Print Email Facebook Twitter The Influence of Convective Momentum Transport and Vertical Wind Shear on the Evolution of a Cold Air Outbreak Title The Influence of Convective Momentum Transport and Vertical Wind Shear on the Evolution of a Cold Air Outbreak Author Saggiorato, B. (TU Delft Atmospheric Remote Sensing) Nuijens, Louise (TU Delft Atmospheric Remote Sensing) Siebesma, A.P. (TU Delft Atmospheric Remote Sensing; Royal Netherlands Meteorological Institute (KNMI)) de Roode, S.R. (TU Delft Atmospheric Remote Sensing) Sandu, I. (European Centre for Medium Range Weather Forecasts) Papritz, L. (Singapore-ETH Centre) Date 2020 Abstract To study the influence of convective momentum transport (CMT) on wind, boundary layer and cloud evolution in a marine cold air outbreak (CAO) we use large-eddy simulations subject to different baroclinicity (wind shear) but similar surface forcing. The simulated domain is large enough, (Formula presented.) km2), to develop typical mesoscale cellular convective structures. We find that a maximum friction induced by momentum transport (MT) locates in the cloud layer for an increase of geostrophic wind with height (forward shear, FW) and near the surface for a decrease of wind with height (backward shear, BW). Although the total MT always acts as a friction, the interaction of friction-induced cross-isobaric flow with the Coriolis force can develop supergeostrophic winds near the surface (FW) or in the cloud layer (BW). The contribution of convection to MT is evaluated by decomposing the momentum flux by column water vapor and eddy size, revealing that CMT acts to accelerate subcloud layer winds under FW shear and that mesoscale circulations contribute significantly to MT for this horizontal resolution (250 m), even if small-scale eddies are nonnegligible and likely more important as resolution increases. Under FW shear, a deeper boundary layer and faster cloud transition are simulated, because MT acts to increase surface fluxes and wind shear enhances turbulent mixing across cloud tops. Our results show that the coupling between winds and convection is crucial for a range of problems, from CAO lifetime and cloud transitions to ocean heat loss and near-surface wind variability. Subject cold air outbreakconvective momentum transporthorizontal windkinetic energy budgetmomentum transportwind shear To reference this document use: http://resolver.tudelft.nl/uuid:7a7fa833-4074-481d-9a91-0737237cc092 DOI https://doi.org/10.1029/2019MS001991 ISSN 1942-2466 Source Journal of Advances in Modeling Earth Systems, 12 (6), 1-22 Part of collection Institutional Repository Document type journal article Rights © 2020 B. Saggiorato, Louise Nuijens, A.P. Siebesma, S.R. de Roode, I. Sandu, L. Papritz Files PDF 2019MS001991.pdf 16.62 MB Close viewer /islandora/object/uuid:7a7fa833-4074-481d-9a91-0737237cc092/datastream/OBJ/view