共查询到18条相似文献，搜索用时 93 毫秒
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介绍兰州干旱气象研究所研制的大型电子蒸渗计的工作原理,以及参数的设定,室内、田间标定方法。此蒸渗计经几年推广应用,取得大量农气蒸散方面的资料,效果很好。 相似文献
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王小军 《沙漠与绿洲气象(新疆气象)》2020,14(1):138-143
为探求绿洲棉区膜下滴灌条件下不同种植密度棉田蒸散发规律，运用大型称重式蒸渗仪对膜下滴灌棉田蒸散过程连续监测，结果表明：在不同种植密度条件下，棉花的日蒸散量曲线都表现为单峰曲线，不同生育时期一膜六行（30株/m2）种植的棉田蒸散量比一膜四行（20株/m2）大，花铃期棉田的蒸散发强度最大，一膜四行、一膜六行分别为4.76mm/d、5.94mm/d。同时，一膜六行种植的叶面积指数大于一膜四行种植,株高小于一膜四行种植。花铃期棉田的蒸散发量与日平均气温（p<0.01）和空气相对湿度(p<0.01)具有很好的相关性，与日平均风速和日平均水汽压的关系不大。 相似文献
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利用大型称重式蒸渗计测得的地面降雨量 (P) 和自记雨量筒测得的次降雨量 (P′) 进行比较, 结果表明两者之间存在较好的线性关系, 而且地面雨量大于雨量筒测量的次降雨量, 平均雨量订正系数K为0.037.当降雨持续时间小于6 h时K值在0.04~0.045之间, 不同降雨持续时间之间差值不大; 当降雨持续时间大于6 h时, K值为0.027.随着降雨强度的增大, 降雨订正系数呈下降趋势.根据不同降雨强度下的降雨订正系数对甘肃河东19个气象站6~9月的雨量修正结果表明, 各站降雨量比次降雨量多11.7~27.4 mm, 区域平均降雨量比次平均降雨量高18.4 mm. 相似文献
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水量平衡和蒸散发过程研究是水文循环研究的重要方面。正确的观测和计算地表实际蒸散发量对认识气候变化条件下的水循环特征、实现区域水资源的可持续开发利用具有非常重要的意义。传统蒸渗仪功能单一,不仅安装费用较高,日常维护和观测需要大量的人力物力,观测精度也常常受到仪器系统误差或人为因素的影响。围绕着陆面蒸散发观测和解决"蒸发悖论"的科学问题,设计了用于研究气候变化对水循环、陆面蒸散发影响的野外自动观测实验的新系统,站址选择在江西省南昌县生态实验站。该新型蒸渗仪(Lysimeter)系统采用先进的高分辨率称重系统(陆面蒸散发观测精度:0.01 mm)、高精度土壤水分水势传感器(pf:0-7,国际专利号:102004010518.9)和动态IP解析技术的GPRS数据采集器(24 bit,512 k),通过地表气象站、土壤水分水势、蒸渗仪和地下水位等独立的观测实验对比,确定陆地表面实际蒸散发量以及蒸散发过程的有关参数。该系统无论在测量的精度及频次上都比传统观测方法有极大的提高。另外,除了应用于陆面实际蒸散发量的观测外,该系统装置了2004年获得国际专利的新型土壤水分、温度和水势传感器,观测精度较高,观测频次可调节幅度较大,且适应多种环境条件,能够根据不同的科学目标进行新的组合和设计。 相似文献
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几种蒸散计算方法在怀来地区的适用性研究 总被引：3，自引：0，他引：3
作物蒸散量即为植株蒸腾与棵间蒸发之和,准确地测定作物实际蒸散量,对研究农作物节水种植技术、加强水资源管理和制定合理的灌溉计划具有十分重要的意义。文章应用2013年生长季(5-10月)自动称重式蒸渗仪实测河北怀来地区夏玉米的蒸散量,从月、日两个时间尺度评价Penman-Monteith(FAO P-M)、Hargreaves、Priestley-Taylor三种基于参考作物蒸散量计算实际蒸散的方法在怀来地区的适用性,结果表明:(1)三种方法计算的夏玉米月、日实际蒸散相对于蒸渗仪实测结果均存在一定偏差,FAO P-M方法与Hargreaves方法表现较好,准确度相差不大,Priestley-Taylor方法准确性最差;(2)影响实际蒸散计算结果的主要气象因子为太阳净辐射和温度,Hargreaves方法计算结果在怀来地区可信度较高;(3)Hargreaves方法所需参数较少,在计算量方面占有很大的优势,在怀来地区适用性最好。 相似文献
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怀来地区蒸渗仪测定玉米田蒸散发分析 总被引：3，自引：0，他引：3
《高原气象》2015,(4)
利用2012年和2013年怀来遥感综合试验站蒸渗仪、涡动相关仪和自动气象站观测资料,分析了土壤蒸发和玉米农田蒸散的日、季节变化,用多元回归分析法研究了气象因子(净辐射、空气温度、空气湿度、风速)、土壤水分和农田蒸散量的关系,并将蒸渗仪蒸散观测值与涡动相关仪蒸散量观测值进行了比较。结果表明,土壤蒸发和玉米农田蒸散日变化曲线较一致,季节性差异明显;怀来地区日蒸散量与净辐射和土壤水分相关性较好,与其他影响因子相关性不明显;蒸渗仪的农田代表性受其观测范围内的作物长势影响显著,涡动相关仪观测的蒸散量与蒸渗仪观测值相关关系较好,蒸渗仪观测值较涡动相关仪观测值高10.5%,这是由于不能同周围农田进行热交换,蒸渗仪内平均土壤温度较农田高了9.5%,导致蒸渗仪对蒸散量的相对高估。 相似文献
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As part of the research programme of the Atmospheric Environment Service, a large, sensitive weighing lysimeter was constructed on the Atmospheric Environment Service research site north of Toronto. Features of the instrument include: measurement of runoff, percolation, drainage of water held in tension, addition of water from below during dry conditions, equalization of soil temperature profile inside with that outside the lysimeter, humidity control to eliminate condensation, low area of discontinuity at the rim to reduce edge effects, and quasimonolith filling. This paper describes the construction and installation of the lysimeter, the problems encountered and some infrequently considered sources of error. 相似文献
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黄土高原陆面水分的凝结现象及收支特征试验研究 总被引：7，自引：2，他引：5
中国黄土高原是全球独特的地理区域,其陆面水分过程比较特殊。利用黄土高原陆面过程试验研究(LOPEX)的陇中黄土高原定西陆面过程综合观测站的资料,分析了陆面水分凝结现象及其出现频率与局地微气象条件的关系,研究了露水(霜)量及其出现频率的季节分布特征以及受降水和天气阴、晴的影响规律。同时,对比分析了降水、露水、雾水和土壤吸附水对陆面水分的贡献率,讨论了涡动相关法、蒸渗计和蒸发皿观测的陆面蒸发量的差别及其与陆面水分来源的年平衡关系,给出了半干旱区陆面水分平衡的日循环特征。发现露水对风速、大气湿度、近地层温度梯度的依赖很强,一般在风速为1.5 m/s、相对湿度大于80%和逆温强度为0.25℃的情况下露水(霜)量最大;刚降水后的晴天露水量比较大;实际蒸散量与蒸发力的差距十分明显,陆面水分平衡特征表现为一个"呼吸"过程。 相似文献
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The imbalance of land-surface water budget was discovered in past studies, but there have been few
further investigations on the relevant causes. To probe into the problem, annual variations of precipitation
and land-surface evapotranspiration were analyzed by using the historical observation data from a comprehensive
land-surface observation base of LOPEX (Loess Plateau Experiment). A remarkable imbalance in
the land-surface water budget was found, and the total annual imbalance reached 20.6%. Then, the impact
factors related to additional water budget components and observational methods were studied. The total
annual imbalance could be reduced to 3.8% by using a combination of compensated land-surface water budget
components and the surface evapotranspiration values obtained from the large-scale weighing lysimeter
rather than from the eddy correlation method. 相似文献
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Experimental study of the imbalance of water budget over the Loess Plateau of China 总被引：1，自引：0，他引：1 
下载免费PDF全文
下载免费PDF全文 The imbalance of land-surface water budget was discovered in past studies, but there have been few further investigations
on the relevant causes. To probe into the problem, annual variations of precipitation and land-surface evapotranspiration
were analyzed by using the historical observation data from a comprehensive land-surface observation base of LOPEX (Loess
Plateau Experiment). A remarkable imbalance in the land-surface water budget was found, and the total annual imbalance reached
20.6%. Then, the impact factors related to additional water budget components and observational methods were studied. The
total annual imbalance could be reduced to 3.8% by using a combination of compensated land-surface water budget components
and the surface evapotranspiration values obtained from the large-scale weighing lysimeter rather than from the eddy correlation
method. 相似文献
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D. I. Campbell 《Boundary-Layer Meteorology》1989,46(1-2):133-152
The energy balance was measured for the dry canopy of narrow-leaved snow tussock (Chionochloa rigida), and measurements of transpiration were obtained from a large weighing lysimeter.Typical maximum summer transpiration rates of 0.21–0.43 mmhr-1 (140–290 W m-2) were recorded. The latent heat flux accounted for less than 40% of net radiation. The estimated value of the bulk stomatal resistance (r
ST) for 29 days was 158 s m-1, and the decoupling parameter () was 0.17. Transpiration rates were not driven directly by net radiation, but were closely linked to the size of the regional saturation deficit imposed at the level of the canopy by efficient overhead mixing, and were constrained by a large bulk stomatal resistance. A linear relationship between r
ST and the saturation deficit is proposed as a realistic method for estimating transpiration for water yield studies of tussock catchments. 相似文献
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Summary A methodological study on a tall canopy in a Mediterranean region was carried out in order to identify the most suitable method for measuring the actual evapotranspiration (ET). ET from a sweet sorghum crop was measured by 4 different methods: (i) energy balance/eddy correlation, (ii) energy balance/Bowen ratio, (iii) energy balance/aerodynamic simplified, and (iv) floating lysimeter (ETmeter). In order to compare a very large range of ET values and to reduce experimental errors due to low gradients of air humidity and temperature, the crop was submitted to two soil drying-wetting cycles. To evaluate the main limitations of each method with respect to crop height, crop ET was monitored during the entire vegetative cycle, from stem elongation (crop height 0.85 m, full canopy) to grain filling (when the crop was 2.5 m high). The comparison between the micrometeorological methods (i, ii, and iii) was made on hourly and daily time steps, while the analysis of ETmeter measurements was made on a daily time step only. On an hourly scale: eddy correlation ET was 106% of Bowen ratio ET and simplified aerodynamic ET was 116%, 125% and 135% of Bowen ratio ET with the first sensors are placed at the top of the canopy and the second sensors at 0.7 m, 1.4 m and 2.8 m from the first sensors, respectively. On a daily scale: eddy correlation ET was 102% of Bowen ratio ET, simplified aerodynamic was 114% of Bowen ratio ET and ETmeter ET was 97% of Bowen ratio ET. In the last case the values are very widely spread and the correlation is really not so good. The results show that the Bowen ratio method and the eddy correlation method are in good agreement on daily scales, however, certain precautions, must be taken concerning the eddy correlation method on an hourly scale. The simplified aerodynamic method failed when crop height was > 1.5 m and the ETmeter failed under windy conditions (wind speed > 2.0 m/s) and limited crop water conditions.With 13 Figures 相似文献
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雷暴下近地面电特性及其对人工引雷的影响 总被引：2，自引：5，他引：2
利用已建立的一维时变模式，对雷暴下近地面的电特性进行了计算。计算结果表明：由于地面的不规则性所产生的电晕电流密度可达２．０ｎＡ／ｍ＾２，由此而形成的空间电荷密度在１００ｍ密度以下可达１．１ｎＣ／ｍ＾３，传导电流可达３．５ｎＡ／ｍ＾２，并可延伸到１０００ｍ高度，形成０．１ｎＣ／ｍ＾３和１．０ｎＡ／ｍ＾２的电荷密度和电流密度。 相似文献
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Wm. A. Dugas 《Theoretical and Applied Climatology》1990,42(4):215-221
Summary Whole-plant transpiration (T) measurements have many applications, but appropriate methods have remained somewhat elusive. A new method using a constant power heat balance gauge, wherein the xylem mass flow rate is calculated from a balance of heat into and out of a stem, has been shown to provide accurate stem flow measurements. To evaluate the applicability of this promising method to field experiments, cotton (Gossypium hirsutum L. GP 3774) stem flow measurements were compared withT measured from a weighing lysimeter. Initially to confirm method accuracy, stem flow values were compared in the glasshouse withT values determined by mass measurements of a potted plant. The root mean square error (RMSE) between the daylight losses from both (n = 16) was 8.6% of the mean measuredT values. In the field, hourly stem flow and lysimeterT values were also similar, but there was a large variation in stem flow values among the different plants. To account for differences in plant size between the plants with gauges and all lysimeter plants, stem flow values were adjusted using a stem area ratio factor, which adjusted values, on the average for the season, by 25%. Before adjustment, daylight stem flow totals were consistently greater than lysimeterT values. After adjustment, the means differed by only 9%, and theRMSE was reduced from 129 to 69 g plant–1 d–1. The coefficient of variation of daylight stem flow totals increased throughout the season. In the glasshouse, method accuracy was comparable (errors < ± 10%) to what has been previously determined. In the field, determining method accuracy was confounded by plant-to-plant variability and, possibly, by errors, unique to the gauge design used in this study, at high flow rates. Thus, this method can provide accurate flow measurements from individual herbaceous plants and is a valuable technique for many applications.With 7 Figures 相似文献