The Austrian radiation monitoring network ARAD – best practice and added value

• Published in: Atmospheric measurement techniques 2016-04, Vol.9 (4), p.1513-1531
• Main Authors: Olefs, Marc, Baumgartner, Dietmar J., Obleitner, Friedrich, Bichler, Christoph, Foelsche, Ulrich, Pietsch, Helga, Rieder, Harald E., Weihs, Philipp, Geyer, Florian, Haiden, Thomas, Schöner, Wolfgang
• Format: Article
• Language: English
• Subjects: Accuracy; Actinometers; Algorithms; Atmospheric models; Automatic control; Best practice; Broadband; Calibration; Climate change; Climate models; Climate monitoring; Confidence intervals; Control equipment; Corrections; Data acquisition; Data analysis; Data processing; Data quality control; Diffuse radiation; Dimensions; Direct solar radiation; Fluxes; Global radiation; Infrared instruments; Infrared radiation; Instrument accuracy; Instrumentation; Instruments; Measurement; Monitoring; Monitoring instruments; Pyranometers; Quality assurance; Quality control; Quality standards; Radiation measurement; Radiation monitoring; Radiation standards; Short wave radiation; Solar energy; Solar radiation; Stations; Uncertainty
• ISSN: 1867-8548; 1867-1381; 1867-8548
• DOI: 10.5194/amt-9-1513-2016

The Austrian RADiation monitoring network (ARAD) has been established to advance the national climate monitoring and to support satellite retrieval, atmospheric modeling and the development of solar energy techniques. Measurements cover the downward solar and thermal infrared radiation using instruments according to Baseline Surface Radiation Network (BSRN) standards. A unique feature of ARAD is its vertical dimension of five stations, covering an altitude range between about 200 m a.s.l (Vienna) and 3100 m a.s.l. (BSRN site Sonnblick). The paper outlines the aims and scopes of ARAD, its measurement and calibration standards, methods, strategies and station locations. ARAD network operation uses innovative data processing for quality assurance and quality control, utilizing manual and automated control algorithms. A combined uncertainty estimate for the broadband shortwave radiation fluxes at all five ARAD stations, using the methodology specified by the Guide to the Expression of Uncertainty in Measurement indicates that relative accuracies range from 1.5 to 2.9 % for large signals (global, direct: 1000 W m−2, diffuse: 500 W m−2) and from 1.7 to 23 % (or 0.9 to 11.5 W m−2) for small signals (50 W m−2) (expanded uncertainties corresponding to the 95 % confidence level). If the directional response error of the pyranometers and the temperature response of the instruments and the data acquisition system (DAQ) are corrected, this expanded uncertainty reduces to 1.4 to 2.8 % for large signals and to 1.7 to 5.2 % (or 0.9–2.6 W m−2) for small signals. Thus, for large signals of global and diffuse radiation, BSRN target accuracies are met or nearly met (missed by less than 0.2 percentage points, pps) for 70 % of the ARAD measurements after this correction. For small signals of direct radiation, BSRN targets are achieved at two sites and nearly met (also missed by less than 0.2 pps) at the other sites. For small signals of global and diffuse radiation, targets are achieved at all stations. Additional accuracy gains can be achieved in the future through additional measurements, corrections and a further upgrade of the DAQ. However, to improve the accuracy of measurements of direct solar radiation, improved instrument accuracy is needed. ARAD could serve as a useful example for establishing state-of-the-art radiation monitoring at the national level with a multiple-purpose approach. Instrumentation, guidelines and tools (such as the data quality control) developed w