October 15, 2021

13th WMO International Pyrheliometer Comparisons IPC-XIII

Physikalisch-Meteorologisches Observatorium Davos und Weltstrahlungszentrum

Welcome to the IPC-XIII, FRC-V and IPgC-III Comparisons which will be held between Monday 27 September and Friday 15 October 2021 at PMOD/WRC in Davos Dorf, Switzerland. Participation is free-of-charge and open to all WMO-affiliated (RRC, NRC) or WMO-related institutions, such as national hydrometeorological services. Manufacturers of radiometric equipment, calibration and research institutions, and other stakeholders are also welcome to register.

The IPC-XIII will issue WRR factors to all pyrheliometers that are participating in this campaign. WRR factors from IPCs are a generally accepted proof of metrological traceability to the World Radiometric Reference (WRR).

Covid Guidelines during the IPC/FRC/IPgC Inter-Comparisons

Important – Please read our updated Covid Guidelines → 

Organisation of the Measurements

The measurement will be taken in series of 19.5 mins duration, re-starting every 30 mins. The starting time of the series is defined as the time of the first irradiance measurement. Self-calibration sequences or closed measurements should be completed before the starting time of the series. The measurement cadence is one irradiance reading per 90 seconds, resulting in 14 irradiance values per series. Please configure your pyrheliometers and/or data acquisition systems to run with this cadence or any integer fraction of it.

As an example, if the series starting time is announced at 09:30, make sure to complete any preparatory sequence in time to take irradiance readings at 09:30:00, 09:31:30, 09:33:00, 09:34:30, … 09:37:30, or any suitable subset of these times. The next following series will then start at 10:00. All times are CET (Central European Standard Time), which is one hour behind local time.

All submitted data will be evaluated every evening and the preliminary results will be made available for checking by the participants. On sunny days (including weekends), we will start measurements around 08:00 CET (09:00 local time) and continue until sunset shortly after 16:00 CET (17:00 local time). On overcast/rainy/snowy days we will hold the IPC-XIII Symposium at PMOD/WRC. The symposium will not be held at the weekends.

Each participant will be assigned indoor shelf space for storage and outdoor working space for installing his or her equipment including a table-top solar tracker during measurements. Electricity (230 V, 50 Hz) will be available at each working space. In addition, 6 V DC will be provided for Ångström operators. A voltage of 110 V at 60 Hz can be provided upon request. Requests for additional space (e.g. for a tripod) or special electricity requirements should be sent to Christian Thomann (christian.thomann@pmodwrc.ch), if not already indicated on the registration form. Wireless internet access will be available throughout the institute and measurement field.

Timing and File Format

It is extremely important that all participating pyrheliometers read simultaneously. Therefore, all participants are asked to comply with the timing and data format requirements.

Data Submission

Participants will have to bring all equipment necessary to take irradiance measurements, including voltmeters and solar trackers. The measurement data can be submitted either as raw voltages or irradiance values.

Measurements can be submitted as ASCII files or be typed in manually using the IPC-XIII data submission tool. If you plan to use the IPC-XIII data submission tool please make sure you have a recent web browser installed on your computer or wireless device.

Automated data acquisition systems are required to produce data files according to the timing and data format. A separate file is required for each pyrheliometer.

Event website: https://www.pmodwrc.ch/en/IPC-XIII/