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Post-processing method to reduce noise while preserving high time resolution in aethalometer real-time black carbon data
Citation:
HAGLER, GAYLE SW, TIFFANY LB YELVERTON, R. VEDANTHAM, AND A. Hansen. Post-processing method to reduce noise while preserving high time resolution in aethalometer real-time black carbon data. AEROSOL AND AIR QUALITY RESEARCH . Chinese Association for Aerosol Research in Taiwan, , Taiwan, Province Of China, 11(5):539-546, (2011).
Impact/Purpose:
journal article
Description:
Real-time aerosol black carbon (BC) data, presented at time resolutions on the order of seconds to minutes, is desirable in field and source characterization studies measuring rapidly varying concentrations of BC. The Optimized Noise-reduction Averaging (ONA) algorithm has been developed to post-process data from the aethalometer, one of the widely used real-time BC instruments. The ONA program conducts adaptive time-averaging of the BC data, with the light attenuation through the instrument's internal filter as the variable determining the time window of averaging. Therefore, averaging windows are expanded at low filter loading rates and reduced at high filter loading rates, allowing significant trends in data to be displayed with minimum distortion, while reducing overall noise in the data. Analysis of instrument noise and the ONA algorithm performance was conducted using aethalometer 1-second data from a soot generation experiment, where BC concentrations were maintained at a constant level and thus instrument-generated noise could be isolated. In this study, the ONA process leads to noise exponentially dropping with an increasing minimum value. The cook stove and indoor studies both originally had approximately 30% negative values in their data, a consequence of instrument noise combined with low sample concentrations. The ONA process reduced the occurrence of negative values to 0% while preserving the display of significant variations in the measurements
