Two energy balance closure approaches: applications and comparisons over an oasis-desert ecotone
PAN Xin1,2, LIU Yuanbo1*, FAN Xingwang1, GAN Guojing1
1 Key Laboratory of Watershed Geographic Sciences, Nanjing Institute of Geography and Limnology, Chinese Academy of
Sciences, Nanjing 210008, China; 2 University of Chinese Academy of Sciences, Beijing 100049, China
Two energy balance closure approaches: applications and comparisons over an oasis-desert ecotone
PAN Xin1,2, LIU Yuanbo1*, FAN Xingwang1, GAN Guojing1
1 Key Laboratory of Watershed Geographic Sciences, Nanjing Institute of Geography and Limnology, Chinese Academy of
Sciences, Nanjing 210008, China; 2 University of Chinese Academy of Sciences, Beijing 100049, China
摘要 Studies of energy balance that rely on eddy covariance (EC) are always challenged by energy
balance closure, which is mainly caused by the underestimations of latent heat flux (LE) and sensible heat
flux (Hs). The Bowen ratio (BR) and energy balance residual (ER) approaches are two widely-used
methods to correct the LE. A comprehensive comparison of those two approaches in different land-use
types is essential to accurately correcting the LE and thus improving the EC experiments. In this study,
two energy balance approaches (i.e., BR and ER) were compared to correct the LE measured at six EC
sites (i.e., three vegetated, one mixed and two non-vegetated sites) in an oasis-desert ecotone of the Heihe
River Basin, China. The influences of meteorological factors on those two approaches were also
quantitatively assessed. Our results demonstrated that the average energy closure ratio ((LE+Hs)/(Rn–Gs);
where Rn is the surface net radiation and Gs is the surface soil heat flux) was approximately close to 1.0 at
wetland, maize and village sites, but far from 1.0 at orchard, Gobi and desert sites, indicating a significant
energy imbalance at those three latter sites. After the corrections of BR and ER approaches that took into
account of soil heat storage, the corrected LE was considerably larger than the EC-measured LE at five of
six EC sites with an exception at Gobi site. The BR and ER approaches yielded approximately similar
corrected LE at vegetated and mixed sites, but they generated dissimilar results at non-vegetated sites,
especially at non-vegetated sites with low relative humidity, strong wind, and large surface-air temperature
difference. Our findings provide insight into the applicability of BR and ER approaches to correcting
EC-based LE measurements in different land-use types. We recommend that the BR-corrected and
ER-corrected LE could be seriously reconsidered as validation references in dry and windy areas
Abstract：
Studies of energy balance that rely on eddy covariance (EC) are always challenged by energy
balance closure, which is mainly caused by the underestimations of latent heat flux (LE) and sensible heat
flux (Hs). The Bowen ratio (BR) and energy balance residual (ER) approaches are two widely-used
methods to correct the LE. A comprehensive comparison of those two approaches in different land-use
types is essential to accurately correcting the LE and thus improving the EC experiments. In this study,
two energy balance approaches (i.e., BR and ER) were compared to correct the LE measured at six EC
sites (i.e., three vegetated, one mixed and two non-vegetated sites) in an oasis-desert ecotone of the Heihe
River Basin, China. The influences of meteorological factors on those two approaches were also
quantitatively assessed. Our results demonstrated that the average energy closure ratio ((LE+Hs)/(Rn–Gs);
where Rn is the surface net radiation and Gs is the surface soil heat flux) was approximately close to 1.0 at
wetland, maize and village sites, but far from 1.0 at orchard, Gobi and desert sites, indicating a significant
energy imbalance at those three latter sites. After the corrections of BR and ER approaches that took into
account of soil heat storage, the corrected LE was considerably larger than the EC-measured LE at five of
six EC sites with an exception at Gobi site. The BR and ER approaches yielded approximately similar
corrected LE at vegetated and mixed sites, but they generated dissimilar results at non-vegetated sites,
especially at non-vegetated sites with low relative humidity, strong wind, and large surface-air temperature
difference. Our findings provide insight into the applicability of BR and ER approaches to correcting
EC-based LE measurements in different land-use types. We recommend that the BR-corrected and
ER-corrected LE could be seriously reconsidered as validation references in dry and windy areas
The National Natural Science Foundation of China (41430855, 91125004).
通讯作者: LIU Yuanbo
E-mail: ybliu@niglas.ac.cn
引用本文:
PAN Xin,LIU Yuanbo,FAN Xingwang等. Two energy balance closure approaches: applications and comparisons over an oasis-desert ecotone[J]. Journal of Arid Land, 2017, 9(1): 51-64.
PAN Xin,LIU Yuanbo,FAN Xingwang et al. Two energy balance closure approaches: applications and comparisons over an oasis-desert ecotone[J]. Journal of Arid Land, 2017, 9(1): 51-64.
2017, Vol. 9 
