CO observations of Southern molecular clouds. Outflows from young stellar objects GRV 8 and GRV 16

¹²CO (1-0) observations of two Southern dark clouds (globules) associated with cometary nebulae GRV 8 (a biconical nebula) and GRV 16 (a conelike nebula) are presented. GRV 8 shows an outflow from the central part of the nebula (where in 2MASS images a star is located, which is perhaps responsible for this outflow); however, both lobes of the outflow are redshifted with a velocity of +1.95 km/s with respect to the molecular cloud. The two opposite redshifted lobes are a rather rare phenomenon that could be explained by the presence of a double star instead of a single one as the engine responsible for the outflow. The two lobes are almost parallel to the axis of symmetry of the biconical nebula. In the case of the conelike nebula GRV 16 we observe a bipolar outflow, where the eastern blueshifted lobe has a velocity of –4 km/s with respect to the molecular cloud, and the western redshifted one has a velocity +2.5 km/s. The outflow has a direction almost coinciding with the axis of symmetry of the conelike nebula. The star associated with the conelike nebula is responsible for this outflow.Published in Astrofizika, Vol. 48, No. 1, pp. 101–112 (February 2005).     

On the detection of the linear C5 molecule in the interstellar medium

An upper limit of the column density of the C₅ linear molecule in translucent interstellar clouds is estimated from high-resolution ( R =80 000) and very high signal-to-noise ratio (∼1000) echelle spectra. It is 10¹² cm⁻² per E ( B − V )=1 (two orders of magnitude lower than that of C₂).     

Adiabatic predictions and observations of cloud droplet spectral broadness

The evolution of cloud droplet size spectra is calculated using an adiabatic condensational growth model. Broadness (e.g., standard deviation of diameter) of cloud droplet spectra in adiabatic cloud parcels was determined to be critically dependent on cloud supersaturation. Although droplet spectra become narrower as growth continues, the rate of narrowing is slower when cloud supersaturation is lower. This actually leads to broader droplet spectra for more continental clouds or for weaker updrafts because both of these conditions are associated with lower cloud supersaturations. More continental type clouds, which have higher concentrations of smaller droplets, were indeed found to have larger dispersions (standard deviation of diameter/mean diameter of cloud droplets). Some of these results were consistent with observations, but the larger dispersions that were much more commonly observed for continental compared to maritime clouds were due almost exclusively to smaller droplets rather than broader droplet distributions. Contrary to the model calculations, typical observations show that cleaner clouds usually have broader droplet spectra. The gaps in magnitude between theory and observations of broadness are significant in all clouds. When cloud parcels that had ascended under different updraft conditions were compared at a constant cloud altitude, parcels with lower updrafts were predicted to have broader droplet spectra with larger mean diameters. This trend of apparent spectral broadening was consistent with observations for some near-adiabatic cloud parcels.     

基于多分辨率方向预测的LIDAR点云滤波方法

为了快速提取LIDAR点云中的地面点,生成高精度的DTM,提出了一种基于多分辨率方向预测的LIDAR点云滤波方法。该方法首先构建多种分辨率数据集,然后基于方向预测法以分辨率由低到高的顺序逐层进行数据集的平滑处理,最后以最高分辨率数据集的平滑结果为基准标记原始LIDAR点云。本方法通过分析反距离权重插值模型的不足,利用改进的模型进行裸露地面点的插值,得到高精度的DTM。实验表明,本文方法能有效地滤除地物,并保持原有的地形特征,算法效率高,具有一定的实用价值。     

机载激光雷达森林垂直结构剖面参数的沿海平原人工林林分特征反演

中国是世界上人工林面积最大的国家,实时、定量、精确地获取人工林林分特征对于人工林资源监测、管理以及全球碳循环具有重要意义。以北亚热带沿海平原人工林为研究对象,借助机载激光雷达LiDAR(Light Detection And Ranging)点云数据并结合地面实测的55个样地来反演人工林林分特征。首先,构建冠层高度分布剖面CHD(Canopy Height Distribution)和枝叶剖面FP(Foliage Profile);然后,通过Weibull函数分别对CHD和FP进行拟合并提取Weibull参数作为特征变量(第1组);同时,还直接基于点云提取了LiDAR高度变量HRM(HeightRelated Metrics)和冠层密度变量DRM(Density-Related Metrics)(第2组);最后,结合地面实测数据和两组特征变量构建了多元回归模型用于预测各林分特征(即林分密度、平均胸径、胸高断面积、Lorey’s树高、蓄积量和地上生物量)。结果表明:(1)与只使用基于点云的特征变量(即第2组)相比,结合点云特征变量(第2组)和冠层垂直结构剖面特征变量(第1组)的各林分特征预测精度均有所提升(ΔAdjusted R2=0—0.13,ΔrRMSE=0.08—3.65%);(2)对各林分特征预测的结果中,Lorey’s树高(Adjusted R2=0.85, rRMSE=7.66%)和蓄积量(Adjusted R2=0.84,rRMSE=14.27%)的预测精度最高,地上生物量(Adjusted R2=0.78, rRMSE=14.15%)、胸高断面积(Adjusted R2=0.73, rRMSE=14.70%)和平均胸径(Adjusted R2=0.64, rRMSE=15.05%)次之,林分密度(Adjusted R2=0.58,rRMSE=26.16%)的预测精度最低;(3)Weibull函数较准确地反映了亚热带人工林垂直冠层结构,可以有效提高林分特征反演精度。     

太行山东麓一次强对流冰雹云结构的观测分析

利用“太行山东麓人工增雨防雹作业技术试验示范”项目在冰雹发生区获取的综合观测资料,从强对流单体出现的天气背景、降雹特征、雷达回波演变、大冰雹的形成机制及动力结构等方面对2018年5月12日下午发生于太行山东麓的一次强对流单体降雹天气过程进行了分析。结果显示,午后不稳定能量的增大形成了有利的热力条件,低层风场的辐合扰动以及中层的冷空气侵入是产生本次强冰雹过程的触发因素。通过对雹云降雹时段雷达回波具有超长“悬挂回波”和对应大雹形成特征分析表明,云中存在着上、中、下相互衔接的0线（域）,主上升气流2次逆时针转弯增加了雹胚再入主上升气流区继续长成大雹的机会,据此勾画出了云体主上升气流框架及大冰雹的形成机制,表明冰雹在雹云中的生长有多种模式。      

华北积层混合云中冰晶形状、分布与增长过程的飞机探测研究

利用中国国家科技支撑计划重点项目环北京地区3架飞机联合云探测试验数据,分析了2009年4月18日和5月1日两次积层混合云中冰晶形状、分布与增长过程。结果表明：飞机在0—-16℃范围的云层内观测到的冰晶形状主要包括板状、针柱状、柱帽状、辐枝状和不规则状。云中低层的冰晶形状受云顶温度影响,云顶温度不同,冰晶形状不同,当云顶温度高于-8℃时,云中低层的冰晶以板状和针柱状为主;当云顶温度低于-13℃时,在云中低层可观测到辐枝状冰晶;当云顶温度低于-18℃时,在云中低层可观测到柱帽状冰晶。同时冰晶形态还受其所处云中位置的影响,在积层混合云中的嵌入对流区含有更多的凇附状冰晶;在融化层以上,冰晶的增长过程主要包括凝华、凇附和聚合过程,在垂直方向上,随着高度降低云中过冷水增多,冰晶的凇附增长也相应增强。积层混合云中的对流区和层云区粒子谱下落拓宽速率有明显差别,在4.8—4.2 km（-11.6—-8℃）高度层,对流区粒子谱拓宽速率为3 mm/km,而层云区为3.67 mm/km,层云中粒子拓宽增长的速率略高于对流区;而在4.2—3.6 km（-8—-5℃）高度层,对流区的粒子谱拓宽速率为6.67 mm/km,层云区为2.33 mm/km,对流区的粒子拓宽增长速率是层云区的近3倍,主要原因是对流区低层的过冷水含量较高。     

Effects of Doubled Carbon Dioxide on Rainfall Responses to Radiative Processes of Water Clouds

The effects of doubled carbon dioxide on rainfall responses to radiative processes of water clouds are investigated in this study.Two groups of two-dimensional cloud-resolving model sensitivity experiments with regard to pre-summer heavy rainfall around the summer solstice and tropical rainfall around the winter solstice are conducted and their five-day averages over the model domain are analyzed.In the presence of radiative effects of ice clouds,doubled carbon dioxide changes pre-summer rainfall from the decrease associated with the enhanced atmospheric cooling to the increase associated with the enhanced infrared cooling as a result of the exclusion of radiative effects of water clouds.Doubled carbon dioxide leads to the reduction in tropical rainfall,caused by the removal of radiative effects of water clouds through the suppressed infrared cooling.In the absence of radiative effects of ice clouds,doubled carbon dioxide changes pre-summer rainfall from the increase associated with the strengthened atmospheric warming to the decrease associated with the weakened release of latent heat caused by the elimination of radiative effects of water clouds.The exclusion of radiative effects of water clouds increases tropical rainfall through the strengthened infrared cooling,which is insensitive to the change in carbon dioxide.     

�����Ƚ���Ȩ������С���˵ĵ�������ƽ�����

??????????????????????????????????С???????????????????????????????????????????????????????????????????????????????????????С???????????????????????????????????????????????????????淽?????????????λ???????С???????????????     

山东三类降水云雨滴谱分布特征的观测研究

利用激光雨滴谱仪2009年8月—2010年10月观测获取的滴谱资料,分析了山东省三类云降水雨滴微结构参量特征及滴谱随降水过程的演变特征。按照降水云系不同分别对各微物理参量进行比较,结果表明,各值由大到小排序依次均为积雨云、混合云和层状云。三类云降水过程中雨强与雨滴数浓度和最大直径间存在较好的相关关系;层状云和混合云降水以直径小于2 mm的雨滴为主,而积雨云降水以1~3 mm的雨滴对雨强贡献最大。层状云降水雨滴谱很窄,呈单峰或双峰型;积雨云降水雨滴谱宽,在大滴端呈多峰结构;混合云降水谱宽介于前两者之间。另外,统计得到该地区三类云降水的Z-I关系式,为雷达定量测量降水提供了一定的参考。