雷达资料在孤立单体雷电预警中的初步应用

利用多普勒雷达资料,结合探空、闪电资料对2005年夏季北京地区的20个单体过程进行综合分析,结果表明:40 dBz是比较适合该地区雷电预警的一个雷达回波特征参量;在此基础之上,将0℃层结高度作为基础特征高度,并结合-10℃层结高度和强回波所占比例对孤立单体的雷电发生进行综合预警是一种较为接近实际应用的方法。根据以上分析,该文针对孤立单体能否发生闪电、以及闪电发生的起始时间给出了一个初步的预报方法,并利用22个孤立单体进行了检验。检验结果证明:该方法在对单体是否会发展为雷暴单体,以及雷暴单体中初次闪电发生时段的预报方面效果较好。同时还发现,雷暴单体中从25 dBz回波出现到单体的35 dBz回波厚度变化率达到极值的时间差,与雷暴中最早的云闪与最早的地闪之间的时间差,两者存在一定的线性关系。这为进一步预测地闪的发生提供了一个参考依据。

Exploration and Research of Deep Crustal Structures in the Zhangzhou Basin and Its Vicinity

The Zhangzhou basin is located at the middle section of the southeast coast seismic zone of the mainland of China. Using high-resolution refraction and wide-angle reflection/refraction seismic profiling of Zhangzhou basin and its vicinity, we have obtained the crustal geometric structure and velocity structure as well as the geometric configuration and structural relationship between the deep and shallow fractures. The results show that the crust in the region is divided into the upper crust and lower crust. The thickness of the upper crust is 16.5km- 18.8km, and that of the lower crust is 12.0km- 13.0km. The upper crust is further divided into an upper and lower section. In the lower section of the upper crust, there is a low-velocity layer with a velocity of about 6.00km/s; the depth of the top surface of the low-velocity layer is about 12.0km, and the thickness is about 5.0km. The lower crust is also divided into an upper and lower section. The depth of Moho is 29.0km- 31 .8km There are 6 normal faults in the shallow crust in this region, and most of them extend downwards to a depth of less than 4kin, the maximum depth is about 5km. Below the shallow normal faults, there is a conjectural high-dip angle deep fault zone. The fault zone extends downwards till the Moho and upwards into the low-velocity layer in lower section of the upper crust. The deep and shallow faults are not tectonically connected. The combination character of deep and shallow structures in the Zhangzhou basin indicates that the Jiulongjiang fault zone is a deep fault zone with distinct characteristics and a complex deep and shallow structure background. The acquisition of deep seismic exploration results obviously enhanced the reliability of explanation of deep-structural data and the exploration precision of the region. The combination of deep and shallow structures resulted in uniform explanation results. The delamination of the crust and the characteristic of the structures are more precise and explicit. We discovered for the first time the combination characteristics of extensional structures and listric faults in the upper crust. This is not only helpful to the integrative judgment of earthquake risk in Zhangzhou and its vicinity, but also of importance for deepening the knowledge of deep dynamic processes in the southeast coast seismic zone.

Analysis of raft foundation design based on considering influence of superstructure stiffness

The finite element method was used for analysis of raft foundation design in high-rise building.Compared with other conventional methods,this method is more adapted to the practical condition since both superstructure stiffness and soil conditions were considered in calculation.The calculation results by example show that the base reaction is more uniform and the maximum reaction decreases obviously.Accordingly,the raft foundation design is more economic without any loss of security for high-rise building.

Turbulent Energy Budgets of a Ground Vortex Flow

Turbulent kinetic energy budgets are presented for a highly curved flow generated by the collision of plane wall turbulent jet with a low-velocity boundary layer. The different terms are obtained in the vertical plane of symmetry by quadratic interpolation of the LDV （Laser Doppler Velocimetry） measurements, for a wall jet-to-boundary layer velocity ratio of 2. The results, which have relevance to flows encountered in powered-lift aircraft operating in ground effect, quantify the structure of the complex ground vortex flow. The analysis of turbulent energy equation terms using the measured data revealed that production by normal and shear stresses are both very important to the turbulent structure of the impact zone of the ground vortex. This is an indication that the modeling of turbulence of a ground vortex requires a good representation of the production by normal stresses which is most important in the collision zone.

STRUCTURE OF SOUTH ASIA HIGH IN THE STRATOSPHERE AND INFLUENCE OF ENSO

The structure of the South Asia High(SAH)in the stratosphere and the influence of ENSO on the SAH are systematically investigated with the long-term ECMWF reanalysis data.The results show that the SAH only exists in low levels of the stratosphere.The maximum intensity of the High is located at around 150 hPa and there is no obvious anti-cyclonic structure above 50 hPa.The axis of the SAH center tends to be northwest slanting from lower levels to higher levels.Further analyses show that the geopotential height and temperature fields of the SAH have dramatic anomalies during El Ni?o years and La Ni?a years. Corresponding to the ENSO,the SAH is weaker(stronger)at the warm(cold)phase.