Evaluation of the dust-dominated total AOD extracted from the PMAp satellite Climate Data Record

Abstract. The Polar Multi-Sensor Aerosol optical properties product (PMAp) provides global Aerosol Optical Depth (AOD) observations that are retrieved using a combination of measurements from instruments onboard the Metop satellites, including the Global Ozone Monitoring Experiment-2 (GOME-2), the Infrared Atmospheric Sounding Interferometer (IASI), and the Advanced Very High Resolution Radiometer (AVHRR). The PMAp Climate Data Record (CDR), published in 2022, comprises data from the Metop-A and Metop-B satellites covering the period from 2007 to 2019. The PMAp also includes classification for selected aerosol types, including dust. Based on the classification, a dust-dominated total AOD can be extracted. The focus of this work is to assess the dust aerosols in the PMAp CDRs, by analysing the spatio-temporal occurrence of dust and aerosol classification reliability, as well as by carrying out dust-dominated total AOD validation against AErosol RObotic NETwork (AERONET) observations. Our results show that the occurrence and classification of PMAp dust-dominated AOD agrees well with AERONET metrics. For PMAp dust-dominated total AODs, moderate to strong correlations with AERONET (0.45–0.8) are observed, while mean biases exhibit relatively high variability. The root-mean-square errors (RMSEs) typically represent 50–80 % of the mean AERONET AOD conditions. As most of the comparisons here occur at relatively high AOD levels over bright land surfaces, where measurement uncertainties and variability are inherently greater, this is somewhat expected. The results also bring up certain challenges, e.g. PMAp AOD overestimation at Central Asian AERONET stations or occasional occurrences of dust-dominated total AODs that appeared as clear outliers in AERONET comparisons. Further investigation is needed to determine their underlying causes. On a larger spatial scale, The PMAp CDRs can capture the expected seasonal variation in dust-affected AODs, such as over the Saharan outflow area, but sampling density can vary across seasons, especially over land. Therefore, full AOD distributions, along with median and mean, should be analyzed to ensure accurate conclusions. Despite challenges, the PMAp CDRs show potential for monitoring global dust aerosol patterns.