Typical Meteorological Year (TMY)

Created by
Team E3P Webmaster
European Commission - DG JRC, Directorate C - Energy, Transport and Climate
Urban Areas

What is a Typical Meteorological Year (TMY)?

A typical meteorological year (TMY) is a set of meteorological data with data values for every hour in a year for a given geographical location. The data are selected from hourly data in a longer time period (normally 10 years or more). For each month in the year the data have been selected from the year that was considered most "typical" for that month. For instance, January might be from 2007, February from 2012 and so on.

How it is calculated?

The solar radiation data used for the TMY have been calculated from satellite data by the CM SAF collaboration (www.cmsaf.eu). All other data have been taken from the ECMWF ERA-interim reanalysis (www.ecmwf.int). Air temperature data have been corrected for elevation. The selection of the months for the TMY is done using the method described in the international Standard ISO 15927-4. The selection is done based on air temperature, global horizontal irradiance and relative humidity.

What can it be used for?

To download data: TMY data are used in many fields to perform calculations that need meteorological data, and where a calculation involving many years would be too time-consuming. One example is the EnergyPlus software for calculating the energy performance of buildings. You can choose output in the EPW format needed for EnergyPlus or a generic CSV format.

To interactively visualise the dataset: The buttons in the upper left corner zoom in to predefined temporal ranges (1 day, 1 week, 1 month, 6 months or all). The navigator, located below the main series, shows the entire dataset. It can be used to interactively zoom in and out on parts of the data as well as panning across the dataset.

Besides, once a location is selected, several data will be provided: elevation (in meters above sea level), average temperature (in °C), Heating Degree Days (HDD, using 15° as base temperature) and Cooling Degree Days (CDD, using 24° as base temperature).

How do I make a horizon file?

The horizon file is a text file (with extension ".txt" with one number on each line giving the height of the horizon in degrees. Each line represents one direction, starting from north and going east-south-west. The values should be for equally-spaced directions (for instance 8 values would be for north, north-east, east, and so on). For an example, see: tmy_horizon_example.txt

Visit the TMY website

TMY website

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