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Simplified Surface Energy Balance

Source: R/SSEB.R
sseb.Rd

Senay etal (2011) Simplified Surface Energy Balance (SSEB) approach for estimating landscape ET

Usage

sseb(
  Ts,
  welev = NULL,
  TH = "auto",
  TC = "auto",
  sunelev = NULL,
  NDVI = NULL,
  DEM = NULL,
  albedo = NULL,
  NDVImax = 0.7,
  cc = 0.65,
  KL = 0.0065,
  ETo = NULL,
  wmo = NULL,
  airport = NULL,
  Krs = 0.16,
  surface = "grass",
  x = 1,
  Tmax = NULL,
  Tmin = NULL,
  zx = NULL,
  u = 2,
  DOY = NULL,
  latitude = NULL,
  n = NULL,
  RHmax = NULL,
  RHmin = NULL,
  clip = NULL,
  folder = NULL
)

# Default S3 method
sseb(
  Ts = NULL,
  welev = NULL,
  TH = "auto",
  TC = "auto",
  sunelev = NULL,
  NDVI = NULL,
  DEM = NULL,
  albedo = NULL,
  NDVImax = 0.7,
  cc = 0.65,
  KL = 0.0065,
  ETo = NULL,
  wmo = NULL,
  airport = NULL,
  Krs = 0.16,
  surface = "grass",
  x = 1.2,
  Tmax = NULL,
  Tmin = NULL,
  zx = NULL,
  u = 2,
  DOY = NULL,
  latitude = NULL,
  n = NULL,
  RHmax = NULL,
  RHmin = NULL,
  clip = NULL,
  folder = NULL
)

Arguments

Ts

A RasterLayer data that indicates radiometric surface temperature values from remote sensing image, preferably in Kelvin (K). You can also point to raster file on your computer.

welev

Weather station elevation in meters

TH

the average of the representative 3 hot pixels selected for hot "bare" areas. If it is set to "auto" TH will be estimated from hotTs

TC

the average of representative 3 cold pixels selected from the irrigated fields. When it is set to "auto" TC will be estimated from coldTs

sunelev

Angle of Sun elevation in degrees, as found in the meta data of the satellite image

NDVI

A RasterLayer data that indicates NDVI (Normalized Difference Vegetation Index) values. You can also point to a file on your computer.

DEM

A digital elevation model[m]

albedo

A RasterLayer data that has albedo values. You can also provide file path or location on your computer

NDVImax

numeric, NDVI value for heavily green-vegetated area in the image

cc

numeric, the correction coefficient if the NDVI approaches 0.0

KL

numeric, the assumed lapse rate of air moving along the terrain

ETo

numeric, a standardized clipped grass reference ET. when it is set to NULL, it is automatically estimated from ETo

wmo

numeric. World Meteorological Organization weather station code. You can use the Worldwide Station List at https://www.wunderground.com/ [Accessed on 2016-5-6] or https://www.wetterzentrale.de/ [Accessed on 2016-5-6]

airport

numeric. IATA or ICAO code. They are alphabetically listed at https://en.wikipedia.org/wiki/List_of_airports_by_IATA_code:_A [Accessed on 2016-5-6]

Krs

Relationship between the fraction of extraterrestrial radiation that reaches the earth's surface, Rs/Ra, and the air temperature difference Tmax - Tmin for interior (Krs = 0.16) and coastal (Krs = 0.19) regions

surface

character. It is either "grass" or "alfalfa"

x

multiplier needed to estimate ET for tall, full cover crops such as alfalfa, corn and wheat. Default is 1.2.

Tmax

Numeric. Maximum air Temperature in degree Celsius

Tmin

Numeric. Minimum air Temperature in degree Celsius

zx

The height above the weather station where the wind speed is measured [m]

u

The satellites overpass time wind speed at the weather station [m/s]

DOY

Numeric or Date [YYYY-mm-dd]. Day of the Year. If you give data in the form of date [YYYY-mm-dd], it will be converted to DOY

latitude

geographical coordinates in decimal degrees. It should be negative for southern hemisphere

n

Sunshine hours

RHmax

Maximum Relative Humidity in percent

RHmin

Minimum Relative Humidity in percent

clip

extent object or raster object or polygon from which an Extent object can be extracted. A polygon or raster will be reprojected to conform the data to be cropped. for example clip can take the form of c(xmin, xmax, ymin, ymax)

folder

An original directory of the images that contains all landsat 5,7 or 8 bands and metadata. At the moment only Landsat folder is supported

Value

ET24:

Actual 24 hour ET

EF:

ET fraction

ETo:

24 hour reference ETo

References

Senay, G. B., Budde, M. E., & Verdin, J. P. 2011. Enhancing the Simplified Surface Energy Balance (SSEB) approach for estimating landscape ET: Validation with the METRIC model. Agricultural Water Management, 98(4): 606-618.

Author

George Owusu

Examples

if (FALSE) { # \dontrun{
albedo=raster(system.file("extdata","albedo.grd",package="sebkc"))
Ts=raster(system.file("extdata","Ts.grd",package="sebkc"))
NDVI=raster(system.file("extdata","NDVI.grd",package="sebkc"))
#minimal data
modsseb=sseb(Ts=Ts,TH="full",TC="full",sunelev=50,NDVI=NDVI,DEM=NULL,
albedo=albedo,NDVImax=0.7,cc=0.65,KL=0.0065,
ETo="auto",x=1.2,Tmax=31,Tmin=28,zx=10,
u=2,DOY=37,latitude=5.6,n=NULL,RHmax=NULL,RHmin=NULL)

#uaing the folder parameters
folder=system.file("extdata","stack",package="sebkc")
ssebauto=sseb(folder=folder,welev=317,Tmax=31,Tmin=28, latitude=5.6)

#Another interactive example
#get Ts, Albedo, NDVI, SAVI, sunelev, DOY from landsat data 
welev=278
data=landsat578(rawdata,welev=welev)
#perform semi-auto simulation 
#Determine xyhot. Digitize polygon on the Ts map
modhot=hotTs(data,welev=300,extent="auto",cluster=2)
#determine the cold. Digitize polygon on the Ts map
modcold=coldTs(data,welev=275,extent="auto",cluster=2)
xyhot=modhot$Tshot
xycold=modcold$Tscold
#use object of \code{\link{coldTs}} or \code{\link{hotTs}} in different ways
modsseb=sseb(Ts=Ts,TH=xyhot,TC=modcold,sunelev=50,NDVI=NDVI,DEM=NULL,
albedo=albedo,NDVImax=0.7,cc=0.65,KL=0.0065,
ETo="auto",x=1.2,Tmax=31,Tmin=28,zx=10,
u=2,DOY=37,latitude=5.6,n=NULL,
RHmax=NULL,RHmin=NULL)
} # }