Preliminary Results of 4-D Water Vapor Tomography in the Troposphere Using GPS   总被引：6，自引：2，他引：6  

毕研盟  毛节泰  李成才 《大气科学进展》2006,23(4):551-560

Slant-path water vapor amounts (SWV) from a station to all the GPS (Global Positioning System) satellites in view can be estimated by using a ground-based GPS receiver. In this paper, a tomographic method was utilized to retrieve the local horizontal and vertical structure of water vapor over a local GPS receiver network using SWV amounts as observables in the tomography. The method of obtaining SWV using ground-based GPS is described first, and then the theory of tomography using GPS is presented. A water vapor tomography experiment was made using a small GPS network in the Beijing region. The tomographic results were analyzed in two ways: (1) a pure GPS method, i.e., only using GPS observables as input to the tomography; (2) combining GPS observables with vertical constraints or a priori information, which come from average radiosonde measurements over three days. It is shown that the vertical structure of water vapor is well resolved with a priori information. Comparisons of profiles between radiosondes and GPS show that the RMS error of the tomography is about 1–2mm. It is demonstrated that the tomography can monitor the evolution of tropospheric water vapor in space and time. The vertical resolution of the tomography is tested with layer thicknesses of 600 m, 800 m and 1000 m. Comparisons with radiosondes show that the result from a resolution of 800m is slightly better than results from the other two resolutions in the experiment. Water vapor amounts recreated from the tomography field agree well with precipitable water vapor (PWV) calculated using GPS delays. Hourly tomographic results are also shown using the resolution of 800 m. Water vapor characteristics under the background of heavy rainfall development are analyzed using these tomographic results. The water vapor spatio-temporal structures derived from the GPS network show a great potential in the investigation of weather disasters.  相似文献   

希尔伯特-黄变换技术及在边界层湍流研究中的应用   总被引：1，自引：0，他引：1  

魏伟  张宏升 《气象学报》2013,71(6):1183-1194

大气边界层中的湍流运动可以视为由许多不同时空尺度的湍涡叠加形成的,谱分析方法可以将这些不同尺度的涡旋分离开来。在介绍希尔伯特-黄变换（HHT）的基础上,选取2011年4月16日00—01时（北京时）、05—06时、12—13时不同时段的大气湍流观测数据,采用希尔伯特-黄变换技术分析了内蒙古科尔沁沙地地区的谱分布特征,得到的各内在模函数对应的中心瞬时频率可以表现出不同尺度上的湍流波动,其中,包含周期为3—5和10—13 min的阵风和重力内波,并在希尔伯特边际谱中体现。三维希尔伯特谱分布表明湍流能量多集中在频率小于0.5 Hz的低频段;大气湍流脉动较强的时段,其内在模函数和希尔伯特谱也对应着较大的能量。对比传统的快速傅里叶变换（FFT）方法,希尔伯特-黄变换可以更清晰地表现出湍流的频谱分布。  相似文献   

Wind flow and wind loads on the surface of a towershaped building: Numerical simulations and wind tunnel experiment     

Jiang YuJun  Liu HuiZhi  Zhang BoYin  Zhu FengRong  Liang Bin  Sang JianGuo 《中国科学D辑(英文版)》2008,51(1):103-113

Flow structure and wind pressure distribution caused by obtuse obstacles are usually the focuses in Computational Wind Engineer researches (CWE). By solving the non-hydrostatical dynamic equations, PUMA model (Peking University Model of Atmospheric Environment) was developed and applied to simulating the flow structure and wind pressure distribution around a tower-shaped building. Evaluation about the wind environment and wind loads around the building was obtained through the analysis of the numerical simulation results and wind tunnel data. Comparisons between the simulation and wind tunnel study indicate that numerical simulation results agree well in the flow field and wind pressure distribution around the tower-shaped building. On the other hand, the horizontal grid interval of 2 m and the vertical grid of 3 m were still too crude to simulate the flow structure and wind pressure distribution on the building surface more exactly in detail; and the absence of suitable pressure perturbation parameterization scheme between the solid and the adjacent space also limits the accuracy of the numerical simulation. The numerical simulation model can be used to evaluate the wind environment and wind load around high buildings.  相似文献   

Numerical simulation for the coupling effect of local atmospheric circulations over the area of Beijing,Tianjin and Hebei Province   总被引：8，自引：0，他引：8  

ShuHua Liu  ZhenXin Liu  Ju Li  YinChun Wang  YanJun Ma  Li Sheng  HePing Liu  FuMing Liang  GuoJun Xin  JianHua Wang 《中国科学D辑(英文版)》2009,52(3):382-392

Using the model system MM5.V3 and multi-layer grid nesting technique, we have done a multi-scale numerical simulation over the area of Beijing, Tianjin and Hebei Province to analyze the temperature and wind field there and study its local circulations. The results show a coupling effect of Urban Heat Island Circulation (UHIC), Mountain Valley Breeze (MVB) and Sea Land Breeze (SLB) occurs in this area when the synoptic system is weak. The SLB can penetrate deep into the mainland for about 200 km when it is blooming. MVB can extend to south and cover almost the whole plain area in Beijing. Both MVB and SLB are diurnal periodical; meanwhile the phase of MVB drops behind that of SLB for about six hours. As a local circulation, the UHIC weakens the two circulations above, and it also has a diurnal period. As a result, the coupling effect of circulations reveals not only different features in spring-summer period and autumn-winter period in a year but also the difference between early morning to noonday and afternoon to night in a day. We noted the diffusion of contamination over the area around Beijing, and found the steady presence of a transport routine of contamination over North-China throughout the year caused by the Coupling Effect mentioned above. This find is important for studying the environment pollution in this area. Supported by Central Public Welfare Special Fund Program for the Institute and Higher Education (Grant No. IUMKY200701), Public Welfare Special Fund Program (Meteorology) of China Scientific and Technological Ministry (Grant Nos. CYHY20080620, CYHY200706004), Spread New Technology Program of China Meteorological Administration (Grant No. CMATG2007M15) and Urban Meteorology Scientific Research Fund Program of the Institute of Beijing Urban Meteorology, China Meteorological Administration (Grant No. UMRF200702)  相似文献   

全新世气候   总被引：4，自引：0，他引：4       下载免费PDF全文

王绍武 《气候变化研究进展》2009,5(4):247-248

全新世指我们目前所在的间冰期.一般把新仙女木事件(YD)结束的时间(11.5 kaBP)作为全新世的开始.当前国际上对全新世的气候变化有3点共识:1)进入全新世温度大幅度回升,中全新世以后逐渐下降,20世纪由于人类活动的影响全球变暖;2)早全新世北半球亚非季风区气候湿润,5 kaBP以后逐渐变干,但是ENSO加强;3)在以上变化的背景下发生了若干次冷干事件,这些事件开始与结束均较迅速,所以也被为气候突变.  相似文献   

太阳常数   总被引：2，自引：0，他引：2       下载免费PDF全文

王绍武 《气候变化研究进展》2009,5(1):61-62

Pouillet认为达到地球大气上界的太阳辐射是一个常定的量,因此,1838年命名为太阳常数.但是随即有不少学者提出反对,认为太阳常数不是一个真正的常数.其中有代表性的是Abbot,他利用大黑子群过日中时太阳常数下降的事实,证明太阳常数是变化的.但是,由于计算大气对太阳辐射削弱的不确定性,以及太阳辐射观测精度不高,计算出来的太阳常数的误差约1%,而不同时间、地点得到的太阳常数的变化也在1%以内.所以长期以来无法通过直接观测回答太阳常数是否是一个真正常数的问题.  相似文献   

陆表自然和人文要素相互作用——“全球变化及应对”重点专项研究进展          下载免费PDF全文

王开存  王灿  李龙辉  汪涛  吴国灿  付永硕  马倩  张井勇  蔡闻佳  曹静  喻朝庆  朱华晟  南卓铜  陈旻  张晶  纪多颖  沈妙根  唐文君  何斌  占文凤 《大气科学学报》2024,47(1):1-22

在国家重点研发计划支持下,项目提出了陆表不均一性检测和订正的新方法,解决了渐变型不均一性检测和订正的难题,构建了中国地表太阳辐射、气温、地温、风速和降水等参数均一化站点和格点数据集,修订了关于中国地表风速变化趋势、增温格局及其形成机制的结论。融合多源数据,构建并验证了千米级、流域级或县域级的电厂、人口、生物质能、取水量、氮排放、二氧化碳排放等影响自然系统的关键人文要素历史和未来预估数据集。构建了未来关键人文要素情景,研制了碳中和目标下甲烷和氧化亚氮排放情景和用于驱动全球模式的未来情景,预估了中国碳中和战略的实施对全球变暖的减缓作用,发现中国碳中和对远期和中期全球变暖的减缓作用显著。给出了中国各省份水体氮排放安全阈值及超越时间,阐明了中国粮食产量与氮施肥的关系,提出了在保障粮食安全的前提下减少水体氮排放的有效途径,指出重构城乡养分循环体系是同时保障粮食安全和恢复水质的必要途径。发现全球饱和水汽压差的年际变化与大气二氧化碳浓度上升速率的年际变化显著相关,阐明了饱和水汽压差变化在调控生态系统生产力中的重要角色以及多因素耦合作用在生态系统生产力变化中的复杂影响。建议更全面细致地评估中国各种碳中...  相似文献   

夏季西藏4个站点大气向下长波辐射观测分析   总被引：1，自引：0，他引：1       下载免费PDF全文

刘梦琪  郑向东  赵春生 《应用气象学报》2018,29(5):596-608

对2011—2016年部分夏季时段分别在西藏那曲、拉萨、林芝和阿里观测的大气向下长波辐射（L_↓）进行分析,结果显示:L_↓具有明显的日变化,最大值出现在北京时间15:00前后,而最低值出现在凌晨至10:00,日平均值林芝最高（368 W·m-2）,其次是拉萨（319 W·m-2）、阿里（305 W·m-2）和那曲（299 W·m-2）。晴天L_↓ ?ngstr?m（1915）的经验公式最适合林芝,而Konzelmann（1994）的公式则适合那曲、拉萨和阿里;随着人工观测总云量的增加,L_↓增强趋势明显,满云（云量7~10成）情形4个站点云增强效应均从20 W·m-2上升至50 W·m-2以上,低云量对L_↓的增强效应明显高于总云量。云份额数（C_F）上升所对应天顶方向平均云底高度下降,但云增强效应上升。在晴天（C_F为-5%~5%、平均云底高度大于4 km）时,云增强效应仅为5 W·m-2左右（林芝接近20 W·m-2）,但当C_F为90%以上（云底高度小于3.5 km）时,云增强效应则上升到60 W·m-2（林芝接近50 W·m-2）。固定云底高度,C_F与L_↓云增强效应呈显著相关（r2为0.91~0.97）,远高于云底高度与L_↓云增强效应的相关（r2为0.32~0.58）。  相似文献   

国家自然科学基金大气科学学科二级申请代码下设研究方向与关键词解读:D0506大气化学     

丁爱军  王炜罡  张霖  张强  车慧正  张庆竹 《大气科学》2023,47(1):145-153

国家自然科学基金委员会深入推进新时代科学基金改革的背景下,地球科学部大气科学学科率先开展申请代码设置改革,新版申请代码设置方案于2020年投入使用并在实施过程中不断优化。本文主要针对大气学科二级代码D0506大气化学下设研究方向和关键词设置的主要依据进行解读;同时基于文献计量学方法对该代码下不同研究方向的词频、研究热点和趋势进行分析和讨论。新版代码设置方案统筹考虑主要研究方向和研究手段,并根据关键词属性进行分类,便于基金项目申请和评审。基于关键词的文献计量分析明晰了分支学科当前存在的问题及资助导向,有助于进一步促进大气化学及相关方向的发展。  相似文献   

A Numerical Case Study of the Implications of Secondary Circulations to the Interpretation of Eddy-Covariance Measurements Over Small Lakes     

William T. Kenny  Gil Bohrer  Timothy H. Morin  Chris S. Vogel  Ashley M. Matheny  Ankur R. Desai 《Boundary-Layer Meteorology》2017,163(2):311-326

The CASES-99 experimental data are used to analyze turbulence behaviour under a range of stable conditions using an adaptive method based on Hilbert spectral analysis. The characteristic scales of intrinsic mode functions vary between different stratifications. The second-order Hilbert marginal spectra display clear separation between fine-scale turbulence and large-scale motions. After removing the large-scale motions, the statistical characteristics of the reconstructed signals confirm the distinction of different stratifications in the fine-scale range. The correlation coefficient analyses reveal that the Hilbert spectral analysis method separates turbulence from large-scale motions in the stable boundary layer.  相似文献