The convective weather and lightning disasters occurred frequently in the northeastern verge of Tibetan Plateau. In order to analyze the characteristics of cloud-to-ground (CG) lightning flashes, the CG location data and daily precipitation collected by the advanced toa and direction （ADTD） system of Gansu Provincial Meteorological Administration and CIMISS during 2017-2020 are used to investigate the spatial and temporal characteristics of the CG lightning frequency, current intensity and the CG flashes density in the northeastern verge of Tibetan Plateau, and the relationship between the CG flashes density and precipitation. The results show that the annual average number of the CG lightning in this region in recent four years was about 2.71×104 times. The annual average negative CG and positive CG lightning accounted for 84.27% and 15.73% of the total CG lightning flashes, respectively. The monthly distribution of the CG lightning flashes presented a single-peak pattern. Specifically, the CG lighting flashes mainly occurred in summer, which accounted for 70.11% of the CG lightning in the whole year. In spring and autumn, the percentage of the CG lightning was less than that in summer, and in winter the number was least. The diurnal distribution of the CG lightning frequency also showed a single peak. The peak value of the total CG and negative CG lightning occurred mainly from 10:00 BST to 12:00 BST in a day. The occurring time of peak value for positive CG lightning lagged one hour than the negative CG lightning. Although the number of monthly-averaged positive CG lightning was much less than that of negative CG lightning from April to October, the ratio of average current intensity of positive CG lightning flashes to that of negative CG flash was 1.56. The CG lightning flashes density greater than 0.24 fl·km-2·a-1 concentrated in Yongdeng County of Lanzhou, Luqu County, Maqu County and Hezuo City in Gannan Tibetan Autonomous Prefecture, Zhangjiachuan County in Tianshui City, Huachi County, Huan County, Zhenyuan County and Qingcheng County in Qingyang City, Wen County and the south of Longnan City. And the high incidence areas of positive CG lightning mainly occurred in Maqu County, Luqu County, the junction of Dingxi City and Gannan Tibetan Autonomous, and the central and southern part of Qingyang City. Lighting protection measures should be strengthened in the above areas. By comparing the density of the CG lightning and precipitation, it is found that the spatial and temporal distributions of lightning activity was consistent with precipitation in the northeastern verge of Tibetan Plateau.
Water or drought stress is one of the most important factors limiting crop growth world - wide. Some changes would be observed in p lant growth, physiologicalmechanisms and hormone level under soil drying stress. In arid or semi - arid region, water deficit in soil evidently inhibit the root and the shoot growth, and decrease biomass, yields and harvest index. Usually, water stress during the grain - filling period would decrease photosynthesis, shorten the grain - filling period, decline the grain - filling rate and induce early senescence, however, itwould increase the remetabolism of non - structural carbohydrate (NSC) from the vegetative tissues to the grain. Grain filling is an intensive transportation p rocess regulated by soil drying and p lant hormones. The concentration ofABA, which is generally regarded as an inhibitory growth hormone, would increase markedly in leaves, floral organs and develop ing grains in responses to soil drying. Some of the adap tive responses to drought are due to physiological and morphological changes, such as changes in p lant structure, dry matter accumulation, tissue osmotic potential and stomatal conductance. Soil drying is unfavorable to p lant growth butmay be favourable to the critical point of p roducing stress. So it is possible to take advantage of soil drying to induce whole - p lant senescence and better carbon remetabolism to imp rove grain yield during the slow grain filling period. If mild soil drying is p roperly controlled during the later grain - filling period in some crop s such as rice (Oryza sativa) and wheat ( Triticum aestivum) , it could enhance yield and harvest index, and might contribute to water saving, which is imminently needed to develop sustainable agriculture in many parts of the world.
The relation between rice plant height increasing rate and meteorological factors was studied in this paper. 'hhe climate models for rice plant height and its increasing rate, rice plant height distillation function in Ningxia irrigation area Were established respectively. The change of rice growth and development with climate factors and different irrigation volume was given out.
System dynamics (SD) based on feedback control theory and applied by computer simulating techniques is an effective methodology for modeling and analyzing complex social, economic and ecological systems. With the great development of computer teChnlqLIPS and System dynamlCS theOTleS, the SD meth0(lOlOgy has been broadly applied In many f1e1dS. Th1S artlCle TPV1eWS hTlefly the WOTkS dOrie In TeglOnal SLIStalnahle deVelOpment LISlng the SD meth0(lOlOgy In TPCent years, arid d1Se11SSeS Some further TPSeaTC11eS which can he carried out in this area.
The northwest region in China is considered to be one of the worst regions in shortage of water resources. The shortage and irrational exploitation of water resources have become a major factor for limiting sustainable development of the region’s economy and society. Based on analysis and evaluation of the present situation of water resources and its utilization in northwest China, this paper suggests that establishing water-saving society is the key to achieving sustainable utilization of water resources in the region. The key strategies for promoting the establishment of water-saving society are to (1) establish and perfect administrative system, market -oriented system and legal system for water resource management; (2) set up target system for scientific utilization of water resource; (3) adjust agricultural structure to form a water-saving agricultural system; and (4) adjust industrial structure to establish a water-saving industry system.
