Rehabilitation of SRRL Aerosol Optical Depth Photometer Data

NREL’s Solar Radiation Research Laboratory (SRRL) utilizes a Prede POM-01 Photometer to collect aerosol optical depth (AOD) information, necessary for determining the performance of solar collector systems. Inconsistencies and errors exist in SRRL’s AOD data due to errors in the calibration factors as well as the data reduction algorithms. Langley plots of five of the channels were performed to calibrate the necessary constants for AOD calculations. Clear sky data was determined based on the ratio of direct to global radiation and on the scatter between morning and afternoon TWC 500 nm photometer (an NREL custom photometer) data. Plots of calculated intercept values over time indicate two filter channels have slightly degraded while five others have remained constant. Established coefficients were applied to reprocess AOD values, which were then compared with nearby Aeronet data at the BSRN-BAO Boulder site. Averages between the sites in comparison with the former AOD values indicate the new algorithm to be highly successful.