Simulation of bora in Novorossiysk

The bora event observed in Novorossiysk on February 6–8, 2012 was analyzed using the WRF numerical model of regional atmospheric circulation. The main meteorological parameters are reproduced. It is demonstrated that the maximum wind speed is reached in the area of the lee slope directly over the bay. It is obtained that the bora development is accompanied by intensive waves associated with the flowing around coastal mountains whose regime changes in time. Computed and measured changes in the surface wind speed are in a good agreement.     

A real data simulation of the Adriatic bora and the impact of mountain height on bora trajectories

Summary This study addresses simulation of the local bora wind and its properties as reflected on typical trajectories. Trajectory calculations are implemented in the Eta Model. The Eta Model has a vertical coordinate which permits a step-like representation of mountains and quasi-horizontal coordinate surfaces, the so-called eta coordinate. A realistic real data simulation of a bora wind case in achieved using the model with a 28 km horizontal resolution and 16 layers in the vertical. Numerical experiments with different mountain heights and shapes in the bora wind region are performed. These are motivated by observational indications and theoretically based expectations that a certain intermediate mountain elevation is required for generation of downslope windstorms with bora wind properties. Three-dimensional trajectories over various mountains mimicing real mountains but differing primarily in elevation are calculated and analysed. The maximum bora wind speed is predicted as expected through three-dimensional channels in the step mountain representations. The results illustrate and are in agreement with the observational evidence that mountain barriers of the elevation of about 1000 m are a necessary requirement for the occurrence of the bora-type downslope windstorms.With 10 Figures     

Bases and algorithm for nowcasting of the bora

Summary A detailed outline of a nowcasting model of the bora is presented for the region NE of the Gulf of Trieste. An exhaustive knowledge of results of bora behavior and the findings by the frontal bora model are used to couple the mesoscale and nowcasting models to predict the beginning, strength and cessation of the bora.With 5 Figures     

On a bora event simulated by the Eta Model

Summary ¶This study presents a numerical simulation of the bora wind as it occurs in form of a severe wind blowing down coastal mountains and over the Adriatic Sea. A typical cyclonic bora event, occurring during the period January 3–6, 1995, is simulated using a nested limited area model. An integration, with horizontal resolution of about 14km, and a nested one, with higher resolution, about 5.5km, are presented. The 1997 version of the Eta Model is used for both the lower resolution and the higher resolution runs. Numerous details of the simulation are found to be in good agreement with the understanding as well as the observational knowledge of the bora, thus supporting confidence in the realism of the results. In particular, features of the simulated flow are seen strongly indicative of some basic characteristics of the hydraulic model of the phenomenon, such as the mountain wave breaking and the upstream flow acceleration. Moreover, the increase in horizontal resolution, in combination with an improvement of the coastal SST information, led to a still improved realism of the low-level wind representation over the Adriatic Sea.Received December 31, 2001; revised March 25, 2002; accepted July 19, 2002 Published online: February 20, 2003     

Upper boundary of the bora as a stationary frontal surface

Summary For the inclined stationary internal atmospheric boundary as is the upper boundary of the bora flow down the lee-side slope of an orographic obstacle, the dynamic forces must be appropriately balanced, similar as at the atmospheric frontal surfaces. Starting from this idea, a model for the bora flow conditions was developed. Introducing some special suppositions, the model finally consists of four partial differential equations, which are solved numerically.Numerical experiments with the model by changing parameters such as friction and warm air stratification, as well as initial values of the flow: thickness, velocity, inclination and air mass temperature difference, show interesting results and finings. The shape of upper bora boundary and the distribution of the bora velocity above and downward the slope are graphycally presented, as they develop under the influence of different values of the mentioned parameters.With 5 Figures     

Meteorological and synoptic aspects of the formation and evolution of the Novorossiysk Bora

The genetic and synoptic classifications of the Novorossiysk Bora are created using the data of daily observations at the Novorossiysk meteorological station and other available synoptic information. Obtained are the quantitative criteria of these classifications, and on this base worked out are the basic scenarios of the generation and evolution of this dangerous phenomenon on the Black Sea coast of Russia. According to the genetic classification, the Bora was divided into four types: frontal, air-mass, monsoon, and gravity. Quantitative criteria worked out for each type can be used for the more accurate forecast of this destructive phenomenon near Novorossiysk. According to the synoptic classification, four classes were distinguished: Azores, North Atlantic, Siberian, and Arctic.     

Improved bora wind simulation using a nested Eta Model

Summary In connection with a number of recent publications on anomalous (excessive) absorption of shortwave radiation (SWR) by clouds, the data of aircraft observations of spectral and total SWR vertical profiles in the troposphere obtained within the CAENEX, GAAREX and FGGE programmes have been discussed. These data demonstrated persuasively the existence of substantial SWR absorption by clouds in the visible wavelength region. In this context, the results of simulation numerical medelling of the SWR transfer in clouds have been considered. These show a significant enhancement of the SWR absorption by clouds due to an increase of the mean free path of photons under an impact of multiple scattering in clouds. Another important consideration may be the impact of SWR-absorbing pollutants in clouds, especially soot aerosols.With 4 Figures     

Gustiness and coherent structure under weak wind period in atmospheric boundary layer

Statistical analysis of turbulent and gusty characteristics in the atmospheric boundary layer under weak wind period has been carried out.The data used in the analysis were from the multilevel ultrasonic anemometer-thermometers at 47 m,120 m,and 280 m levels on Beijing 325 m meteorological tower.The time series of 3D atmospheric velocity were analyzed by using conventional Fourier spectral analysis and decompose into three parts:basic mean flow(period 10 min),gusty disturbances(1 min period 10 min)and turbulence fluctuations(period 1 min).The results show that under weak mean wind condition:1)the gusty disturbances are the most strong fluctuations,contribute about 60% kinetic energy of eddy kinetic energy and 80% downward flux of momentum,although both the eddy kinetic energy and momentum transport are small in comparison with those in strong mean wind condition;2)the gusty wind disturbances are anisotropic;3)the gusty wind disturbances have obviously coherent structure,and their horizontal and vertical component are negatively correlated and make downward transport of momentum more effectively;4)the friction velocities related to turbulence and gusty wind are approximately constant with height in the surface layer.     

GAMIL1.0大气模式模拟的西北太平洋夏季风：阵风参数化方案的影响

本文分析了中国科学院大气物理研究所大气科学和地球流体力学数值模拟国家重点实验室( LASG/IAP)发展的大气环流格点模式(GAMIL1.0)对1980～1999年西北太平洋夏季风的模拟,讨论了阵风参数化方案对模拟效果的影响.结果表明:GAMIL1.0能合理再现西北太平洋夏季风气候态和年际变率的主要特征,不足之处在于其...     

Gustiness and Coherent Structure of Strong Winds and Their Role in Dust Emission and Entrainment

After the passage of a cold front,spring in northern China,the outbreak of strong wind is often accompanied by dust emissions.Through analyses of data in the atmospheric boundary layer during a typical case,it is revealed there are rather regular gust wave packets superimposed on the basic strong wind flow.The gust-wind wave packets have a period equal to around 3-6 mins and possess coherent structure.As the vertical transport of momentum is decomposed into separate parts by(a) basic flow,(b) gust-wind,and(...     

加强业务管理提高测报质量

我局从1999～2003年,测报工作连续4年未出现错情,在此期间共有1个250个班,9个百班无错通过上级业务部门验收.在仪器保管、使用、维护上符合要求,对外报送的各种表、簿都能做好出门合格.     

Addressing the necessity of the registration of the effects of causal mechanics in the example of a simple barotropic model of the atmosphere

Summary Considering the effects of causal mechanics on geophysical problems enables us to explain a number of phenomena, which cannot be explained from conventional positions. This paper shows that the introduction of the force of causality in a simple barotropic hydrodynamic model of weather forecasts results in the outcomes, which, on the one hand, can not be described from the positions of classical hydro-thermodynamics, whilst on the other hand, exist in nature.     

Modeling the evolution of the family of Mediterranean cyclones using the regional model of the atmosphere

Due to the complex orography and the presence of the moisture-saturated air, the Mediterranean region is characterized by the increased baroclinic and convective instability, that leads to the sudden cyclogenesis and the formation of dangerous weather phenomena. The results are given of the investigation of formation mechanisms of Mediterranean cyclones, peculiarities of stages of their evolution and dynamical processes, which occur throughout the atmosphere, using the regional numerical ETA model of the atmosphere by the example of individual cases of the cyclogenesis over the Mediterranean Sea. It is revealed that the cold Arctic air outbreak (the intrusion of the cold Arctic air) to the south of the Western Europe, leading to the formation of the areas of the baroclinic instability and the increased moisture content of the air in the area of the vortex origin, favors the cyclogenesis. The use of the vertical coordinate η in the model enabled to compute more precisely the vertical wind speed, therefore, the influence of the orography on the moisture content and precipitation increase became pronounced. The transformation of the structure of meteorological fields in the course of the development of vortexes is considered. The computation of the helicity is made, and it is shown that this characteristic can be one of the earliest predictors of cyclogenesis.     

流场配置及地形对西南低涡形成的动力作用

本文采用定常二层模式讨论较小地形及高、低层流场配置对西南低涡形成的动力作用。指出了西南低涡的形成是与盆地、河谷以及其上气流分层有关的一种定常态.在上、下为西风分层时期,低层的浅薄暖湿西风有利于西南低涡的形成.在上、下为东、西风分层时期,上层浅薄东风亦有利于西南低涡的形成.小型的凸起山脉对西南低涡的形成没有作用.     

Analysis of the Characteristics of the Low-level Jets in the Middle Reaches of the Yangtze River during the Mei-yu Season

Here, we analyze the characteristics and the formation mechanisms of low-level jets(LLJs) in the middle reaches of the Yangtze River during the 2010 mei-yu season using Wuhan station radiosonde data and the fifth generation of the European Centre for Medium-Range Weather Forecasts(ERA5) reanalysis dataset. Our results show that the vertical structure of LLJs is characterized by a predominance of boundary layer jets(BLJs) concentrated at heights of 900–1200 m.The BLJs occur most frequently at 230...     

On the determination of the height of the Ekman boundary layer

The heighth of the Ekman turbulent boundary layer determined by the momentum flux profile is estimated with the aid of considerations of similarity and an analysis of the dynamic equations. Asymptotic formulae have been obtained showing that, with increasing instability,h increases as ¦¦^1/2 (where is the non-dimensional stratification parameter); with increasing stability, on the other hand,h decreases as ^–1/2. For comparison, a simple estimate of the boundary-layer heighth _u determined by the velocity profile is given. As is shown, in unstable stratification,h _u behaves asymptotically as ¦¦^–1, i.e., in a manner entirely different from that ofh .     

阴山山脉对内蒙古中部地区气象要素影响初探

文章选用阴山山脉山北乌拉特后旗、白云、达茂旗、苏尼特左旗、化德,山南杭后旗、包头、呼和浩特、察右前旗、兴和1971—2000年气温、降水量、天气现象等资料进行对比分析,得到阴山山脉对内蒙古自治区中部地区气象要素影响初步结论。     

2003年黑龙江省主要灾害性天气及其对作物生长发育和粮食产量的影响

利用40年气温、降水资料和历史上千旱、低温严重的年份与2003年进行对比分析．评估黑龙江省2003年发生的严重灾害的分布范同,灾害程度,及其对主要粮食作物生长发育和产量的影响。得出2003年的灾害是30年未遇的全省性严重灾害年,各种灾害对各种作物都产生了不同程度的影响,受害最重的作物是小麦。