SEBAL
Encyclopedia
The Surface Energy Balance Algorithm for Land (SEBAL) uses the energy balance
to estimate aspects of the hydrological cycle. SEBAL maps evapotranspiration
, biomass
growth, water deficit and soil moisture. Its main creator is Prof. Dr. W.G.M. Bastiaanssen
SEBAL quantifies the energy balance using satellite data as an input. Land surface characteristics such as surface albedo
, leaf area index
, vegetation index and surface temperature are derived from satellite imagery. In addition to satellite images, the SEBAL model requires meteorological data, such as wind speed
, humidity
, solar radiation and air temperature. It uses meteorological data from the moment of the recording of the satellite data to solve the 'instantaneous' energy balance, and uses extrapolation to calculate daily evapotranspiration. Using a time series of satellite and meteorological data, periodic cumulative (e.g. weekly, monthly, yearly) evapotranspiration data can be calculated.
The SEBAL model uses the energy balance, as opposed to in hydrology common water balance
to solve for evapotranspiration.
performance..
The combination of the energy balance with input from remote sensing data is applied by farmers , irrigation districts, catchment management agencies and regional and national governments.
Energy balance
Energy balance may refer to:* First law of thermodynamics, according to which energy cannot be created or destroyed, only modified in form* Energy balance , a measurement of the biological homeostasis of energy in living systems...
to estimate aspects of the hydrological cycle. SEBAL maps evapotranspiration
Evapotranspiration
Evapotranspiration is a term used to describe the sum of evaporation and plant transpiration from the Earth's land surface to atmosphere. Evaporation accounts for the movement of water to the air from sources such as the soil, canopy interception, and waterbodies...
, biomass
Biomass
Biomass, as a renewable energy source, is biological material from living, or recently living organisms. As an energy source, biomass can either be used directly, or converted into other energy products such as biofuel....
growth, water deficit and soil moisture. Its main creator is Prof. Dr. W.G.M. Bastiaanssen
Model background
The basis of SEBAL is the energy balance : the energy driving the hydrological cycle is equal to the incoming energy minus:- the energy going to heating of the soil and air, and
- the energy reflected back to space.
SEBAL quantifies the energy balance using satellite data as an input. Land surface characteristics such as surface albedo
Albedo
Albedo , or reflection coefficient, is the diffuse reflectivity or reflecting power of a surface. It is defined as the ratio of reflected radiation from the surface to incident radiation upon it...
, leaf area index
Leaf Area Index
Leaf Area Index The Global Climate Observing System defines LAI as "one half the total green leaf area per unit groundsurface area. On sloping surfaces, the LAI should be projected to the normal to the slope. LAI is expressed in terms of square meters of leaf per square meter of ground...
, vegetation index and surface temperature are derived from satellite imagery. In addition to satellite images, the SEBAL model requires meteorological data, such as wind speed
Wind speed
Wind speed, or wind velocity, is a fundamental atmospheric rate.Wind speed affects weather forecasting, aircraft and maritime operations, construction projects, growth and metabolism rate of many plant species, and countless other implications....
, humidity
Humidity
Humidity is a term for the amount of water vapor in the air, and can refer to any one of several measurements of humidity. Formally, humid air is not "moist air" but a mixture of water vapor and other constituents of air, and humidity is defined in terms of the water content of this mixture,...
, solar radiation and air temperature. It uses meteorological data from the moment of the recording of the satellite data to solve the 'instantaneous' energy balance, and uses extrapolation to calculate daily evapotranspiration. Using a time series of satellite and meteorological data, periodic cumulative (e.g. weekly, monthly, yearly) evapotranspiration data can be calculated.
The SEBAL model uses the energy balance, as opposed to in hydrology common water balance
Water balance
In hydrology, a water balance equation can be used to describe the flow of water in and out of a system. A system can be one of several hydrological domains, such as a column of soil or a drainage basin....
to solve for evapotranspiration.
Applications
The energy balance applies to all scales, ranging from global to river basin to region to farm and to field level. Satellite images come in a wide variety of spatial and temporal resolutions. Evapotranspiration and biomass production are key indicators for water management and irrigationIrrigation
Irrigation may be defined as the science of artificial application of water to the land or soil. It is used to assist in the growing of agricultural crops, maintenance of landscapes, and revegetation of disturbed soils in dry areas and during periods of inadequate rainfall...
performance..
The combination of the energy balance with input from remote sensing data is applied by farmers , irrigation districts, catchment management agencies and regional and national governments.