华南夏季降水两次年代际转折的水汽输送异常成因初探     

曲姝霖  苏涛  韩子轩  赵俊虎  封国林 《大气科学》2021,45(2):273-286

本文利用NCEP/NCAR再分析资料和中国2374站日降水资料,通过水汽收支方程分解方法分析了华南夏季降水在1993~2002年时段年代际增多以及2003~2013年时段年代际减少的水汽输送特征及其成因。结果表明:1993~2002年时段（2003~2013年时段）,局地环流导致异常下沉（上升）气流,南亚高压偏东（偏西）和西太平洋副热带高压（简称副高）偏西（偏东）,菲律宾及副高西南侧水汽输送加强（减弱）,华南地区低层出现强的水汽辐合（辐散）,导致降水偏多（偏少）。华南地区夏季降水两次年代际变化主要与风速变化引起的水汽输送动力散度项的异常有关,同时还受到与比湿变化引起的水汽输送热力散度项异常、及天气尺度的涡旋引起的水汽输送涡流散度项异常影响。此外,研究发现水汽输送的异常与环流和海温异常均密切相关。  相似文献   

青藏高原冬季1月绕流的变化特征及其对中国气候的影响     

姜润  巩远发  袁源  康潆文  陈彦伟  侯劭禹 《大气科学》2021,45(6):1313-1326

利用1979～2019年NCEP/NCAR再分析资料和中国地面基本气象要素日值数据集（V3.0）的气温和降水资料,首先定义了客观表征冬季青藏高原南北两支绕流变化的指数,然后分析了其不同的变化特征,并采用相关分析、合成分析等方法初步研究了青藏高原南北两支绕流异常变化对中国气温和降水的影响机制。主要结果有:（1）青藏高原冬季北支绕流和南支绕流之间呈显著的负相关;北支（南支）绕流强、南支（北支）绕流弱时,对流层中低纬度地区从高原西部到我国东部沿岸为一个大范围的异常反气旋式（气旋式）环流系统,500 hPa高原的中部为一个异常反气旋（气旋）环流中心。（2）青藏高原冬季南北两支绕流的变化对中国冬季天气气候有显著影响。当青藏高原北支绕流强（弱）时,中国除东北是气温偏低（高）、降水偏多（少）外,河套、青藏高原及长江以南则是气温偏高（低）、降水偏少（多）;当南支绕流强（弱）时,中国气温普遍偏低（高）,东北及新疆北部是降水偏少（多）,南方大部分地区是降水偏多（少）。（3）分析高原绕流异常变化对中国天气气候的影响机制表明:当青藏高原北支绕流强、南支绕流弱时,中国东部35°N以北的对流层中都是异常西北风,35°N以南都是异常东北风,受高原异常纬向绕流影响,对流层大气为明显的“正压结构”;相应的对流层底层从南到北为一致的异常西南风,850 hPa以上35°N的之间为反气旋式切变和下沉运动异常,300 hPa以下异常偏暖,这些条件加强了下沉增温,导致中国东部气温偏高、降水偏少。当青藏高原南支绕流强、北支绕流弱时,对流层中的纬向风异常则为明显的“斜压特征”,异常西风呈现为从对流层低层到高层、低纬度到高纬度的倾斜的带状特征,其下方自华南近地面到华北200 hPa的“三角形”状异常东风,配合相应的经向风异常和华南到华北的异常上升运动,低层为“三角形”状的异常冷气团向南切入到中国南海,中上层为异常偏暖的西南气流在冷气团上自南向北爬升到中高纬度地区,导致中国大范围的气温异常偏低、降水偏多。  相似文献   

The Key Supply Source of Long-Distance Moisture Transport for the Extreme Rainfall Event on July 21, 2012 in Beijing     

李娟  徐祥德  李跃清  赵天良  吴翀 《热带气象学报(英文版)》2021,27(1):34-47

In this study, the Weather Research and Forecasting (WRF) model and meteorological observation data were used to research the long-distance moisture transport supply source of the extreme rainfall event that occurred on July 21, 2012 in Beijing. Recording a maximum rainfall amount of 460 mm in 24 h, this rainstorm event had two dominant moisture transport channels. In the early stage of the rainstorm, the first channel comprised southwesterly monsoonal moisture from the Bay of Bengal (BOB) that was directly transported to north China along the eastern edge of Tibetan Plateau (TP) by orographic uplift. During the rainstorm, the southwesterly moisture transport was weakened by the transfer of Typhoon Vicente. Moreover, the southeasterly moisture transport between the typhoon and western Pacific subtropical high (WPSH) became another dominant moisture transport channel. The moisture in the lower troposphere was mainly associated with the southeasterly moisture transport from the South China Sea and the East China Sea, and the moisture in the middle troposphere was mainly transported from the BOB and Indian Ocean. The control experiment well reproduced the distribution and intensity of rainfall and moisture transport. By comparing the control and three sensitivity experiments, we found that the moisture transported from Typhoon Vicente and a tropical cyclone in the BOB both significantly affected this extreme rainfall event. After Typhoon Vicente was removed in a sensitivity experiment, the maximum 24-h accumulated rainfall in north China was reduced by approximately 50% compared with that of the control experiment, while the rainfall after removing the tropical cyclone was reduced by 30%. When both the typhoon and tropical cyclone were removed, the southwesterly moisture transport was enhanced. Moreover, the sensitivity experiment of removing Typhoon Vicente also weakened the tropical cyclone in the BOB. Thus, the moisture pump driven by Typhoon Vicente played an important role in maintaining and strengthening the tropical cyclone in the BOB through its westerly airflow. Typhoon Vicente was not only the moisture transfer source for the southwesterly monsoonal moisture but also affected the tropical cyclone in the BOB, which was a key supply source of long-distance moisture transport for the extreme rainfall event on July 21, 2012 in Beijing.  相似文献   

A CRPS-Based Spatial Technique for the Verification of Ensemble Precipitation Forecasts     

赵滨  张博  李子良 《热带气象学报(英文版)》2021,27(1):24-33

Traditional precipitation skill scores are affected by the well-known“double penalty”problem caused by the slight spatial or temporal mismatches between forecasts and observations. The fuzzy (neighborhood) method has been proposed for deterministic simulations and shown some ability to solve this problem. The increasing resolution of ensemble forecasts of precipitation means that they now have similar problems as deterministic forecasts. We developed an ensemble precipitation verification skill score, i.e., the Spatial Continuous Ranked Probability Score (SCRPS), and used it to extend spatial verification from deterministic into ensemble forecasts. The SCRPS is a spatial technique based on the Continuous Ranked Probability Score (CRPS) and the fuzzy method. A fast binomial random variation generator was used to obtain random indexes based on the climatological mean observed frequency, which were then used in the reference score to calculate the skill score of the SCRPS. The verification results obtained using daily forecast products from the ECMWF ensemble forecasts and quantitative precipitation estimation products from the OPERA datasets during June-August 2018 shows that the spatial score is not affected by the number of ensemble forecast members and that a consistent assessment can be obtained. The score can reflect the performance of ensemble forecasts in modeling precipitation and thus can be widely used.  相似文献   

Influence of Sea Surface Temperature on the Predictability of Idealized Tropical Cyclone Intensity     

钟权加  李建平  李舒文  王羱  丁瑞强  张立凤 《热带气象学报(英文版)》2021,27(4):355-367

The role of sea surface temperature (SST) forcing in the development and predictability of tropical cyclone (TC) intensity is examined using a large set of idealized numerical experiments in the Weather Research and Forecasting (WRF) model. The results indicate that the onset time of rapid intensification of TC gradually decreases, and the peak intensity of TC gradually increases, with the increased magnitude of SST. The predictability limits of the maximum 10 m wind speed (MWS) and minimum sea level pressure (MSLP) are ~72 and ~84 hours, respectively. Comparisons of the analyses of variance for different simulation time confirm that the MWS and MSLP have strong signal-to-noise ratios (SNR) from 0-72 hours and a marked decrease beyond 72 hours. For the horizontal and vertical structures of wind speed, noticeable decreases in the magnitude of SNR can be seen as the simulation time increases, similar to that of the SLP or perturbation pressure. These results indicate that the SST as an external forcing signal plays an important role in TC intensity for up to 72 hours, and it is significantly weakened if the simulation time exceeds the predictability limits of TC intensity.  相似文献   

2014年夏季长江流域持续性低温的大尺度环流异常          下载免费PDF全文

杜雪婷  陆尔  赵玮 《大气科学学报》2021,44(5):795-803

采用中国地面站气温逐日观测资料、NOAA全球逐日海表温度资料,及NCEP/NCAR的全球日均再分析资料,研究了2014年持续性低温的三维结构及大尺度环流异常。结果表明,2014年的低温异常,除了在陆地上区域性地出现在长江流域,还以大尺度带状的形式、从陆地延伸到海洋上。这种带状异常不只出现在近地面,在大气各层（925～500 hPa）都能看到。分析指出,大气中的这个低温带主要由高纬大气环流异常造成。在位势高度场上,最重要的异常出现在高纬60°N,有呈带状的位势高度正距平,它引导（距平意义上的）偏北气流从正北和东北偏东方向侵入,在其南侧形成一带状的偏低温区。大气各层均呈现出这种在高纬有位势高度正距平、相应地在稍南的低纬（40°N）有位势高度负距平、两者之间为低温区的分布特征。从低层往上,这种配置型式整体表现出由南往北的倾斜,其垂直剖面表现为距平意义上的、大尺度、类似于锋面的倾斜结构。文中用简单的概念模型对此进行理解,认为这种结构是由大气动力异常和热力异常相互影响、共同作用而形成的。  相似文献   

TLS技术在环境地质灾害监测中的应用进展   总被引：2，自引：1，他引：1  

杜超  赵进  任宪友  张亮  庄艳华 《测绘科学》2018,(6):65-71,105

针对地面三维激光扫描技术在环境地质灾害监测中的应用问题,该文在系统介绍此技术关键指标和数据处理的基础上,从滑坡监测、土壤侵蚀监测、敏感地貌微变形监测和水灾害边界追踪4个方面,详细介绍了该技术在环境地质灾害监测领域的应用历史和现状,其研究热点包括该技术在应用中的适宜性评价、监测精度评价、滤波算法的开发及灾害发生趋势预判等方面。另外,应用中高植被覆盖度和降雨天气的干扰问题可通过继续优化软硬件并加强与其他技术联合应用予以弥补。  相似文献   

陆态网络GNSS基准站地壳运动速度场分析     

马下平  赵立都 《测绘科学》2018,(8):1-6

针对中国大陆构造环境监测网络(陆态网络)中观测数据处理的期数过少或解算成果的坐标系统不统一等问题,该文在ITRF2008中对陆态网络239个GNSS基准站从2010年1月至2013年8月的观测数据进行解算,获取站点的坐标时间序列,估计了站点的水平和垂直运动速度场,并分析了中国大陆地壳运动特征。结果表明:GNSS基准站在ITRF2008中的坐标时间序列整体上符合线性变化趋势,东西方向的幅度变化大,高程方向受观测噪声的影响较大一些;高程方向相比较水平方向的年周期性更为明显;水平速度场明显有自西向东运动的趋势,且西藏块体中测站变化最为明显;垂直运动速度场中,华中、华南、华东块体中测站存在较低速率的下降,其他块体的测站存在较低速率的隆升。  相似文献   

校正地基摄影获取树枝倾角     

李雷  孟治国  郑兴明  赵凯  李晓洁  李晓峰 《测绘科学》2018,(5):109-114

针对传统树枝倾角测量方法的复杂性和精度低的问题,该文提出了通过校正地基摄影获取树枝倾角的方法。基于投影变换和小孔成像原理,通过自制树枝模型的方法,分析了直接图上量取树枝倾角与真实值之间误差的成因,提出了基于投影变化的树枝倾角计算公式。结果表明:该研究获取树枝倾角的相对误差2.72%明显优于传统测量的31.33%,同时随拍摄距离变化,树枝倾角估算结果具有稳定性。该研究方法简单、有效,非常适合复杂环境下树枝倾角的大量提取,并提出了一种基于摄影成像原理获取树枝倾角的方法,发展了树枝倾角测量系统软件,提高测量精度并降低了测量难度。  相似文献   

AHP-灰色关联度分析法的耕地质量评价——以湖北省襄阳市为例   总被引：5，自引：0，他引：5  

曾荣  赵荣  梁勇 《测绘科学》2018,(8):90-96

针对传统耕地质量评价方法的单一性和局限性,该文提出一种将层次分析法与灰色关联度分析法融合的主客观相结合的耕地质量评定新方法。依据第一次全国地理国情普查数据成果,选取湖北省襄阳市作为研究区,建立试点区耕地质量综合评价指标体系,并对评价结果的可靠性进行验证。结果表明,该方法对耕地质量评价是科学有效的,能为耕地合理规划提出相关建议。  相似文献