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991.
详细讨论了远震体波SV分量接收函数的特点及其在反演地壳S波速度结构中的优势.与径向接收函数类似,SV分量接收函数可通过对远震体波的SV分量直接反褶积P分量获得.研究分析表明:与径向接收函数相比,SV分量接收函数的振幅随震中距的变化更加稳定,波形简单且突出了对结构最敏感的PS转换波信息.理论数值实验显示:在反演地壳S波速度结构时,SV分量接收函数比径向接收函数具有更好的收敛性.作为实例,利用SV分量接收函数反演方法反演了海拉尔台下的S波速度结构. 相似文献
992.
世界应力图(WSM,World Stress Map)计划的应力指标,目前已累积数据共计10 920个,这些应力指标代表了该地区最大水平主应力的实际观测方向;与此同时,可以假定全球各个板块的绝对运动方向表征了相应各板块的最大水平主应力方向的长波分量.根据应力场的叠加原理,得到由该地区局部构造运动等因素贡献的短波分量的相对大小和方向.将全球划分成2.52.5的基本单元,对每个单元的WSM数据进行加权统计分析,得到其平均应力观测取向,利用HS2-NUVEL1全球绝对板块运动模型计算应力场的长波分量;平均观测应力取向和长波分量取向之间的夹角,决定了相应短波分量相对于观测应力场的大小及其取向的范围,并反映了特定研究地区局部应力场对总应力场的贡献程度.本文的计算结果表明,全球板块的绝大部分地区及各板块的平均效果,长波分量与短波分量对观测应力场的贡献程度相当.对于某些大陆板块内部,局部构造活动对观测应力场的贡献起到重要作用,因而控制着地震的孕育与发生. 相似文献
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998.
Summary ?Using the data of 6 automatic heat balance observation (AWS) stations and a data set of 52 surface observation stations over
the Qinghai-Tibetan Plateau (“the Plateau”) and surroundings, the horizontal distribution is studied of “apparent atmospheric heat sources” 〈Q
1〉 and of “apparent atmospheric moisture sinks” 〈Q
2〉. The AWS stations were established during the period May to August 1998 of the Tibetan Plateau Meteorological Experiment
(second TIPEX) by a cooperation of China and Japan. For this period the Plateau mean of 〈Q
1〉 is positive. Its value of 74 W/m2 is a little greater than a climate value and than values from MONEX and the first TIPEX in 1979, respectively. Also the corresponding
〈Q
2〉 is positive. Hence during that time the Plateau is a heat source and a moisture sink. A day-to-day change of 〈Q
1〉 and 〈Q
2〉 is more pronounced over the middle and east part of the Plateau than over the west part.
Diagnostics accompanied by numerical simulations are used to study the daily relationship between 〈Q
1〉 over the Plateau and the weather over China and Asia for this summer. The results suggest that 〈Q
1〉 may affect precipitation over northern China and position of the west Pacific subtropical high. Abnormal southward retreat
of this Pacific high seems to have caused the second flood over the middle and lower Yangtse river basin in July.
Received May 20, 2001; revised February 2, 2002 相似文献
999.
Numerical simulation of a South China Sea typhoon Leo (1999) 总被引:6,自引:0,他引:6
K.-H. Lau Z.-F. Zhang H.-Y. Lam S.-J. Chen 《Meteorology and Atmospheric Physics》2003,83(3-4):147-161
Summary ?A South China Sea typhoon, Leo (1999), was simulated using the Penn State/NCAR mesoscale model MM5 with the Betts-Miller
convective parameterization scheme (BMEX). The simulation had two nested domains with resolutions at 54 and 18 km, and the
forecast duration was 36 hours. The model was quite successful in predicting the track, the rapid deepening, the central pressure,
and the maximum wind speed of typhoon Leo as verified with reports from the Hong Kong Observatory (HKO). The structure of
the eye, the eye wall, and the spiral convective cloud band simulated in the model are found to be comparable to corresponding
features identified in satellite images for the storm, and also with those reported by other authors.
A trajectory analysis was performed. Three kinds of trajectory were found: (1) spirally rising trajectories near the eye wall;
(2) spirally rising/descending trajectories in the convective/cloud free belt; (3) straight and fast rising trajectories in
a heavy convection zone along one of the cloud bands on the periphery of the tropical cyclone.
Both the HKO and the U.S. Joint Typhoon Warning Center (JTWC) reported the rapid deepening of Leo started around 00 UTC 29
April. In the model, the eye was first formed in the lower troposphere, and it extended to the upper troposphere within a
few hours. We speculate that the spin-up of cyclonic rotation in the low-level eye enhanced the positive vorticity along the
low-level eye wall. The positive vorticity was then transported to the upper troposphere by convection, leading to an extension
and growth of the eye into the upper troposphere.
To examine the impact of convective parameterization scheme (CPS) on the simulation, the Grell scheme (GLEX) was also tested.
The GLEX predicted a weaker typhoon with a wilder eye that extended not as high up in the upper troposphere as BMEX. The different
structures of the eye between the BMEX and GLEX suggest that the mesoscale features of the eye are dependent on the convection.
In other words, the vertical and horizontal distribution of convective heating is essential to the development and structure
of the eye.
Received December 18, 2001; accepted May 7, 2002
Published online: March 20, 2003 相似文献
1000.
The changes in the response of near surfaceaerosol properties to land- and sea-breezecirculations, associated with the changes in the prevailing synoptic meteorological conditions, are examined for a tropical coastal station. Aerosol properties are nearly similar in both the breeze regimes (land and sea) during seasons of marine airmass while they are distinct during seasons of continental airmass. As the prevailing winds shift from continental to marine and the ambient weather changes from winter conditions to the humid monsoon season, the submicron mode, which dominated the aerosol mass-size distribution, is largely suppressed and the dominance of the super micron mode increases. During periods of continental air mass (winter), the aerosol loading is significantly higher in the land-breeze regime, (particularly in the submicron range) but as the winds shift to marine, the loading initially becomes insensitive to the breeze regimes and later becomes higher in the sea-breeze regime, particularly in the super micron range. 相似文献