Makiko Hashimoto

Development of a remote sensing algorithm to retrieve atmospheric aerosol properties using multiwavelength and multipixel information

We developed a satellite remote sensing algorithm to retrieve the aerosol optical properties using satellite-received radiances for multiple wavelengths and pixels. Our algorithm utilizes spatial inhomogeneity of surface reflectance to retrieve aerosol properties, and the main target is an urban aerosols. This algorithm can simultaneously retrieve aerosol optical thicknesses (AOT) for fine- and coarse-mode aerosols, soot volume fraction in fine-mode aerosols (SF), and surface reflectance over heterogeneous surfaces such as urban areas that are difficult to be obtained by conventional pixel-by-pixel methods. We applied this algorithm to radiances measured by the Greenhouse Gases Observing Satellite / Thermal and Near Infrared Sensor for Carbon Observations-Cloud and Aerosol Image (GOSAT/TANSO-CAI) at four wavelengths and were able to retrieve the aerosol parameters in several urban regions and other type surfaces. A comparison of the retrieved AOTs with those from the Aerosol Robotic Network (AERONET) indicated retrieval accuracy within ±0.077 on average. It was also found that the column-averaged SF and the aerosol single scattering albedo (SSA) underwent seasonal changes as consistent with the ground surface measurements of SSA and black carbon at Beijing, China.

Simultaneous retrieval of aerosol optical thickness and chlorophyll concentration from multiwavelength measurement over East China Sea

A flexible inversion algorithm is proposed for simultaneously retrieving aerosol optical thickness (AOT) and surface chlorophyll a (Chl) concentration from multiwavelength observation over the ocean. In this algorithm, forward radiation calculation is performed by an accurate coupled atmosphere-ocean model with a comprehensive bio-optical ocean module. Then, a full-physical nonlinear optimization approximation approach is used to retrieve AOT and Chl. For AOT retrieval, a global three-dimensional spectral radiation-transport aerosol model is used as the a priori constraint to increase the retrieval accuracy of aerosol. To investigate the algorithms availability, the retrieval experiment is conducted using simulated radiance data to demonstrate that the relative errors in simultaneously determining AOT and Chl can be mostly controlled to within 10% using multiwavelength and angle covering in and out of sunglint. Furthermore, the inversion results are assessed using the actual satellite observation data obtained from Cloud and Aerosol Imager (CAI)/Greenhouse gas Observation SATellite GOSAT and MODerate resolution Imaging Spectroradiometer (MODIS)/Aqua instruments through comparison to Aerosol Robotic Network (AERONET) aerosol and ocean color (OC) products over East China Sea. Both the retrieved AOT and Chl compare favorably to the reported AERONET values, particularly when using the CASE 2 ocean module in turbid water, even when the retrieval is performed in the presence of high aerosol loading and sunglint. Finally, the CAI and MODIS images are used to jointly retrieve the spatial distribution of AOT and Chl in comparison to the MODIS AOT and OC products.

Development of a quality control algorithm for analysis of SKYNET data and an estimation of the single scattering albedo

We conducted sensitivity tests for parameters in the process of analysis by SKYRAD.pack to investigate the error causes in aerosol single scattering albedo (SSA) for SKYNET, and we found that ground surface albedo (Ag), instrument solid view angle (SVA) and calibration constant (F0), which are input values in analysis, are the error causes in SSA, and F0 is also an error cause in AOT. Testing the inversion methods used in SKYNET, we found advantages and disadvantages in present (Phillips-Twomey) and MAP method in the cases that there are large particles in the atmosphere, e.g. large dusts or cirrus contaminations. The results suggest a new data screening or quality control method to select high quality data to be used for aerosol retrievals. We applied this screening method for real data at the Pune site in India, and found a large number of data, for which the values of SSA are close to unity, were removed as cirrus contamination data, and the variability of SSA was reduced.