彭曼-蒙特斯公式在参考作物需水量中的应用研究   总被引：6，自引：1，他引：5  

张丹  张广涛  王丽学  胡冰  孙毅  吴琼 《安徽农业科学》2006,34(18):4513-4514

介绍了作物需水量计算的几种方法,采用彭曼—蒙特斯(Penman-Monteith)公式,计算了浑蒲灌区水稻的需水量,结果比以往直接算法更为精确,为灌区工程的规划、设计和管理提供了依据。  相似文献   

和林格尔县近40年气候变化浅析     

云冬梅  杨旺林  王冰利 《内蒙古农业科技》2012,(5):97-98

对和林格尔县1971-2010年的气温、降水、蒸发量、大风日数、无霜期日数等资料进行统计分析,得出和林格尔县近40年的气候变化特征。结果表明:近40年来,和林格尔县年平均气温呈波动上升趋势,每10年平均上升0.43℃;年降水量1971-1990年为下降趋势,1991-2010年呈波动上升趋势;年蒸发量1971-2000年为下降趋势,2001-2010年呈波动上升趋势;大风日数在1～38d;无霜期107～212d。  相似文献   

温室细雾风机系统的参数设计和调节     

徐刚毅  田东风 《农业工程学报》1991,7(4):48-54

本文通过对不同直径的雾粒在0.001秒有效时间内蒸发引起直径变化的计算,确定了不同出口直径雾粒蒸发所需要的时间。首次结合北京地区的气象条件,绘制出适用于北京地区夏季的四张qEtφ图,为蒸发降温系统的参数设计和调节提供了理论依据。并给出了温室细雾风机系统在北京地区使用随气象条件变化的参数调节数据。  相似文献   

温室细雾风机系统几个主要设计参数对细雾蒸发的影响   总被引：6，自引：2，他引：6  

徐刚毅  周长吉 《农业工程学报》1996,12(3):135-138

温室细雾风机系统降温的主要缺点是蒸发不完全，地面有积水。文章对温室细雾风机系统在降温过程中的实际蒸发量及细雾风机系统的几个主要设计参数如系统的工作压力、喷嘴高度、细雾的雾化程度等对细雾蒸发的影响进行了试验分析，为解决蒸发不完全问题提供依据  相似文献   

Mulch resistance to water vapor transport   总被引：2，自引：0，他引：2  

M. Fuchs  A. Hadas 《Agricultural Water Management》2011,98(6):990-998

Mulches augment soil moisture availability to plants by restraining direct evaporation of soil water. Yet, in field conditions wind decreases their resistance to water vapor transport, diminishing their efficiency as a water conservation measure. The relation between vapor transport resistance and wind speed was investigated in a wind tunnel where air flow was turbulent. The mulch material was chopped straw with bulk densities of 31 and 37 kg m⁻³, and chemically stabilized aggregates segregated in diameter classes 1-2, 2-4, 4-8, 8-11.2 mm, in layers 10-100 mm thick. The resistance decreased exponentially with increasing wind speed from the molecular diffusion value at zero wind speed, suggesting that turbulence penetrates the pores of the mulch and drives convective water vapor transport. Resistance rose exponentially with increasing layer thickness, a mirror reflection of the turbulence decay profile. Higher bulk density of the straw and finer aggregates augmented the resistance. The convective component of the vapor transport resistance was related to mulch area index, defined as the surface area of the solid elements of mulch per unit covered ground area. This procedure merged the effect of layer thickness and that of straw bulk density or aggregates size into a single function, indicating that friction forces proportional to internal area of the solid fabric restrain the penetration of momentum in the porous medium. Two-layered mulches combining straw and aggregates have a higher resistance than the sum of the resistances of the individual components as is expected from the attenuation of convection in the top layer. The functions derived in this study can serve as input for models evaluating the impact of mulches on soil water balance.  相似文献   

Skin layer evaporation to account for small precipitation events—An enhancement to the FAO-56 evaporation model     

Richard G. Allen 《Agricultural Water Management》2011,99(1):8-18

The FAO-56 soil water evaporation model is a simple ‘slab’ model that has been found to produce good estimates of evaporation from bare soil over a range of conditions due to its adherence to conservation of mass and energy. The simplicity of the model makes it straightforward to apply and to parameterize. An enhancement is made to the original formulation to accommodate light wetting events that wet the soil ‘skin’ near the surface and evaporate relatively quickly, even when the underlying soil is dry. In effect, the evaporation process, when the soil skin is wetted, reverts temporarily into stage 1 evaporation. The enhancement utilizes the ‘readily evaporable water’ (REW) term of the original model so that no new parameters are required. The extended model performs similar to the original model in the absence of small precipitation events, but increases the evaporation rate when small events occur. The FAO-56 method with the skin evaporation enhancement is shown to compare well against simulations made using the HYDRUS 1D model that bases evaporation on the Richards equation. The enhanced model also closely followed evaporation recorded by weighing lysimeter for a silt loam soil at Kimberly, Idaho, with root mean square difference of 0.39 and 0.69 mm d⁻¹ for two wetting/drying sequences. Total cumulative evaporation during the longest and wettest sequence was estimated at 92% of the measured value.  相似文献   

Comparison of Penman-Monteith and non-linear energy balance approaches for estimating leaf wetness duration and apple scab infection     

Alexandre Leca  Luciana ParisiAndré Lacointe  Marc Saudreau 《Agricultural and Forest Meteorology》2011,151(8):1158-1162

Leaf Wetness Duration (LWD) is the main parameter involved in the apple scab development in apple orchards. LWD values can be inferred from weather conditions by solving a non-linear energy balance equation. Such energy balance equation is usually linearized leading to the Penman-Monteith equations. However this approximation leads to significant errors in the evaporative term and by consequence in the LWD computation. In this work, consequences of the use of the Penman-Monteith equations instead of the exact solution were firstly investigated on single droplets and compared to experimental values obtained in controlled and constant conditions. For these studies, the LWD is overestimated by 12% when Penman-Monteith equations were used. The ability of LWD estimate from the linearized energy balance equation to forecast risk infection of a leaf by V. inaequalis conidia was investigated. For some conditions, the error in LWD estimate by Penman-Monteith approached 6 h, leading to an incorrect risk assessment of apple scab development.  相似文献   

The effect of long-term Maresha ploughing on soil physical properties in the Central Rift Valley of Ethiopia     

Birhanu Biazin  Leo Stroosnijder  Melesse Temesgen  Abdu AbdulKedir  Geert Sterk 《Soil & Tillage Research》2011,111(2):115-122

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娄烦县农业气候特征分析     

韩锦涛  李素清  乔利鹏 《安徽农学通报》2006,12(7):191-193

利用1959-2004年的气象资料,从气候基本要素气温、降水、蒸发方面,对娄烦县1959-2004年的农业气候特征及其发展趋势进行了分析。目的是揭示该区域的农业气候条件下的生态环境变化特征。研究表明:娄烦县近40年来气候变化明显,气温呈现周期变化和整体逐渐上升趋势,降水减少,气候向不利于区域农业生产的方向发展。  相似文献   

地膜覆盖栽培甜菜的需水特点     

熊念曾  李彦  苏文斌  史永清  樊福义 《中国糖料》1990,(1)

甜菜地膜覆盖栽培从全生育期看需水量并未减少,各生育期的需水规律与裸地栽培相一致,只是叶面蒸腾量与棵间蒸发量比例发生了变化。因此,当无灌溉条件降雨又少时,地膜覆盖甜菜受干旱威胁更大,故在干旱无灌溉地区不宜推广地膜覆盖技术。  相似文献