AEROMAP

Global mapping of aerosol properties using neural network inversions of ground and satellite based data

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 Obiettivo del progetto (Objective)

'This project, AEROMAP, is designed to produce accurate, daily-updated, global atmospheric aerosol maps. To achieve this, AEROMAP will use the daily, full-Earth coverage of the aerosol optical depth (AOD) provided by the MODerate resolution Imaging Spectrometer (MODIS) satellite instrument in 3 wavelength bands (438-448nm, 673-683nm, 862-877nm), to extrapolate local, ground-based retrievals of aerosol microphysical properties (AMP) from AEROsol robotic NETwork (AERONET) stations to the entire Earth-surface. Extrapolation will be achieved with multiple-input multiple-output universal function-approximating artificial neural networks that will be trained on AERONET data (the AOD at 440nm, 675nm and 870nm) as input and AERONET-AMP retrievals (the aerosol size distribution, the complex refractive index, the effective radius, and the single scattering albedo) as output, in order to learn the inversion function. A portion of the training dataset will be reserved for validation. In the second step, MODIS broad-band AOD data that is spatially co-located with AERONET single-wavelength AOD data will be used to train a second neural network to learn the mathematical relationship between the broad-band and single-wavelength measurements. Then, the worldwide, daily coverage provided by MODIS will be used extrapolate and retrieve the sought-after AMP worldwide. Modern statistical methods of cluster analysis will be used to classify aerosol type regions and global maps of AMP will be used to provide a new full-Earth (near) real-time monitor to globally characterise atmospheric aerosols. Aerosol dispersal during selected events will test the validity of the monitor and a project website/portal will provide users access to global AMP maps, raw data and early-warning alerts of extreme aerosol conditions worldwide.'

Introduzione (Teaser)

An EU study worked to determine the role of atmospheric aerosols in climate processes. Satellite data show the distribution of atmospheric particle sizes, facilitating constant monitoring, issue of warnings, and better understanding of the dynamics.

Descrizione progetto (Article)

Aerosols are small particles suspended in the air, and can be of either natural or man-made origin. They play a significant role in climate change; however, the exact extent is unknown.

The issue is an international research priority, and the EU funded the two-year AEROMAP project to investigate. The key question was how aerosol quantities and compositions vary around the globe and over time, which the project addressed using daily whole-Earth satellite maps. The goal was to subdivide the globe into distinct aerosol types, and to show the distribution of particle sizes in the atmosphere.

Additionally, the project tested the feasibility of performing global real-time aerosol monitoring. The team further considered constructing an air quality index to assess climatic risks and issue alerts regarding aerosol impact. The project wound up in early 2014.

AEROMAP developed and validated new data mining tools, based on cluster analysis and neural networks. The tools convert satellite data into aerosol microphysical properties for various globally distributed aerosol types. The near-daily maps allow monitoring and classification of aerosols as they move about the Earth.

Concerning the feasibility studies, AEROMAP determined that average global distribution of aerosols can be separated into 10 distinct regions, each having a particular composition. Neural network models analysed eight years of daily data for each region. The models were validated in terms of being able to retrieve aerosol microphysics.

Hence, the project produced global maps showing size distributions of atmospheric aerosols, used to monitor the evolution of atmospheric events. It was not previously possible to observe the evolution of such events, especially over large uninhabited areas such as deserts or oceans. The study also created the first near-daily maps of global air quality produced from aerosol microphysics rather than chemistry. The team developed two indices showing potential impact on health and visibility.

The research yielded two conference presentations and four journal papers.

AEROMAP provided a new understanding of the dynamics of atmospheric aerosols, an important factor in climate change. The project enabled use of satellite data to create almost-daily whole-Earth maps of aerosol properties and their effects.