Weather Data

The weather data is the starting point of the evaluation of a project. It is also the main source of uncertainty.

This help section will guide you in different options, for discovering the management and organization of weather data in PVsyst. From the PVsyst start page, click the ++Databases++ button to access the weather database. The available functions are:

Geographical site: browse your existing .SIT files or create new ones
Weather data table and graphs: browse weather files (.MET files)
Compare weather data: compare irradiance between diffferent weather files
Import a know format: Convert a formatted .csv to a .MET file from supported weather data providers
Import a custom file: Convert a CSV file into a .MET file. The import requires a formatting file (.MEF), which can be created using the weather data import assistant
Synthetic data generation: Generate hourly data from monthly data
TMY generation: combine 10 or more .MET files from different years into one TMY.

Weather files overview

Geographical sites (.SIT)

.SIT files are associated with every geographic site used for simulation. They contain monthly weather data and can be used as a base for Synthetic data generation. They can be defined from the Geographical sites window and are stored in the PVsyst Data \Sites\ directory.

Weather files (.MET)

.MET files contain the hourly or sub-hourly weather data used to run simulations. These files are stored in the PVsyst Data \Meteo\ directory.

The content of a .MET file can be browsed using the weather data tables and graphs window. Tine label correspond to the start of the measurement interval (12h00 is data recorded from 12h00 until 13h00). Weather files can be up to one year long or less.

There are 4 main types of .MET files

Typical Meteorological Year (TMY): imported directly from a provider or generated in PVsyst
Synthetic: generated from monthly data
Time series (year is then specified): imported directly from a provider
Imported: files generated from custom import

Weather data files can be obtained through several processes:

Synthetic hourly data generation from monthly data
Know format import: file was imported from a supported provider
Custom import: meant to import any data, such as user's own measurements or providers not covered yet by the know format option

Finally, the list of variables that can be present in a .MET file is given in the table below.

The Global Horizontal Irradiation (GlobHor or GHI), Diffuse Horizontal Irradiation (DiffHor) and Ambient temperatures are required, the rest is optional.

Name	Available units	Description
GlobHor	W/m², MJ/m²/h	Global Horizontal Irradiance - must be present
DiffHor	W/m², MJ/m²/h	Diffuse Horizontal Irradiance - must be present
T_Amb	°C	Ambient Temperature - must be present
GIPMeas	W/m², MJ/m²/h	Measured Global Irradiation on Plane, also known as plane of array (POA) irradiance. (present if source measurement was a POA measurement)
BeamNor	W/m², MJ/m²/h	Beam Normal Irradiance
BeamHor	W/m², MJ/m²/h	Horizontal Beam Irradiation
WindVel	m/s, km/h	Wind Velocity
TArrMes	°C	Measured Module Temperature
PrecWat	mm, cm, in	Precipitable Water Column
RelHum	ratio, %, ‰	Relative Humidity (0–1)
Linke	ratio, %, ‰	Linke Turbidity Coefficient
AoD	ratio, %, ‰	Aerosol Optical Depth
Albedo	ratio, %, ‰	Ground Albedo
T_DewPt	°C	Dew Point Temperature

Weather format files (.MEF)

When importing a custom weather file, a formatting file called .MEF is required. This file defines the mapping of your custom data to be imported. These files are stored in the PVsyst Data \Meteo\ directory.

Updates

Sub-hourly weather files

Sub-hourly simulation was introduced in PVsyst 8.1.0 and at this time, sub-hourly weather files can only be generated using:

Custom import (from sub-hourly data)
Site creation, importing Meteonorm data and choosing the minute option
Synthetic data generation, choosing the minute option