EMDO senior research scientist, Dr. Jianjun Liu attended the 99th American Meteorological Society (AMS) annual conference during early January 2019 in Phoenix, AZ. He gave two presentations entitled “Estimating Hourly PM2.5 Concentration from Satellite Measured Top of Atmosphere Reflectance by Using a Machine Learning Algorithm” and “Aerosol Swelling: A Major Source of Error When Estimating the Aerosol First Indirect Effect”, respectively.In the PM2.5 presentation, Dr. Liu introduced a novel method to estimate the surface PM2.5 concentrations based on an ensemble machine learning algorithm by directly using the satellit emeasured top-of-atmosphere (TOA) reflectance as inputs instead of AODs, which are the most previous studies used. The algorithm is demonstrated to perform well across China with high accuracies at different temporal scales. This study proposes a short-cut solution for PM2.5 concentration estimations from satellite observations by directly using TOA reflectance which can circumvent the numerous sources of errors in the retrievals of AOD.
In his aerosol first indirect effect studies, he identified and quantified the influence of aerosol hygroscopicity and the swelling effect on the aerosol first indirect effect (FIE) by using the extensive measurements of aerosol and cloud properties made at four Atmospheric Radiation Measurement (ARM) sites around the world. This study indicated that a one-unit enhancement in the aerosol scattering coefficient by the swelling effect leads to a systematic underestimation of the FIE by about 23%. The result likely contributes significantly to the systematic difference between observation-based, especially satellite-based, estimates of the FIE and those simulated by general circulation models.
Dr. Liu has engaged in a wide range of studies concerning remote sensing of air pollution and their impact on the radiation, cloud and climate issues. As young scientist, Dr.Liu has dedicated his expertise to share with peers and society. Congratulations to him! We are always happy to connect with community, and discuss future trends, contribute more efforts to the world’s environmental development. It’s going to be a great motivation for us to promote open science, broad communication and public engagement in earth science.
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