Revisiting daily MODIS evapotranspiration algorithm using flux tower measurements in China

2021 ◽  
Author(s):  
Lei Huang ◽  
Tammo S. Steenhuis ◽  
Yong Luo ◽  
Qiuhong Tang ◽  
Ronglin Tang ◽  
...  
Keyword(s):  
Flux Tower

Required flux tower height for measurement of re-suspended road dust

2021 ◽  
Author(s):  
Seung-Yoon Noh ◽  
Jun-Ho Ji ◽  
Hyung-Seok Kim ◽  
Se-Jin Yook
Keyword(s):  
Road Dust ◽  
Flux Tower ◽  
Tower Height

Regional evaporation estimates from flux tower and MODIS satellite data

2007 ◽  
Vol 106 (3) ◽  
pp. 285-304 ◽  
Author(s):  
Helen A. Cleugh ◽  
Ray Leuning ◽  
Qiaozhen Mu ◽  
Steven W. Running
Keyword(s):  
Satellite Data ◽  
Flux Tower

scholarly journals MODIS vegetation products as proxies of photosynthetic potential along a gradient of meteorologically and biologically driven ecosystem productivity

2016 ◽  
Vol 13 (19) ◽  
pp. 5587-5608 ◽  
Author(s):  
Natalia Restrepo-Coupe ◽  
Alfredo Huete ◽  
Kevin Davies ◽  
James Cleverly ◽  
Jason Beringer ◽  
...  
Keyword(s):  
Leaf Area Index ◽  
Leaf Area ◽  
Photosynthetic Active Radiation ◽  
Ecosystem Structure ◽  
Ecosystem Productivity ◽  
Area Index ◽  
Active Radiation ◽  
Flux Tower ◽  
Photosynthetic Potential ◽  
Assimilation Capacity

Abstract. A direct relationship between gross ecosystem productivity (GEP) estimated by the eddy covariance (EC) method and Moderate Resolution Imaging Spectroradiometer (MODIS) vegetation indices (VIs) has been observed in many temperate and tropical ecosystems. However, in Australian evergreen forests, and particularly sclerophyll and temperate woodlands, MODIS VIs do not capture seasonality of GEP. In this study, we re-evaluate the connection between satellite and flux tower data at four contrasting Australian ecosystems, through comparisons of GEP and four measures of photosynthetic potential, derived via parameterization of the light response curve: ecosystem light use efficiency (LUE), photosynthetic capacity (Pc), GEP at saturation (GEPsat), and quantum yield (α), with MODIS vegetation satellite products, including VIs, gross primary productivity (GPPMOD), leaf area index (LAIMOD), and fraction of photosynthetic active radiation (fPARMOD). We found that satellite-derived biophysical products constitute a measurement of ecosystem structure (e.g. leaf area index – quantity of leaves) and function (e.g. leaf level photosynthetic assimilation capacity – quality of leaves), rather than GEP. Our results show that in primarily meteorological-driven (e.g. photosynthetic active radiation, air temperature, and/or precipitation) and relatively aseasonal ecosystems (e.g. evergreen wet sclerophyll forests), there were no statistically significant relationships between GEP and satellite-derived measures of greenness. In contrast, for phenology-driven ecosystems (e.g. tropical savannas), changes in the vegetation status drove GEP, and tower-based measurements of photosynthetic activity were best represented by VIs. We observed the highest correlations between MODIS products and GEP in locations where key meteorological variables and vegetation phenology were synchronous (e.g. semi-arid Acacia woodlands) and low correlation at locations where they were asynchronous (e.g. Mediterranean ecosystems). However, we found a statistical significant relationship between the seasonal measures of photosynthetic potential (Pc and LUE) and VIs, where each ecosystem aligns along a continuum; we emphasize here that knowledge of the conditions in which flux tower measurements and VIs or other remote sensing products converge greatly advances our understanding of the mechanisms driving the carbon cycle (phenology and climate drivers) and provides an ecological basis for interpretation of satellite-derived measures of greenness.

scholarly journals Analysing surface energy balance closure and partitioning over a semi-arid savanna FLUXNET site in Skukuza, Kruger National Park, South Africa

2016 ◽  
Author(s):  
Nobuhle P. Majozi ◽  
Chris M. Mannaerts ◽  
Abel Ramoelo ◽  
Renaud Mathieu ◽  
Alecia Nickless ◽  
...  
Keyword(s):  
Energy Balance ◽  
Surface Energy ◽  
Latent Heat ◽  
Surface Energy Balance ◽  
Heat Fluxes ◽  
Surface Energy Budget ◽  
Radiation Budget ◽  
Energy Balance Closure ◽  
Flux Tower ◽  
The Impact

Abstract. Flux tower sites and data are in great demand to provide essential terrestrial climate, water and radiation budget information needed for environmental monitoring and evaluation of climate change impacts on ecosystems and society in general. They are also intended for calibration and validation of satellite-based earth observation and monitoring efforts, such as for example assessment of evapotranspiration from land and vegetation surfaces using surface energy balance approaches. Surface energy budget methods for ET estimation rely to a large extend on the basic assumption of a surface energy balance closure, assuming the full conversion of net solar radiation reaching the land surface into soil heat conduction and turbulent fluxes, i.e. the sensible (or convection) and latent heat components of the energy balance. Evapotranspiration is the conversion of the latent heat exchange fraction of the balance. In this paper, the Skukuza flux tower data were analysed in order to verify their use for validation of satellite–based evapotranspiration methods, under development in South Africa.Data series from 2000 until 2014 were used in the analysis. The energy balance ratio (EBR) concept, defined as the ratio between the sum of the turbulent convective and latent heat fluxes and radiation minus soil heat was used. At first typical diurnal patterns of EB partitioning were derived for four different seasons, well illustrating how this savannah-type biome responses to the weather conditions. Also the particular behaviour of the EB components during sunrise and sunset conditions, being important but usually neglected periods of energy transitions and inversions were noted and analysed. Annual estimates of the surface energy balance and its components were generated, including an evaluation of the balance closure. The seasonal variations were also investigated as well as the impact of nocturnal observations on the overall EB behaviour.

scholarly journals Modelling soil temperature and moisture and corresponding seasonality of photosynthesis and transpiration in a boreal spruce ecosystem

2012 ◽  
Vol 9 (5) ◽  
pp. 6419-6455
Author(s):  
S. H. Wu ◽  
P.-E. Jansson
Keyword(s):  
Soil Temperature ◽  
Transition Period ◽  
Temperature Response ◽  
Net Ecosystem Exchange ◽  
Ecosystem Model ◽  
Heat Fluxes ◽  
Soil Conditions ◽  
Eddy Flux ◽  
Flux Tower ◽  
Wide Range

Abstract. Recovery of photosynthesis and transpiration is strongly restricted by low temperatures in air and/or soil during the transition period from winter to spring in boreal zones. The extent to which air temperature (Ta) and soil temperature (Ts) influence the seasonality of photosynthesis and transpiration of a boreal spruce ecosystem was investigated using a process-based ecosystem model (CoupModel) together with eddy covariance (EC) data from one eddy flux tower and nearby soil measurements at Knottåsen, Sweden. A Monte Carlo based uncertainty method (GLUE) provided prior and posterior distributions of simulations representing a wide range of soil conditions and performance indicators. The simulated results showed sufficient flexibility to predict the measured cold and warm Ts in the moist and dry plots around the eddy flux tower. Moreover, the model presented a general ability to describe both biotic and abiotic processes for the Norway spruce stand. The dynamics of sensible heat fluxes were well described the corresponding latent heat fluxes and net ecosystem exchange of CO2. The parameter ranges obtained are probably valid to represent regional characteristics of boreal conifer forests, but were not easy to constrain to a smaller range than that produced by the assumed prior distributions. Finally, neglecting the soil temperature response function resulted in fewer behavioural models and probably more compensatory errors in other response functions for regulating the seasonality of ecosystem fluxes.

scholarly journals Comparing in-situ leaf observations in early spring with flux tower CO2 exchange, MODIS EVI and modeled LAI in a northern mixed forest

2019 ◽  
Vol 278 ◽  
pp. 107673 ◽  
Author(s):  
Alison Donnelly ◽  
Rong Yu ◽  
Lingling Liu ◽  
Jonathan M. Hanes ◽  
Liang Liang ◽  
...  
Keyword(s):  
Mixed Forest ◽  
Co2 Exchange ◽  
Early Spring ◽  
Flux Tower ◽  
Modis Evi

scholarly journals Modeling gross primary production of irrigated and rain-fed maize using MODIS imagery and CO2 flux tower data

2011 ◽  
Vol 151 (12) ◽  
pp. 1514-1528 ◽  
Author(s):  
Joshua L. Kalfas ◽  
Xiangming Xiao ◽  
Diana X. Vanegas ◽  
Shashi B. Verma ◽  
Andrew E. Suyker
Keyword(s):  
Primary Production ◽  
Gross Primary Production ◽  
Co2 Flux ◽  
Flux Tower ◽  
Modis Imagery
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