Item

Abstract

The water vapor transport in the extratropics is mainly organized along narrow elongated filaments. Depending on the context, these filaments are often referred to with different terms. When making landfall, they are generally referred to as atmospheric rivers; when occurring at high latitudes, many authors regard them as warm moist intrusions; when occurring along a cold front and near a cyclone core, they might constitute the feeder airstream or warm conveyor belt. Here, we propose an algorithm that detects these various features as lines tracing well-defined maxima in the instantaneous vertically integrated water vapor transport. We call these lines moisture transport axes. The definition of moisture transport axes is based on the structure of the moisture transport, and thus does not require a threshold in the absolute magnitude of this transport (or the total column water vapor). This makes the moisture transport axes particularly suited for applications connecting polar to mid and subtropical latitudes and across changing climates. We link moisture transport axes to precipitation in polar regions using case studies and composite analyses. Finally, we show that in the Arctic more than 30% of the climatological precipitation and 56% of extreme precipitation events are associated with moisture transport axes, despite these occurring less than 1% of the time steps.