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141.
142.
内蒙古温带半干旱羊草草原N2O通量及其影响因素 总被引:5,自引:2,他引:5
利用静态箱 -气相色谱法于 2 0 0 1~ 2 0 0 3年对内蒙古锡林河流域羊草草原进行了连续 2年的野外定位试验 ,获得羊草草原原状群落与土壤N2 O年排放通量分别在 3 91~ 4 71μgm- 2h- 1以及 5 5 0~ 10 0 3μgm- 2 h- 1范围内变动 ,证明内蒙古温带半干旱羊草草原生态系统是大气中N2 O的源 ;系统分析了羊草草原N2 O通量的季节变化、源汇特征以及关键的环境因子对草地N2 O通量的影响等 ,建立了N2 O通量与环境因子间的回归方程 ;并利用两年连续完整的观测数据对羊草草原N2 O年排放量进行了估算 相似文献
143.
对比云南富宁2001年“8·25”与2004年“5·15”两次大暴雨过程前后的雨量分布、灾情、大气环流背景,以及反映大气水汽、热力、动力条件的部分物理量场,分析它们在两次过程中的异同点,讨论各类条件对暴雨落区的指示性情况,并对“5·15”过程的雷达回波资料作简单的定量分析。 相似文献
144.
会展经济,在云南社会经济的发展过程中有着十分重要的意义,云南应该尽快、尽早制定相应的发展对策。首先应深刻地认识到发展会展经济对云南具有十分重要的战略意义,与此同时成立相应的领导机构,同时制定合理的发展目标,并按照会展发展的原则和云南发展会展经济的步骤逐步实施。 相似文献
145.
146.
从工作实际出发,将测量过程中常用的计算和换算工作,用VisualBasic语言编写成计算程序,最后将各模块集成为一个“测量工具箱”,从而方便了测量工作者处理日常工作中的一些计算和换算问题。 相似文献
147.
On August 5, 2001, Shanghai was struck by a torrential rainfall due to the passage of a tropical depression (TD). The rainfall intensity has been the strongest in recent 50 years. In this paper, a set of mesoscale re-analyses data and the planetary boundary layer observation from a wind profiler are used to understand the possible mechanism of such a heavy rain. Results show that the outburst of a southerly jet in the lower atmosphere triggered the explosive development of cyclonically vertical vorticity in the region with steep potential temperature surfaces in front of the TD; while the cyclonic vorticity increased notably at higher levels due to the small atmospheric vertical stability of westerly currents in the vicinity of Shanghai. The simultaneous sharp development of cyclonic vorticity at different levels should be the main cause for the torrential rainfall. 相似文献
148.
2004年“云娜”台风的监视和预报工作中,在应用常规天气资料的基础上加强了对历史热带气旋资料、天气雷达资料和过去对台风与台风暴雨分析预报研究成果的运用。在台风登陆前、登陆过程中和登陆后三个不同阶段中,应用多种资料进行有针对性的分析判断,并向防台风指挥部门及时提供信息服务,在防台工作中发挥了有效作用。, 相似文献
149.
Wen−Cheng Liu 《Environmental Geology》2005,47(4):535-546
Settling velocities of suspended cohesive sediment in estuaries vary over a range of several orders in magnitude. Variations in the suspended sediment concentration are often considered as the principal cause. Turbulence and the suspended sediment concentration, as well as other factors such as salinity, dissolved organic substances, flocculation ability, and the rate of floc growth affect setting velocities. A laterally–averaged finite difference model for hydrodynamics and cohesive sediment transport is developed and applied in the Tanshui River estuary, Taiwan. The model has been calibrated and verified with water surface elevation, longitudinal velocity, salinity, and cohesive sediment measured. The overall performance of the model is in qualitative agreement with the available data. The model is used to investigate the influence of settling velocity on cohesive sediment transport dynamics. The simulation indicates that the turbidity maximum zone is near Kuan–Du. When settling velocities increase the surface cohesive sediment concentration at Kuan–Du station trends to decrease and bottom cohesive sediment concentration increases. Both surface and bottom cohesive sediment concentrations decrease at Taipei Bridge and Pa–Ling Bridge. This implies that suspended sediment advected seaward and deposited. There is consequently a net seaward flux of suspended sediment near surface, and a net landward flux near the bed. 相似文献
150.
Hydrochemical characteristics and salinity of groundwater in the Ejina Basin, Northwestern China 总被引:8,自引:0,他引:8
A hydrochemical investigation was conducted in the Ejina Basin to identify the hydrochemical characteristics and the salinity
of groundwater. The results indicate that groundwater in the area is brackish and are significantly zonation in salinity and
water types from the recharge area to the discharge area. The ionic ration plot and saturation index (SI) calculation suggest
that the silicate rock weathering and evaporation deposition are the dominant processes that determine the major ionic composition
in the study area. Most of the stable isotope δ18O and δD compositions in the groundwater is a meteoric water feature, indicating that the groundwater mainly sources from
meteoric water and most groundwater undergoes a long history of evaporation. Based on radioactive isotope tritium (3H) analysis, the groundwater ages were approximately estimated in different aquifers. The groundwater age ranges from less
than 5 years, between 5 years and 50 years, and more than 50 years. Within 1 km of the river water influence zone, the groundwater
recharges from recent Heihe river water and the groundwater age is about less than 5 years in shallow aquifer. From 1 km to
10 km of the river water influence zone, the groundwater sources from the mixture waters and the groundwater age is between
5 years and 50 years in shallow aquifer. The groundwater age is more than 50 years in deep confined aquifer. 相似文献