The 1.5–5-day eastward waves in the upper stratosphere–mesosphere as observed by the Esrange meteor radar and the SABER instrument

Data of neutral meridional wind obtained by the meteor radar at Esrange and data of temperature and pressure measured by the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument on board the Thermosphere–Ionosphere–Mesosphere Energetics and Dynamics (TIMED) spacecraft were studied with respect to a day-to-day atmospheric variability with periods ranging from 1.5 to 5 days. The detailed analysis was carried out for February 2004. Perturbations of the atmospheric parameters at the examined periods appeared mainly as eastward-propagating waves of zonal wavenumbers 1 and 2. We suggested that these waves excited by the jet instability on both flanks of the polar-night jet in the upper stratosphere and mesosphere interact nonlinearly with each other, and this interaction generates secondary waves. The radar observed both primary and secondary waves at mesospheric heights. The data analysis supports this suggestion. Under conditions of weaker instability observed in February 2003 the perturbations of atmospheric parameters of periods ranging from 1.5 to 5 days had smaller amplitudes at heights of the mesosphere than those in February 2004. It was found that the Eliassen-Palm fluxes calculated for the waves generated by the jet instability were mainly downward directed. This result suggests a possible dynamical influence of the mesospheric layers on the lower atmospheric levels.     

家用太阳能热水器防雷工程设计

通过对家用太阳能热水器结构以及它安装在屋顶的特殊性的认识,从直击雷防护和防雷电波侵入两个方面进行了讨论,并进行了相应的防雷工程设计。     

用远震接收函数研究滇西地区的深部结构

滇西地区地处欧亚板块碰撞或俯冲的边界地带,曾受到多期构造运动的影响,其地质环境和构造背景十分复杂,是我国地震活动比较活跃的地区之一. 本文选用国家、地方和流动数字台网的16个台站的远震记录. 其中PASSCAL甚宽频带流动地震台站4个,提取有效接收函数近2 000条. 两条测线的直线距离分别为650 km和450 km, 横切了滇西地区的一些主要构造单元. 研究表明,怒江断裂可能是一条具有俯冲性质的缝合线. 川滇菱形块体东西两侧的分界线¾红河断裂和小江断裂可能是直立的缝合线或碰撞带. 攀西构造带仍具有大陆裂谷的特征,即地表凹陷、上地幔隆起. 滇西地区的构造格局具有一定的规律性,造山带与缝合线相间分布. 滇西地区由北向南地壳厚度渐次减薄,S波速度整体偏低.     

1830年磁县7．5级地震震源区尾波衰减特征

利用磁县数字地震台记录到的近震波形资料,采用Aki尾波单次散射模型,计算1830年磁县7．5级大地震震源区50km范围内的尾波Qc值;经多地震拟合得出在尾波流逝时间为20s时,Qc=（70．2±29．3）f^（0.8054±0.1615）;40s,时Qc=（96．6±25．3）,f^（0.7772±0.1098）。结果表明,磁县震源区Q0值较低,震区地震波衰减比邢台、唐山震区快;η值表明Qc值对频率的依赖性弱于邢台和唐山震区。     

P.S测井技术的工程应用

P．S测井技术是地震勘探方法之一，也是一种简便、快速、准确的原位测试技术。通过P．S测井可测定岩土体的弹性波速（Vp、Vs)，为工程设计提供所需的动弹性力学参数、划分建筑物场地类别、评价地震效应、进行场地地震反应分析和地震破坏潜势分析等。文中简述了P．S测井技术的工作原理、现场实测技术以及数据处理和资料分析过程。最后结合两个实例说明了P．S测井技术在岩土工程勘察过程中的应用及其效果。     

Flow resistance adjustments of channel and bars in the middle reaches of the Yangtze River in response to the operation of the Three Gorges Dam

Journal of Geographical Sciences - Since the Three Gorges Dam (TGD) was put into operation, the flood water level at an identical discharge rate has not displayed a decreasing trend along the...     

Obtaining the distribution of quiescent periods directly from the power spectral densities of Sea waves

There is a growing practical interest in the ability to increase the sea states at which marine operations can be safely undertaken by exploiting the quiescent periods that are well known to exist under a wide range of sea conditions. While the actual prediction of quiescent periods at sea for the control of operations is a deterministic process, the long term planning of future maritime tasks that rely on these quiescent periods is a statistical process involving the anticipated quiescence properties of the forecasted sea conditions in the geographical region of interest. It is in principle possible to obtain such data in tabular form either large scale simulation or from field data. However, such simulations are computationally intensive and libraries of appropriate field data are not common. Thus, it is clearly attractive to develop techniques that exploit standard wave spectral models for describing the quiescence statistics directly from such spectra. The present study focuses upon such techniques and is a first step towards the production of a computationally low-cost quiescence prediction tool and compares its efficacy against simulations. Two significant properties emerge for a large class of wave spectral models that encompasses the ubiquitous Neumann and Pierson Moskowitz or Bretschneider forms. Firstly, the auto-correlation function of the wave profile that are required to produce the quiescence property can be obtained analytically in terms of standard special functions. This considerably reduces the computational cost making desktop computer-based planning tools a reality. Secondly, for each class of these parametric spectra, the probability of a given number of consecutive wave heights (normalised to the significant wave heights) less than some critical value is in fact independent of absolute wave height. Thus, for a broad class of practically interesting wave spectra all that is required to obtain the statistical distribution of the quiescent periods is simple rescaling.     

Dynamical Tropopause Variability and Potential Vorticity Streamers in the Northern Hemisphere —— A Climatological Analysis

This study presents a 44-year climatology of potential vorticity （PV） streamers in the Northern Hemisphere based upon analyses of the ERA-40 reanalysis data set. A comparison to an existing 15-year climatology yields very good agreement in the locations of PV streamer frequency maxima, but some differences are found in the amplitude of frequencies. The climatology is assessed with the focus on links between PV streamer frequencies and the synoptic- and planetary-scale variability of the dynamical tropopause.
A comprehensive overview is provided on where （zonally） and when （seasonally） short-term variability throughout the extra-tropical and sub-tropical tropopause is enhanced or reduced. Several key processes that influence this variability are discussed. Baroclinic processes, for example, determine the variability in the storm-track areas in winter, whereas the Asian summer monsoon significantly influences the variability over Asia.
The paper also describes links between the frequency of PV streamers in the extra-tropical and subtropical tropopause and three major northern hemisphere teleconnection patterns. The observed changes in the PV streamer frequencies are closely related to concomitant variations of PV and its gradient within the tropopause region. During opposite phases of the North Atlantic Oscillation the location of the streamer frequency maxima shifts significantly in the Atlantic and European region in both the extra-tropics and subtropics. The influence of ENSO on the streamer frequencies is most pronounced in the subtropical Pacific.     

近44年无锡寒潮天气变化特征分析

利用无锡市1959～2002年共44a的逐日最低气温资料,分析了无锡寒潮发生的特点.分析结果表明:无锡寒潮的年发生次数有线性减少趋势;寒潮减少主要发生在10月、12月、4月.分年代看,从20世纪60年代到80年代逐年代减少,但90年代又增多.寒潮减少与降温幅度减小、最低气温升高有关,其中最低气温升高是其主要影响因素.特征区域的500 hPa高度场偏高是寒潮发生次数减少的直接原因.最后,针对多寒潮年和少寒潮年的环流特点,给出了500 hPa典型距平场特征.     

外源NO对野生早熟禾幼苗抗寒性的影响

以野生草地早熟禾（Poa pratensis）和硬质早熟禾（Poa sphondylodes）为材料,通过人工室内模拟低温逆境胁迫,研究外源一氧化氮（NO）供体亚硝基铁氰化钠（硝普钠,SNP）对低温胁迫下野生早熟禾幼苗生长、渗透调节和抗氧化系统的影响,探讨外源NO提高早熟禾抗寒性的生理机制。结果表明,低温胁迫下：0~700 μmol·L^-1浓度范围内,随SNP浓度的增大,两个供试材料的地上生物量和生长速度先增大后减小,相对膜透性、丙二醛（MDA）含量、游离脯氨酸（F-Pro）含量先减小后增大,可溶性糖（SS）和可溶性蛋白（SP）含量先增加后减小,超氧化物歧化酶（SOD）、过氧化物酶（POD）和过氧化氢酶（CAT）活性先增强后减弱;高浓度NO产生伤害,低浓度NO则有保护作用;SNP浓度100 μmol·L^-1时,膜脂过氧化水平最低,渗透调节物质积累最多,保护酶活性最强,对低温胁迫的缓解效果最佳。硬质早熟禾对低温胁迫下外源NO的缓解较草地早熟禾敏感。