A New Climatology of Continentality Based on Lagrangian Air Mass Travel Times From the Ocean

Abstract Climate classifications such as the Köppen classification have a long tradition and wide fields of application. An important classification aspect is continentality, for which we present a new metric based on Lagrangian dispersion model calculations. It measures the time it takes for air to travel from the marine boundary layer to the continental boundary layer, mapped onto the continental arrival locations. We find the highest annual mean values of the Lagrangian continentality over arid regions, with an absolute maximum of about 50 days over the Taklamakan desert. We also find strong seasonal variations, with summer values often being higher by about a factor 2 than winter values. Exceptions are summer minima over areas affected by monsoon systems. Generally, we find that the Lagrangian continentality metric demarcates different known climate zones well and also produces meaningful seasonal variations, which previous classifications could not capture.