Accurate inversion of land surface evapotranspiration （ET） in arid areas is of great significance for understanding global eco-hydrological process and exploring the spatio-temporal variation and ecological response...Accurate inversion of land surface evapotranspiration （ET） in arid areas is of great significance for understanding global eco-hydrological process and exploring the spatio-temporal variation and ecological response of water resources. It is also important in the functional evaluation of regional water cycle and water balance, as well as the rational allocation and management of water resources. This study, based on model validation analysis at varied scales in fiwe Central Asian countries and China＇s Xinjiang, developed an appropriate approach for ET inversion in arid lands. The actual ET during growing seasons of the study area was defined, and the changes in water participating in evaporation in regional water cycle were then educed. The results show the simulation error of SEBS （Surface Energy Balance System） model under cloud amount consideration was 1.34% at 30-m spatial scale, 2.75% at 1-km spatial scale and 6,37% at 4-kin spatial scale. ET inversion for 1980-2007 applying SEBS model in the study area indicates： （1） the evaporation depth （May-September） by land types descends in the order of waters （660.24 ram） 〉 cultivated land （464.66 mm） 〉 woodland （388.44 mm） 〉 urbanized land （168.16 mm） 〉 grassland （160.48 mm） 〉 unused land （83.08 mm）; and （2） ET during the 2005 growing season in Xinjiang and Central Asia was 2,168.68x108 m3 （with an evaporation/precipitation ratio of 1.05） and 9,741.03x108 m3 （with an evaporation/precipitation ratio of 1.4）, respectively. The results unveiled the spatio-temporal variation rules of ET process in arid areas, providing a reference for further research on the water cycle and water balance in similar arid regions.展开更多
Land surface evapotranspiration （ET） determines the local and regional water-heat balances. Accurate estimation of regional surface ET provides a scientific basis for the formulation and implementation of water cons...Land surface evapotranspiration （ET） determines the local and regional water-heat balances. Accurate estimation of regional surface ET provides a scientific basis for the formulation and implementation of water conservation programs. This study set up a table of the momentum roughness length and zero-plane displacement related with land cover and an empirical relationship between land surface temperature and air temperature. A revised quantitative remote sensing ET model, the SEBS-Taiwan model, was developed. Based on Moderate Resolution Imaging Spectroradiometer （MODIS） data, SEBS-Taiwan was used to simulate and evaluate the typical actual daily ET values in different seasons of 2002 and 2003 in Taiwan. SEBS-Taiwan generally performed well and could accurately simulate the actual daily ET. The simulated daily ET values matched the observed values satisfactorily. The results indicate that the net regional solar radiation, evaporation ratio, and surface ET values for the whole area of Taiwan are larger in summer than in spring, and larger in autumn than in winter. The results also show that the regional average daily ET values of 2002 are a little higher than those of 2003. Through analysis of the ET values from different types of land cover, we found that forest has the largest ET value, while water areas, bare land, and urban areas have the lowest ET values. Generally, the Northern Taiwan Region, including llan County, Nantou County, and Hualien County, has higher ET values, while other cities, such as Chiayi, Taichung, and Tainan, have lower ET values.展开更多
Near-surface air temperature(Ta)plays important roles in the interactions between the atmosphere and land covers,serving as crucial indicators for characterizing urban heat island and pedestrian thermal comfort.Althou...Near-surface air temperature(Ta)plays important roles in the interactions between the atmosphere and land covers,serving as crucial indicators for characterizing urban heat island and pedestrian thermal comfort.Although satellite-based observations and numerical simulations have been proposed to obtain Ta across various spatiotemporal scales,there is a lack of physically grounded,precise and easy-to-implement means to spatially resolve Ta at the centimeter level.Based on multimodal images derived from the unmanned aerial vehicle and synchronously measured meteorological parameters,this study combined the surface energy balance model and the automated machine learning to predict air temperature near the observed surfaces(Ta_predicted).The validations via near-ground measurements demonstrate the accuracy of this methodology,biases between predicted values and measured ones were almost maintained within 0.55℃.According to the spatial distribution of Ta_predicted,it can be inferred that,at clear and calm noon in subtropical regions,dense shrubs or lawns exhibit limited significant cooling effect on Ta_predicted compared to granite paving with higher reflectance.Such a finding can be attributed to limited evapotranspiration from insufficient irrigation,lower reflectance increasing shortwave absorption of vegetation surfaces,and weak winds limiting convective heat removal.The developed model can be extended to other outdoor settings with similar meteorological conditions and morphologies of local climate zone 4,but further refinement is required for robust application across more diverse spatiotemporal scenarios.展开更多
基金supported by the National Natural Science Foundation of China (40730633 and 40571030)
文摘Accurate inversion of land surface evapotranspiration （ET） in arid areas is of great significance for understanding global eco-hydrological process and exploring the spatio-temporal variation and ecological response of water resources. It is also important in the functional evaluation of regional water cycle and water balance, as well as the rational allocation and management of water resources. This study, based on model validation analysis at varied scales in fiwe Central Asian countries and China＇s Xinjiang, developed an appropriate approach for ET inversion in arid lands. The actual ET during growing seasons of the study area was defined, and the changes in water participating in evaporation in regional water cycle were then educed. The results show the simulation error of SEBS （Surface Energy Balance System） model under cloud amount consideration was 1.34% at 30-m spatial scale, 2.75% at 1-km spatial scale and 6,37% at 4-kin spatial scale. ET inversion for 1980-2007 applying SEBS model in the study area indicates： （1） the evaporation depth （May-September） by land types descends in the order of waters （660.24 ram） 〉 cultivated land （464.66 mm） 〉 woodland （388.44 mm） 〉 urbanized land （168.16 mm） 〉 grassland （160.48 mm） 〉 unused land （83.08 mm）; and （2） ET during the 2005 growing season in Xinjiang and Central Asia was 2,168.68x108 m3 （with an evaporation/precipitation ratio of 1.05） and 9,741.03x108 m3 （with an evaporation/precipitation ratio of 1.4）, respectively. The results unveiled the spatio-temporal variation rules of ET process in arid areas, providing a reference for further research on the water cycle and water balance in similar arid regions.
基金supported by the National Natural Science Foundation of China (Grant No. 40901023)
文摘Land surface evapotranspiration （ET） determines the local and regional water-heat balances. Accurate estimation of regional surface ET provides a scientific basis for the formulation and implementation of water conservation programs. This study set up a table of the momentum roughness length and zero-plane displacement related with land cover and an empirical relationship between land surface temperature and air temperature. A revised quantitative remote sensing ET model, the SEBS-Taiwan model, was developed. Based on Moderate Resolution Imaging Spectroradiometer （MODIS） data, SEBS-Taiwan was used to simulate and evaluate the typical actual daily ET values in different seasons of 2002 and 2003 in Taiwan. SEBS-Taiwan generally performed well and could accurately simulate the actual daily ET. The simulated daily ET values matched the observed values satisfactorily. The results indicate that the net regional solar radiation, evaporation ratio, and surface ET values for the whole area of Taiwan are larger in summer than in spring, and larger in autumn than in winter. The results also show that the regional average daily ET values of 2002 are a little higher than those of 2003. Through analysis of the ET values from different types of land cover, we found that forest has the largest ET value, while water areas, bare land, and urban areas have the lowest ET values. Generally, the Northern Taiwan Region, including llan County, Nantou County, and Hualien County, has higher ET values, while other cities, such as Chiayi, Taichung, and Tainan, have lower ET values.
基金supported by the Postdoctoral Fellowship Program of CPSF under Grant Number GZC20251115Chengdu Science and Technology Bureau under the Technological Innovation and R&D Program(No.2025-YF05-00029-SN)+1 种基金National Natural Science Foundation of China(No.52278108,No.52378039,No.52578130)Guangdong Natural Science Foundation(No.2024A1515011415,No.2023A1515012188).
文摘Near-surface air temperature(Ta)plays important roles in the interactions between the atmosphere and land covers,serving as crucial indicators for characterizing urban heat island and pedestrian thermal comfort.Although satellite-based observations and numerical simulations have been proposed to obtain Ta across various spatiotemporal scales,there is a lack of physically grounded,precise and easy-to-implement means to spatially resolve Ta at the centimeter level.Based on multimodal images derived from the unmanned aerial vehicle and synchronously measured meteorological parameters,this study combined the surface energy balance model and the automated machine learning to predict air temperature near the observed surfaces(Ta_predicted).The validations via near-ground measurements demonstrate the accuracy of this methodology,biases between predicted values and measured ones were almost maintained within 0.55℃.According to the spatial distribution of Ta_predicted,it can be inferred that,at clear and calm noon in subtropical regions,dense shrubs or lawns exhibit limited significant cooling effect on Ta_predicted compared to granite paving with higher reflectance.Such a finding can be attributed to limited evapotranspiration from insufficient irrigation,lower reflectance increasing shortwave absorption of vegetation surfaces,and weak winds limiting convective heat removal.The developed model can be extended to other outdoor settings with similar meteorological conditions and morphologies of local climate zone 4,but further refinement is required for robust application across more diverse spatiotemporal scenarios.
