一次攀西地区飑线天气过程形成机制分析

利用地面气象常规观测资料、区域自动站观测资料、雷达及卫星资料和NCEP 1°×1°的逐6h再分析资料,对2018年5月13日攀西地区南部的飑线天气过程的形成机制进行分析。结果表明:飑线发生在高空槽前,高空槽逐渐东移推动冷性气流沿背风坡东移,然后与前方低层暖空气汇合抬升形成对流;露点锋触发了飑线天气过程的形成;产生飑线天气区域的大气具有上干下湿、不稳定能量高、垂直风切变强、高层风速大和形成之前存在逆温层的特点;高空急流和动量下传对飑线的发生和加强具有促进作用;地形对飑线的形成和天气现象的分布有影响。     

The nexus between nationally determined contributions and technology needs assessments: a global analysis

The role of technology in combatting climate change through mitigation and adaptation to its inevitable impacts has been acknowledged and highlighted by the Parties to the United Nations Framework Convention on Climate Change (UNFCCC). In the developing world, this has received particular attention through the technology needs assessment (TNA) process. As Parties put forward their national pledges to combat climate change, the scarcity of resources makes it important to assess (i) whether national processes designed to tackle climate change are working together and (ii) whether existing national processes should be terminated with the initiation of new ones. This study presents an assessment of the existing TNA process and its linkages to the nationally determined contributions (NDCs) under the Paris Agreement. The conclusions stem from an assessment of the TNAs completed to date, as well as 71 NDCs from developing countries at various stages of the TNA process. The analyses show that further developing the TNAs could play a vital role in filling gaps in the existing NDCs, specifically those relating to identifying appropriate technologies, their required enabling framework conditions and preparing implementation plans for their transfer and diffusion.

Key policy insights

• The full potential of the TNAs has still to be rolled out in many countries.

• Developing countries can maximize the potential of their TNAs by further developing them to explicitly analyse what is needed to implement existing NDCs, including by better aligning their focus, scope and up-to-dateness with the priority sectors included in the NDCs.

• Requests of developing countries for international assistance, through technology transfer, will be better guided by the completion of the TNA process.

• Policies for strengthening the NDCs will benefit from the results of completed, ongoing and future TNA processes.

     

基于ERA5的快速辐射传输模式与FY-4A成像仪观测结果的偏差分析

2016年12月发射升空的FY-4A是中国第二代静止轨道气象卫星,该星上搭载了可提供东半球近实时高分辨率卫星观测数据的扫描辐射成像仪——AGRI（Advanced Geostationary Radiation Imager）。在其观测数据应用于大气参数反演或同化前,数据偏差的定量化分析是一个必要环节。采用快速辐射传输模式RTTOV（Radiative Transfer for the TIROS Operational Vertical Sounder）,基于欧洲中期天气预报中心（ECMWF）第5个全球再分析数据产品（ERA5）对AGRI的7个红外通道（通道08—14）进行了模拟,并利用MODIS云检测产品对模拟结果进行了晴空筛选,以期得到一些对AGRI的定量应用有价值的偏差分析结果。观测-模拟（O-B）的偏差分析结果显示:海洋和陆地上,通道10（7.1 μm）存在明显大于其他红外通道的系统性偏差,这很可能来源于ERA5在对流层中层对水汽的高估。通道08为近红外短波通道,地表反射作用影响强烈,陆地上存在较大的平均偏差,而海洋上平均偏差小于0.4 K。通道14在ERA5近地层气温偏高及定标偏差的影响下,海洋存在接近1 K的平均偏差;陆地上存在2 K左右的平均偏差。其余各红外通道在海洋和陆地上的平均偏差分别在0.6和1.3 K以下。偏差影响因子分析结果显示:地表海拔高度、观测天顶角对偏差也存在一定程度的影响;海洋上偏差分布存在季节变化可能来源于再分析资料中海表温度估算的季节性误差。      

那曲高寒草地总体输送系数及地面热源特征

利用中国科学院那曲高寒气候环境观测研究站那曲/BJ观测点的野外观测数据,估算了青藏高原那曲地区典型高寒草地下垫面的热量和水汽总体输送系数以及地表大气相对湿度因子,在此基础上利用中国气象局那曲气象站1980-2016年的常规业务观测数据,采用总体输送法计算并分析了那曲高寒草地地表通量特征。研究结果表明:(1)那曲/BJ观测点地表大气相对湿度因子γ的数值在33%~62%,9月最大,2月最小,热量和水汽输送系数CH和Cλ的季节变化范围分别在1.6×10^-3~2.7×10^-3和1.0×10^-3~2.0×10^-3,两者存在较大的差异。(2)1980-2016年那曲高寒草地感热通量总体呈现减弱趋势,而潜热通量呈现增强趋势,导致地面热源变化趋势不明显;分阶段来看,感热通量的变化在2004年前后发生转折,转折点前后的趋势为先减弱后增加,潜热通量在1994-2005年下降趋势明显,这也导致地面热源在1995-2005年有一个明显的减少。(3)年内季节变化上潜热通量相较于感热通量更明显,地面热源的季节变化更依赖于潜热通量的季节变化。     

Atmospheric radiative transfer simulation for atmospheric correction of remote sensing data

The radiance leaving the earth-atmosphere system which can be sensed by a satellite borne radiometer is the sum of radiation emission from the earth surface and each atmospheric level that are transmitted to the top of the atmosphere. The radiation emission from the earth surface and the radiance of each atmospheric level can be separated from the radiance at the top the atmospheric level measured by a satellite borne radiometer. However, it is very difficult to measure the atmospheric radiance, especially the synchronous measurement with the satellite. Thus some atmospheric radiative transfer models have been developed to provide many options for modeling atmospheric radiation transport, such as LOWTRAN, MODTRAN, 6S, FASCODE, LBLRTM, SHARC, and SAMM. Meanwhile, these models can support the detailed detector system design, the optimization and evaluation of satellite mission parameters, and the data processing procedures. As an example, the newly atmospheric radiative transfer models, MODTRAN will be compared with other models after the atmospheric radiative transfer is described. And the atmospheric radiative transfer simulation procedures and their applications to atmospheric transmittance, retrieval of atmospheric elements, and surface parameters, will also be presented.     

ON THE CHARACTERISTICS OF NON-LINEAR SOIL RESPONSE AND DYNAMIC SOIL PROPERTIES USING VERTICAL ARRAY DATA IN JAPAN

Non-linear response of the soil is investigated by comparing the spectral ratios (uphole/downhole) using weak and strong motions. Data from seven vertical arrays in Japan are analysed in this study. The frequency-dependent transfer function of soil is calculated as a ratio of the spectrum at uphole to the spectrum at downhole, considering the horizontal component of shear wave. In spectral ratio analysis auto- and cross-spectra are employed. The reduction in the predominant frequency of the transfer function with increases in excitation level reflects the non-linear response of the soil. Results of analysis demonstrate a significant non-linear ground response at six sites with surface PGA exceeding 90 gal. However, the results of one site show the linear response up to 130 gal surface PGA. Furthermore, the in situ strain-dependent soil behaviour is examined through the shear modulus – shear strain relationship. When compared, the actual and laboratory results of the shear strain – shear modulus relationship are in agreement. Additionally, a good consistency between the tendency of reduction in shear modulus ratio with shear strain increases, and reduction of predominant frequency with ground motion increases, confirms the significance of non-linearity in site effects study.     

坐标转换模型在盾构姿态计算中的应用

在附有条件的间接平差模型的基础上,提出用归一化大角度坐标转换模型计算盾构机姿态,并从其原理、方法以及精度上进行了分析。应用结果表明:利用坐标转换法计算盾构机姿态,与常规解方程法相比较更能有效利用参考点的所有信息,计算过程简明,且便于程序实现。     

全球海平面变化研究新进展

综述了近10年来海平面变化研究的主要成果,分析了影响海平面变化的主要因素,探讨了海平面变化研究中存在的一些问题。结果表明：①近10年全球平均海平面上升幅度大约为2.5~3.84 mm/a,热膨胀是引起海平面上升的主因;②海平面变化具有时空分布差异——西太平洋和东印度洋地区上升最快,其值高出全球平均值的10倍以上;大西洋与太平洋30~40°N地区季节变化最明显;③将海平面季节高值时段与北半球热带气旋出现时间进行对比,发现每年8~10月份,在20~50°N的西北太平洋与北大西洋沿岸地区出现海平面最高值与热带气旋相叠加的全球危险海岸带,该地带包括中国大陆东部、日本沿海地区、美国东部海岸带、墨西哥湾地区和加勒比海地区。     

型钢混凝土梁柱框支剪力墙结构抗震性能试验研究

框支剪力墙结构在实际工程中经常被采用,震害表明钢筋混凝土框支剪力墙结构抗震性能较差,本文提出型钢混凝土梁柱框支剪力墙结构对此加以改进。作者进行了4个1/4缩尺模型在竖向荷载和单调及低周反复水平荷载作用下的对比试验,其中3个试件采用型钢混凝土转换梁、型钢混凝土框支柱,1个试件采用钢筋混凝土转换梁、钢筋混凝土框支柱。我们分析其承载力、刚度、变形、延性和破坏形态等。试验结果表明,型钢混凝土梁柱框支剪力墙结构承载力高、延性好、滞回曲线丰满,变形能力和耗能能力较强。     

竖向断层对场地地面运动的影响

本文采用二维显式有限元结合透射边界的数值方法,考虑均匀弹性半空间内存在着不同宽度及深度的断层,由下向上分别垂直和斜(30°)入射一个脉冲波,研究非发震断层地面运动的一些特点。通过计算断层内外地震地面运动传递函数的幅值谱,并与自由场反应对比,以说明竖向断层对地震波传播和附近地面运动的影响,在此基础上进一步对断层周边一般结构抗震设计是否要考虑断层影响提出了几点建议。