PLANETARY BOUNDARY LAYER HEIGHT MEASURED BY A WIND PROFILER BASED ON THE WAVELET TRANSFORM     

艾未华  戈书睿  魏浩  胡明宝 《热带气象学报(英文版)》2017,23(4):396-407

Planetary boundary layer height (PBLH) is an important input parameter for any boundary layer study or model, either climate or atmospheric. The variation of the PBLH is also of great significance to the physical processes of numerical prediction, diagnosis of weather forecasting and monitoring urban pollutants. However, effective ways to monitor the PBLH continuously are lack. Wind profilers are commonly used in monitoring PBLH continuously because of its high temporal and spatial resolution, coupled with capability of continuous detection. In this paper, the covariance wavelet transform (CWT) is used to analyze the range-corrected signal-to-noise ratio (SNR) of the wind profiler to determine the PBLH, which is then compared with the results measured by the gradient method and the radiosonde. The conclusions are as follows: (1) The scaling parameter a and translation parameter b of the wavelet are critical in determination of the PBLH by applying the CWT as different values may get completely different results, which requires to select appropriate values in the calculation carefully. (2) Quality control is crucial in determining the PBLH because good quality control can help remove mutation points, which makes the determined PBLH more consistent with the actual situation. (3) In clear-air, the gradient method is not applicable if the boundary layer turbulence is inhomogeneous and the impact of noise is large for that it is easy to be impacted by the mutation of SNR caused by the atmosphere turbulence instability and other factors, which will cause large errors, while the CWT method as an improvement of the gradient method can determine the PBLH quite well. (4) Through quality control, the PBLHs determined by the CWT are consistent with those of radiosonde, and the correlation coefficient between them is 0.87.  相似文献   

WIND SHEAR IDENTIFICATION WITH THE RETRIEVED WIND OF DOPPLER WEATHER RADAR     

周生辉  魏鸣  王黎俊  郑辉  张博越  林春英 《热带气象学报(英文版)》2017,23(2):210-216

Wind shear reflects that the wind field is not uniform, which is one of the primary factors which make the retrieval of the wind field difficult. Based on volume velocity process(VVP) wind field retrieval technique, the intensity of wind shear is identified in this paper. After analyzing the traditional techniques that rely on the difference of radial velocity to identify wind shear, a fixed difference among radial velocities that may cause false identification in a uniform wind field was found. Because of the non-uniformity in wind shear areas, the difference of retrieved results between surrounding analysis volumes can be used as a measurement to show how strong the wind shear is. According to the analysis of a severe convective weather process that occurred in Guangzhou, it can be found that the areas of wind shear appeared with the strength significantly larger than in other regions and the magnitude generally larger than4.5 m/(s·km). Besides, by comparing the variation of wind shear strength during the convection, it can be found that new cells will be more likely to generate when the strength is above 3.0 m/(s·km). Therefore, the analysis of strong wind shear's movement and development is helpful to forecasting severe convections.  相似文献   

兰州市城市热岛效应与地表指数定量分析     

尹柯柯  魏冠军  胡玉玺  陈海鹏 《测绘科学》2017,42(4)

针对现有兰州市城市热岛效应研究多以地面气象站的观测资料为数据源,以遥感影像为数据源较少的现状,该文利用Landsat 8影像,研究了兰州市城市热岛效应与修改后的土壤调节植被指数(MSAVI)、增强型水体指数(EWI)、土壤亮度指数(NDSI)、土壤湿度指数(NDMI)之间的关系。结果表明,兰州城市热岛效应较为严重,城市热岛效应与土壤湿度指数、增强型水体指数、土壤亮度指数呈正相关,与修改后的土壤调节植被指数呈负相关。  相似文献   

山东省农村居民点转型的空间特征及其经济梯度分异   总被引：12，自引：2，他引：10  

曲衍波  姜广辉  张佰林  李慧燕  魏淑文 《地理学报》2017,72(10):1845-1858

为探究农村居民点转型的空间结构及其与经济发展的关联性,以山东省为例,基于农村宅基地转型的理论假设与测度方法,运用空间关联分析方法研究农村居民点转型的空间布局和集聚特征,并以人均GDP作为特征指标划分各县级行政区的经济发展梯度,从省级全域层面和“点、线、面”特征单元综合的角度,揭示农村居民点转型与经济发展的相关性及其耦合关系。结果显示,在空间分布上,2005-2014年山东省农村居民点转型指数呈现西高东低和南高北低的态势;在全局趋势上,Moran's I指数达到0.6317,说明农村居民点转型存在显著的空间集聚现象;在局部趋势上,农村居民点转型的热点区和次热点区集中分布在鲁西黄泛平原、鲁西南淮河平原以及鲁中沂蒙山区,次冷点区分布在次热点区外围,冷点区分布在胶东丘陵地区和鲁北黄河三角洲地带;在相关性分析上,农村居民点转型与经济发展水平具有明显的数理统计相关性和空间耦合性,无论是全域层面还是特征单元,农村居民点转型均表现出从低级到高级经济梯度的递减规律、且乘幂变化趋势显著。本文探索了农村居民点转型的空间特征,弥补了土地利用转型空间性分析的不足;同时研究结果也较好地验证了前人提出的理论假设。  相似文献   

民族文化资源的类型特征及成因分析——以格萨尔（果洛）文化生态保护实验区为例   总被引：2，自引：1，他引：1  

朱鹤  刘家明  桑子文  魏文栋  魏宗财 《地理学报》2017,72(6):1118-1132

由人类非物质文化遗产《格萨（斯）尔》史诗派生出的格萨尔文化是青藏高原地区独特的区域文化形态。文化资源是文化的载体和展示形式,具有价值性和不可替代性。研究格萨尔文化资源的分类、空间分布及成因对于探讨青藏高原地区人地关系,保护人类非物质遗产有非常重要的意义。果洛藏族自治州是格萨尔文化资源最为富集的区域,并于2014年被授予格萨尔文化生态保护实验区。本文首先对格萨尔文化资源进行界定和分类,并以果洛为例,探讨格萨尔文化资源的空间分布特征及与自然地理条件（高程、水源、坡度、坡向、可达性）的关系,并分析影响文化资源分布的原因,得出以下结论：① 格萨尔文化资源可以分为4大类,11个亚类和60个子类,果洛的格萨尔文化资源覆盖全部类型,共1189个;② 果洛格萨尔文化资源空间分布具有聚集性,其中A类文化人（团体）类集聚程度最高,并通过最近邻分析和密度分析对各类文化资源的集聚空间进行识别;③ 格萨尔文化资源的空间分布与自然地理条件有关,多位于海拔相对较低、距水源地较近的位置,不同类型的文化资源分布对坡度、坡向和可达性的关系不同。  相似文献   

Analysis of the Spatio-temporal Changes in Acid Rain and Their Causes in China (1998-2018)     

CHEN Xuan  SHAN Xiaoran  SHI Zhaoji  ZHANG Jiaen  QIN Zhong  XIANG Huimin  WEI Hui 《资源与生态学报(英文版)》2021,12(5):593-599

With the rapid development of the economy, acid rain has become one of the major environmental problems that endanger human health. Being the largest developing country, the environmental problems caused by acid rain are of increasing concern with the rapid industrialization and urbanization in China. Recently, many researchers have focused on acid rain. To better understand the temporal and spatial dynamics of acid rain in China, the monitoring data on acid rain from 1998 to 2018 were studied using ArcGIS 10.2. The results show that the proportion of acid rain cities, the frequency, and the area of acid rain were decreasing, however, the situation still remains serious. Overall, the chemical type of acid rain was mainly sulfuric acid rain. However, the concentration ratio of SO₄ ^2-/NO₃ ^- decreased by 81.90% in 2018 compared with 1998, and presented a decreasing trend, which indicates that the contribution of nitrate to precipitation acidity has been increasing year by year. This research will help us to understand the distribution characteristics and causes of acid rain in China, and it may provide an effective reference for the prevention and control of acid rain in China.  相似文献   

Effects of Enclosure on Plant and Soil Restoration in the Junggar Desert     

WEI Peng  AN Shazhou  KE Mei  LI Chao  HOU Yurong  LAN Jiyong  KANG Shuai  JIN Junpeng 《资源与生态学报(英文版)》2021,12(6):840-848

Enclosure is commonly used in the restoration of degraded grasslands. However, the effects of enclosure on grassland plant and soil restoration remain controversial, particularly in deserts. To assess the effects of enclosure on desert plants and soil properties, using high throughput sequencing, the differences between plants and soil were systematically analyzed before and after enclosure construction. The soil organic carbon, total nitrogen and total phosphorus contents of the three desert flora increased and decreased, but the difference was not significant; enclosure increased plant height, coverage, aboveground biomass, and species richness by 58.99%, 59.35%, 33.29%, and 51.21%, respectively, in a Seriphidium transiliense formation; by 15.49%, 33.52%, 20.85%, and 5.13%, respectively, in a Haloxylon persicum formation; and by 83.80%, 31.51%, 76.66% and 33.33%, respectively, in an Anabasis salsa formation. For soil bacteria, enclosure significantly increased the average number of operational taxonomic units and Shannon-Wiener index by 12.74% and 2.92%, respectively, under S. transiliense formation and by 17.08% and 3.17%, respectively, under H. persicum formation. However, enclosure had no significant effect on the average number of operational taxonomic units or Shannon-Wiener index under A. salsa formation. Enclosure significantly increased desert plants, soil bacterial diversity, and desert plant community productivity; however, the increase in soil nutrient content was not significant. These results demonstrate that enclosure is effective for restoring desert ecosystems but may have little effect on the soil nutrient content.  相似文献   

北冰洋沉积物和海水叶绿素α浓度分布的区域性特征     

刘子琳  陈建芳  刘艳岚  张宏  陈忠元  张海生 《沉积学报》2008,26(6):1035-1042

2003年夏季中国第二次北极科学考察期间,在北冰洋楚科奇海陆架、楚科奇海台、陆坡流区、门捷列夫海岭和加拿大海盆等不同区域进行了200 m以浅海水和部分观察站沉积物表层叶绿素a浓度的现场观测。结果表明,观测水体叶绿素α浓度变化范围为0.002～39.008 μg/dm3。表层浓度分布范围为0.037～4.644 μg/dm3,平均值为0.612 μg/dm3;高叶绿素α浓度出现在水深20～30 m的次表层水。叶绿素α浓度分布具有明显的区域性特征,水柱平均浓度的次序为楚科奇海陆架区>陆坡流区>楚科奇海台区>加拿大海盆区>门捷列夫海岭区。表层沉积物叶绿素α浓度从未能检出～3.978 μg/g(湿重),平均浓度为0.954 μg/g(湿重),表现为沉积物表层的浓度高于下层,陆架和陆坡流区的浓度高于海岭区以及海台和海盆区的分布特征。  相似文献   

Statistics-based Optimization of the Polarimetric Radar Hydrometeor Classification Algorithm and Its Application for a Squall Line in South China     

Chong WU  Liping LIU  Ming WEI  Baozhu XI  Minghui YU 《大气科学进展》2018,35(3):296-316

A modified hydrometeor classification algorithm(HCA) is developed in this study for Chinese polarimetric radars. This algorithm is based on the U.S. operational HCA. Meanwhile, the methodology of statistics-based optimization is proposed including calibration checking, datasets selection, membership functions modification, computation thresholds modification,and effect verification. Zhuhai radar, the first operational polarimetric radar in South China, applies these procedures. The systematic bias of calibration is corrected, the reliability of radar measurements deteriorates when the signal-to-noise ratio is low, and correlation coefficient within the melting layer is usually lower than that of the U.S. WSR-88D radar. Through modification based on statistical analysis of polarimetric variables, the localized HCA especially for Zhuhai is obtained,and it performs well over a one-month test through comparison with sounding and surface observations. The algorithm is then utilized for analysis of a squall line process on 11 May 2014 and is found to provide reasonable details with respect to horizontal and vertical structures, and the HCA results—especially in the mixed rain–hail region—can reflect the life cycle of the squall line. In addition, the kinematic and microphysical processes of cloud evolution and the differences between radardetected hail and surface observations are also analyzed. The results of this study provide evidence for the improvement of this HCA developed specifically for China.  相似文献   

定量测量降水量的回波结构自适应算法研究          下载免费PDF全文

魏鸣  宋羽轩  张蕾 《大气科学学报》2018,41(5):676-683

为提高临近预报中对流性降水估测的准确性,分析了统计法估算降水的局限性。依据降水物理机制和降水回波结构,研究雷达反射率因子定量测量降水量(QPE-Qualitative Precipitation Estimate)的自适应算法,旨在减少由于雨滴谱变化导致的Z-I关系不稳定所引起的降水量测量误差。同时考虑组合反射率因子RC和垂直液态水含量VIL两个参量对降水的影响,建立适于城市区域的动态自适应的Z-I关系,改进对强降水严重低估的问题。  相似文献