江淮流域夏季持续性强降水的低频特征分析   总被引：10，自引：2，他引：8       下载免费PDF全文

曹鑫  任雪娟  孙旭光 《气象科学》2013,33(4):362-370

利用1979-2009年夏季(6-8月)中国气象观测站点逐日降水资料、NCEP/NCAR的再分析资料以及向外长波辐射资料等,选取低频降水事件来表征江淮流域夏季持续性强降水,然后分析其基本特征及伴随的低频大气环流形势,利用位相合成的方法对该低频信号的来源和传播特征进行研究.结果表明:江淮流域夏季持续性强降水在6-7月份发生次数较多;在持续性强降水期间,江淮流域低层受低频气旋控制,南海至菲律宾海一带则是很强的低频反气旋,该低频反气旋西侧,向北的低频水汽输送将水汽不断送至江淮流域形成辐合;与持续性强降水相关联的850 hPa上的低频信号,来源于黄河河套地区低频振荡的东南向传播和西北太平洋上空低频振荡的西北向传播;在高层,当持续性强降水发生时,江淮流域的西北侧(37.5°N,80 ～100°E)附近为强烈的低频气旋式环流,紧邻该环流的西北侧,则是一个低频反气旋,两者同南海—菲律宾海一带的低频反气旋构成了一个西北—东南向的低频波列;西太平洋副热带高压和南亚高压在持续性强降水期间表现出了显著的相向而行、相背而去的特征.  相似文献   

利用低频磁场天线遥感测量人工引雷中的初始连续电流   总被引：2，自引：2，他引：0  

樊艳峰  陆高鹏  蒋如斌  张鸿波  刘明远  郄秀书 《大气科学》2017,41(5):1027-1036

2014年夏季的山东人工引雷实验中,我们利用高灵敏度宽频段磁场天线在距引雷点78 m的距离上开展了对人工引雷初始连续电流过程的遥感测量。通过分析实验期间5次人工引雷的综合观测数据,发现磁场遥感方法对人工引雷中特有的初始连续电流有很好的反演效果。通过对78 m距离上获得的磁场测量信号进行积分处理,能够有效地抑制测量过程中白噪声的影响,从而反演得到初始连续电流的低噪声时变波形。该方法为获取空中引雷实验中的初始连续电流波形提供了一种解决方案,同时也可用于反演近距离自然闪电中地闪回击中的长连续电流的时变波形。  相似文献   

论动力相似预报的物理基础问题   总被引：1，自引：0，他引：1  

任宏利  封国林  张培群 《地球科学进展》2007,22(10):1027-1035

为了更好地发展动力相似预报的策略和方法，基于非线性动力学成果，综合探讨了动力相似预报的物理基础问题。分析表明，“相似预报—低频流型—可预报性”在物理上存在密切联系，这在统计相似预报和动力相似预报问题中均适用。通过类比集合预报，并对实际大气不同尺度模式预报的个例分析，初步证实了相似初值对应的动力预报结果及其预报误差行为具有相似性。在此基础上，进一步提出三类相似性问题，并归纳了动力相似预报的物理基础：在初始状态相似性持续的情况下，动力预报结果以及预报误差行为具有相似性。  相似文献   

A Study of Spectra, Structure and Correlation Functions and Their Implications for the Stationarity of Surface-Layer Turbulence     

Nelson L. Dias  Marcelo Chamecki  Akemi Kan  Cristhiane M. P. Okawa 《Boundary-Layer Meteorology》2004,110(2):165-189

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Notes on extended–range atmospheric prediction in the Northern Hemisphere winter     

Shingo Yama  Shuhei Mae  K. Gambo 《大气科学进展》1997,14(1):23-40

We examined the characteristic feature and predictability of low frequency variability (LFV) of the atmosphere in the Northern Hemisphere winter (January and February) by using the empirical orthogonal functions (EOFs) of the geopotential height at 500 hPa. In the discussion, we used the EOFs for geostrophic zonal wind (Uznl) and the height deviation from the zonal mean (Zeddy). The set of EOFs for Uznl and Zeddy was denoted as Uznl-1. Uznl-2, …, Zeddy-1, Zeddy-2…, respectively. We used the data samples of 396 pentads derived from 33 years of NMC, ECMWF and JMA analyses, from January 1963 to 1995. From the calculated scores for Uznl-1, Uznl-2, Zeddy-1, Zeddy-2 and so on we found that Uznl-1 and Zeddy-1 were statistically stable and their scores were more persistent than those of the other EOFs. A close relationship existed between the scores of Uznl-1 and those of Zeddy-1 30-day forecast experiments were carried out with the medium resolution version of JMA global spectral model for 20 cases in January and February for the period of 1984-1992. Results showed that Zeddy-1 was more predicta?ble than the other EOFs for Zeddy Considering these results, we argued that prediction of the Zeddy-1 was to be one of the main target of extended range forecasting  相似文献   

The effect of heating anomaly on the Asian circulation—A GCM experiment     

Wang Huijun 《大气科学进展》1997,14(1):81-86

A numerical experiment was done by using the IAP 9-Level AGCM to study the effects of radiation anomaly over East Asia on the Asian general circulation. The results show that the changes of Asian summer general circula-tion are remarkable in the Indian and China southwest monsoon, precipitation in India and the Yellow River and Huaihe River valley in China and area around the north Japan, the easterly anomaly of low-level zonal wind in the tropical Pacific and so on.  相似文献   

强地震前兆低频波的实验研究   总被引：7，自引：0，他引：7  

唐林波  李世愚  苏昉  孙为  和雪松  刘建新 《中国地震》2003,19(1):48-57

声波透射实验表明，对于板状材料，声音的一部分能量可以透射到空气中。另一部分能量在板中产生简正波，使板产生较大的振幅，在空气中产生能被话筒接收到的声音信号，而信号的简正频率与板的尺寸有关。另外，破裂过程中的声发射实验证实：随着微破裂的集结和裂纹的扩展，所辐射波的频谱会逐渐向低频移动，而且当频率很低时，可以透射出岩石，被话筒接收到。根据尺度相似性原理，推广到野外，强地展前破裂集结可能会辐射出超低频波，这种超低频波不能被常规的地震仪记录到，但可以被超低频传感器或次声接收器记录到。在地震前，产生前兆的源非常复杂，大多数情况下可能并非脆性破裂，而是塑性蠕滑或者有流体的参与。而后两种情况产生的波的周期会更长，而且缺乏脆性破裂所固有的高频成分，这可能就是多数地震前缺乏前震的原因。  相似文献   

上海市区地下管道探测技术的探讨     

何仁汉  师先进 《上海国土资源》1990,(2):57-61

本文介绍一种新型低频雷达技术,它可在上海市区潜水面高、土层湿度大的地质条件下,快速而有效地探测地下管道的分布情况,以促进上海市区城市建设的发展。  相似文献   

Experimental Research on the Low Frequency Wave That Radiates into the Air before the Failure of Rock     

Li Shiyu 《中国地震研究》2005,19(1):86-96

INTRODUCTIONThephenomenonof“quiescence”beforestrongearthquakeshaswidelybeenaccepted .However,isitreallyquietbeforeanearthquake ?Accordingtorecordsfromshortperiodseismographs,itis“quiet”beforeearthquake ,butaccordingtotherecordsofbroadbandseismograph ,thismaynotbetrue .Thekeytothismatterishowtogetreliableinformation .Earlyinthe 1 970’s,manyseismologiststhoughtthattheultra lowfrequencywaveformrecordedbybroadbandseismometersbeforeearthquakescamefromfore sliporslow extending (Rikitake ,…  相似文献   

Seismic activity related to the 2000 eruption of the Hekla volcano, Iceland     

Heidi Soosalu  Páll Einarsson  Bergþóra S. Þorbjarnardóttir 《Bulletin of Volcanology》2005,68(1):21-36

The 2000 Hekla eruption took place from February 26 to March 8. Its seismic expressions were a swarm of numerous small earthquakes related to its onset, and low-frequency volcanic tremor that continued throughout the eruption. A swarm of small earthquakes was observed some 80 min before the onset of the eruption, and the size of the events increased with time. Low-frequency volcanic tremor, with a characteristic frequency band of 0.5–1.5 Hz and dominant spectral peak(s) at 0.7–0.9 Hz, became visible at 18:19 GMT on February 26, marking the onset of the eruption. The tremor amplitude rose quickly and was very high in the beginning of the eruption. However, it soon began to decrease after about an hour. In general, the seismic activity related to the 2000 Hekla eruption was very similar to what was observed in the previous eruption in 1991. Based on knowledge gained from seismicity and strain observations from 1991, this was the first time that a Hekla eruption was predicted.Editorial responsibility: J Stix  相似文献