Mapped Variables for the ET project

 

VariableSymbolDescriptionMonths per year1Maps per month2Total mapsAvailable For DownloadIncluded in Interactive Map
Clear sky radiation Kclear-sky

Solar radiation estimated for clear sky (no clouds) condition

12

15

180

x

x

Cloud frequency CF

Frequency of occurrence of cloud cover

12

24

288

x

x

Solar radiation Kd

Solar radiation estimated with effects of clouds included

12

15

180

x

x

Diffuse radiation Kdiffuse

Solar radiation that reaches surface after reflection

12

15

180

x

 

Albedo α

Proportion of incident solar radiation reflected by the surface

12

1

12

x

x

Downwelling longwave radiation Ld

Longwave radiation from atmosphere and clouds reaching surface

12

24

288

x

 

Upwelling longwave radiation Lu

Longwave radiation emitted by the surface

12

24

288

x

 

Net radiation Rnet

The difference between incoming and outgoing radiation

12

24

288

x

x

Terrain Shading

For each pixel, this variable indicates whether it is shaded or not shaded by surrounding terrain for the given month and time of day

12

1

12

x

 

Clear Sky Radiation with Terrain Shading

Clear sky radiation with the effects of terrain shading included. If the pixel is shaded, direct radiation is set to zero. Diffuse radiation is assumed to be unchanged

12

24

288

x

 

Available Energy A

Available energy is equal to net radiation minus energy stored in the biomass, air layer, and soil

12

24

288

x

 

Soil heat flux G

Sensible heat conducting into or out of the soil

12

24

288

x

 

Biomass heat storage Qb

Sensible heat conducting into or out of the biomass

12

24

288

x

 

Air layer heat storage Qa

Increase or decrease in sensible and latent heat stored in air layer

12

24

288

x

 

Air Density

The density of air, estimated as a function of air pressure, temperature, and humidity

12

24

288

x

 

Air Temperature T

Air temperature

12

24

288

x

x

Relative Humidity RH

Relative Humidity

12

24

288

x

x

Surface Temperature Ts

Temperature of the exposed surface (canopy and/or soil)

12

24

288

x

 

Vapor pressure e

Partial pressure of water vapor in the air

12

24

288

 

 

Saturation vapor pressure esat

Maximum vapor pressure at a given air temperature

12

24

288

 

 

Vapor pressure deficit VPD

Saturation vapor pressure minus Vapor pressure

12

24

288

x

x

Wind speed U

Wind speed at reference level of vegetation height plus 2 m

12

24

288

x

x

Land cover type LCT

Land cover type

1

1

1

x

x

Vegetation height h

Vegetation height

12

1

12

x

 

Leaf area index LAI

Leaf area (one-sided) divided by ground area

12

1

12

x

 

Vegetation cover fraction fc

Fraction of ground area covered by vegetation

12

1

12

x

 

Canopy wetness fraction fw

Fraction time vegetation is wet from rain, fog, or dew

12

24

288

x

 

Canopy Conductance
A parameter that describes the control exerted on gas exchanges by the stomata of plant leaves. This parameter incorporates the stomatal conductance, based on species-specific maximum stomatal conductance modulated by light level, temperature, humidity, and available soil moisture

12

24

288

x

 

Roughness Length
A parameter that describes the influence of surface (vegetation) roughness on the flow of air and the generation of turbulent eddies

12

1

12

x

 

Enhanced Vegetation Index (EVI)
A gridded vegetation index made available by MODIS (NASA). See http://modis.gsfc.nasa.gov/data/dataprod/

12

1

12

x

 

Normalized Difference Vegetation Index (NDVI)
A gridded vegetation index made available by MODIS (NASA). See http://modis.gsfc.nasa.gov/data/dataprod/

12

1

12

x

 

Available Soil Moisture
Soil moisture available for evapotranspiration divided by the available soil moisture capacity, expressed as a ratio (0 to 1)

12

1

12

x

 

Soil moisture constraint factor (transpiration) fΘ-transp

Factor representing the effects of soil moisture on transpiration

12

1

12

 

 

Soil moisture constraint factor (soil evaporation) fΘ-soil

Factor representing the effects of soil moisture on soil evaporation

12

1

12

 

 

Potential ET - Priestley Taylor PETP-T

Potential evapotranspiration based on the Priestley-Taylor model

12

24

288

x

x

Potential ET - Penman-Monteith PETP-M

Potential evapotranspiration based on the Penman-Monteith model

12

24

288

x

x

Potential ET - Grass reference surface PET0

Potential evapotranspiration based on the FAO grass reference surface model

12

24

288

x

x

Wet canopy evaporation Ewet-canopy

Evaporation of water from vegetation wetted by rain and/or fog

12

24

288

x

x

Transpiration Etransp

Transpiration

12

24

288

x

x

Soil evaporation Esoil

Evaporation of water from soil

12

24

288

x

x

Evapotranspiration ET

Sum of wet canopy evaporation, transpiration, and soil evaporation

12

24

288

x

x

Latent energy flux LE

Energy equivalent of evapotranspiration

12

24

288

x

x

1For variables with different maps for each month, annual maps were also created by averaging (or summing) the monthly values at each grid location. The annual maps are not included in these totals. 

2For variables with different maps for each hour, annual hourly maps were also created by averaging the hourly values at each grid location across the 12 months, creating an addition 24 maps (15 maps for shortwave radiation maps that only include daylight hours). These annual hourly maps are not included in the totals.