# Actual evapotranspiration (ETa) using Sentinel-2 images with single agrometeorological data. ```r evapo_s2(doy, RG, Ta, ET0, a, b) ``` ## 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 ## Returns 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). ## Examples ```r 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) ```

evapo_s2 function