An analysis of the tendency of reference evapotranspiration estimates and other climate variables during the last 45 years in Southern Spain

Climate change will have important implications in the agriculture of semi-arid regions, such as Southern Spain, where the expected warmer and drier conditions might augment crop water demand. To evaluate these effects, a data set consisting of observed daily values of air temperature, relative humidity, sunshine duration and wind speed from eight weather stations in Andalusia and covering the period 1960-2005 was used for estimating reference evapotranspiration (ET_o). ET_o was calculated using five methods: the more complex Penman-Monteith FAO-56 (PM) equation, considered as a reference in this study, and four alternative methods with fewer data requirements, Hargreaves, Blaney-Criddle, Radiation and Priestley-Taylor. These methods were compared to PM with respect to ET_o average values and trends. The non-parametric Mann-Kendall test was used to evaluate annual and seasonal trends in the main climate variables and ET_o.Due to increases in air temperature and solar radiation, and decreases in relative humidity, statistically significant increases in PM-ET_o were detected (up to 3.5 mm year⁻¹). Although the Hargreaves equation provided the closest average values to PM, this method did not detect any ET_o trend. On the other hand, trends found from Blaney-Criddle and Radiation ET_o values were similar to those obtained from PM. In addition, after a local adjustment, these two methods gave accurate ET_o average values. Therefore, Blaney-Criddle and Radiation methods have shown themselves to be the most accurate approaches for ET_o determination in climate change studies, when available data provided by climate models are limited.     

基于Penman-Monteith方程的温室番茄蒸腾量估算模型

作物的蒸腾是作物生命过程中十分重要的组成部分。为寻求适合于温室栽培条件下番茄植株蒸腾量的计算模型,本文以Penman-Monteith方程为基础,针对温室特定的小气候环境,对番茄冠层整体气孔阻力、空气动力学阻力等参数进行合理修正,建立了包含气象数据、番茄叶面积指数和冠层高度为主要参数的温室番茄蒸腾量估算模型。分别采用2009年5月2-13日（开花坐果期）和2009年6月9-20日（成熟采摘期）2个时段内的实测蒸腾量对模型模拟结果进行验证,2个时段内模型模拟结果的平均相对误差分别为8.48%和9.20%,表明所建模型可以较好地的计算温室番茄的蒸腾量。本研究提出的蒸腾量估算模型对温室番茄作物水分关系的深入研究具有重要参考价值。     

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

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.     

西北地区近49年生长季参考作物蒸散量的敏感性分析

基于FAO Penman-Monteith公式计算了西北地区126个站点1961-2009年的生长季参考作物蒸散量（ET0）对气温、风速、相对湿度和太阳总辐射的敏感系数,并对敏感系数的时空变化特征进行分析。结果表明：西北地区生长季ET0对太阳总辐射最敏感,其次是气温和相对湿度,对风速的敏感性最低。气象要素分布的不均匀性导致敏感系数的空间差异显著,气温和风速的敏感系数在西风带气候区较大,相对湿度敏感系数在较湿润地带形成高值区,太阳总辐射敏感系数南部明显大于北部。生长季内,各气象因子的敏感系数均存在一定程度的波动,气温和太阳总辐射的敏感系数呈单峰型分布,风速敏感系数呈单谷型分布,相对湿度敏感系数的绝对值持续上升。49a来,太阳总辐射敏感系数显著上升,相对湿度敏感系数明显下降,其趋势系数均通过0.05水平的显著性检验,而气温和风速的敏感系数以波动为主,无明显变化趋势。     

Trend analysis of reference evapotranspiration in the western half of Iran

Reference evapotranspiration (ET_o) is an important element of the hydrological cycle, and changes in ET_o are of great significance for agricultural water use planning, irrigation system design and management. In this study, annual, seasonal and monthly trends in the Penman-Monteith ET_o at 20 meteorological stations during 1966-2005 in the western half of Iran were examined using the Mann-Kendall test, the Sen's slope estimator and the linear regression. Annual analysis of the ET_o series indicated a positive trend in 70% of the stations according to the Mann-Kendall test and the Sen's slope estimator and in 75% of the stations according to the linear regression. The magnitude of significant positive trends in annual ET_o varied from (+)11.28 to (+)2.30 mm/year. On the seasonal scale, stronger increasing trends were identified in ET_o data in winter and summer compared with those in autumn and spring. Meanwhile, the highest numbers of stations with significant trends were found in the monthly ET_o series in February, while the lowest numbers of stations with significant trends were observed in November. Analysis of the impact of climatic variables on the significant increasing trend in ET_o showed that the increasing trend was mainly caused by a significant increase in air temperature during the study period.     

不同冠层阻力模型对冬小麦返青-成熟期蒸散量估算的影响

蒸散量是农田水循环的重要组成部分,其准确估算对精准灌溉及农业节水具有重要意义。PenmanMonteith(P-M)模型是常用的估算方法之一,但冠层阻力/表面阻力的准确表达一直是应用中的难点。选取常用的7种冠层阻力模型,根据北京市顺义区2a(2020年和2021年)的波文比实测结果,对不同模型模拟的小麦冠层阻力及P-M估算的小麦蒸散量进行比较,并进一步分析影响小麦冠层阻力的主要因子。结果表明,7种模型均低估了小麦冠层阻力,同时高估了蒸散量。总体而言,Todorovic模型（TD）模拟效果最好,其模拟的冠层阻力和蒸散量的R2均大于0.605,平均偏差（MBE）分别为-82.8s·m-1和10.4W·m-2,相应的均方根误差（RMSE）分别为254.4s·m-1和33.5W·m-2;其余6种模型表现均较差,所模拟的冠层阻力R2仅0.113～0.241,MBE和RMSE在-236.4～-61.3s·m-1、277.2～373.8s·m-1;基于6种模型模拟阻力得到的小麦蒸散量与实测值的R2在0.046～0.184,MBE和RMSE分别在44.5～97.4W·m-2、81.4～147.9W·m...     

基于径流曲线数模型的江淮丘陵区塘坝复蓄次数计算模型

针对江淮丘陵区塘坝体系复蓄次数计算问题的重要性与复杂性,提出运用SCS模型处理塘坝灌区无资料水文模拟计算问题,构建了塘坝灌区降雨径流模拟模型,并依据Penman-Monteith公式计算了各典型作物的需水量,进而实现了对江淮丘陵区塘坝灌溉系统的水量平衡分析,合理地推算了塘坝系统复蓄次数,找出塘坝灌区现状灌溉体系中存在的问题,可为江淮丘陵区塘坝工程规划、种植结构调整以及灌溉制度的确定提供理论支撑,具有明显的实际指导意义和重要的推广应用价值。     

基于水汽扩散理论的水稻需水量数学模型

首先分析了气象要素包括气温、风速、空气饱和差、日照时数及蒸发量对水稻需水量的影响.然后,根据水汽扩散理论建立需水量基本方程,考虑气象要素对水汽交换系数的影响,建立水汽交换系数公式,从而导出计算水稻需水量的五因素数学模型.将该数学模型FAO56 Penman-Monteith公式需水量模型在寒地稻区进行对比分析.结果表明,该模型比Penman-Monteith公式具有较高的精度,可以作为区域性计算公式在稻作灌区中应用.     

新疆塔里木盆地北缘日参考作物腾发量计算模型评价

采用4种常用的腾发量模型(Makkink模型,Turc模型,Priestley-Taylor模型以及Hargreaves模型)计算日腾发量,并以Penman-Monteith FAO 56公式计算结果为标准值进行对比,旨在寻找出建模数据少、模拟精度高以及适合研究区的腾发量计算模型。结果表明:Turc模型的日参考作物蒸发蒸腾量与Penman-Monteith FAO 56差异较小,其次是Makkink模型与Priestley-Taylor模型,Hargreaves模型的差异最大。     

简化参照作物蒸散量（ETo）计算公式在青海省高寒区的适用性分析

【目的】以Penman-Monteith FAO-56公式为参照,分析Hargreaves、Priestley-Taylor和Makkink 3种简化的参照作物蒸散量(ETo)公式在青海高寒区的适用性。【方法】以青海省5个气候区(湿润、半湿润、半干旱、干旱和极端干旱)11个气象站1984-2011年的旬气象资料计算ETo,建立分析3种简化公式旬ETo与PenmanMonteith FAO-56公式的线性回归方程,并对比其年值的均方根误差率,分析3种简化公式的适用性。【结果】Hargreaves公式在大多数站点都低估了ETo,但在湿润和半湿润区的计算结果较好;Priestley-Taylor公式在多数站点都高估了ETo;Makkink公式在所有站点都低估了ETo,但其旬ETo值的误差最小,其与PMF-56公式的线性回归结果也最好。除极端干旱区外,Priestley-Taylor和Makkink公式计算的ETo与PMF-56公式的年均方根误差率均小于15%。【结论】Hargreaves公式只适用于青海省的湿润和半湿润区,Priestley-Taylor和Makkink公式可以直接用于青海省极端干旱区以外地区ETo的计算。