A study on correlations between precipitation ETCCDI and airborne pollen/fungal spore parameters in the NE Iberian Peninsula

Precipitation is one of the meteorological variables usually involved in the aerobiological studies, which presents a complex relationship with atmospheric levels of pollen and fungal spores and the temporal characteristics of their seasons. This complexity is due in a large part to rainfall’s twofold impact of having, prior to pollination, a positive influence on subsequent pollen production and of contributing, during pollination, to pollen removal from the air through a wash-out effect. To better explore this impact, we place particular emphasis on extreme rainfall by calculating the correlation between airborne pollen and fungal spore parameters and the precipitation indices that the Expert Team on Climate Change Detection and Indices (ETCCDI) proposed for characterising climate extremes. Parameters for twenty-seven pollen and fungal spore taxa measured in six aerobiological stations in the NE Iberian Peninsula have been considered. We have distinguished between annual and winter ETCCDI in order to compare the correlations between extreme rainfall and airborne pollen concentrations and to avoid the wash-out effect as far as possible. Results show a positive influence from an increase in moderately extreme winter rainfall, specifically on subsequent pollen/fungal spore production: the percentage of all possible significant correlations is higher for winter than for annual rainfall. Furthermore, while annual rainfall in this region has nearly the same number of positive as negative correlations, the positive correlations for winter rainfall are more than twice that of the negative ones. The seasonal consideration on rainfall ETCCDI made with the aim to avoid the confounding overlapping of different rainfall impacts has led to more sharpened observations of its positive and negative effects on airborne pollen and fungal spore concentrations. Graphical abstract