Vertical Distribution Characteristics of PM<Subscript>2.5</Subscript> Observed by a Mobile Vehicle Lidar in Tianjin,China in 2016

We present mobile vehicle lidar observations in Tianjin, China during the spring, summer, and winter of 2016. Mobile observations were carried out along the city border road of Tianjin to obtain the vertical distribution characteristics of PM_2.5. Hygroscopic growth was not considered since relative humidity was less than 60% during the observation experiments. PM_2.5 profile was obtained with the linear regression equation between the particle extinction coefficient and PM_2.5 mass concentration. In spring, the vertical distribution of PM_2.5 exhibited a hierarchical structure. In addition to a layer of particles that gathered near the ground, a portion of particles floated at 0.6–2.5-km height. In summer and winter, the fine particles basically gathered below 1 km near the ground. In spring and summer, the concentration of fine particles in the south was higher than that in the north because of the influence of south wind. In winter, the distribution of fine particles was opposite to that measured during spring and summer. High concentrations of PM_2.5 were observed in the rural areas of North Tianjin with a maximum of 350 μg m^–3 on 13 December 2016. It is shown that industrial and ship emissions in spring and summer and coal combustion in winter were the major sources of fine particles that polluted Tianjin. The results provide insights into the mechanisms of haze formation and the effects of meteorological conditions during haze–fog pollution episodes in the Tianjin area.     

吉林省一次降水性层状云消散期的微观结构特征

利用2012年6月29日的通辽和白城飞机联合探测资料(包括DMT和PMS)及雷达资料,对吉林省一次层状云降水消散期微观物理结构特征进行分析研究。结果表明:该天气过程是在东北锋面气旋影响下发展起来的,给东北地区带来大范围降水,属于吉林地区春季常见的降水性层状云系As-Ac-Ns云型。Ns云底约在1000m左右,云顶不超过4000m,Ns云层较厚,在该云系发展过程中雨层云下伴有碎雨云。结合DMT和PMS,小粒子在每个高度层上都占主要部分,0.61～2μm的小粒子浓度可达100cm-3,直径大于2μm的粒子谱型基本都是单调递减型;云内含水量较少,极大值也不足0.01g·m-3;粒子有效直径随高度变化呈多峰分布,粒子有效直径与粒子浓度在0℃层以下范围内,大的粒子有效直径对应小的粒子浓度,随着高度的升高粒子有效直径呈递减趋势。     

Aerodynamic grain‐size distribution of blown sand

Aeolian sand entrainment, saltation and deposition are important and closely related near surface processes. Determining how grains are sorted by wind requires a detailed understanding of how aerodynamic sand transport processes vary within the saltating layer with height above the bed. Grain‐size distribution of sand throughout the saltation layer and, in particular, how the associated flux of different grain size changes with variation in wind velocity, remain unclear. In the present study, a blowdown wind tunnel with a 50 cm thick boundary layer was used to investigate saltating sand grains by analyzing the weight percentage and transport flux of different grain‐size fractions and the mean grain size at different wind velocities. It was found that mean grain size decreases with height above the sand bed before undergoing a reversal. The height of the reversal point ranges from 4 to 40 cm, and increases with wind velocity following a non‐linear relationship. The content of the finer fractions (very fine and fine sand) initially increases above the sand bed and then decreases slightly with height, whereas that of the coarser fractions (medium and coarse sand) exhibits the opposite trend. The content of coarser grains and the mean grain size of sand in the saltation layer increase with wind velocity, indicating erosional selectivity with respect to grains in multi‐sized sand beds; but this size selectivity decreases with increasing wind velocity. The vertical mass flux structure of fine sand and very fine sand does not obey a general exponential decay pattern under strong wind conditions; and the coarser the sand grain, the greater the decrease rate of their transport mass with height. The results of these experiments suggest that the grain‐size distribution of a saltating sand cloud is governed by both wind velocity and height within the near‐surface boundary layer.     

北京市建筑设计产业空间分布与区位选择

超大城市的城市空间结构调整需求日益迫切,城市内细分产业的空间分布及区位选择的研究也变得更加重要.以北京市为例,从微观视角分析了超大城市内部企业空间分布规律,以期为城市优化建筑设计产业空间结构提供理论支撑.运用核密度估计方法、Ripley's K(d)函数以及负二项模型,分析了建筑设计企业的空间分布及其区位选择的影响因素...     

基于钻孔抽水试验和示踪试验的岩溶地区含水层结构研究

岩溶含水层具有强异质性和各向异性特征,其空间结构的调查和认识是地下水流动和污染物迁移研究的重要基础。然而,岩溶含水层特殊的地质结构导致岩溶区水文地质调查非常困难。为了更好地掌握研究区岩溶含水层结构特征,本文在进行抽水试验的同时开展多示踪剂（荧光素钠、罗丹明、荧光增白剂）示踪试验。利用Theis标准曲线对比法分析抽水试验数据,计算试验场地渗透张量,根据示踪试验结果分析含水层结构性质。计算出研究区渗透张量主方向的导水系数分别为:0.297 m2·h-1和0.028 m2·h-1,给水度为1.19E-04,优势方向为东偏南18.47°。抽水条件下示踪试验获得3种示踪剂的回收率分别为:荧光素钠97.98%,罗丹明B47.34%,荧光增白剂39.54%;平均流速分别为:0.378 m·h-1、0.3 m·h-1和0.14 m·h-1,反映研究区岩溶孔隙、裂隙较小,示踪剂运移慢、时间长。荧光素钠和荧光增白剂的BTC曲线表现为单峰型,罗丹明B的BTC曲线表现为多峰型,表明研究区既发育优势流裂隙,又发育相对均匀裂隙。同时,示踪剂最大回收率方向与抽水实验所得渗透张量主方向相符。研究结果为岩溶含水层精细结构的刻画,水文模型物理参数的确定提供了方法和依据。      

西南黄海2018年夏季溶解氧分布特征及其影响因素的初步分析

利用2018年夏季在西南黄海的现场调查资料,分析了海温、盐度和溶解氧(dissoloved oxygen,DO)分布特征.海区西侧的江苏沿海有明显的冷水带,冷水带对应表层较高的DO浓度.在海区南侧的长江口附近,盐度由南向北升高,上部海水DO浓度高,下部海水DO浓度低.综合现场观测数据、CCMP (Cross Calib...