TMYs vs satellite Recent Meteorological Decade solar radiation data

TMYs vs AMYs: Join us for a discussion to understand whether we should rethink weather data for building simulation

Comparison of TMYs with satellite Recent Meteorological Decade solar radiation data.

A novel approach + unexpected findings = ‘radical’ proposals

Speakers: John Mardaljevic & Matt Eames

The standardised weather files commonly used for building simulation are compiled from many years of data. Particular to a specific location, these standardised weather files are generally known as Typical Meteorological Years (TMYs).

In contrast, Actual Meteorological Years (AMYs) comprise data for a specific site over a defined period of an actual calendar year. The Copernicus Atmosphere Monitoring Service (CAMS) provides freely available satellite-derived radiation data covering Europe, Africa, the Middle East and parts of South America.

CAMS data were used as the basis for solar radiation AMYs.

For three locations in Europe, a Recent Meteorological Decade (RMD) of AMYs are used to test the suitability of TMY files as a reliable representation of prevailing sun and sky conditions. Examples are given for London, Rome and Stockholm, where, for all three locations, RMDs of CAMS data at both 15 minute and one hour time-steps are evaluated alongside four contending standardised TMY files.

For all three locations, the decade of AMY data proved to be surprisingly homogeneous, whereas the four TMYs were at variance with each other, and markedly dissimilar to the AMYs. Consequently, we make a number of proposals for the reconsideration of the use of TMYs for compliance purposes in particular, and building simulation in general.

The event will include plenty of opportunity for discussion of the proposals.

Items for discussion include:

• Replacing single-year compliance simulations with Recent Meteorological Decade evaluations.
• Benefits of 15 min solar data to represent daylight / sunlight variability.
• Weather data for CBDM ‘rights of light’ applications.

The presentation is based on research from the article “Daylight solar radiation AMY data derived from satellite remote sensing: Validation against ground measurements and comparison with TMYs”, J. Mardaljevic, E. Brembilla, and M. Eames, Building Services Engineering Research and Technology, (in press), 2025.

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