A real-time calibration method for the numerical pollen forecast model COSMO-ART

Technologies for monitoring pollen concentrations in real-time made substantial advances in the past years and become increasingly available. This opens the possibility to calibrate numerical pollen forecast models in real-time and make a significant step forward regarding the quality of pollen forecasts. We present a method to use real-time pollen measurements in numerical pollen forecast models. The main idea is to calibrate model parameterizations and not to assimilate measurements in a nudging sense. This ensures that the positive effect persists throughout the forecast period and does not vanish after a few forecast hours. We propose to adapt in real-time both the model phenology scheme and the overall tuning factor that are present in any numerical pollen forecast model. To test this approach, we used the numerical pollen forecast model COSMO-ART (COnsortium for Small-scale MOdelling-Aerosols and Reactive Trace gases) on a mesh size of 1.1 km covering the greater Alpine domain. Test runs covered two pollen seasons and included Corylus , Alnus , Betula and Poaceae pollen. Comparison with daily measurements from 13 Swiss pollen stations revealed that the model improvements are large, but fine-tuning of the method remains a challenge. We conclude that the presented approach is a first valuable step towards comprehensive real-time calibration of numerical pollen forecast models.