CHARACTERISTICS OF TURBULENCE SPECTRA IN DIFFERENT WEATHER PROCESSES UNDER UNSTABLE CONDITIONS*

In this paper,the data chosen from measurements by supersonic anemometers in Tongxian County of Beijing in 1990 are used to study characteristics of turbulence spectra in precipitation weather.Some turbulence parameters such as turbulence intensity,heat and momentum fluxes,friction velocity,M-O length and stability parameter are calculated and their dependence on turbulence spectra in different stability conditions are analyzed.Some encouraging results are obtained and compared with others' results.     

Development of Artificial Intelligence Technology in Weather Forecast

Numerical weather prediction, which is the major basis of current weather forecast, has some shortcomings, such as the understanding of the law of atmospheric motion, the assimilation and application of observation data, the expression of model physics, etc., leading to the forecast error of weather. The rapid development of artificial intelligence technology in recent years provides a new possibility for the advancement and innovation of weather forecast. In this paper, the background of the development of artificial intelligence, the current situation of the application of artificial intelligence technology to weather forecast and the future development trend are mainly described to account for this possibility. After that, the idea for development of weather forecast technology based on the integration of artificial intelligence and numerical forecast is put forward. Particularly, this study stresses that, in order to advance the AI algorithm of weather forecast in the future, it is requested to focus on the nonlinear and chaotic characteristics of atmospheric motion leading to the uncertainty of forecast. Starting from the essence of mathematics and physics, we need to realize the hybrid modeling of mathematics and physics, not only to establish the framework of input-output mapping, but also to provide solutions to the bottleneck problems of weather forecast.     

台风影响期间珠江三角洲局地强风暴和大暴雨发生的环境条件

采用１９７６－１９８３年６－８月珠江三角洲地区受台风影响期间区内各站逐日的强风暴和降水资料以及广泛站的探空资料，用相关对比度分析方法，对台风环流中的珠江三角洲局地强风暴和大暴雨发生的环境条件进行统计诊断，得出台风影响珠江三角洲时这两种强天气发生的有利的环境条件，并发现二者在气压、风速、层结稳定度和中下层位势不稳定等方面显著不同。     

Characteristics of air flow over Andaman islands including precipitation

The characteristics of simulated air flow over Andaman Islands are studied with a two-dimensional version of the University of Virginia meso scale model (UVMM). Using the observed synoptic data as initial conditions, 24 hr simulations are obtained for a day each in April and November. These days are chosen to study the variations in the simulated flow pattern under different synoptic conditions including precipitation effects. A large scale condensation scheme is employed to consider the effect of latent heat release on the perturbations. The results show that the latent heat released by condensation strengthens the intensity of perturbations and the topography accelerates the arrival of sea breeze by about an hour. The model-simulated results, given in graphical form, are discussed and compared with available observations.     

Statistics on the vertical structure of rainshowers

A large sample of summertime data from the McGill Radar Weather Observatory was analyzed to determine the variation with altitude of the horizontal extent of individual rainshowers. For echoes defined by a reflectivity factor of 39 dBz (equivalent to a rainfall rate of about 10 mm/h) it was found that the mean area of the total population of echoes decreases linearly with altitude from approximately 20 km² at 2 km to 11 km² at 8 km. Subsets of the total population were investigated, consisting of only the echoes penetrating the altitudes of 6, 7, and 8 km. On the average these relatively tall echoes are much greater in horizontal extent than the total population. Whereas the sizes of the total population of echoes at any altitude are distributed approximately exponentially in terms of the square root of area, the sizes of the “survivors” that extend to high altitudes may be described by the gamma distribution with a mean value decreasing approximately linearly with height above 3 km and a dispersion of 0.55. Some characteristics are also reported for echoes defined by reflectivities of 31 dBz and 47 dBz. Estimates are given of the fraction of the total area in a horizontal plane that contains echoes in each of these categories.     

Statistics on the sizes and internal structures of rainshowers

A large sample of radar reflectivity data from essentially a full summer of operation was analyzed to determine the horizontal extents and internal structure of rain areas observed at altitude levels from 2 to 10 km. Results are given on the size distributions of individual cells or patches defined by reflectivity thresholds approximately 4 dBz apart, on the dependence of mean size on altitude and reflectivity threshold, and on the interior structure of the patches as characterized by the number and sizes of higher-threshold patches contained in each echo. In a more detailed analysis of internal structure, the data were restricted to convective echoes in which certain prescribed reflectivities, ranging from about 30 to 50 dBz, were exceeded. It was found that the dependence of mean quantities, such as patch area, on reflectivity and altitude could be approximately described by simple functions, but that the scatter of observations about the mean was usually large.     

THE CHARACTERISTICS OF GENERAL CIRCULATION, POLAR ICE AND SNOW DAYS / COVER OF EXTREMELY SEVERE COLD MONTHS IN SOUTH CHINA WINTER

The work has made a statistic study of the variations of extremely severe cold winter months in the south of China and general circulation and external forcing factors in preceding periods. The result shows that from the current month to the preceding March the subtropical high in the west Pacific is persistently weak or located more to the east and south. When the summer monsoon is weak in East Asia in the year before, the winter monsoon will be strong in the current year in which the extremely severe cold month occurs. The Asian polar vortex expands in the preceding July, August and September and the current winter. The Tibetan Plateau has fewer days of snow cover in the November and December before the cold month occurs. There is less snow in the Tibetan Plateau in the preceding winter / spring of each extremely severe cold month. There are more polar ice in the polar Region for the 11 months before the current February, especially the previous March through August, and in Region in January ~ November before the current cold month of December but less ice in Region in March ~ August.     

浅谈自动气象站的防雷设计要点

运用当代防雷领域中的有关理论，对自动气象站容易遭受雷击的原因和途径进行分析，提出了自动气象站的防雷设计要点。     

新一代天气雷达在泥石流灾害中的应用探讨

天气雷达的发展大致经历了4个阶段，其主要用于监测强对流天气、定量估计降水，是气象部门的重要探测和监测手段之一。新一代天气雷达观测的实时回波强度（Z）、径向风速（V）、速度谱宽（W）的回波图像中，提供了丰富的有关强对流天气的信息，综合使用Z、V、W的图像分析，有利于较准确和及时地监测灾害性天气。云南滑坡泥石流灾害高发区与云南暴雨中心有很好的对应关系，云南滑坡泥石流灾害空间分布与暴雨空间分布的空间相关系数为0．19，通过了0．05的显著性水平检验，也进一步说明云南暴雨在滑坡泥石流灾害发生中起着重要作用。以2004年7月5日德宏州特大山洪泥石流灾害为例子，探讨了新一代天气雷达在泥石流灾害的临阵预警中的应用。