documentation/tutorial.md

@@ -2,6 +2,7 @@
 title: Tutorial
 ---
 
+
 This tutorial provides a guide to simulate an agrivoltaic system with PASE.
 
 [[_TOC_]]
@@ -36,6 +37,39 @@ The parameters are located in several subdirectories according to their purpose:
 - SCENARIOS/ : define the parameters of the simulation scenario, such as location, latitude and longitude, altitude, simulation options, start and end year of the simulation, etc.
 - WEATHER_FILES/ : the simulation can run on data fetched from an online database or on data files located in this subdirectory.
 
+## Daily weather files - precipitation and vapour pressure data
+
+The crop modeling component of PASE requires daily weather data to compute evapotranspiration and related processes.
+Two key variables are needed: daily precipitation and water vapor pressure.
+
+### Data Sources
+
+You can obtain the necessary data in one of two ways:
+
+From Agri4Cast: if your study area is covered, you can download the daily weather dataset directly from the Agri4Cast Data Portal.
+
+Manual creation: if no Agri4Cast data is available, you must prepare a custom CSV file containing the required variables (see below).
+
+### File Structure
+
+The input file must be a **semicolon-separated** CSV with the following columns:
+
+| Column Name      | Description                        | Units | Example  |
+| ---------------- | ---------------------------------- | ----- | -------- |
+| `DAY`            | Calendar date in `yyyymmdd` format | -     | 20210415 |
+| `VAPOR_PRESSURE` | Daily mean vapor pressure          | hPa   | 12.3     |
+| `PRECIPITATION`  | Daily total precipitation          | mm/d  | 4.7      |
+
+### Formatting Requirements
+
+- Use UTF-8 encoding and `;` as the column separator.
+- Include a header row exactly matching the column names above.
+- Ensure all dates are valid (mind **leap years***) and continuous if the simulation requires complete coverage.
+
+### Example File
+
+A minimal reference file is provided in the repository under INPUTS/WEATHER_FILES/minimal_PRECIP_VP.csv
+
 # Running a simulation
 
 Once the parameters are set, the simulation can start.