Extended aerosol optical depth (AOD) time series analysis in an Alpine valley: a comparative study from 2007 to 2023

Abstract

This study presents an extended analysis of aerosol optical depth (AOD) at 501 nm in the Alpine valley of Innsbruck, Austria, from 2007 to 2023, and offers a comparative analysis with the Alpine station of Davos, Switzerland. AOD is derived from ground-based sun photometer measurements of direct spectral irradiance during daytime. The Davos Station is part of the AErosol Robotic NETwork (AERONET), a global network providing high-quality, ground-based remote sensing aerosol data, and complies with the relevant requirements. The Innsbruck Station does not belong to AERONET, but the AOD retrieval algorithm is very similar. Building upon previous research conducted until 2012, the presented study aims to provide a comprehensive understanding of the long-term trends and seasonal variations in aerosol characteristics in central Alpine regions. We observed the typical mid-latitude annual cycle with a maximum in July and a minimum in December. The AOD trends per decade for both stations are declining: -27.9×10-3 for Innsbruck and -9.9×10-3 for Davos.