Physical Characterization of Aerosols by Using Space-Borne and Ground-Based Observations in the Eastern Mediterranean Basin

Abstract

Aerosol particles in the atmosphere have many impacts regarding global energy budget, air quality, and climate. Among these particles, mineral dust is one of the most abundant, with millions of tons lifted from deserts and transported across the globe each year. This movement of desert dust affects atmospheric processes, impacts regional and global climate patterns. My research is a part of TUBITAK COST Project “Determination of Dust Transport Pathways & Natural Dust Contribution in Southern Regions of Turkey”. The objective of the project is to determine the effect of natural desert dust transport on air quality in Eastern Anatolia and Western Mediterranean regions, both qualitatively and quantitatively. The goal of my research aim is to investigate the physical characteristics of atmospheric aerosols by using observations in the Eastern Mediterranean region including Türkiye. Since the physical properties of the aerosols are needed to be examined better, satellite-based remote sensing and ground observations have a fundamental importance for the understanding of aerosol processes and desert dust contribution to air quality. This study presents a comprehensive analysis of aerosol optical depth (AOD) over the Eastern Mediterranean and Levantine regions, focusing on long-term trends, seasonal variations, and validation of satellite-derived AOD measurements using ground-based AERONET data. The first objective to analyze AOD of Moderate Resolution Imaging Spectroradiometer (MODIS) on the Aqua satellite and Visible Infrared Imaging Radiometer Suite (VIIRS) on Suomi NPP satellite and compare datasets of these two instruments. Satellite observations from MODIS (2003–2023) and VIIRS (2012–2023) instruments are compared, providing insights into spatial and temporal aerosol patterns. Another objective is to evaluate the variability and reliability of AOD measurements between satellite and ground-based observations and to determine how well they represent regional climatology. Therefore, the study evaluates the performance of MODIS and VIIRS AOD products with a comparative analysis of AOD data from AERONET during different periods between 2003 and 2023 at four stations: IMS-METU-ERDEMLI (Mersin/Türkiye) (2004–2019), CUT-TEPAK (Limassol/Cyprus) (2010–2023), Cairo_EMA_2 (Cairo/Egypt) (2010–2023), and SEDE_BOKER (Sede Boker/Israel) (2003–2023). These stations provide diverse environmental conditions, ranging from coastal to desert regions, enabling a comprehensive evaluation of aerosol behavior. The study also considers the influence of cloud fraction on MODIS measurements and includes aerosol classification based on AERONET data. Results reveal distinct seasonal trends, with higher AOD values in spring and summer, driven by dust transport from North Africa and the Arabian Peninsula, while winter months show lower AOD due to reduced dust activity. Among the regions studied, the Northern Arabian Peninsula exhibits the highest mean AOD, while Türkiye has the lowest mean AOD AOD trends show an increasing pattern from 2003 to 2009, followed by a statistically significant decrease from 2009 to 2023 in most sub-regions, especially in the Eastern Mediterranean Basin and Türkiye. Validation of MODIS and VIIRS data against AERONET measurements shows strong correlations at IMS-METU-ERDEMLI (MODIS: R=0.86 and VIIRS: R=73) and CUT-TEPAK (MODIS: R=0.87 and VIIRS: R=76), but weaker correlations at SEDE_BOKER and Cairo_EMA_2. The highest percentage of measurements within the expected error envelope was observed at the IMS-METU-ERDEMLI station, indicating the best agreement between MODIS and AERONET data at this location. The Seasonal-Trend Decomposition using Loess (STL) method revealed consistent spring and summer peaks influenced by dust transport from the Sahara and the Middle East, with lower values in winter. This study utilizes the longest data sets ever used for the Levant region, and no similarly comprehensive research has been conducted in this area before. The results of this study agree with those of previous research on the atmospheric aerosols, emphasizing the importance of integrating satellite and ground-based observations.