Evaluation of a fine-scale Eulerian modeling system for pollen in Thessaloniki, Greece

This study presents an enhanced high-resolution modeling system (WRF-NEMO-CAMx) designed to simulate airborne pollen concentrations for three key taxa for Mediterranean climates, Quercus, Pinus spp. and Olea europaea L. , in the broader Thessaloniki area, Greece, at a spatial resolution of 2 km for the year 2019. Three emission scenarios (“Base,” “Max,” and “Min”) were implemented using literature-based pollen production values. The system was evaluated using ground-based meteorological observations and daily airborne pollen concentrations. The evaluation of simulated pollen concentrations confirmed the overall satisfactory performance of the modeling system. Among the three scenarios examined, the “Min” simulation yielded the best agreement with observations for Quercus (Index of Agreement, IOA = 0.81) and Pinus spp. (IOA = 0.76), while for Olea , the “Max” scenario demonstrated superior performance (IOA = 0.89). Analysis of subcategory contributions revealed that QRPR ( Quercus Robur/Petraea ) was the dominant contributor to Quercus pollen concentrations, while PMSC, representing Pinus species excluding Pinus pinaster and Pinus sylvestris , accounted for the largest share among the Pinus spp. categories. The spatial distribution of seasonal emissions indicated higher values in areas with dense vegetation cover for Quercus and Pinus spp., and in coastal and agricultural zones for Olea , reflecting the known patterns of species occurrence in the study region. These findings support the future integration of the modeling system into a high-resolution pollen health-warning framework, aimed at improving exposure forecasts.