Data files from a Multifilter Rotating Shadowband Radiometer (MFR-7)
MFR data files are ASCII files in monthly blocks from 1999 to present. The file names start with "EUMFR" to denote the type of data. This is followed by the year and the month. The last digits indicate if the file has 1-minute (01), 2.5-minute (02.5), or 5-minute (05) data. The first line of the file has the header with information on the data in each column. The first three columns are time columns. The first column is the yearday and fraction of the day, the second column is related to UTC time, and the third column is the minutes into the day.
These files contain global, diffuse, and direct normal beam measurements from one broad band sensor and six narrow band sensors. A shadowband shades the sensor once each measurement interval to measure the diffuse radiation. The diffuse irradiance is corrected for the shading of the shadowband itself by performing similar measurements with the shadow band positioned slightly to the left and right of the sensor immediately prior to, and after, the diffuse measurement. The direct normal values are obtained by subtracting the diffuse irradiance from the global irradiance and projecting the result to normal incidence (dividing by the cosine of the solar zenith angle).
The spectral filters of MFR degrade with time and the instrument should be regularly calibrated. Since calibrations are not done regularly, Langley plots can be used to track the filter's response degredation and obtain a more accurate absolute estimate of the incident radiation measured by each of the six narrowband filters. The Langley plots yield fairly accurate corrections since the incident solar radiation outside the earth's atmosphere is well known. One can use Lanley plots during clear mornings or evenings to adjust the absolute values. Langley plot can also be used to estimate the aerosols in the atmosphere.
Each MFR-7 ships with calibration and angle correction files (having file extensions ".cal" and ".sol", respectively) Occasionally, along with the equipment itself, these files undergo modifications, and care must be taken to ensure that the correct set of these supplementary files are used along with specific data files. We have used these files when creating the ASCII files and they are available for download on the MFR page as supplementary information.
© 2013, UO Solar Radiation Monitoring Laboratory.
Last revised: July 11, 2013.
Home page URL: solardat.uoregon.edu