Diabatic processes modulating the vertical structure of the jet stream above the cold front of an extratropical cyclone: sensitivity to deep convection schemes

Abstract. The effect of deep convection parameterisation on the jet stream above cold front an explosive extratropical cyclone is investigated in global numerical weather prediction model ARPEGE, operational at Météo-France. Two hindcast simulations differing only scheme used are systematically compared with each other, (re)analysis datasets and NAWDEX airborne observations. representation has important vertical structure 1-d lead time. simulation less active shows a deeper stream, associated stronger potential vorticity (PV) gradient middle troposphere. This due to larger deepening dynamical tropopause air side higher PV destruction warm side, near 600 hPa. To better understand origin this gradient, Lagrangian backward trajectories computed. On jet, numerous undergo rapid ascent from boundary layer mid-levels scheme, whereas they stay other simulation. explains noted that scheme. These ascending masses form mid-level ice clouds not observed microphysical retrievals radar-lidar measurements. conveyor belt region, heating occurring lower In contrast, most both extend further up into upper