Abstract
The monitoring capability of a polarized instrument (POLDER) under high aerosol loading conditions over China is investigated. The aerosol optical thickness (AOT), which infers the aerosol burden, is used to measure the satellite monitoring capabilities. AOT products retrieved from POLDER on low aerosol loading days, and products from a radiometric instrument (MODIS) on high and low aerosol loading days, are presented for comparison. Our study reveals that for high aerosol days, the monitoring capability of the polarized instrument is lower than that of the traditional instrument. The accuracy of matched POLDER fine-AOTs is lower than that of MODIS-matched AOTs. On low aerosol loading days, the performance of the polarized instrument is good when monitoring the aerosol optical thickness. Further analysis reveals that for the high aerosol loading days, the mean relative errors of matched POLDER fine AOTs and MODIS AOTs with respect to AERONET measurements are 44% and 16%, respectively. For the low aerosol loading days, the mean relative errors of POLDER and MODIS measurements with respect to AERONET measurements are 41% and 40%, respectively. During high aerosol days, POLDER-retrieved fine-AOTs reveal a poor accuracy with only 14% of matches falling within the error range, which is nearly one fourth of the MODIS regression results (51.59%). For the low aerosol loading days, the POLDER regression results are good. Approximately 62% of the POLDER measurements fall within the expected error range ±(0.05 + 15%) compared with the AERONET observed values.
Highlights
Atmospheric aerosols are composed of solid and liquid particles suspended in air, and they play a significant role in climate change [1,2]
The aerosol optical thickness retrieved products from polarization and directionality of the earth reflectance (POLDER) under low aerosol loading days and from a traditional instrument (MODIS) under high/low aerosol loading days are presented for comparison
Linear regression analysis was performed for MODIS and POLDER aerosol optical thickness (AOT) with respect to Aerosol Robotic Network (AERONET) AOTs, according to the following equation: AOTsatellite =m × AOTAERONET +c where m is the slope, c is the intercept, AOTAERONET represents AERONET AOT, and AOTsatellite represents AOT from the MODIS and POLDER satellites
Summary
Atmospheric aerosols are composed of solid and liquid particles suspended in air, and they play a significant role in climate change [1,2]. Compared with traditional instrumentation (e.g., radiometers), the space-borne multi-angular spectropolarimeters can provide a large amount of raw data, reaching 100 to 400 measurements (components of the Stokes vector for several observation directions and wavelengths) for a given satellite pixel. This abundance of data should increase the accuracy for the retrieval of aerosol properties.
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