A Proposed Algorithm for Moisture Fluxes from Atmospheric Rivers

TLDR

Tropospheric rivers are filamentary moisture flux structures that, together with broad fields, represent the total meridional transport in the extratropics. The authors apply a new algorithm to European Centre for Medium‑Range Weather Forecasts wind and moisture data to quantify tropospheric moisture fluxes. The algorithm shows that tropospheric rivers carry almost all meridional transport yet occupy only about 10 % of the longitudinal extent, revealing that traditional transient flux estimates underestimate river contributions and that the new method yields more realistic mean and eddy fluxes.

Abstract

A new algorithm is applied to study water vapor fluxes in the troposphere using wind and moisture data from the European Centre for Medium-Range Weather Forecasts. The fluxes are divided into filamentary structures known as tropospheric rivers and what are termed here broad fields. The results show that the tropospheric rivers may carry essentially the total meridional transport observed in the extratropical atmosphere but may occupy only about 10% of the total longitudinal length at a given latitude. The transient fluxes in traditional studies do not catch the filamentary structures completely and may therefore underestimate the fraction of transport assigned to moving systems, as well as omitting the geographical concentration. The mean flow and eddy fluxes evaluated by the new algorithm are considered to be more physically realistic.