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1.
为准确估算科尔沁沙地青贮玉米实际蒸散量的变化规律,选用ASCE Penman-Monteith(ASCE-PM)模型计算参考作物蒸散发(ET0);利用双作物系数模型模拟土壤含水率与对应实测值进行统计分析,根据均方根误差、一致性指数、平均绝对误差和Nash-Sutcliffe效率指数4个指标以及回归系数和决定性系数对双作物系数模型进行率定和验证,然后模拟青贮玉米的作物系数,与ASCE-PM模型结合后模拟青贮玉米的蒸散发、棵间土壤蒸发和作物蒸腾规律,并分析其影响因素。结果表明:双作物系数模型准确地模拟土壤含水率和棵间土壤蒸发的变化过程,率定各阶段基础作物系数为0.25、0.9和0.5。棵间土壤蒸发先由播种时峰值下降到较低水平,于收割前有所回升;蒸腾速率除刚出苗和收割前呈单峰变化外大部分时段呈双峰变化,日内变化规律大体为中午高,早晚低,自出苗之日起生长中期后半段处于较高水平,之后逐渐减弱。青贮玉米蒸散量与太阳辐射线性关系最为显著(R=0.643),与气温、空气湿度和风速的相关性依次次之。ASCE-PM模型空气动力项5 d尺度贡献率为27.94%~77.66%,且随风速同增减。综上所述,ASCE-PM模型结合双作物系数可较好估算科尔沁沙地青贮玉米的实际蒸散量,以及棵间土壤蒸发和作物蒸腾量。  相似文献   

2.
新疆冬小麦农田蒸散估算模型的研究   总被引:1,自引:0,他引:1  
本文在田间试验资料的基础上,综合考虑了影响冬小麦农田蒸散的气象、生物学特性和土壤水分等因素,选用蒸发力、冬小麦的叶面积指数和相对有效土壤湿度建立了新疆冬小麦农田蒸散估算模型,并且检验了该模型的计算效果。  相似文献   

3.
本文旨在探讨以不同波段组合垂直植被指数所建立的高光谱模型对玉米叶面积指数(Leaf Area Index,LAI)的反演精度。在不同水肥耦合作用条件下,实测玉米冠层的高光谱反射率与叶面积指数数据以及裸土的高光谱反射率数据,在高光谱红光波段(631~760 nm)与近红外波段(760~1050 nm)逐波段构建土壤线,并在此基础上构建垂直植被指数(Perpendicolar Vegetation Index,PVI),找出与LAI具有最佳相关性波段组合PVI,建立玉米LAI估算模型。结果显示,采样波段间隔越窄,反演精度越高,在采样波段间隔1.4 nm的PVI(R677,R918)反演2004年的玉米LAI模型中,最佳回归方程是指数函数,精度达91.1%,标准差为0.1997,RMSE=0.0399,通过了0.01极显著验证。采用高光谱数据构建的PVI植被指数对玉米LAI的估算可以取得较高的精度。  相似文献   

4.
用中子水分仪于2003年对新疆阿瓦提县丰收三场膜下滴灌条件下不同水肥处理棉田的土壤含水率进行了测定,根据水量平衡原理计算了不同水肥处理的棉花蒸散量,综合考虑影响棉田蒸散的热量条件、土壤水分状况和棉花本身的生物学特性,选用蒸发力、相对土壤有效含水率和播种后天数三因素建立了缺水条件下膜下滴灌棉花蒸散量的计算模型。模型的模拟值与实测值吻合较好,经F检验具有极显著性水平。该模型仅需常规气象资料,计算简便,具有一定的应用价值。  相似文献   

5.
石羊河流域蒸散发遥感反演方法   总被引:7,自引:2,他引:7  
蒸散是水资源管理的一个重要参数。与传统的蒸散计算方法相比,利用遥感进行蒸散研究具有快速、准确、大区域尺度及地图可视化显示等特点。本文通过研究,提出了基于能量平衡方法遥感反演蒸散发的计算模型,指出了模型参数的求解方法,建立了基于MOD IS遥感数据的大区域蒸散发遥感反演技术方法。通过对石羊河流域进行试验,证明该方法具有很强的实用性,并且具有进一步推广的技术前景。  相似文献   

6.
干旱区区域蒸散发量遥感反演研究   总被引:3,自引:2,他引:1  
为研究干旱半干旱区蒸散发量,以新疆为研究区域,基于地表能量平衡,依据地表温度与反照率关系确定蒸发比,利用MODIS影像遥感估算新疆地区的蒸散发量。通过野外验证,模拟蒸散量与涡度相关仪野外观测量一致,平均误差在0.40mm/d。在干旱区,蒸散发量与降水的相关性在82%,与气温的相关性分别为46%。通过模型反演,2005年研究区在空间上以裸土蒸发为主,蒸发量在0-2mm/d之间,主要在塔里木盆地、准噶尔盆地和吐鲁番盆地,而蒸散发量较高地区主要为天山山脉下垫面为林地草地和平原绿洲农田区域,蒸散发量最大达6mm/d。  相似文献   

7.
蒸散发是水循环中水量、能量平衡的关键过程。REDRAW模型对典型遥感蒸散发模型SEBAL干湿限选取方式进行改进,使用理论计算法估算干湿限地表温度以降低空间歧义性。为检验这两个模型在柴达木地区的适用性,以及气象校正对于蒸散发的敏感性,文中使用ERA5再分析数据、地表站点观测融合作为气象输入,采用REDRAW和SEBAL两种单源遥感蒸散发模型反演柴达木盆地2001-2020年1km×1km分辨率逐月蒸散发,由此求得多年平均蒸散发并水量平衡闭合验证。结果表明:REDRAW模型估算的柴达木盆地年均蒸散发为178.5mm,水量平衡闭合度为89.2%,较SEBAL模型能更好地描述该区域蒸散发特征;基于随机森林模型的气象校正算法可以纠正ERA5再分析数据的系统性偏差,能一定程度上消除缺乏气象站点观测引起的蒸散发估算误差。  相似文献   

8.
蒸散发估算方法及其驱动力研究进展   总被引:2,自引:0,他引:2  
蒸散发是水文循环的重要组成部分,也是度量土壤-植被-大气耦合系统中水文与能量传输的关键指标。因此,准确估算蒸散发,充分理解蒸散发的驱动力对干旱半干旱区水资源高效利用具有重要意义。本文对区域蒸散发估算方法进行了总结与归纳,并从气候变化和人类活动两个角度总结了干旱半干旱地区蒸散发变化的驱动力。最后,评论了当前蒸散发估算方法及其驱动力研究存在的问题,提出未来应加强蒸散发估算模型的改进与完善,合理规划土地利用,提高水资源利用效率,从而促进区域的可持续发展。  相似文献   

9.
针对水文水资源分析计算中最难估算的分量-蒸散发(Evapotranspiration,ET),以典型干旱区流域-玛纳斯河流域为研究对象,采用理论基础坚实、区域应用限制小、反演陆面蒸散发较为合理准确的双层阻抗模型,并根据研究区实际情况进行了模型参数化的基础上,结合MOIDS数据、气象观测数据和DEM数据,估算了该流域的陆面蒸散发量,并分析了其时空分布特征。研究结果表明:中高山区和绿洲平原区,由于植被覆盖度高,以植被蒸腾为主,蒸散发量小;而低山丘陵区和沙漠区,由于植被稀疏,以土壤蒸发为主,蒸发强烈,因而蒸散发量最大。  相似文献   

10.
GLDAS数据产品在渭河流域潜在蒸散发模拟中的应用研究   总被引:2,自引:0,他引:2  
蒸散发量是水资源管理的一个重要参数,目前的蒸散发模型中需要的大量气象参数,一般都是通过气象站点数据插值得到,对于缺资料和无资料地区有巨大的局限性。文中在对GLDAS气压、气温和风速数据产品年、月、日尺度进行有效性分析的基础上,将其应用于渭河流域潜在蒸散发模拟研究中,模型选用Penman-Manteith公式,对渭河流域2006-2009年日尺度上的潜在蒸散发时空结构进行了定量分析。结果表明:GLDAS数据产品精度较高,完全满足蒸散发研究的需要,较地面气象站点观测,具有较好的时空连续性,在全国性及区域性蒸散发模拟中具有较好的应用前景。  相似文献   

11.
黑龙港地区夏玉米生长期综合ET试验研究   总被引:1,自引:0,他引:1  
为了研究人类活动影响下流域二元水循环中农作物耗水通量特征,在华北平原黑龙港地区夏玉米生长期内,使用FDR与中子仪对土壤表层和剖面含水率分别进行了田间测量,对玉米的不同生长阶段特性、生长期内降雨以及土壤含水率的变化进行了分析.并以此为基础,对玉米苗期,拔节,抽雄,灌浆等各生长阶段利用水量平衡法进行了蒸散发量(ET)计算和...  相似文献   

12.
Greenhousing is a technique to bridge season gap in vegetable production and has been widely used worldwide. Calculation of water requirement of crops grown in greenhouse and determination of their irrigation schedules in arid and semi-arid regions are essential for greenhouse maintenance and have thus attracted increased attention over the past decades. The most common method used in the literature to estimate crop evapotranspiration(ET) is the Penman-Monteith(PM) formula. When applied to greenhouse, however, it often uses canopy resistance instead of surface resistance. It is understood that the surface resistance in greenhouse is the result of a combined effect of canopy restriction and soil-surface restriction to water vapor flow, and the relative dominance of one restriction over another depends on crop canopy. In this paper, we developed a surface resistance model in a way similar to two parallel resistances in an electrical circuit to account for both restrictions. Also, considering that wind speed in greenhouse is normally rather small, we compared three methods available in the literature to calculate the aerodynamic resistance, which are the r_a~1 method proposed by Perrier(1975a, b), the r_a~2 method proposed by Thom and Oliver(1977), and the r_a~3 method proposed by Zhang and Lemeu(1992). We validated the model against ET of tomatoes in a greenhouse measured from sap flow system combined with micro-lysimeter in 2015 and with weighing lysimeter in 2016. The results showed that the proposed surface resistance model improved the accuracy of the PM model, especially when the leaf area index was low and the greenhouse was being irrigated. We also found that the aerodynamic resistance calculated from the r_a~1 and r_a~3 methods is applicable to the greenhouse although the latter is slightly more accurate than the former. The proposed surface resistance model, together with the r_a~3 method for aerodynamic resistance, offers an improved approach to estimate ET in greenhouse using the PM formula.  相似文献   

13.
Remote sensing tools are becoming increasingly important for providing spatial information on water use by different ecosystems. Despite significant advances in remote sensing based evapotranspiration (ET) models in recent years, important information gaps still exist on the accuracy of the models particularly in arid and semi-arid environments. In this study, we evaluated the Penman-Monteith based MOD16 and the modified Priestley-Taylor (PT-JPL) models at the daily time step against three measured ET datasets. We used data from two summer and one winter rainfall sites in South Africa. One site was dominated by native broad leaf and the other by fine leafed deciduous savanna tree species and C4 grasses. The third site was in the winter rainfall Cape region and had shrubby fynbos vegetation. Actual ET was measured using open-path eddy covariance systems at the summer rainfall sites while a surface energy balance system utilizing the large aperture boundary layer scintillometer was used in the Cape. Model performance varied between sites and between years with the worst estimates (R2<0.50 and RMSE>0.80 mm/d) observed during years with prolonged mid-summer dry spells in the summer rainfall areas. Sensitivity tests on MOD16 showed that the leaf area index, surface conductance and radiation budget parameters had the largest effect on simulated ET. MOD16 ET predictions were improved by: (1) reformulating the emissivity expressions in the net radiation equation; (2) incorporating representative surface conductance values; and (3) including a soil moisture stress function in the transpiration sub-model. Implementing these changes increased the accuracy of MOD16 daily ET predictions at all sites. However, similar adjustments to the PT-JPL model yielded minimal improvements. We conclude that the MOD16 ET model has the potential to accurately predict water use in arid environments provided soil water stress and accurate biome-specific parameters are incorporated.  相似文献   

14.
参考条件下苜蓿冠层阻力变化规律试验研究   总被引:1,自引:0,他引:1       下载免费PDF全文
冠层阻力是参考作物蒸发蒸腾量计算公式中的一个重要参数,对准确计算参考作物蒸发蒸腾量(ET0)及诊断作物缺水等都有非常重要的意义.本研究以FAO(1994)推荐的ET0公式(Penman-Monteith公式)假定条件为出发点,结合ET0值的实测资料,对经过修剪的苜蓿冠层阻力进行试验分析.结果表明:在参考条件下,冠层阻力随着作物生育期的延长,呈递增趋势.日变化过程呈现"U"型,最低点出现在中午(低于50 s/m),最高点出现在早晨8∶00和傍晚18∶00(高于100 s/m).  相似文献   

15.
测定了玉米各生育时期干旱胁迫下冠层叶绿素密度及冠层光谱数据,利用原始光谱反射率与冠层叶绿素密度进行相关性分析,采用常用植被指数、波段自由组合、连续小波变换构建玉米冠层叶绿素密度估测模型,并用决定系数(R~2)、均方根误差(RMSE)进行精度检验。结果表明:冠层叶绿素密度在抽雄期相较于正常对照,轻度、中度、重度干旱胁迫处理分别下降7.8%、29.5%、44.2%;波段自由组合指数RVI(555,538)、NDVI(555,538)和敏感小波系数bior5.5(26,792)、rbio2.6(22,790)、gaus6(21,791)与叶绿素密度的相关性较高,相关系数绝对值均达到0.900以上;基于敏感小波系数构建的冠层叶绿素密度估测模型验证集R~2均在0.850以上,相较于其他植被指数模型R~2平均提升20.6%,RMSE平均降低32.6%;最优模型为以gaus6(21,791)为自变量的一元线性回归模型,R~2为0.864,RMSE为1.532。利用连续小波变换对光谱数据进行预处理,可以有效提升玉米冠层叶绿素密度估测模型的精度。  相似文献   

16.
As a main component in water balance, evapotranspiration is of great importance for water saving and irrigation-measure making, especially in arid or semiarid regions. Although studies of evapotranspiration have been conducted for a long time, studies concentrated on oasis-desert transition zone are very limited. On the basis of the meteorological data and other parameters(e.g. leaf area index(LAI)) of an oasis-desert transition zone in the middle stream of Heihe River from 2005 to 2011, this paper calculated both reference(ET0) and actual evapotranspiration(ETc) using FAO56 Penman-Monteith and Penman-Monteith models, respectively. In combination with pan evaporation(Ep) measured by E601 pan evaporator, four aspects were analyzed:(1) ET0 was firstly verified by Ep;(2) Characteristics of ET0 and ETc were compared, while the influencing factors were also analyzed;(3) Since meteorological data are often unavailable for estimating ET0 through FAO56 Penman-Monteith model in this region, pan evaporation coefficient(Kp) is very important when using observed Ep to predict ET0. Under this circumstance, an empirical formula of Kp was put forward for this region;(4) Crop coefficient(Kc), an important index to reflect evapotranspiration, was also analyzed. Results show that mean annual values of ET0 and ETc were 840 and 221 mm, respectively. On the daily bases, ET0 and ETc were 2.3 and 0.6 mm/d, respectively. The annual tendency of ET0 and ETc was very similar, but their amplitude was obviously different. The differences among ET0 and ETc were mainly attributed to the different meteorological variables and leaf area index. The calculated Kc was about 0.25 and showed little variation during the growing season, indicating that available water(e.g. precipitation and irrigation) of about 221 mm/a was required to keep the water balance in this region. The results provide an comprehensive analysis of evapotranspiration for an oasis-desert transition zone in the middle stream of Heihe River, which was seldom reported before.  相似文献   

17.
The accurate estimation of evapotranspiration(ET) in arid regions is important for improving the water use efficiency of vegetation. Based on successive observations from May to October of 2014, we estimated the ET of a Populus euphratica Oliv. forest during the growing season in an extremely arid region using the PM(Penman-Monteith), SW(Shuttleworth-Wallace) and SSW(an improved canopy transpiration model) models. Estimated ET values were compared with those of the eddy covariance measurements. Results indicated that the actual ET of the P. euphratica forest was always overestimated by the PM model. The accuracy of the SW model was higher than that of the PM model. However, some data were not easily obtained because of the complicated structure of the SW model. The newly proposed SSW model gave the most accurate ET values, and its accuracy was higher at hourly than at daily time scale. In conclusion, the SSW model is more suitable for sparse vegetation system at large scales in extremely arid regions.  相似文献   

18.
蒸散发观测研究进展及绿洲蒸散研究展望   总被引:3,自引:0,他引:3  
蒸散发是绿洲水文循环中最重要的水文过程和生态过程之一,开展绿洲蒸散发研究是提高水资源利用的基础.从叶面、个体、田间到景观尺度,系统综述了国内外蒸散发观测研究的最新进展,结合荒漠绿洲的特点及研究现状,指出应加强:①涡度相关技术在异质性强的绿洲的应用技术研究;②如何分割蒸散发中植物蒸腾和土壤蒸发,以及时空动态、驱动机制和调...  相似文献   

19.
利用2015年6月1日至7月24日干旱区地膜覆盖玉米农田下垫面的观测资料,分析地表反照率在植被生长期间的变化特征及其与土壤湿度的关系。与未覆盖地膜情形的下垫面相比,地膜覆盖农田下垫面地表反照率的变化特征及其与土壤湿度的相关性具有显著性差异。为此建立了相应的地表反照率动态参数化方案,并将修改的地表反照率动态参数化方案应用到陆面过程模式Co LM中进行了3组模拟试验,分析和检验新方案在地膜覆盖农田下垫面的准确性和适用性。数值模拟结果表明:3组试验都能很好地反映陆面过程特征的日变化趋势,但是相比较而言,利用新建立的地表反照率动态参数化方案模式的模拟效果最好,明显提高了模式对向上短波和长波辐射的模拟能力,使浅层土壤温度和湿度的模拟效果有了一定的改善。因此,地表反照率动态参数化方法对干旱区地膜覆盖农田下垫面陆面过程的模拟效果有一定的改进,对今后陆面过程模式的发展和完善有较好的参考价值。  相似文献   

20.
通过大田试验,在不同供水水平下,研究了交替灌溉小麦间作玉米的耗水量、土面蒸发特征及其主要影响因子。结果表明:小麦间作玉米耗水量较单作小麦、玉米耗水量的加权平均高12.7%~20.1%,与传统灌溉相比,交替灌溉可降低间作耗水量;小麦间作玉米的日均土面蒸发量较相应单作的加权平均增大了9.19%~13.6%,交替灌溉小麦间作玉米的日均土面蒸发量较平作漫灌低10.1%;与单作相比,间作土面蒸发量占蒸散量的比例(E/ET)高于单作。间作较低的平均叶面积指数(LAI)和较大的叶日积(LAD)是耗水量增大的重要原因之一。与传统灌溉相比,交替灌溉可降低间作表土层的含水量,可作为减小间作土面蒸发技术的切入点。  相似文献   

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