Long-term water stress and drought monitoring of Mediterranean oak savanna vegetation using thermal remote sensing

Abstract. Drought is a devastating natural hazard, difficult to define, detect and quantify. Global meteorological data and remote sensing products present new opportunities to characterize drought in an objective way, and to extend this analysis in space and time. In this paper, we applied the surface energy balance model SEBS (Surface Energy Balance System) for the period 2001–2018, to estimate evapotranspiration and other energy fluxes over the dehesa area of the Iberian Peninsula, with a monthly temporal resolution and 0.05° pixel size. A satisfactory agreement was found between the fluxes modelled and the measurements obtained for three years by two flux towers located over representative sites (RMSD = 21 W m−2 and R2 of 0.76, for all energy fluxes and both sites). The estimations of the convective fluxes (LE and H) showed higher deviations, with RMSD = 26 W m−2 on average, than Rn and G, with RMSD = 15 W m−2. At both sites, annual ET was very close to total precipitation with the exception of a few wet years in which intense precipitation events, producing high run-off, were observed. The analysis of the anomalies of the ratio of evapotranspiration (ET) to reference ET (ETo) was used as an indicator of agricultural drought on monthly and annual scales. Hydrological years 2004/2005 and 2011/2012 stood out for their negative values, with the first one being the severest of the series, the impact observed on vegetation coverage and grain production. On a monthly scale, this event was also the longest and most intense, with peak negative values in January–February and April–May of 2005, explaining its great impact on cereal production (up to 45 % reduction). During the drier events, the changes in vegetation ground cover over the months, with a preponderant presence of grasslands compared with those in which only oak trees were active, allowed a separate analysis of the strategies adopted by the two strata to cope with water stress. These results indicate that the drought events characterized for the period did not cause any permanent damage on the vegetation of dehesa systems. The approach tested has proved useful to provide insight into the characteristics of drought events over this ecosystem and will be helpful to identify areas of interest for future studies at finer resolutions.

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Long-term water stress and drought assessment of Mediterranean oak savanna vegetation using thermal remote sensing

Hydrology and Earth System Sciences ◽

10.5194/hess-25-755-2021 ◽

2021 ◽

Vol 25 (2) ◽

pp. 755-768

Author(s):

María P. González-Dugo ◽

Xuelong Chen ◽

Ana Andreu ◽

Elisabet Carpintero ◽

Pedro J. Gómez-Giraldez ◽

...

Keyword(s):

Water Stress ◽

Energy Balance ◽

Surface Energy ◽

Surface Energy Balance ◽

Agricultural Drought ◽

Vegetation Coverage ◽

Balance Model ◽

Separate Analysis ◽

Energy Fluxes ◽

Remotely Sensed Data

Abstract. Drought is a devastating natural hazard that is difficult to define, detect and quantify. The increased availability of both meteorological and remotely sensed data provides an opportunity to develop new methods to identify drought conditions and characterize how drought changes over space and time. In this paper, we applied the surface energy balance model, SEBS (Surface Energy Balance System), for the period 2001–2018, to estimate evapotranspiration and other energy fluxes over the dehesa area of the Iberian Peninsula, with a monthly temporal resolution and 0.05∘ pixel size. A satisfactory agreement was found between the fluxes modeled and the measurements obtained for 3 years by two flux towers located over representative sites (RMSD = 21 W m−2 and R2=0.76, on average, for all energy fluxes and both sites). The estimations of the convective fluxes (LE and H) showed higher deviations, with RMSD = 26 W m−2 on average, than Rn and G, with RMSD = 15 W m−2. At both sites, annual evapotranspiration (ET) was very close to total precipitation, with the exception of a few wet years in which intense precipitation events that produced high runoff were observed. The analysis of the anomalies of the ratio of ET to reference ET (ETo) was used as an indicator of agricultural drought on monthly and annual scales. The hydrological years 2004/2005 and 2011/2012 stood out for their negative values. The first one was the most severe of the series, with the highest impact observed on vegetation coverage and grain production. On a monthly scale, this event was also the longest and most intense, with peak negative values in January–February and April–May 2005, explaining its great impact on cereal production (up to 45 % reduction). During the drier events, the changes in the grasslands' and oak trees' ground cover allowed for a separate analysis of the strategies adopted by the two strata to cope with water stress. These results indicate that the drought events characterized for the period did not cause any permanent damage to the vegetation of dehesa systems. The approach tested has proven useful for providing insight into the characteristics of drought events over this ecosystem and will be helpful to identify areas of interest for future studies at finer resolutions.

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Modelling seasonal and spatial variations in the surface energy balance of Haut Glacier d’Arolla, Switzerland

Annals of Glaciology ◽

10.3189/172756400781820183 ◽

2000 ◽

Vol 31 ◽

pp. 53-62 ◽

Cited By ~ 68

Author(s):

Ben W. Brock ◽

Ian C. Willis ◽

Martin J. Sharp ◽

Neil S. Arnold

Keyword(s):

Energy Balance ◽

Surface Energy ◽

Surface Energy Balance ◽

Roughness Length ◽

Meteorological Conditions ◽

Aerodynamic Roughness Length ◽

Energy Fluxes ◽

Surface Energy Fluxes ◽

Aerodynamic Roughness ◽

The Impact

AbstractThe impact of spatial and temporal variations in the surface albedo and aerodynamic roughness length on the surface energy balance of Haut Glacier d’Arolla, Switzerland, was examined using a semi-distributed surface energy-balance model (Arnold and others, 1996). The model was updated to incorporate the glacier-wide effects of albedo and aerodynamic roughness-length variations using parameterizations following Brock (1997). After the model’s performance was validated, the glacier-wide patterns of the net shortwave, turbulent and melt energy fluxes were examined on four days, representative of surface conditions in late May, June July and August. In the model, meteorological conditions were held constant on each day in order that the impact of albedo and aerodynamic roughness-length variations could be assessed independently. A late-summer snowfall event was also simulated. Albedo and aerodynamic roughness-length variations, particularly those associated with the migration of the transient snowline and the decay of the winter snowpack, were found to exert a strong influence on the magnitude of the surface energy fluxes The importance of meteorological conditions in suppressing the surface energy fluxes and melt rate following a fresh snowfall was highlighted

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Determining maize water stress through a remote sensing-based surface energy balance approach

Irrigation Science ◽

10.1007/s00271-020-00668-1 ◽

2020 ◽

Vol 38 (5-6) ◽

pp. 501-518 ◽

Cited By ~ 1

Author(s):

Edson Costa-Filho ◽

José L. Chávez ◽

Louise Comas

Keyword(s):

Remote Sensing ◽

Water Stress ◽

Energy Balance ◽

Surface Energy ◽

Surface Energy Balance ◽

Balance Approach ◽

Energy Balance Approach

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EVAPOTRANSPIRATION AND EVAPORATION/TRANSPIRATION RETRIEVAL USING DUAL-SOURCE SURFACE ENERGY BALANCE MODELS INTEGRATING VIS/NIR/TIR DATA WITH SATELLITE SURFACE SOIL MOISTURE INFORMATION

ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences ◽

10.5194/isprs-archives-xlii-3-w6-9-2019 ◽

2019 ◽

Vol XLII-3/W6 ◽

pp. 9-12

Author(s):

G. Boulet ◽

E. Delogu ◽

W. Chebbi ◽

Z. Rafi ◽

V. Le Dantec ◽

...

Keyword(s):

Remote Sensing ◽

Soil Moisture ◽

Water Stress ◽

Energy Balance ◽

Surface Energy ◽

Surface Temperature ◽

Surface Energy Balance ◽

Source Surface ◽

Dual Source ◽

Energy Balance Models

<p><strong>Abstract.</strong> Evapotranspiration is an important component of the water cycle. For the agronomic management and ecosystem health monitoring, it is also important to provide an estimate of evapotranspiration components, i.e. transpiration and soil evaporation. To do so, Thermal InfraRed data can be used with dual-source surface energy balance models, because they solve separate energy budgets for the soil and the vegetation. But those models rely on specific assumptions on raw levels of plant water stress to get both components (evaporation and transpiration) out of a single source of information, namely the surface temperature. Additional information from remote sensing data are thus required. This works evaluates the ability of the SPARSE dual-source energy balance model to compute not only total evapotranspiration, but also water stress and transpiration/evaporation components, using either the sole surface temperature as a remote sensing driver, or a combination of surface temperature and soil moisture level derived from microwave data. Flux data at an experimental plot in semi-arid Morocco is used to assess this potentiality and shows the increased robustness of both the total evapotranspiration and partitioning retrieval performances. This work is realized within the frame of the Phase A activities for the TRISHNA CNES/ISRO Thermal Infra-Red satellite mission.</p>

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Utility of remote sensing-based surface energy balance models to track water stress in rain-fed switchgrass under dry and wet conditions

ISPRS Journal of Photogrammetry and Remote Sensing ◽

10.1016/j.isprsjprs.2017.10.010 ◽

2017 ◽

Vol 133 ◽

pp. 128-141 ◽

Cited By ~ 17

Author(s):

Nishan Bhattarai ◽

Pradeep Wagle ◽

Prasanna H. Gowda ◽

Vijaya G. Kakani

Keyword(s):

Remote Sensing ◽

Water Stress ◽

Energy Balance ◽

Surface Energy ◽

Surface Energy Balance ◽

Dry And Wet Conditions ◽

Energy Balance Models

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Estimation of Evapotranspiration using Remote Sensing and Surface Energy Balance Algorithm for Land (SEBAL) in Canal Command

Journal of Agricultural Engineering ◽

10.52151/jae2021581.1751 ◽

2021 ◽

Vol 58 (03) ◽

pp. 274-285

Author(s):

H. V. Parmar ◽

N. K. Gontia

Keyword(s):

Remote Sensing ◽

Energy Balance ◽

Surface Energy ◽

Land Surface ◽

Surface Energy Balance ◽

Crop Growth ◽

Growth Stages ◽

Landsat 8 ◽

Surface Temperatures ◽

Canal Command

Remote sensing based various land surface and bio-physical variables like Normalized Difference Vegetation Index (NDVI), Land Surface Temperature (LST), surface albedo, transmittance and surface emissivity are useful for the estimation of spatio-temporal variations in evapotranspiration (ET) using Surface Energy Balance Algorithm for Land (SEBAL) method. These variables were estimated under the present study for Ozat-II canal command in Junagadh district, Gujarat, India, using Landsat-7 and Landsat-8 images of summer season of years 2014 and 2015. The derived parameters were used in SEBAL to estimate the Actual Evapotranspiration (AET) of groundnut and sesame crops. The lower values NDVI observed during initial (March) and end (May) stages of crop growth indicated low vegetation cover during these periods. With full canopy coverage of the crops, higher value of NDVI (0.90) was observed during the mid-crop growth stage. The remote sensing-based LST was lower for agricultural areas and the area near banks of the canal and Ozat River, while higher surface temperatures were observed for rural settlements, road and areas with exposed dry soil. The maximum surface temperatures in the cropland were observed as 311.0 K during March 25, 2014 and 315.8 K during May 31, 2015. The AET of summer groundnut increased from 3.75 to 7.38 mm.day-1, and then decreased to 3.99 mm.day-1 towards the end stage of crop growth. The daily AET of summer sesame ranged from 1.06 to 7.72 mm.day-1 over different crop growth stages. The seasonal AET of groundnut and sesame worked out to 358.19 mm and 346.31 mm, respectively. The estimated AET would be helpful to schedule irrigation in the large canal command.

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

10.5194/hess-2016-76 ◽

2016 ◽

Cited By ~ 3

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.

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Potential evaporation estimation through an unstressed surface-energy balance and its sensitivity to climate change

Hydrology and Earth System Sciences ◽

10.5194/hess-17-4625-2013 ◽

2013 ◽

Vol 17 (11) ◽

pp. 4625-4639 ◽

Cited By ~ 16

Author(s):

A. Barella-Ortiz ◽

J. Polcher ◽

A. Tuzet ◽

K. Laval

Keyword(s):

Climate Change ◽

Energy Balance ◽

Surface Energy ◽

Surface Energy Balance ◽

Aerodynamic Resistance ◽

Neutral Stability ◽

Potential Evaporation ◽

Time Step ◽

Humidity Gradient ◽

The Impact

Abstract. Potential evaporation (ETP) is a basic input for many hydrological and agronomic models, as well as a key variable in most actual evaporation estimations. It has been approached through several diffusive and energy balance methods, out of which the Penman–Monteith equation is recommended as the standard one. In order to deal with the diffusive approach, ETP must be estimated at a sub-diurnal frequency, as currently done in land surface models (LSMs). This study presents an improved method, developed in the ORCHIDEE LSM, which consists of estimating ETP through an unstressed surface-energy balance (USEB method). The results confirm the quality of the estimation which is currently implemented in the model (Milly, 1992). The ETP underlying the reference evaporation proposed by the Food and Agriculture Organization, FAO, (computed at a daily time step) has also been analysed and compared. First, a comparison for a reference period under current climate conditions shows that USEB and FAO's ETP estimations differ, especially in arid areas. However, they produce similar values when the FAO's assumption of neutral stability conditions is relaxed, by replacing FAO's aerodynamic resistance by that of the model's. Furthermore, if the vapour pressure deficit (VPD) estimated for the FAO's equation, is substituted by ORCHIDEE's VPD or its humidity gradient, the agreement between the daily mean estimates of ETP is further improved. In a second step, ETP's sensitivity to climate change is assessed by comparing trends in these formulations for the 21st century. It is found that the USEB method shows a higher sensitivity than the FAO's. Both VPD and the model's humidity gradient, as well as the aerodynamic resistance have been identified as key parameters in governing ETP trends. Finally, the sensitivity study is extended to two empirical approximations based on net radiation and mass transfer (Priestley–Taylor and Rohwer, respectively). The sensitivity of these ETP estimates is compared to the one provided by USEB to test if simplified equations are able to reproduce the impact of climate change on ETP.

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