Concentration of suspended particulate matter less than 2.5 μm (PM2.5) is a representative parameter of air quality.
Simultaneous measurements of PM2.5 and the column aerosol optical thickness (AOT) have been performed at a
NASA/AERONET station, Higashi-Osaka, Japan since March 2004. They successfully provide a linear correlation
between PM2.5 and AOT. A Mie scattering lidar instrument was deployed at the same observational site in April, 2008.
It provides us with the attenuated backscattering coefficients of aerosols at wavelengths of 0.532 and 1.064 μm, which
indicate the vertical distribution of aerosols. This work intends to improve the correlation between AOT and PM2.5 by
using the measurements of lidar.
Acquisition of aerosol information on a global scale, especially over the continent, is an urgent task for the better understanding of Earth's radiation budge and climate change. However, it is known that aerosol retrieval over land is much more difficult than that over ocean due to the complication of surface properties. A polarization sensor POLDER boarded on the satellite ADEOS-1 and -2 has shown that the polarization information is useful to extract the aerosol properties such as AOT (Aerosol Optical Thickness), and its wavelength tendency (Angstrom exponent) not only over the ocean but also over the land. Recently the polarization sensor becomes to be noticed. At such a time, this work focuses on role of polarization information from the point of view for aerosol retrieval. As a result, an improved map of aerosol is obtained based on POLDER-2 data. The obtained space based aerosols are examined with the radiometric measurements from the ground.
Improved retrieval algorithms for aerosols, clouds and water vapor content from satellite data are described. A POLDER sensor, mounted on the Earth observation satellite ADEOS in 1996, is a unique sensor, which can gather multi-directional (up to 14) polarization measurements of one target. The POLDER sensor has been mounted on the satellite ADEOS-II launched on 14 December in 2002. Aerosol and cloud properties are derived from the POLDER polarization data over the land and the ocean. In addition POLDER data in the near infrared wavelengths are available to estimate the total column content of atmospheric water vapor. It is well known that the thermal data are useful for retrieval of cloud properties and water vapor contents over the ocean. Therefore combination use of ADEOS/POLDER and OCTS is considered for retrieval of atmospheric hydrologic substances in this study. The satellite derived results are validated with the ground-based data as AERONET. The obtained global maps of aerosol and cloud properties, and water vapor content are compared with one another. It is shown that column number density of aerosols has a negative correlation with the effective radius of cloud particles and proportionally correlates with the optical thickness and the column number density of cloud particles. These results confirm the indirect effect of aerosols, namely aerosols play sufficient role as cloud condensation nuclei.
We intend to propose the effective procedure for aerosol retrieval for ocean color remote sensing. Ocean color sensors are designed to monitor the oceanic and atmospheric environments with near infrared (NIR) data as well as ocean color data. Aerosol properties such as optical thickness of aerosols. Angstrom exponent etc. are usually retrieved from reflectance observed in the NIR region based on one- or two- channel algorithm. In addition we found that polarization degree is useful to estimate such an optical constant of aerosols as refractive index, and polarized reflectance is especially available to retrieve the continental aerosols. It is of interest to mention that the aerosol retrieval is greatly improved once the observed quantities have been provided together with the sufficient directional information. Several algorithms for aerosol retrieval are examined and compared with each other using ocean color sensor data from CZCS to SeaWiFS.
This paper describes how to retrieve the optical properties of atmospheric aerosols over the ocean from ADEOS/POLDER measurements. POLDER provides the polarization and directional information of reflected light by the Earth's atmosphere and/or surface. The extracting algorithm for aerosols is based on the look-up table method. Our look-up table is compiled by multiple scattering simulations in an atmosphere-sea surface system. As result, global monthly mean aerosol properties, e.g. optical thickness of aerosols and Angstrom exponent, are obtained. It is found that the specific features of maritime aerosols are shown from our result. In addition, it seems that continental aerosols are blown over the ocean in April in the west Pacific Ocean and in the west coast of middle Africa. Our procedure is validated using the ship-based measurements.
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