MORDOR (MObile RaDiation ObseRvatory)

The MObile RaDiation ObseRvatory (MORDOR) was developed at TROPOS for a complete as possible measurement of radiation parameters. The flexible mounting design enables operation in worldwide measurement campaigns of TROPOS since 2013. A long-term goal is to suffocate the BSRN requirements. MORDOR includes several stations, ready to be set up on upcoming campaigns or integrated into the LACROS infrastructure. So far, MORDOR has been used in a number of TROPOS measurement campaigns, including HOPE-Melpitz, MelCol, PASCAL, Cy-CARE, MetPVNet.

MORDOR provides ground-based reference observations of radiation parameters for the investigation of cloud and aerosol radiative effects (e.g., Fountoulakis et al., 2021), satellite product evaluation and cross-calibration of the Pyranometer-Network (Madhavan et al., 2016, 2017).

Elements of a MORDOR station

• Secondary standard pyranometer: Up to three secondary standard pyranometers (models: Kipp & Zonen CMP21; EKO Instruments MS-80) are used to measure the global, diffuse, and upwelling shortwave (solar) irradiance.

• Photoelectrical pyranometer: Measurements of secondary standard pyranometers (thermoelectric) are accompanied by photoelectrical pyranometers (model: EKO Instruments ML-020VM). The spectral response is limited to 0.3 to 1.1 μm, and is a well known constraint of this type of pyranometer, due to the narrow spectral response of the used silicon photodiode. But, in comparison to a secondary standard thermopile pyranometer, this sensor has a superior response time, which enables a sampling frequency of 10 Hz. The pyranometer models used are the same as used for the Pyranometer-Network to enable evaluation and cross-calibration techniques.

• Pyrgeometer: Up to two thermoelectrical pyrgeometer model CGR-4 (Kipp & Zonen) are used to measure the global and upwelling longwave (terrestrial) irradiance.

• Pyrheliometer: The direct shortwave irradiance is measured with a pyrheliometer model MS-56 or MS-57 (EKO Instruments) mounted on the sun tracking system.

• Meteorological Station: MORDOR radiation observations are accompanied by regular observations of surrounding air pressure, temperature and humidity using the weather station model WS-300 (Lufft).

• Suntracker: As sun tracking system, the EKO Instruments models STR-21 and STR-22 are used. The suntracker follows the sun in azimuth- and zenith-angle. Inside the suntracker a GPS-module is mounted to get an exact positioning as well as a sun position retrieval. The pyrheliometer is mounted at one arm of the suntracker, so that it looks exactly into the sun. The pyranometers mounted on top of the suntracker are shaded with a shading-ball system, which was build by the TROPOS-Workshop, to measure the diffuse irradiance.

• Total-sky Imager: Images of the full sky are taken on a regular basis using a fish-eye camera   (model Vivotek FE8172V). These images provide insight on the current atmospheric state, enable products of cloud fraction and are used for maintenance on remote locations.

• Datalogger: For data acquisition, a datalogger model CR1000 from Campbell Scientific is used.