agriwater (version 1.0.2)

evapo_s2: Actual evapotranspiration (ETa) using Sentinel-2 images with single agrometeorological data.

Description

Actual evapotranspiration (ETa) using Sentinel-2 images with single agrometeorological data.

Usage

evapo_s2(doy, RG, Ta, ET0, a, b)

Value

It returns in raster format (.tif) the Surface Albedo at 24h scale ("Alb_24"), NDVI, Surface Temperature ("LST"), net radiation ("Rn_MJ"), Crop Coefficient ("kc") and Actual Evapotranspiration (evapo).

Arguments

doy

is the Day of Year (DOY)

RG

is the global solar radiation

Ta

is the average air temperature

ET0

is the reference evapotranspiration

a

is one of the regression coefficients of SAFER algorithm

b

is one of the regression coefficients of SAFER algorithm

Examples

library(agriwater)

# dependencies of package 'agriwater'
library(terra)


# Using a temporary folder to run example
wd <- tempdir()
initial = getwd()
setwd(wd)

# creating raster which simulate Sentinel-2 reflectances - for using
# real data, please download:
# https://drive.google.com/open?id=14E1wHNLxG7_Dh4I-GqNYakj8YJDgKLzk

xy <- matrix(rnorm(4, mean = 0.07, sd = 0.01), 2, 2)
rast <- rast(xy, crs="+proj=longlat +datum=WGS84")
ext(rast) <- c(-40.5,-40.45,-9.5,-9.45)
writeRaster(rast, file.path(wd, "B2.tif"),filetype = "GTiff", overwrite=TRUE)
xy <- matrix(rnorm(4, mean = 0.05, sd = 0.015),2, 2)
rast <- rast(xy, crs="+proj=longlat +datum=WGS84")
ext(rast) <- c(-40.5,-40.45,-9.5,-9.45)
writeRaster(rast, file.path(wd, "B3.tif"),filetype = "GTiff", overwrite=TRUE)
xy <- matrix(rnorm(4, mean = 0.03, sd = 0.018),2, 2)
rast <- rast(xy, crs="+proj=longlat +datum=WGS84")
ext(rast) <- c(-40.5,-40.45,-9.5,-9.45)
writeRaster(rast, file.path(wd, "B4.tif"),filetype = "GTiff", overwrite=TRUE)
xy <- matrix(rnorm(4, mean = 0.05, sd = 0.015),2, 2)
rast <- rast(xy, crs="+proj=longlat +datum=WGS84")
ext(rast) <- c(-40.5,-40.45,-9.5,-9.45)
writeRaster(rast, file.path(wd, "B8.tif"),filetype = "GTiff", overwrite=TRUE)
mask <- as.polygons(rast)
writeVector(mask, file.path(getwd(),"mask.shp"), overwrite=TRUE)

# using "agriwater"
evapo_s2(doy = 134, RG = 17.6, Ta = 27.9, ET0 = 3.8, a = 1.8, b = -0.008)

#Exiting temporary folder and returning to previous workspace
setwd(initial)