Automated Algorithm for Analysis of Long-Term MFRSR Datasets
Abstract
A substantial upgrade of our previously developed MFRSR data analysis algorithm (Alexandrov et al. 2002) is presented.The new version features an automated cloud screening procedure based on optical thickness variability analysis. The technique is objective, computationally efficient and is able to detect short clear-sky intervals under broken cloud cover conditions. A bimodal gamma distribution is adopted as aerosol particle size model. A size of the fine mode particles and a ratio between optical thicknesses of the two modes are retrievable, the coarse mode has a fixed particle size. The aerosol optical thicknesses (total, fine, and coarse) obtained from our analysis were successfully compared with the corresponding AERONET almucantar retrievals from a CIMEL sunphotometer colocated with MFRSR. Besides the aerosol optical thicknesses and the fine mode size, the products of our analysis include time series of column amounts of ozone and nitrogen dioxide. Our algorithm is applied simultaneously to a set of daily MFRSR records covering at least a month of measurements and runs level by level: first all days are cloud screened, then all 870 nm records are calibrated using compatibility between the direct and diffuse measurements, etc. This approach allows for stabilization of the daily calibration constants on each level using a robust smoothing technique. Our preliminary results for September 2000 dataset from the MFRSR network at the Southern Great Plains (U.S. DOE Atmospheric Radiation Measurement (ARM) Program site) showed differences in aerosol fine mode size between the measurement locations. The fine particles appeared to be smaller in the South than in the North with notable anti-correlation observed between the daily mean aerosol fine mode size and the ground temperatures in the data from the northern part of the site.
- Publication:
-
AGU Spring Meeting Abstracts
- Pub Date:
- May 2004
- Bibcode:
- 2004AGUSM.A21A..05A
- Keywords:
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- 0305 Aerosols and particles (0345;
- 4801);
- 0345 Pollution: urban and regional (0305);
- 0394 Instruments and techniques