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241.
利用中尺度数值预报模式MM5对山西省2009年发生的几场典型雾个例进行数值模拟。结果表明:模拟2 m温度比观测值偏低约2 ℃,相对湿度模拟结果比观测值偏大约15 %,10 m的模拟风速比观测的偏大0-2 m·s-1。山西省雾的预报指标为20 m液态水含量大于等于0.13 g·kg-1而小于0.60g·kg-1、20-1500 m高度大气层存在逆温层、地面风速小于4 m·s-1。利用太原测站日平均能见度、日平均相对湿度以及空气污染指数进行拟合建立太原能见度预报模型,并利用实测资料订正MM5、CAPPS模式预报误差,给出订正后的能见度预报方程并以两次实例对区域及太原雾天能见度预报表明该能见度预报模型有一定的适用性。 相似文献
242.
利用天津铁塔观测资料、加密自动站和常规观测资料,针对4次渤海西岸典型降雪过程,分析了偏东风在降雪发生前后的演变特征。结果表明:4次降雪过程均属于回流降雪,其水汽来源与西南气流的水汽输送和近地面层的东风水汽输送有关;地面东风出现在降雪开始之前8 h以上,风速一般在2 m·s-1左右,220 m高度可达12 m·s-1左右。从造成东风的系统看,由南部北上的低压系统造成的东风或东南风湿度比较大,而由东北南下的冷高压造成的东风或东北风都比较干。出现最大降雪的时段,塔层的东风显著加大,而地面的风速变化不明显。 相似文献
243.
Effects of forest gaps on some microclimate variables in Castanopsis kawakamii natural forest 总被引:1,自引:0,他引:1
Zhongsheng He Jinfu Liu Caiting Wu Shiqun Zheng Wei Hong Songjin Su Chengzhen Wu 《山地科学学报》2012,9(5):706-714
The objective of this study was to understand the effects of forest gap and variations in different seasons, gap size, locations and diurnal variations on forest microclimate and soil water content. Spatial and temporal distribution features of air temperature (TA ), soil temperature (TS ), relative humidity (h) and soil water content (Ψ) were measured in Castanopsis kawakamii natural forest gaps created by a severe typhoon or fallen dead trees. The results showed that: (1) the variations of TA , h, and TS in four seasons were extremely significant. The variations of Ψ in four seasons were extremely significant except for those between spring and summer. (2) The diurnal variations of TA and T S were expressed with a single peak curve. The diurnal variations of h and Ψ presented a high-low-high trend. (3) The variations of TA , h, and TS were extremely significant among the large, medium and small gaps in C. kawakamii natural forest. Medium gaps had the highest TA and the lowest h while small gaps were just contrary to medium gaps. The variations of Ψ were extremely significant for large, medium and small gaps except those between the medium and large gaps. (4) The TA , h, TS and Ψ were decreased from the gap center, canopy gap, expanded gap to understory. These results will help further our understanding of the abiotic and consequent biotic responses to gaps in the mid-subtropical broadleaved forests, which also provide a theoretical basis for the scientific management and population restoration of C. kawakamii natural forest. 相似文献
244.
多孔结构无机材料比表面积和孔径分布对调湿性的影响 总被引:1,自引:0,他引:1
测试海泡石、沸石、硅藻土和坡缕石粘土的孔径和比表面积,研究其孔径和比表面积与吸放湿能力的对应关系.利用氮气等温吸附对孔隙结构进行测试、分析,通过BET法计算得出其比表面积分别为81.56、2.46、1.68和187.70 m2/g,平均孔径分别为8.53、18.20、31.57和11.79 nm.在温度25℃相对湿度分别为75%和35%的条件下进行吸放湿试验,4种样品的最大吸湿量分别为5.6%、2.2%、1.8%和6.0%,放湿量分别为4.4%、1.8%、1.6%、5.0%.数据对比发现,比表面积大且孔径分布符合在相应温湿度下以Kelvin公式计算出的孔径分布特点的矿物材料,如海泡石,吸放湿能力强. 相似文献
245.
不同盐度养殖Ⅰ龄花鲈(Lateolabrax japonicus)的生长特性差异分析 总被引:1,自引:0,他引:1
利用室外水泥池,采用全人工配合饵料投喂的方法对花鲈(Lateolabrax japonicus)进行为期274d的养殖实验,分别测定其在不同养殖盐度条件下的生长状况、成活率、特定生长率和饲料系数。结果表明,在盐度12—18时花鲈生长速度、成活率和特定生长率较高。通过回归分析得出,其生长速度的最适盐度为16—17;盐度12和18组饲料系数较低,分别为1.57和1.62,盐度30组最高;各组间在成活率方面差异不显著。因此,Ⅰ龄花鲈养殖的最适宜生长盐度理论值为16—17,在此条件下可实现较高的生长速度、特定生长率和饲料转换率。 相似文献
246.
247.
Understanding and quantifying sediment load is important in catchments draining highly erodible materials that eventually contribute to siltation of downstream reservoirs. Within this context, the suspended sediment transport and its temporal dynamics have been studied in the River Isábena (445 km2, south-central Pyrenees, Ebro basin) by means of direct sampling and turbidity recording during a 3-year dry period. The average flood-suspended sediment concentration was 8 g l− 1, with maximum instantaneous values above 350 g l− 1. The high scatter between discharge and suspended sediment concentrations (up to five orders of magnitude) has not permitted the use of rating curve methods to estimate the total load. Interpolation techniques yielded a mean annual sediment load of 184,253 t y− 1 for the study period, with a specific yield of 414 t km− 2 y− 1. This value resembles those reported for small torrents in nearby mountainous environments and is the result of the high connectivity between the badland source areas and stream courses, a fact that maximises sediment conveyance through the catchment. Floods dominated the sediment transport and yield. However, sediment transport was more constant through time than that observed in Mediterranean counterparts; this can be attributed to the role of base flows that entrain fine sediment temporarily stored in the channel and force the river to carry high sediment concentrations (i.e., generally in the order of 0.5 g l− 1), even under minimum flow conditions. 相似文献
248.
Statistical characteristics of detectable inhomogeneities [IHs] in more than 600 observed meteorological time series have
been investigated using 16 objective homogenisation methods. Forty and 100 year long series of monthly or annual characteristics
of surface air temperature, precipitation total and relative air humidity from the Czech Republic and Hungary were examined.
The area of the part of the Czech observing network used here is smaller, and the density of sites is larger, than in the
Hungarian network, resulting in higher spatial correlations among data in the Czech dataset relative to the Hungarian dataset.
Time series with low number of gaps were supplied with interpolated data. Before homogenisation relative time series were
created, using weighted averages of time series from the same geographical region as reference series. For ease of comparison,
the magnitudes of the detected IHs are normalised with the standard deviation of the noise in the relative time series.
Results show that observed meteorological time series usually contain large number of small IHs, and that the magnitude distribution
of IHs from different data segments are surprisingly similar. Effects of different spatial coherences on the results are discussed. 相似文献
249.
准确的湿度垂直廓线对短期数值天气预报和中长期气候研究分析均具有重要参考价值,但太阳辐射与高空云雨等因素导致探空湿度测量精度较低.针对探空仪GTS1白天进行湿度测量时存在明显偏干误差的现象,本文建立了GTS1湿度测量结构模型,采用计算流体动力学方法重点研究了太阳辐射对GTS1湿度测量的影响,同时探讨了其防雨/防辐射罩的防雨效果.结合改进的太阳辐射计算模型,利用Fluent模拟分析了防雨/防辐射罩云雨滴轨迹和内部温度场分布,数值仿真结果表明:在垂直气流下防雨/防辐射罩基本保护湿度传感器免受高空云雨的影响,对太阳辐射也起到一定防护作用.但太阳辐射对GTS1湿度测量的偏干影响仍较显著,海拔30km左右相对误差甚至高达70%.通过与RS92及GTS1探空湿度测量中的太阳辐射偏干误差相对比,发现基于流体动力学数值计算的湿度相对误差随海拔高度的变化趋势与之基本吻合.本文也给出了理论计算与实验测量存在一定差异的原因,进而以南京探空站2014年不同季节的温度、气压、气球的上升速度等探空数据为计算参数,获取了太阳辐射误差与海拔及环境温度的关系,并对四组探空湿度廓线进行太阳辐射误差修正,提升了GTS1探空仪高空湿度测量的精度.本文研究结果为探空湿度测量太阳辐射偏干误差的有效修正提供了一定的参考. 相似文献
250.