The Formation to Long-term Trend of Fine-mode Particles: In-situ Observation and Remote Sensing of Anthropogenic Aerosols in China

Abstract:

Anthropogenic aerosols are typically of fine size chiefly consist of secondary aerosols originated from new particle formations (NPF). Of no doubt, the NPF entails the presence of aerosol precursor gases whose concentrations in a generally polluted environment like China are always plentiful so that its occurrence should ubiquitously popular. Observations of NPF and growth in numerous places in China do not support this from which we proposed a physical mechanism, namely turbulence, that also plays a key role in the NPF. Turbulence dictates both the NPF and its growth/decay and thus influence the fine-mode fraction of aerosols. Aerosol optical depth (AOD) has been a standard product generated from virtually all satellite sensors with visible and/or UV channels. However, much less has been retrieved for the fine-mode AOD, or fine-mode fraction (FMF), which is fraught with much larger uncertainties than total AOD, and so are for ground-level particulate matter (PM). PM with diameters less than 1 and 2.5 μm (PM₁ and PM_2.5, respectively) are key measures of surface air pollution primarily generated by human activities, which is exceptionally heavy in China. We have developed a suite of novel remote sensing algorithms, including both physical and machine learning (ML) approaches, for retrieving the three quantities of fine-mode aerosols that have been applied to a series satellite sensors (MODIS, VIIRS, Himawari, etc.) for generating the climatologies of these anthropogenically dominated aerosols. They are used to tackle with their term-trends and to gauge the effects of numerous emission control measures implemented in China for both short-term events and long-term goals.