Data quality check and data processing
Data quality is controlled with following two manners.
- On-site hardware check (maintenance); once per year in average.
- Replace flashlamp to keep the output power of the Nd:YAG laser.
- Adjust beam alignment.
- Obtain reference profiles for calibrating the depolarization ratio using a sheet polarizer placed before the ploarzation analyzer at an angle of 45 degrees.
- Replace interference filters (occasionally).
- Data processing in NIES
- Estimate (initial) system constant with distribution function of backscatter intensity.
- Determine the upper limit of the analysis based on SNR.
- Detect cloud base and apparent cloud top height with gradient method.
- Reject rainy/snowy/foggy profiles.
- Invert lidar equation with Fernald's method.
- Determine (final) system constant.
References
Atsushi SHIMIZU, Nobuo SUGIMOTO, Ichiro MATSUI, DETAILED DESCRIPTION OF DATA PROCESSING SYSTEM FOR LIDAR NETWORK IN EAST ASIA, 25th International Laser Radar Conference, St. Petersburg, Russia, pp.911-913, 2010. [pdf(197K)]
A. Shimizu, N. Sugimoto, I. Matsui, K. Arao, I. Uno, T. Murayama, N. Kagawa, K. Aoki, A. Uchiyama, and A. Yamazaki, Continuous observations of Asian dust and other aerosols by polarization lidar in China and Japan during ACE-Asia, J. Geophys. Res., 109, D19S17, doi:10.1029/2002JD003253, 2004.