In FilgueirasR/BrazilMet: Download and Processing of Automatic Weather Stations (AWS) Data of INMET-Brazil

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🚀 Design ETo calculation estimation

This article shows a quick example of how to download INMET station data and estimate reference evapotranspiration (ETo) using FAO-56, followed by the calculation of the design ETo.

📦 Load the package

library(BrazilMet)

🌍 View available INMET stations

Before downloading data, you can check the available weather stations with:

see_stations_info()

⬇️ Download daily weather data

Let’s download daily meteorological data for one stations between January 2000 until March 2025:

df <- BrazilMet::download_AWS_INMET_daily(stations = "A001",
                                          start_date = "2000-01-01",
                                          end_date = "2025-03-31")

The resulting data frame includes temperature, solar radiation, wind speed, humidity, and atmospheric pressure

🧠 Calculate daily ETo using FAO-56

Now we use the daily_eto_FAO56() function to estimate daily ETo values:

df$eto <- daily_eto_FAO56(
  lat    = df$latitude_degrees,
  tmin   = df$tair_min_c,
  tmax   = df$tair_max_c,
  tmean  = df$tair_mean_c,
  Rs     = df$sr_mj_m2,
  u2     = df$ws_2_m_s,
  Patm   = df$patm_mb,
  RH_max = df$rh_max_porc,
  RH_min = df$rh_min_porc,
  z      = df$altitude_m,
  date   = df$date
)

💧 Design ETo calculation

And after the ETo calculation, we use the design_eto() function to estimate the design ETo for irrigation project purpose:

eto_design <- BrazilMet::design_eto(eto_daily_data = df, percentile = .80)

📝 Printing the design ETo based on an 80% probability of occurrence

Below is a basic line plot of daily ETo:

print(eto_design)

✅ Summary

The BrazilMet package allows you to download official INMET weather data and compute ETo using the FAO-56 method in a reproducible and efficient way. This is essential for irrigation planning, crop modeling, and climate-based decision support.