Thermodynamics and Microphysical Characteristics of an Extreme Rainfall Event Under the Influence of a Low-level Jet over the South China Coast

In this paper, the data of Automatic Weather Stations (AWSs), ERA5 reanalysis, sounding, wind profile radar, and dual-polarization radar are used to study an extreme rainfall event in the south China Coast on 11 to 12 May 2022 from the aspects of thermodynamics and microphysical characteristics under the influence of low-level jets (LLJs). Results show that: (1) The extreme rainfall event can be divided into two stages: the first stage (S1) from 0000 to 0600 LST on May 12 and the second stage (S2) from 0700 to 1700 LST on the same day. During S1, the rainfall is mainly caused by the upper-level shortwave trough and the boundary layer jet (BLJ), characterized by strong upward motion on the windward side of mountains. In S2, the combined influence of the BLJ and synoptic-system-related low-level jet (SLLJ) increases the vertical wind shear and vertical vorticity, strengthening the rainstorm. In combination with the effect of topography, a warm and humid southwest flow continuously transports water vapor to farther north, resulting in a significant increase in rainfall over the study area (on the terrain’s windward slope). From S1 to S2, the altitude of a divergence center in the upper air decreases obviously. (2) The rainfalls in the two stages are both associated with the mesoscale convergence line (MCL) on the surface, and the wind field from the mesoscale outflow boundary (MOB) in S1 is in the same direction as the environmental winds. Due to a small area of convergence that is left behind the MOB, convection moves eastward quickly and causes a short duration of heavy rainfall. In S2, the convergence along the MOB is enhanced, which strengthens the rainfall and leads to strong outflows, further enhancing the surface convergence near the MOB and forming a positive feedback mechanism. It results in a slow motion of convection and a long duration of heavy rainfall. (3) In terms of microphysics, the center of a strong echo in S1 is higher than in S2. The warm-rain process of the oceanic type characterizes both stages, but the convective intensity in S2 is significantly stronger than that in S1, featuring bigger drop sizes and lower concentrations. It is mainly due to the strengthening of LLJs, which makes small cloud droplets lift to melting levels, enhancing the ice phase process (riming process), producing large amounts of graupel particles and enhancing the melting and collision processes as they fall, resulting in the increase of liquid water content (LWC) and the formation of large raindrops near the surface.     

台风“妮妲”（1604）登陆期间近地层风特性分析

利用深圳350 m气象梯度观测铁塔获取的台风“妮妲”（1604）登陆期间近地多层风观测资料,分析“妮妲”登陆期间风场和阵风系数等变化特征。结果显示：“妮妲”登陆期间,近地面风速随时间呈增强—减弱—增强—减弱的“M”型特征,风向由西北方向转为南东南;风速随高度增加而增加,其中风速垂直变化最大的时段为“妮妲”后风圈经过期间;垂直方向上,“妮妲”前外围向前风圈过渡期间风向多变,而其他时段风向随高度基本不变;在“妮妲”前外围、前风圈和眼区经过期间,350 m高度以下的风速随高度的变化遵循对数关系,而在“妮妲”后风圈和后外围时段仅适用于150 m以下高度;在“妮妲”登陆过程中,铁塔观测的粗糙度长度约为0.52 m;阵风系数随高度增加而减小,“妮妲”登陆前和眼区的阵风系数较大;另外,阵风系数与风速呈负相关关系,随着风速增加而减小,尤其是风速小于10 m/s时。     

小北湖火山台迁建前后观测数据对比分析

小北湖火山台原址位于原始森林保护区,按照林区防火要求,2019年选址迁建。选取迁建前后小北湖火山台观测数据,通过计算不同频段范围内背景噪声记录的加速度功率谱密度,分析了迁建前后地震观测台站的噪声特征。结果表明,在1—20 Hz频段内,迁建后功率谱噪声值普遍降低10—20 dB;从RMS值来看,UD向降低22.0%,EW向降低58.2%,NS向降低62.8%,达到Ⅰ级台基水平,迁建后井下环境抗干扰能力更强,观测效果更好。     

地震应急专题图快速产出系统开发——以黑龙江省为例

为了提升地震应急能力,结合地震应急救援工作对地震专题图的需求,利用VB6.0开发出一套适用于地震应急救援的专题地图快速产出系统。该系统建立了相关地区的独立数据库,完全摆脱了对ArcGis、MapSis等专业制图软件的依赖,建立了独立的地震应急图件产出平台。通过输入地震参数,系统可以快速生成震中位置分布图、地震影响场分布图、震中人口分布图、历史地震分布图等专业图件并批量输出。     

应用于强对流天气预报的模式探空产品

仿照实测探空，根据数值模式站点预报的气象要素设计了包含十种常用稳定度指数的斜T-InP模式探空图。在综合评估的基础上，设计了一种模式探空的订正和产品的形成方法，并制作产品显示系统，它可以方便地提供地面站点模式探空和交互式模式探空的图形产品。模式探空产品的统计评估和具体强对流天气的个例分析中表明，模式探空产品对强对流天气预报有帮助。     

加密探空资料在华南暴雨数值预报的应用试验

应用逐时同化预报系统CHAF进行加密探空资料同化试验,比较了同化加密探空资料与仅同化常规探空资料所得同化分析场和模式预报结果的差异.同化加密探空资料所得分析场水汽的均方根误差减小,水汽条件和大气环流形势与实况更接近.以加密同化探空资料所得分析场为模式初始场进行预报,雨区的分布和降水量级都较控制试验有改善.分析模式预报改...     

基于TM/ETM+影像的不同水体指数对比研究

本文以草海国家级自然保护区为例,基于Landsat ETM+影像从区分度、水体错提率和面积精度3方面对比研究了NDⅥ植被指数和NDWI、MNDWI、RNDWI、NWI、NEW 5种归一化水体指数提取湿地水体信息的准确度.结果表明,NDⅥ提取水体效果较差,5种水体指数均能对水体进行有效提取,其中NWI法综合精度最高,其次是MNDWI、NEW,较差的是RNDWI和NDWI,从而为水体的快速提取提供了参考.     

两种海藻寡糖促乳酸菌增长的转录组比较研究

本研究采用全自动生长曲线分析仪Bioscreen C,比较了不同浓度的新琼四糖、新琼六糖、龙须菜发酵液、低聚果糖、低聚木糖、葡萄糖对乳酸菌Lactobacillus plantarum的促增长作用。结果显示,葡萄糖和龙须菜发酵液最佳的添加浓度分别为0.4 g/L和0.8 g/L,而新琼四糖、新琼六糖、低聚果糖、低聚木糖均为0.6 g/L。在各自的最佳浓度下,促生长效果最好的依次为新琼四糖、低聚果糖、新琼六糖、龙须菜发酵液、低聚木糖和葡萄糖。进一步比较在最佳添加量(0.6 g/L)和低浓度(0.2 g/L)条件下,新琼四糖和新琼六糖对乳酸菌Lactobacillus plantarum的转录组的影响,发现新琼四糖和新琼六糖在促乳酸菌生长的作用机理上有很大的相似性,当浓度升高时对细胞内的“转运活性”有更高的影响。     

自动气象站数据采集故障的诊断

分析了自动气象站数据采集中常出现的一些故障,给出了一些诊断方法.     

SPATIO-TEMPORAL CHARACTERISTICS OF NO2 IN PRD URBAN GROUP AND THE ANTHROPOGENIC INFLUENCES ANALYSIS BASED ON OMI REMOTE SENSING DATA

Spatio-temporal distribution characteristics and variation trends of tropospheric NO_2 in Pearl River Delta(PRD) urban group and its adjacent areas were analyze from 2005 to 2013 based on remote sensing data from ozone monitoring instrument(OMI) satellite, and further explored the impact of human activities on NO_2. Compared with the ground observation data, the OMI NO_2 remote sensing data displayed high reliability. Due to active industrial production, high car ownership, great energy and power consumption, the average tropospheric NO_2concentration(7.4×1015molec/cm2) of PRD region is about 3 times of the adjacent areas. At the same time, the regional high pollution NO_2 in PRD region as a whole, the urban group effect is remarkable. Sinusoidal model can well fit the periodic variation of the NO_2 in PRD and adjacent areas. NO_2 concentration was highest in winter while lowest in summer. The concentration of NO_2 in PRD region is decreasing in recent 9 years, which has a significantly negative correlation with the second industry output and car ownership. This suggests that the nitrogen oxide emissions governance in PRD region had achieved initial results. The concentration of NO_2 increased significantly in the eastern and northern Guangdong Province, there are good positive correlations with the second industrial outputs and car ownerships, it is thus clear that industrial emissions and automobile exhausts are important sources of NO_2 in these regions. The concentration of NO_2 in western Guangdong area is stable.