Evaluating the MONARCH Model with Lidar Data: A Step Toward Improving Global Dust Surface Concentrations

The Barcelona Dust Regional Center (BDRC) provides daily forecasts of dust optical depth and dust surface concentrations, as part and coordination entity of the Northern Africa, Middle East and Europe (NAMEE) node of the World Meteorological Organization Sand and Dust Storm Warning Advisory and Assessment System (WMO SDS-WAS). Dust optical depth forecasts from the NAMEE SDS-WAS ensemble show a relatively good agreement, while the forecasts of dust surface concentrations show larger variability between models. Moreover, the consistency between dust optical depth, as an integrated column quantity, and surface concentration forecasts remains challenging. 

Since July 2024, vertical profiles of dust concentrations from the Multiscale Online Nonhydrostatic AtmospheRe Chemistry (MONARCH) model of the SDS-WAS ensemble have been made public on the BDRC website. This study presents the first evaluation of this new forecast product through comparisons with lidar observations, focusing on vertical profiles of total and dust extinction coefficients. Specifically, we used lidar measurements from the NASA Micro-Pulse Lidar Network (MPLNET) in the Mediterranean and North Africa area. While the comparison of the total extinction coefficient between MONARCH (550 nm) and MPLNET (532 nm) can be performed directly but is affected by unaccounted aerosols (e.g. sea salts, anthropogenic aerosols), the extraction of dust extinction coefficient from MPLNET products required additional processing. To this purpose, the POLIPHON algorithm was exploited to obtain the lidar-derived dust component from the total aerosol load and enable a fair intercomparison with modeled dust profiles. Initial descriptive and quantitative results confirm the model’s reliability in forecasting and predicting dust vertical profile characteristics.

Building on this evaluation, we explore the potential of leveraging lidar data to improve the dust ground concentration estimates of the MONARCH model forecasts. The proposed approach explores empirical adjustments of the model's surface concentration using lidar observations and validates these improvements against independent ground-based PM10 measurements collected by the European Environment Agency (EEA). The analysis is performed for three European sites, namely Tenerife, Barcelona, and El Arenosillo, for the period from July 2024 to January 2025.

The expanded aim of this work is to assess the feasibility of utilizing next-generation space-borne lidar systems, such as EarthCARE (Cloud, Aerosol, and Radiation Explorer), to enhance global dust surface concentration estimations from model forecasts.

This study highlights the synergy between observations and modeling, demonstrating how lidar observations could be exploited for correcting and improving model performance at both regional and global scales.