SWAN雷达产品在甘肃河东地区冰雹短临预报中的应用

选取2011年7月发生在甘肃省河东地区的7次冰雹个例,综合分析SWAN系统输出的雷达产品资料的主要特征,提取冰雹天气的雷达产品资料的指标,根据这些指标利用SWAN系统外推算法资料生成冰雹临近预报产品。通过2012年甘肃河东地区的2次冰雹天气过程对与其同时的临近预报产品检验结果表明,预报效果良好,具有较高的业务应用价值。     

Mosaic desert pavement influences water infiltration and vegetation distribution on fluvial fan surfaces

Desert pavements (DPs) are critical for maintaining ecological stability and promoting near-surface hydrological cycling in arid regions. However, few studies have focused on eco-hydrological processes of DPs in the ecological systems of fluvial fans. Although DP surfaces appear to be barren and flat, we found that the surfaces are characterized by surface mosaic patterns of desert pavement (mosaic DP) and bare ground (mosaic BG). We investigated the effects of mosaic DP on water infiltration and vegetation distribution at six sites in fluvial fans (one on a hillside and five within the sectors of fans) along a southwest belt transect in northern Linze County, in the central Hexi Corridor (China). We found significant differences in mosaic DP between the hillside and sector sites in terms of pavement thickness and vesicular horizon thickness (Av thickness), particle composition, and bulk density, although significant differences were absent for mass soil water content, gravel coverage, and surface gravel size. The mosaic DP inhibited water infiltration by the pavement layer, where the sorptivity (S), initial infiltration rate (i_int), steady-state infiltration rate (i_sat) and infiltration time (T) averaged 1.19 cm/min^-0.5, 0.64 cm/min, 0.13 cm/min and 12.76 min, respectively. Where the pavement layer was scalped, the S, i_int, and i_sat increased by 0.27 cm/min^-0.5, 0.52 cm/min, and 0.40 cm/min, respectively, and the T reduced by 7.42 min. Water infiltration was mainly controlled by the pavement layer thickness (+), Av thickness (−), surface gravel coverage (−), fine earth (+) and fine gravel (−) in the pavement layer. The DP surfaces only had a sparse covering of shrubs, but an abundance of herbs. Few shrubs were present on the mosaic DP, but a greater number of shrubs and herbs grew on the mosaic BG. It can be concluded that DPs can maintain vegetation stability for different surface mosaic patterns. This study deepens our understanding of the eco-hydrological cycle of DP landscapes in arid regions.     

三叠纪牙形石的古环境与古地理意义

牙形石广泛分布于寒武纪至三叠纪的海洋里。三叠纪牙形石的种类、形态、大小和产出频率受海水盐度、深度、温度和水动力条件等因素控制，不同的牙形石生态特征即牙形石相反映不同的沉积环境，所以，根据三叠纪牙形石相和牙形石特征属种的丰度，不但可区分三叠纪不同的沉积相区（台地相区、台地边缘相区、盆地相区），恢复三叠纪古地理面貌，而且可划分出牙形石生物地理区。中国早三叠世牙形石归属特提斯生物大区亚洲生物省，并可进一步划分出两个生物亚省和若干生态区。     

锡同位素研究进展及其在矿床学中的应用展望

锡同位素是一种新兴的非传统稳定同位素,其在考古学及天体化学中的运用显示出非常大的示踪潜力和价值,然而目前其在地质学(尤其是矿床学)中的研究和应用前景缺乏系统介绍。本文总结分析了世界上目前所发表的主要天然及人工样品的锡同位素数据,发现天然样品中锡同位素组成有较大差异,其中玻璃陨石最富重锡(其δ^122/118Sn值可达2.53‰),而黝锡矿(黄锡矿)最富轻锡(其δ^120/116Sn值可达-1.71‰)。其中,含锡矿物(如锡石和黝锡矿)中的锡同位素组成变化范围要远远大于全岩样品。地幔及地壳来源的不同岩性或地质体的全岩锡同位素组成有明显差别;锡同位素在一定条件下可以发生分馏,且分馏程度可能远远大于锡同位素的初始值差异。锡石锡同位素对成矿环境非常敏感,其形成时的流体成分、化学反应速率以及物化条件(如温度、盐度、氧逸度、pH值等)等因素均能影响其锡同位素的组成。深部流体(如岩浆来源)结晶的锡石富重锡,而浅部流体(如地层流体)的加入将使锡石富轻锡,因此锡石的锡同位素具有判别不同矿床成因类型的潜力。展望未来,锡同位素的研究有望在以下三方面取得突破:(1)各地...     

Present land use and cover patterns and their development potential in North Ningxia

With the objectives to acquire the fundamental data of the territorial resource, understand the impacts of human activities on the land use and cover patterns and evaluate the potential of the future exploitation, an intensive land cover classification with an accuracy of 93% has been completed for North Ningxia by remote sensing technique based on the adoption of a combination method composed of texture training, maximum likelihood classification and post-processing such as re-allocation and aggregation. This classification result was incorporated with the contemporaneous socio-economic and meteorological data for cross-sectional regression modelling to reveal the spatial determinants of the land cover patterns and understand the human-environmental relationships. A tentative evaluation on the potential of soil exploitation in the near future was carried out in combination with our land use and cover change detection results aiming at supplying some useful references for the central and local governments in their sustainable land use planning.     

不同气候区灌丛沙堆形态及土壤养分积累特征

灌丛沙堆是干旱、半干旱区绿洲边缘常见景观类型,在绿洲风沙防护及生物多样性保护方面有重要意义.本文对中国西北干旱区不同气候区常见的柽柳(Tamarix chinensis)、泡泡刺(Nitraria sphaerocarpa)和柠条锦鸡儿(Caragana korshinskii)灌丛沙堆形态和养分积累特征进行了对比研究...     

Precipitation seesaw phenomenon and its formation mechanism in the eastern and western parts of Northwest China during the flood season

Extending across three major plateaus,namely the Qinghai-Tibetan Plateau,the Inner Mongolia-Xinjiang Plateau and the Loess Plateau,Northwest China has the complex terrain and spatio-temporal climate variations,and is affected by the interactions among different circulation systems,such as the summer monsoon,the westerlies and the plateau monsoon.The understanding of the climate variability,as well as its characteristics and evolution mechanisms in this area has been limited so far.In this paper,the precipitation characteristics and mechanisms in the eastern and western parts of Northwest China during the flood season are compared and analyzed based on the data from 192 national meteorological observational sites in Northwest China in 1961-2016.The results show that,divided by the northern boundary of the East Asian summer monsoon,there are huge differences in the precipitation variation characteristics between the eastern and western parts.The inter-annual variations,interdecadal variations and total trends in the two parts all show a significant seesaw phenomenon.Moreover,it is found that the seesaw phenomenon of precipitation variation is closely related to the opposite variation between the East Asian summer monsoon index(MI) and the westerly circulation index(WI).In addition,the inverse variations on different time scales are only related to the contributions of precipitation at specific grades.Besides,in the two matching patterns of precipitation in the seesaw phenomenon,the middle and high latitudes are occupied by the "high-low-high" wave trains in the precipitation increases in the east of Northwest China(ENWC) and decreases in the west of Northwest China(WNWC) pattern,meaning precipitation increases in ENWC and decreases in WNWC.Whereas the opposite "low-high-low" wave trains at 500 hPa height are observed in the middle and high latitudes in the WH-EA pattern at 500 hPa height,meaning precipitation increases in WNWC and decreases in ENWC.Thus,the atmosphere circulation situation with two wave train types can support both the precipitation seesaw phenomenon and the opposite variation between MI and WI.Moreover,the seesaw phenomenon is shown to be related to the separate or joint effects of the South Asian High,ENSO and the plateau heating on the common but opposite effect on the summer monsoon and the westerlies,in which the South Asian High probably plays a more critical role.This study could deepen the scientific understanding of precipitation mechanisms and improve the weather forecast technology in Northwest China during the flood season.     

TRMM卫星对青藏高原东坡一次大暴雨强降水结构的研究

利用热带测雨卫星（TRMM）探测资料,NCEP、ERA-Interim再分析资料,结合C波段多普勒雷达和其他地面观测资料,研究了2013年7月21日发生在青藏高原东坡的一次大暴雨强降水结构。结果表明,高能、高湿的不稳定大气在700 hPa切变线及地面辐合线的触发下产生了此次大暴雨,降水具有明显的强对流性质。从水平结构来看,降水系统由成片的层云雨团中分散分布的多个对流性雨团组成,对流样本数远少于层云,但平均雨强是层云的4.7倍,对总降水的贡献达到25.6%;以超过10 mm/h雨强为强度标准,3个20-50 km、回波强度在45-50 dBz的β中尺度对流雨团零散地分布在主雨带中,对应 < 210 K的微波辐射亮温区和≥ 32 mm/h的地面强降水;对流降水的雨强谱集中在1-50 mm/h,其中20-30 mm/h的雨强对总雨强的贡献最大,这与中国东部降水有着显著区别,而90%的层云降水的雨强均小于10 mm/h。从垂直结构来看,对流降水云呈柱状自地面伸展,平均雨顶高度随地面雨强的增强而不断升高（5-12 km）,强降水中心区域的质心在2-6 km;降水廓线反映出强降水系统中降水主要集中在6 km以下高度范围,且降水强度在垂直方向分布不均匀,对流降水和层云降水的强度随高度升高的总趋势是趋于减弱,但在一定高度范围内,对流降水强度随高度升高而增大,并且在多个地表雨强廓线中都有体现。此外,地基雷达的探测结果也表明了强降水的低质心特点及显著的逆风区演变特征,这是对TRMM PR探测的验证和补充。      

贵州百花湖麦西河河口后生浮游动物群落结构及与环境因子的关系

为了探明百花湖麦西河后生浮游动物的群落组成及动态特征,于2009年8月至2011年8月对百花湖麦西河河口后生浮游动物进行调查研究.结果表明:百花湖麦西河河口共监测到轮虫29种,丰度为0.16～837.80 ind./L;桡足类浮游动物仅检测到了温中剑水蚤(Mesocyclops thermocyclopoides)和猛水蚤(Harpacticella sp.)2种,以无节幼体和桡足幼体为主,其丰度为0～642.75 ind./L;枝角类浮游动物9种,丰度为0～31.20 ind./L.后生浮游动物的丰度主要由轮虫和桡足类组成,轮虫丰度比例为4.09%～100%,桡足类丰度比例为0～95.64%.前节晶囊轮虫(Asplanchna priodonta)、卜氏晶囊轮虫(Asplanchna brightwelli)、裂足臂尾轮虫(Brachionus diversicornis)为轮虫类的主要优势种,最高丰度分别达到424.88、392.20和61.99 ind./L;长额象鼻溞(Bosmina longirostris)为枝角类优势种,最高丰度达到27.93 ind./L.轮虫丰度与透明度、总氮、硝态氮呈极显著正相关;枝角类丰度与透明度、硝态氮呈极显著正相关,与温度呈极显著负相关.     

金融发展与海洋经济增长——基于我国沿海地区的实证研究

文章基于1999—2020年我国沿海地区的面板数据,在建立面板向量自回归模型（PVAR）的基础上,运用脉冲响应函数和方差分解等方法,从金融发展规模、效率和结构3个方面,分析金融发展对沿海地区海洋经济增长的影响及其动态关系。研究结果表明：在短期内,金融发展规模会对海洋经济增长产生促进作用,但在长期内可能会制约海洋经济增长;金融发展效率会促进海洋经济增长,并在长期成为主要的影响因素;金融发展结构对海洋经济增长具有促进作用,但持续期较短。因此,海洋经济增长离不开金融有力的支持,应合理控制金融发展规模、提高金融发展效率和优化金融发展结构,为海洋经济增长提供长效支撑,推动海洋经济可持续增长。