EC-thin降水预报与极端天气预报指数在浙江暴雨预报中的检验与释用

利用ECMWF模式降水和极端天气指数资料,以及浙江省68个气象站降水观测资料,评估了ECMWF细网格模式(EC-thin)和降水极端天气指数(EFI)对浙江2018—2020年梅汛期暴雨预报效果。研究表明：对于同一预报时效,随着阈值的增加,EC-thin和降水EFI的暴雨预报评分都呈现“先增加、后减小”的趋势,对于不同预报时效都存在某一阈值使得暴雨预报评分达到最大。从24 h时效到72 h时效,EC-thin的降水预报阈值从45 mm逐渐下降到25 mm,而降水EFI的暴雨预报阈值从07下降到06。EC-thin和降水EFI对暴雨预报的空报率随着阈值的增大而减小,漏报率随着阈值的增大而增大。对于不同预报时效,通过合理组合EC-thin降水阈值和降水EFI阈值,可以得到更好的暴雨预报效果,其评分高于单独使用降水EFI阈值或EC-thin降水阈值得到的评分。     

热带气旋外眼墙形成机制研究综述

介绍了国内外关于热带气旋外眼墙形成和维持过程的相关研究进展,包括大尺度环境场和热带气旋涡旋内部动力学过程,如涡旋罗斯贝波理论、轴对称化过程、涡丝化作用、β-skirt轴对称化外眼墙形成假说和边界层非平衡动力过程等。随着对外眼墙形成机理研究的不断深入,当前存在多种外眼墙形成的机制理论,而这些机制均强调在外眼墙的形成阶段,热带气旋外围有大量对流及位势涡度扰动的发生发展。因此,热带气旋外眼墙的形成很有可能是多种机制相互作用导致的。最后,提出研究多种机制相互作用导致外眼墙处的对流和位势涡度扰动的发生发展过程具有重大意义。     

Current-driven Alfvén waves in dusty magnetospheric plasmas

It is shown that the sheared flow of electrons and ions in the presence of heavy stationary dust gives rise to unstable Alfvén waves. The coupling of newly studied low frequency electrostatic current-driven mode with the electromagnetic Alfvén and drift waves is investigated. The instability conditions and the growth rates of both inertial and kinetic Alfvén waves are estimated. The theoretical model is applied to the night side boundary regions of Jupiter’s magnetosphere which contain positive dust. The growth rates increase with increase in sheared flow speed. In the nonlinear regime, both inertial and kinetic Alfvén waves form dipolar vortices whose speed and amplitude depend upon the magnitude of the zero-order current.     

CIRCULAR-ECONOMY MODELS OF ANIMAL HUSBANDRY INDUSTRY IN JILIN PROVINCE

1INTRODUCTION The circular-economyisan efficient resources metabolic process, based on principles of ecology and system engi- neering.Withcoupledstructure andthe complex ecolo- gical and economic evolution, it has the characteristics of overall integrity, coordination, and circulation (WANG, 2005). Compared with the traditionalecono- mic model, the circular-economy requires the technical model of production process to be changed from the opening flow pattern that is "resourcesconsumption…     

Annual cycle and budgets of nutrients in the Bohai sea

The environmental problems in the Bohai Sea have become more serious in the last decade. High nutrient concentration contributes much to it. A Sino-German cooperation program has been carried out to improve the understanding of the ecosystem by observations and modelling. A three-dimensional ecosystem model, coupled with a physical transport model, is adopted in this study. The simulation for the year 1982 is validated by the data collected in 1982/1983. The simulated annual mean nutrient concentrations are in good agreement with observations. The nutrient concentrations in the bohai Sea, which are crucial to the algal growth, are high in winter and low in summer. There are depletion from spring to summer and elevation from autumn to winter for nutrients. The nutrients’ depletion is a response to the consumption of the phytoplankton bloom in spring. Internal recycle and external compensation affect the nutrient cycle. Their contributions to the nutrient budgets are discussed based on the simulated results. Production and respiration are the most important sink and source of nutrients. The process of photosynthesis consumes 152 kilotons-P and 831.1 kilotons-N while respiration releases 94.5 kilotons-P and 516.6 kilotons-N in the same period. The remineralization of the detritus pool is an important source of nutrient regeneration, It can compensate 23 percent of the nutrient consumed by the production process. The inputs of phosphates and nitrogen from rivers are 0.55 and 52.7 kilotons respectively. The net nutrient budget is −3.05 kilotons-P and 31.6 kilotons-N.     

Runoff and sediment loss responses to rainfall and land use in two agricultural catchments on the Loess Plateau of China

Soil erosion is a severe problem hindering sustainable agriculture on the Loess Plateau of China. Plot experiments were conducted under the natural rainfall condition during 1995–1997 at Wangdongguo and Aobao catchments in this region to evaluate the effects of various land use, cropping systems, land slopes and rainfall on runoff and sediment losses, as well as the differences in catchment responses. The experiments included various surface conditions ranging from bare soil to vegetated surfaces (maize, wheat residue, Robinia pseudoacacia L., Amorpha fruticosa L., Stipa capillata L., buckwheat and Astragarus adsurgens L.). The measurements were carried out on hill slopes with different gradients (i.e. 0 ° to 36 °). These plots varied from 20 to 60 m in length. Results indicated that runoff and erosion in this region occurred mainly during summer storms. Summer runoff and sediment losses under cropping and other vegetation were significantly less than those from ploughed bare soil (i.e. without crop/plant or crop residue). There were fewer runoff and sediment losses with increasing canopy cover. Land slope had a major effect on runoff and sediment losses and this effect was markedly larger in the tillage plots than that in the natural grass and forest plots, although this effect was very small when the maximum rainfall intensity was larger than 58·8 mm/h or smaller than 2·4 mm/h. Sediment losses per unit area rose with increasing slope length for the same land slope and same land use. The effect of slope length on sediment losses was stronger on a bare soil plot than on a crop/plant plot. The runoff volume and sediment losses were both closely related to rainfall volume and maximum intensity, while runoff coefficient was mainly controlled by maximum rainfall intensity. Hortonian overland flow is the dominant runoff process in the region. The differences in runoff volume, runoff coefficient and sediment losses between the catchments are mainly controlled by the maximum rainfall intensity and infiltration characteristics. The Aobao catchment yielded much larger runoff volume, runoff coefficient and sediment than the Wangdongguo catchment. Copyright © 2001 John Wiley & Sons, Ltd.     

利用地基GPS数据研究2006年12月电离层磁暴现象

利用中国大陆全球定位GPS台网数据和中国周边地区国际IGS站数据，研究了2006年12月中旬的 磁暴对中国大陆上空电离层的影响。结果显示,该磁暴对中国大陆上空电离层的影响并不显著。     

地理信息系统的现状及其技术系统的研究动向

地理信息系统作为新兴的高技术系统，已经应用于整个空间信息的处理领域。本文将在分析现有系统应用水平和存在问题的基础上，着重讨论了六个方面值得重视的研究课题。     

A VLBI study of 20 southern extragalactic radio sources

This paper describes a 5 GHz VLBI survey in the southern hemisphere. The first observation of 23 extragalactic radio sources was conducted in November 1992. Twenty VLBI images were obtained, of which 15 sources show core-jet structure, one has a two-sided jet, and three sources are unresolved. No compact double source was found. Eleven of the 16 sources with core-jet (including a two-aided jet) show evidence of jet bending. In addition, four sources appear to be superluminal, of which three sources are new.