After anatomizing the typ ical experiments for turbulence by Thorpe andWoods et al. , some results are obtained as follows:(1) a Taichimodel for turbulence is brought forward; (2) The cascade of turbulence includes two basic contents: one is the small -scale eddies resulted from the large - scale eddies by their inward - rotation motions, the other is the hypo - scale eddies originated from the frontwhich is a bigger - speed - shear interface separating the fluids from each other; (3) The dissipative mechanism of turbulence is associated with the frontwhich always tends to be drawn very long. As a result, the interface linking two fluids is extended infinitely and the p rocess of the molecular diffusion between the interface is then highly enhanced to achieve the high effective diffusion of turbulence; (4) An eddy closure scheme is brought forward to close the Reynolds equations; (5) The mixing length is equal to the outer radius of a turbulent eddy, while Karman constant is a function of ratio of inner radius to outer radius of the eddy; (6) By the ideas of operator and turbulent operator, the actual turbulent dynamical equations are deduced; (7) The invariance p rincip le of relationship is brought forward. What’smore, counter - gradient transport and eddy relationology are also discussed.
Research of the coupled heat-moisturemodelof soilwas developed in the 1950s based on the isothermalmodelof soilwater movement. It is closely related to atmospheric circulation, the use ofwater resources, agriculture and application of remote sensing technique, and italso increasingly became a focus in land surface process research. This paper introduces severalpopular coupled heat -moisturemodels of soil and their characteristics, and analyzes the test effects and the acting trend of thesemodels in some specific regions. Some problems atpresent researches and future development direction on the coupled heat-moisture model of soil are discussed finally.
A series of recent researchs focuses on the impact of climate change on agricultural production, land use, pollution and biodiversity, which implies the potential impactof climate change on food security is awidely debated and investigated issue. Nonetheless, the specific safety influence of food and feed for consumers has remained a less studied topic. This review identifies the various food safety issues from some literatures about climate change impacts on crop cultivation and livestock systems. According to general consensus, crop cultivation is recognized as a relatively susceptible partof the food and feed production sector thatcould be affected by climate change, variations in climatic parameters such as temperature, drought, precipitation, wind, and CO2levels are projected to have notable consequences on crops in terms of changes in the demand for fertilizer and pesticides, deterioration of the quality of soils,and expanding ranges of crop pests and altered transmission dynamics of insects, pests and plant diseases. Livestock production also could be heavily influenced by climate change, and the presence ofpathogenic bacteria in foods followingmore frequentextremeweather conditions, such as flooding and heatwaves. Therefore the challenges facing food securitywill pose new risks to human under the background of the global climate change.
The change of p recip itation at 84 meteorological stations in Beijing, Tianjin and Hebei in recent 47 yearswas analyzed by using linear regression, abrup t change analysis and wavelet analysis in this article. The results showed that annual p recip itation decreased at a climatic tendency of - 15 mm /10 a, and the 11 - year runningmean curve indicated the trend would continue in the future. Precip itation in summerwas decreasing inmost of the areas, while increasing in the other seasons. The abrup t change occurred in summer p recip itation during the early 1990 s. Generally, both annual and seasonal p recip itation p resented four periodic change of three, nine, fourteen and twenty - four years.
The particular ecological and climatic effects of surface land dewfall resource were summarized simp ly, and the theoretic basis for exp loitation of land surface dewfallwas analyzed, especially the scientific ideas and technologicalmeasures for exp loitation land surface dewfallwere discussed from two sides of choosing the local climate condition and imp roving condensation face of dewfall.
In the paper, by using the data observed in“The Field Experiment on Land - atmosphere Interaction over Arid Region of Northwest China”, characteristics of atmospheric humidity, characteristics of soilwater content, characteristics of land surface parameterswith soil water content and other land surface parameters are analyzed. To validate the new surface parameters and parameterization formulae, the comparison is done between simulation and observation. It is found that the new surface parameters and parameterization formulae are better.
Based on the hail suppression operation status at present，the tasks of the technique system，the peripheral technique system，the operational conducting system of the hail suppression and the relations among them are discussed in this paper，and also the relative possibility of the general adaption of the operational conducting system and its realizing way and degree for a single radar station or a city. A concept of " rather empty leak not" is given.
:Minqin oasis lies to the northeast of Hexi corridor and lower reaches of Shiyang river,the environment there had degenerated obviously in recent 40 years.The hungriness of soil, death of vegetation and other facts about Minqin oasis were analysed,the cause of formation from the change of climate and human activity had been analysed too,Several suggestions of environment protection were put forward at last.
A land-surface model is improved by using some new research results.Net radiation, surface temperature, sensible heat, latent heat and temperature, specific humidity and wind velocity in ground layer under precipitation condition are simulated by using the data observed at Dunhuang in the“Field Experiment on Interaction between Land and Atmosphere in the Arid Region of Northwest China”.The results show that the model is ameliorated well.The radiation flux and surface temperature simulation are better than energy. The simulation of the temperature, specific humidity and wind speed in ground layer is well because the ground layer is considered alone in this model.
:Development of hail suppression in China since 1990 are briefly summarized from the point of sciences and techniques in this paper. Some problems of sciences and techniques for hail research and hail suppression are analyzed,some suggests for them are indi- cated.
