Investigation of regional AOD trends in the past 20years using AERONET and MODIS, and their link with biomass burning emissions
Study-Notebook-Functions by Théodore Khadir
Stockholm University, Sweden
Departement of Environmental Science
Work carried out in 2021, within the framework of the eScience course: https://nordicesmhub.github.io/forces-2021/intro.html
This Notebook has been made using the Pangeo Platform
We investigate regional trends in aerosol optical depth (AOD) from both satellite (MODIS) and ground-based (AERONET stations) measurements over land over the past 20 years. A good agreement is found between the two datasets when the spatial coverage of the stations is homogeneous. AOD increases significantly over northern North-America, India, Siberia and southern South America, while it decreases over Europe, Amazonia and southern North-America. In order to estimate the contribution of trends in biomass burning emissions to regional AOD trends, we use the burnt area of the monthly satellite product GFED4 as a proxy to calculate regional trends in biomass burning emissions for the period 2000-2015. Biomass burning emissions increase significantly over northern North America and East Asia, while they decrease over Europe, southern South America and northern Africa. We calculate the correlation between regional area burned and regional AOD to estimate regions where a significant trend in area burned can lead to a significant trend in AOD. We find that the increasing biomass burning emissions in northern North-America is likely to be the cause of the increase in AOD in this region. We also find that the significant increase in biomass burning emissions over East Asia cannot explain the negative observed trend in AOD. The reduction in athropogenic aerosol particle emissions is probably the main driver of the AOD trend in this region. Finally, we construct a multivariate linear model to retrieve the global absolute change in AOD, using only the absolute change in regional burned area for the period 2000-2015. We show that the regional burned area is a good parameter for estimating the trend of AOD in most regions, since the covariation between biomass burning and AOD is strong due to their direct link and dependence to similar teleconnections.
Please contact me if you want to use or cite this work (theodore.khadir@aces.su.se)