研究目的
To assess the quality of AOD measurements retrieved from MODIS data over Tunisia using ground measurements from AERONET, and to validate MODIS aerosol products for monitoring aerosol variability and identifying dust sources.
研究成果
MODIS aerosol products show good agreement with AERONET measurements over Tunisia, with high correlation coefficients (up to R2=0.9) in certain months. The 50 km x 50 km validation method performs better than the pixel-by-pixel method. MODIS data are reliable for monitoring AOD variability and identifying dust sources in the region, supporting their use in air quality monitoring.
研究不足
The study is limited to one AERONET station (Ben Salem) in Tunisia due to data availability and continuity. The validation may be affected by cloud screening and time differences in data acquisition. The pixel-by-pixel method showed lower correlation in some months, indicating potential issues with spatial averaging and point measurements.
1:Experimental Design and Method Selection:
The study uses MODIS Collection 6 aerosol products and AERONET ground-based data for validation. Two validation methods are employed: a spatial-temporal method (50 km x 50 km area around the station) and a pixel-by-pixel method. Statistical analysis with linear regression is used to compute correlation coefficients.
2:Sample Selection and Data Sources:
Data from the Ben Salem AERONET station in Tunisia for the year 2014, specifically for January, April, August, and November. MODIS data from the AQUA satellite are downloaded from the LAADS website.
3:List of Experimental Equipment and Materials:
MODIS sensor on AQUA satellite, AERONET CIMEL sun photometer at Ben Salem station, HDFView software for data extraction, Microsoft Excel for data processing.
4:Experimental Procedures and Operational Workflow:
Extract AOD values from MODIS HDF files for a 50 km x 50 km area centered on the AERONET station. Retrieve AERONET AOD data within 30 minutes of MODIS overpass time. Interpolate AERONET AOD to 550 nm using ?ngstr?m exponent. Compute mean AOD values and perform linear regression analysis to compare MODIS and AERONET data.
5:Data Analysis Methods:
Linear regression analysis to determine correlation coefficients (R2) between MODIS and AERONET AOD values. Use of quality-assured and non-quality-assured data flags from MODIS.
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