Analysis of the Diurnal Pattern of Evaporative Fraction and Its Controlling Factors over Croplands in the Northern China
A key issue of applying remotely sensed data to estimate evapotranspiration (ET) for water management is extrapolating instantaneous latent heat flux (LE) at satellite over-passing time to daily ET total. At present, the most commonly used extrapolation methods have the same assumption that evaporat...
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KeAi Communications Co., Ltd.
2013-08-01
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| Series: | Journal of Integrative Agriculture |
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| Online Access: | http://www.sciencedirect.com/science/article/pii/S2095311913605407 |
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| author | Da-wen YANG He CHEN Hui-min LEI |
| author_facet | Da-wen YANG He CHEN Hui-min LEI |
| author_sort | Da-wen YANG |
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| description | A key issue of applying remotely sensed data to estimate evapotranspiration (ET) for water management is extrapolating instantaneous latent heat flux (LE) at satellite over-passing time to daily ET total. At present, the most commonly used extrapolation methods have the same assumption that evaporative fraction (EF) can be treated as constant during daytime (so-called EF self-preservation). However, large errors are reported by many documents over various ecosystems with the same approach, which indicates that further analysis of the diurnal pattern of EF is still necessary. The aim of this study is to examine the diurnal pattern of EF under fair weather conditions, then to analyze the dependencies of EF to meteorological and plant factors. Long-term flux observations at four sites over semi-arid and semi-humid climate regions in the northern China are used to analyze the EF diurnal pattern. Results show that the EF self-preservation assumption no longer holds over growing seasons of crops. However, the ratio of reference ET to available energy is almost constant during the daytime, which implies the climate factors do not have much effect on the variability of EF. The analysis of diurnal pattern of air temperature, vapor pressure deficiency (VPD), and relative humidity (RH) confirms the assumption that ET diurnal pattern is mainly influenced by stomatal regulation. |
| format | Article |
| id | doaj-art-7c5be9cda6d24edf8d2d810d8c9768c2 |
| institution | Matheson Library |
| issn | 2095-3119 |
| language | English |
| publishDate | 2013-08-01 |
| publisher | KeAi Communications Co., Ltd. |
| record_format | Article |
| series | Journal of Integrative Agriculture |
| spelling | doaj-art-7c5be9cda6d24edf8d2d810d8c9768c22025-08-02T11:55:20ZengKeAi Communications Co., Ltd.Journal of Integrative Agriculture2095-31192013-08-0112813161329Analysis of the Diurnal Pattern of Evaporative Fraction and Its Controlling Factors over Croplands in the Northern ChinaDa-wen YANG0He CHEN1Hui-min LEI2State Key Laboratory of Hydroscience and Engineering, Department of Hydraulic Engineering, Tsinghua University, Beijing 100084, P.R.ChinaCorrespondence CHEN He, Tel: +86-10-62782044, Fax: +86-10-62796971; State Key Laboratory of Hydroscience and Engineering, Department of Hydraulic Engineering, Tsinghua University, Beijing 100084, P.R.ChinaState Key Laboratory of Hydroscience and Engineering, Department of Hydraulic Engineering, Tsinghua University, Beijing 100084, P.R.ChinaA key issue of applying remotely sensed data to estimate evapotranspiration (ET) for water management is extrapolating instantaneous latent heat flux (LE) at satellite over-passing time to daily ET total. At present, the most commonly used extrapolation methods have the same assumption that evaporative fraction (EF) can be treated as constant during daytime (so-called EF self-preservation). However, large errors are reported by many documents over various ecosystems with the same approach, which indicates that further analysis of the diurnal pattern of EF is still necessary. The aim of this study is to examine the diurnal pattern of EF under fair weather conditions, then to analyze the dependencies of EF to meteorological and plant factors. Long-term flux observations at four sites over semi-arid and semi-humid climate regions in the northern China are used to analyze the EF diurnal pattern. Results show that the EF self-preservation assumption no longer holds over growing seasons of crops. However, the ratio of reference ET to available energy is almost constant during the daytime, which implies the climate factors do not have much effect on the variability of EF. The analysis of diurnal pattern of air temperature, vapor pressure deficiency (VPD), and relative humidity (RH) confirms the assumption that ET diurnal pattern is mainly influenced by stomatal regulation.http://www.sciencedirect.com/science/article/pii/S2095311913605407evaporative fractiondaily evapotranspirationmeteorological factorvegetation fractionnorthern China |
| spellingShingle | Da-wen YANG He CHEN Hui-min LEI Analysis of the Diurnal Pattern of Evaporative Fraction and Its Controlling Factors over Croplands in the Northern China Journal of Integrative Agriculture evaporative fraction daily evapotranspiration meteorological factor vegetation fraction northern China |
| title | Analysis of the Diurnal Pattern of Evaporative Fraction and Its Controlling Factors over Croplands in the Northern China |
| title_full | Analysis of the Diurnal Pattern of Evaporative Fraction and Its Controlling Factors over Croplands in the Northern China |
| title_fullStr | Analysis of the Diurnal Pattern of Evaporative Fraction and Its Controlling Factors over Croplands in the Northern China |
| title_full_unstemmed | Analysis of the Diurnal Pattern of Evaporative Fraction and Its Controlling Factors over Croplands in the Northern China |
| title_short | Analysis of the Diurnal Pattern of Evaporative Fraction and Its Controlling Factors over Croplands in the Northern China |
| title_sort | analysis of the diurnal pattern of evaporative fraction and its controlling factors over croplands in the northern china |
| topic | evaporative fraction daily evapotranspiration meteorological factor vegetation fraction northern China |
| url | http://www.sciencedirect.com/science/article/pii/S2095311913605407 |
| work_keys_str_mv | AT dawenyang analysisofthediurnalpatternofevaporativefractionanditscontrollingfactorsovercroplandsinthenorthernchina AT hechen analysisofthediurnalpatternofevaporativefractionanditscontrollingfactorsovercroplandsinthenorthernchina AT huiminlei analysisofthediurnalpatternofevaporativefractionanditscontrollingfactorsovercroplandsinthenorthernchina |