. Rainstorms caused by shear lines are significantly stronger than that caused by other synoptic forcing. (5) Under the influence of stronger water vapor transport and barotropic instability, shear lines and related rainstorms in the north and middle of the SYRV are stronger than those in the south.  相似文献   

循环同化雷达资料对一次飑线系统临近预报的改进作用     

董琪如  邱晓滨  王莹  王泽林  李季  梁绵 《气象与环境学报》2021,37(3):1-11

利用WRF（Weather Research Forecast）模式及其3D-Var（Three-Dimensional Variational assimilation）变分系统,针对2017年7月7日一次飑线进行了雷达资料的循环同化敏感性试验。结果表明：以循环同化雷达资料至飑线成熟期时刻的试验预报效果最好,主要原因在于预报的低层西北冷空气较强,从而导致较强的低层切变,再配合强的热力不稳定条件从而使飑线的发展得以维持。通过七组试验对比表明,对于单次雷达资料,同化的时机更为重要。同化飑线成熟阶段的雷达反射率,对低层热力层结有改善作用,为飑线发展提供了不稳定能量;对于循环同化,通过观测的影响和模式自身的热动力调整,对流场也有较好的修正作用,为对流系统的持续发展提供了充分的动力条件。  相似文献   

华南飑线系统对流与层云区闪电起始和通道位置处的云微物理特征     

赵川鸿  郑栋  张义军  刘显通  张阳  姚雯  张文娟 《热带气象学报》2021,37(3):358-369

利用广州S波段双偏振雷达观测数据和低频电场探测阵列三维闪电定位数据, 分析了2017年5月4日和5月8日华南地区两次飑线过程中闪电起始和通道位置处的雷达偏振参量和降水粒子特征。两次飑线中约80%的闪电起始和通道(统称闪电放电)定位于对流区。对流区闪电放电位置处的雷达反射率(Z_H)要比层云区平均大4~5 dBZ, 其它偏振参量的平均值较为接近。闪电放电位置处的Z_H中值随高度增加而减小, 但差分反射率(Z_DR)、差分传播相移率(K_DP)和共极化相关系数(CC)在-10 ℃层以上随高度变化不大; -10 ℃层以下, 对流区闪电放电位置对应Z_DR和K_DP随高度下降明显增大。闪电起始位置的平均Z_H比闪电通道位置处的平均Z_H大1~2 dBZ, 但前者在对流区内对应Z_H分布峰值区间为25~30 dBZ, 弱于后者的30~35 dBZ; 同时, 它们的对比关系在-20 ℃层上下不同。对流区内闪电放电位置处的主导性粒子是霰和冰晶, 它们的区域占比接近。在层云区内, 闪电放电位置主要是干雪和冰晶, 干雪区域的占比显著大于冰晶。   相似文献   

华南飑线升尺度增长过程中的多尺度能量相互作用分析     

张弛  沈新勇  张玲  王林  郭春燕  李小凡 《热带气象学报》2021,37(1):102-111

采用WRF模式对华南飑线的升尺度增长过程进行模拟,利用Barnes滤波将模式数据分解为三个尺度,分别代入相应的能量方程中进行计算,从能量角度研究飑线升尺度增长过程中动能和位能的变化,以及三个尺度系统能量的相互转化。研究表明:动能的变化与飑线过程中各尺度系统的演变有较好的对应,β中小尺度对流的发展对应β中小尺度系统动能的变化,而在飑线升尺度增长过程中,α中尺度系统动能快速增长。在飑线发展过程中环境场通过位能向动能的转化使得β中小尺度对流快速发展加强,而β中尺度飑线的快速发展与合并加强导致了飑线的升尺度增长。在飑线的升尺度增长过程中,β中小尺度动能大量转化为α中尺度动能使得α中尺度飑线迅速增强,而环境场对飑线升尺度增长过程的直接影响较小。   相似文献