Methodological and interpretative limitations of using dew point temperature in aerobiological studies

Among meteorological variables taken into account in aerobiological studies, air humidity presents a particular methodological challenge, as the atmospheric water vapour content can be described using several interrelated parameters, including relative humidity, absolute and specific humidity, vapour pressure, vapour pressure deficit, and dew point temperature (TD). The TD is the temperature at which air becomes saturated with water vapour at a given pressure. Water vapour condensation may impact, inter alia, the release of fungal spores or pollen grains, which may occur when the air temperature is actually equal to the TD at a given moment. However, as water vapour condensation occurs only in short time intervals during a 24-h period, using the daily average TD in aerobiological analyses is not appropriate from the meteorological standpoint. The manuscript is a methodological commentary rather than an empirical study. We emphasize that it is not the TD itself that is at issue, but its temporal aggregation (daily arithmetic averages) and interpretation in multivariate ecological analyses. We recommend that, in aerobiological studies, TD values be used with caution and preferably be complemented with, or replaced by, alternative humidity-related metrics, particularly when multicollinearity is present. Such an approach may improve the robustness and interpretability of results, as well as help to remove statistical artifact effects from explaining direct biological mechanisms.