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Climate Data
Bauklimatik Dresden

Climate data formats

DELPHIN, NANDRAD and THERAKLES need climate data for the simulation. These are provided in different formats depending on the weather service/climate data source. There are differences, for example, in the manner in which the solar radiation is provided, e.g. direct solar radiation is stored on a horizontal surface or from the normal direction of the sun. Also the global radiation and diffuse radiation is sometimes given.

In addition, some climate data contain driving rain data, while others lack such data. Furthermore, there are contradictory format specifications for different climate file formats, e.g. in EnergyPlus weather files (*.epw files) the specification of the hour and minute is defined differently (1-24; 0-23; or 0-59;1-60 with different interpretations of these times). In order to avoid errors from automated conversions or incorrect file interpretation when using climate data in simulations, the IBK simulation programs use their own climate data format (*.c6b files), which are created with the CCM-Editor and are supplied with the simulation programs.


The tool CCM-Editor (downloadable in the Download area) serves

  • the conversion or import of other climate data formats,
  • the presentation and checking of the data,
  • the data transfer from/to spreadsheet programs (Excel, LibreOffice/Calc, etc.), and naturally
  • the creation or editing of c6b files.

An extenisve documentation explains the import and conversion functionalities, among others also the transfer/import of older ccd files from DELPHIN 5.

The c6b climate data format

The c6b format is a binary data format (therefore not to be edited directly with a text editor), therefore the tool CCM-Editor can be used to create and edit these files.

The data format saves exactly (and exclusively) the climate components, which are used in the IBK simulation programs:

  • temperature,
  • relative humidity,
  • direct short wave solar radiation in normal direction,
  • diffuse short wave solar radiation on a horizontal plain,
  • long wave radiation of the sky,
  • wind direction,
  • wind velocity,
  • air pressure and
  • precipitation.

Not all climate components are used in all simulation programs, e.g. THERAKLES and NANDRAD do not need precipitation data. With DELPHIN, it depends on the choice of the boundary conditions to be considered which climate data are needed.

In c6b files, cyclically applicable yearly data can be stored in hourly grids, as well as any time grids, even over several years, with flexible time steps and start and end times (ideal for measurement data). Missing climate data are marked accordingly in the file, so that simulation programs can check the availability and, if necessary, inform the user about missing data (instead to calculate with incorrect values).

The c6b data format is specified in the following publication:

Nicolai, A.: DELPHIN 6 Climate Data File Specification, Version 1.0, 2017, Technischer Bericht, Qucosa,

Reading C6B with Python

Here is a script to read (and potentially write) C6B data files with Python:


Climate data sources

The IBK simulation programs are delivered with a climate data base. For licensing reasons, most climate data from weather services must be obtained directly from these providers. Basically, this is no problem, because most formats can be read in the CCM-Editor without much effort and then saved in c6b files for DELPHIN, THERAKLES and NANDRAD.

Own climate data can then be copied into the user-specific climate data directory of the respective simulation program (the corresponding import functionality is available in the DELPHIN 6 interface).

EnergyPlus Weather Data Directory

Another data source are the EnergyPlus weather data. Here you can download epw files with the usual climate components for energetic building simulations, but without precipitation data, for worldwide distributed locations. epw data as well as wac- and c6b data can be used directly in IBK simulation programs, but also here the recommendation of a previous sighting and checking of the data in the CCM-Editor applies.

Other sources for climate data

On this page in the DELPHIN forum, you will find further sources for climate data that you can integrate in the IBK software programs.

Implementation of Hygrothermal Reference Years

For hygrothermal simulations at German sites, Hygrothermal Reference Year (HRY) are also used. These climate data have been specially developed for hygrothermal simulations and also allow local climatic influences to be taken into account with the help of correction factors.

The climate data are generated with the so-called local climate generator, which can be downloaded and installed from the webpage The documentation of the local climate generator explains how to adapt a climate, which is then saved in wac format. These data can be used directly in DELPHIN, THERAKLES and NANDRAD (also without conversion) or can be copied directly into the climate data directories/databases. However, we would recommend the import in the CCM-Editor to view the data there again (especially the result of the solar radiation conversion) and then generate c6b files for the simulation.

Implementation of Test Reference Years of the DWD from the year 2017

In their climate databases, the IBK software programs have TRY climate data (Test Reference Year) of the German Weather Service (DWD) from 2011 at their disposal, which also contain the appropriate precipitation data. More recent TRY data of the DWD from the year 2017 can be generated extremely precisely, i.e. down to the square kilometre. However, these data records do not contain precipitation data. The principles of these climate data and a free interface to generate climate files are available on the website

A direct import possibility of such dat files, analogous to e.g. wac files, will be provided shortly. In the meantime, these files can be converted to a c6b file using the CCM-Editor. To do this, you must first import the files into a spreadsheet program (e.g. LibreOffice/Calc or Excel). From there you can copy the individual columns directly into the CCM-Editor and generate a c6b climate file (see help of CCM-Editor). This file again can be imported and used in DELPHIN, THERAKLES or NANDRAD.

Older Test Reference Years of the DWD

Older TRY and TM2 data of the German Weather Service can be imported with the import assistant of the CCM-Editor and converted into c6b files.


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