On the Rivers in the Euro-Atlantic Sky

Abstract We study and revisit the Atmospheric Rivers (AR) over Euro-Atlantic sky using long term reanalysis datasets and widely used methods and parameters. The atmospheric winds, temperature and specific humidity at different pressure levels during 1979-2018 were used to study the spatiotemporal variability of water vapour transport integrated between 1000-300 hPa (IVT300) as a proxy to ARs. The standard deviation (200 kgm-1s-1) of ARs is around 60% of the climatology (>300 kgm-1s-1) in all reanalysis datasets in the North Atlantic. High frequency of ARs over western Europe in winter half-year (WHY) has 6% lower intensity compared to the low frequency of ARs in summer half-year (SHY) with 3% higher intensity than the annual mean. The intensity of ARs in the North Atlantic has been increasing in recent times with large decadal variability and poleward shift in landfalling. The magnitude of atmospheric parameters in the lower atmosphere below 750 hPa dominates the total column water vapour and intensity of ARs. There is a significant impact of the North Atlantic Oscillation and Scandinavian blocking on the location of landfalling of ARs and latitudinal dependence of the source of moisture flux in the open ocean contributing to the formation and enhancing ARs strength.