Generation and evaluation of gross primary productivity using Landsat data through blending with MODIS data     

Devendra Singh 《International Journal of Applied Earth Observation and Geoinformation》2011

Spatial and Temporal Adaptive Reflectance Fusion Model (STARFM) has been used for the blending of Landsat and MODIS data. Specifically, the 30 m Landsat-7 ETM+ (Enhanced Thematic Mapper plus) surface reflectance was predicted for a period of 10 years (2000–2009) as the product of observed ETM+ and MODIS surface reflectance (MOD09A1) on the predicted and observed ETM+ dates. A pixel based analysis for six observed ETM+ dates covering winter and summer crops showed that the prediction method was more accurate for NIR band (mean r² = 0.71, p ≤ 0.01) compared to green band (mean r² = 0.53; p ≤ 0.01). A recently proposed chlorophyll index (CI), which involves NIR and green spectral bands, was used to retrieve gross primary productivity (GPP) as the product of CI and photosynthetic active radiation (PAR). The regression analysis of GPP derived from closet observed and synthetic ETM+ showed a good agreement (r² = 0.85, p ≤ 0.01 and r² = 0.86, p ≤ 0.01) for wheat and sugarcane crops, respectively. The difference between the GPP derived from synthetic and observed ETM+ (prediction residual) was compared with the difference in GPP values from observed ETM+ on the two dates (temporal residual). The prediction residuals (mean value of 1.97 g C/m² in 8 days) was found to be significantly lower than the temporal residuals (mean value of 4.46 g C/m² in 8 days) that correspondence to 12% and 27%, respectively, of GPP values (mean value of 16.53 g C/m² in 8 days) from observed ETM+ data, implying that the prediction method was better than temporal pixel substitution. Investigating the trend in synthetic ETM+ GPP values over a growing season revealed that phenological patterns were well captured for wheat and sugarcane crops. A direct comparison between the GPP values derived from MODIS and synthetic ETM+ data showed a good consistency of the temporal dynamics but a systematic error that can be read as bias (MODIS GPP over estimation). Further, the regression analysis between observed evapotranspiration and synthetic ETM+ GPP showed good agreement (r² = 0.66, p ≤ 0.01).  相似文献   

Carbon and water exchange in semiarid ecosystems in SE Spain     

F. Domingo  P. Serrano-Ortiz  A. Were  L. Villagarcía  M. García  D.A. Ramírez  A.S. Kowalski  M.J. Moro  A. Rey  C. Oyonarte 《Journal of Arid Environments》2011,75(12):1271-1281

The changing climate is affecting biological and physical processes occurring in the biosphere, including the biogeochemical cycles of water and carbon. The response of ecosystem carbon exchange to changes in temperature and the water balance is still very uncertain, a fact that highlights the need for research in order to understand the role of the biosphere in the future global carbon budget. South east Spain is on the borderline between the tropical and mid-latitude climate zones, with climates ranging from sub-humid to arid, and the majority representing the driest area in Europe. Initial predictions on climate change for this region point to decreases in total precipitation and the number of precipitation events, meaning a decrease in water availability underlining the vulnerability of the region to desertification. This region, due to these special climatic conditions, has been the subject of experimental carbon and water field research in recent years. This paper defines the state of the art of carbon and water balance measurement and modelling studies in this region, analyses the different processes involved in aggregate exchanges (vegetation and soil; net ecosystem carbon balance–evapotranspiration, photosynthesis–transpiration, soil respiration–evaporation), and identifies needs for future research.  相似文献   

陆面过程模式SIB2与包气带入渗模型的耦合及其应用   总被引：1，自引：0，他引：1  

周剑  李新  王根绪  潘小多 《地球科学进展》2008,23(6):570-579

土壤含水量对陆—气相互作用过程中的能—水平衡计算以及降雨、农业灌溉对地下水补给的研究起着关键的作用。但现阶段大多数陆面过程模式对土壤含水量的计算采用一维水桶模式,忽略了流域尺度上的侧向补给、地下水位的变化、包气带土壤的非线性渗透特性对土壤含水量的影响。针对这一问题,在国内外研究较为成熟的饱和—非饱和理论的基础上,编程实现了包气带土壤水分传输方程的求解,并与陆面过程模式（SIB2）相耦合,建立起研究分层包气带土壤水分运移、非稳态的地下水位、和地表蒸散发之间定量关系的模型。最后,利用建立的耦合模型,以河西走廊黑河流域中游临泽农业综合观测场的灌溉试验为例,模拟干旱内陆平原区小麦生长期间定额灌水条件下土壤含水量的变化。计算结果表明：模型能够准确计算瞬时土壤含水量、非稳态的地下水位,并对小麦生长过程中的耗水量进行估算,进而为农业合理灌溉提供了科学的理论基础。  相似文献   

河北平原区域蒸发蒸腾量遥感估算     

蔺文静  董华  王贵玲  Z.Su  陈立 《国土资源遥感》2008,(1):86-90,I0007

地表能量平衡系统(SEBS)是一种基于遥感影像的区域地表通量估算模型,能够对区域蒸发蒸腾进行精确估算.在SEBS模型的基础上,以河北平原为例,采取中分辨率成像光谱辐射仪(MODIS)产品影像,根据研究区下垫面的实际情况进行了参数估算,区域实际蒸发蒸腾量计算及模型精确度评价,并在此基础上,结合研究区的地面覆盖,对河北平原区域蒸发蒸腾分布进行了分析.  相似文献   

水—生态—经济系统中人文因素作用研究进展   总被引：6，自引：1，他引：5  

邱国玉 《地球科学进展》2008,23(7):713-722

水资源系统的状态受人文因素与自然因素的影响,人文因素也受水资源系统的状态和自然因素的影响。要从中辨析人文因素的作用,需将人文因素和自然因素纳入统一的框架中分析。目前采用的统一框架主要有统一的分析尺度和时空尺度两种。在辨析当前国内外人文因素作用研究的趋势和热点的基础上,从分析尺度和时空尺度的角度系统全面的总结了相关研究的国内外进展,并针对我国典型内陆河流域的特征,提出了研究水—生态—经济系统中人文因素作用的几点展望。  相似文献   

Application of HYDRUS-1D in understanding soil water movement at two typical sites in the North China Plain          下载免费PDF全文

WANG Shi-qin  SONG Xian-fang  WEI Shou-cai  SHAO Jing-li 《地下水科学与工程》2016,4(1):1-11

Recharge and discharge, such as rainfall infiltration and evapotranspiration in vertical direction, are major processes of water cycle in the shallow groundwater area of the North China Plain. During these processes, soil water movement in the unsaturated zone plays an important role in the transformation from rainfall infiltration to groundwater. The soil water movement models were developed by using HYDRUS-1D software at two typical experimental sites in Cangzhou (CZ) and Hengshui (HS) with different soil, vegetation and similar climate conditions. As shown in the results, the comparison in precipitation infiltration features between the two sites is distinct. The soil water experiences strong evaporation after precipitation infiltration, which accounts for 63% of the total infiltration at the HS site where the soil is homogenous. It is this strong evaporation effect that leads to slight increase of soil water storage. At the CZ site, where the soil is heterogeneous, the evaporation effect exists from July to October of the simulation period. The total evaporation accounts for 33% of the total infiltration, and the evaporation rate is slow. At the end of the simulation period, the soil water storage increases and the water table decreases, indicating a strong storage capacity at this site.  相似文献   

黄河流域蒸散发与气温和降水以及风速的相关性分析     

谷同辉  管晓丹  高照逵  黄小倩  郭书扬 《气象与环境学报》2022,38(1):48-56

黄河流经我国干旱半干旱地区,其流域蒸散发变化对当地的生态安全和经济发展尤其重要。本文利用欧洲中期天气预报中心第五代再分析产品（ERA5）定量分析了1979-2020年黄河流域蒸散发的时空变化特征,并结合气温、降水和风速数据,对黄河流域蒸散发与3种气候因子进行了相关性分析。结果表明：黄河流域蒸散发在1979-2020年呈波动下降趋势,空间分布差异明显,源区附近蒸散发上升,上游的干旱区附近蒸散发基本不变,而中游和下游地区主要呈现下降趋势。1979-2020年黄河流域气温持续上升,降水呈波动下降趋势,风速呈上升趋势。对黄河流域蒸散发与气候因子的相关性分析表明,蒸散发与气候因子的相关性空间差异较为明显,蒸散发与气温、风速呈负相关,与降水呈正相关的区域占流域的较大部分;而在复相关性方面,黄河流域大部分地区蒸散发与气候因子的相关性较强,其中以流域上游的干旱区附近复相关性最强。研究黄河流域不同地区蒸散发与气候因子的相关性可为黄河流域水资源的开发管理和区域气候调节提供科学参考。  相似文献   

科尔沁沙地典型区生长季蒸散发估算及其变化特征          下载免费PDF全文

张圣微  张鹏  张睿  刘廷玺 《水科学进展》2018,29(6):768-778

为揭示科尔沁沙地典型区地表参数和蒸散发的时空分布以及变化特征,采用Landsat-7和气象数据,并结合METRIC(Mapping Evapotranspiration at high Resolution with Internalized Calibration)模型,分析了研究区净辐射(Rn)和蒸散发(ET)的时空变化、不同土地覆被类型ET特征及其影响因素。结果表明:(1)研究区典型土地覆被沙丘和草甸的Rn和ET估算值与涡度相关实测值拟合结果均良好,说明METRIC模型可以为研究区提供合理的ET估算;(2)研究区下垫面Rn和ET的时空分布情况为:各年Rn和ET在年内变化趋势相同,空间上不同土地覆被类型中水体的Rn和ET最大,农田和草甸次之,沙丘最小;(3)沙丘的CV值大于农田与草甸,表明年际间沙丘的ET波动较大,农田和草甸相对稳定,ET年际变化主要受气象因素的影响。  相似文献   

基于实测资料对日蒸散发估算模型的比较   总被引：1，自引：0，他引：1  

刘波  翟建青  高超  姜彤  王艳君 《地球科学进展》2010,25(9):974-980

利用设置于江西省南昌县的新型高精度自动蒸渗仪,于2007年9月1日至2008年8月31日的实测陆面实际蒸散发过程,检验了面蒸散发互补关系模型CRAE (Complementary Relationship Areal Evapotranspiration)、GG模型 (Granger-Gray)、平流-干旱模型AA (Advection-Aridity)3个逐日路面实际蒸散发模型在不同时间尺度上的计算精度,并对计算误差的影响因素进行了讨论.结果表明:该地区实测年蒸散发量为746.1 mm,采用各模型的推荐经验参数对该地区蒸散发的估算结果误差较大,普遍干旱条件下蒸散发的计算值比观测值偏小,而湿润条件下的计算值偏大.通过对各模型的经验参数进行调整,各模型对年蒸散发量的计算精度大为提高,但逐日蒸散发过程的计算精度改进效果有限,在7日的时间尺度上,计算结果显著优于逐日的计算结果,在此时间尺度下,AA模型仍存在一定的系统误差,CRAE模型的估算精度相对较差,GG模型的总体计算效果相对最好.根据与蒸渗仪观测结果的对比分析,根据区域特征进行参数调整后的模型,需要在7日及更长时间尺度上,蒸散发模型的估算结果较为可靠.上述研究对全面认识陆面实际蒸散发特征、理解各蒸散发模型在不同时间尺度上的模拟能力、正确认识气候变化条件下的水循环特征具有重要意义.  相似文献   

黑河流域日蒸散发遥感估算研究   总被引：6，自引：2，他引：4       下载免费PDF全文

李星敏-  卢玲  李新  杨文峰  黄春林  王钊 《高原气象》2010,29(1):109-114

地表蒸散的估算在干旱半干旱区水资源研究中具有重要意义。利用NOAA/AVHRR遥感资料、NCEP再分析格点资料和气象站点资料,根据能量平衡模型和FAO-17 Penman公式,计算了研究区域内逐日蒸散发量;对于晴天,用遥感模型反演出瞬时蒸散,进而推算出日蒸散;同时用FAO-17 Penmen公式和气象资料,计算研究区域内的同一天的蒸散,利用气象资料计算得到的蒸散与遥感估算的蒸散的关系,估算非晴空日的蒸散,进而得到逐日蒸散发结果。与同类研究结果的比较表明:该方法能够估算逐日蒸散发,通过气象与遥感资料结合,提高了气象格点资料的空间分辨率,弥补了难以得到遥感逐日晴空资料的不足,同时也为流域内同类研究提供参考依据。  相似文献