The impact of Gulf Stream meanders on atmospheric fronts in a regional high-resolution atmospheric model.  

<p><span class="TextRun SCXW139905545 BCX0" lang="EN" xml:lang="EN" data-contrast="auto"><span class="NormalTextRun SCXW139905545 BCX0">The location and the degree of instability (meandering) of the Gulf Stream have been suggested to influence, through air-sea interactions, the North Atlantic Jet Stream and weather patterns over Northern Europe. Although the Gulf Stream&#8217;s impact on the marine boundary layer (MABL) is well established, the associated mechanism(s) and timescale(s) are, however, debated. Taking advantage of a 24-member ensemble of ocean-only (12km) integrations in the North Atlantic, we devised an eddy-resolving (~10km) regional atmospheric model (WRF) step up where the same weather system feels different realizations of Gulf Stream turbulence. We compare the experiments forced with the given ensemble members (abundance of mesoscale eddies) with a unique ensemble mean SST (lack of mesoscale eddies) forced investigation to shed further light on the impact of&#160; Gulf Stream SST meandering on midlatitude winter storm track. We find that Gulf Stream meanders recharge/discharge the marine boundary layer with heat and moisture, thus preconditioning the atmosphere so that the passing atmospheric front modulates the produced rainfall. This effect is seen systematically in each member of the ensemble and surprisingly leaves its imprint on the precipitation averaged over a short time period (less than a month). The imprint of the meanders on the dynamical fields (pressure, velocities) is found to reach above the MABL but is less robust in the upper troposphere. </span></span><span class="EOP SCXW139905545 BCX0" data-ccp-props="{">&#160;</span></p>