Microphysics Impacts on the Warm Conveyor Belt and Ridge Building of the NAWDEX IOP6 Cyclone

Mazoyer, Marie; Ricard, Didier; Rivière, Gwendal; Delanoë, Julien; Arbogast, Philippe; Vié, Benoît; Lac, Christine; Cazenave, Quitterie; Pelon, Jacques

doi:10.1175/mwr-d-21-0061.1

Cited by 13 publications

(14 citation statements)

References 76 publications

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“…Display of the earth's surface and shadows place trajectories in spatial context. are sensitive to the cloud microphysical processes implemented in the numerical model, and may in turn, introduce uncertainties to WCB ascent (Joos and Forbes, 2016;Mazoyer et al, 2021). As the scale of cloud microphysical processes responsible for precipitation formation is too small to be explicitly resolved in NWP models, parameterizations are used to calculate the integrated effects on the resolved prognostic variables.…”

Section: Introductionmentioning

confidence: 99%

Visual analysis of model parameter sensitivities along warm conveyor belt trajectories using Met.3D (1.6.0-multivar0)

Neuhauser

Hieronymus

Kern³

et al. 2023

Preprint

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Abstract. Numerical weather prediction models rely on parameterizations for subgrid-scale processes, e.g., for cloud microphysics, which are a well-known source of uncertainty in weather forecasts. Via algorithmic differentiation, which computes the sensitivities of prognostic variables to changes in model parameters, these uncertainties can be quantified. In this article, we present visual analytics solutions to analyze interactively the sensitivities of a selected prognostic variable to multiple model parameters along strongly ascending trajectories, so-called warm conveyor belt (WCB) trajectories. We propose a visual interface that enables to a) compare the values of multiple sensitivities at a single time step on multiple trajectories, b) assess the spatio-temporal relationships between sensitivities and the trajectories' shapes and locations, and c) find similarities in the temporal development of sensitivities along multiple trajectories. We demonstrate how our approach enables atmospheric scientists to interactively analyze the uncertainty in the microphysical parameterizations, and along the trajectories, with respect to the selected prognostic variable. We apply our approach to the analysis of WCB trajectories within the extratropical cyclone "Vladiana", which occurred between 22–25 September 2016 over the North Atlantic.

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Section: Introductionmentioning

confidence: 99%

Visual analysis of model parameter sensitivities along warm conveyor belt trajectories using Met.3D (1.6.0-multivar0)

Neuhauser

Hieronymus

Kern³

et al. 2023

Preprint

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“…Embedded convective activity within WCBs was initially identified using airborne and satellite-derived data within an extratropical cyclone during the Experiment on Rapidly Intensifying Cyclones over the Atlantic (ERICA) field experiment (Neiman et al, 1993). Various ground-based, spaceborne and airborne remote sensing measurements confirm the regular presence of convective activity in the warm sector of extratropical cyclones and WCBs in particular (Crespo and Posselt, 2016;Flaounas et al, 2016Flaounas et al, , 2018Oertel et al, 2019;Blanchard et al, 2020;Jeyaratnam et al, 2020).…”

Section: Introductionmentioning

confidence: 99%

“…Maddison et al (2019Maddison et al ( , 2020 showed that the low predictability of the block onset at medium range was associated with uncertainties in the timing, location and intensity of that cyclone. Blanchard et al (2020) and Blanchard et al (2021) studied the WCB-embedded convection by performing convection-permitting model simulations, while Mazoyer et al (2021) analysed the impact of cloud microphysics on the WCB activity of the Stalactite cyclone with similar convection-permitting simulations. Flack et al (2021) analysed the whole life cycle of the cyclone in simulations of two climate models.…”

Section: Introductionmentioning

confidence: 99%

The impact of deep convection representation in a global atmospheric model on the warm conveyor belt and jet stream during NAWDEX IOP6

Rivière

Wimmer

Arbogast³

et al. 2021

Weather Clim. Dynam.

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Abstract. The effect of parameterized deep convection on warm conveyor belt (WCB) activity and the jet stream is investigated by performing simulations of an explosively developing large-scale cyclone that occurred during the North Atlantic Waveguide and Downstream Impact Experiment (NAWDEX) field campaign using the Météo-France global atmospheric model ARPEGE. Three simulations differing only from their deep convection representation are analysed. The first one was performed with the Bougeault (1985) scheme (B85), the second one with the Prognostic Condensates Microphysics and Transport (PCMT) scheme of Piriou et al. (2007), and the third one without any parameterized deep convection. In the latter simulation, the release of convective instability at the resolved scales of the model generates localized cells marked by strong heating with few degrees extent in longitude and latitude along the fronts. In runs with active parameterized deep convection (B85, PCMT), the heating rate is more homogeneously distributed along fronts as the instability release happens at subgrid scales. This difference leads to more rapid and abrupt ascents in the WCB without parameterized deep convection and more moderate but more sustained ascents with parameterized deep convection. While the number of WCB trajectories does not differ much between the three simulations, the averaged heating rates over the WCB trajectories exhibits distinct behaviour. After 1 d of simulations, the upper-level heating rate is on average larger, with the B85 scheme leading to stronger potential vorticity (PV) destruction. The difference comes from the resolved sensible and latent heating and not the parameterized one. A comparison with (re)analyses and a large variety of airborne observations from the NAWDEX field campaign (Doppler radar, Doppler lidar, dropsondes) made during the coordinated flights of two aircraft in the WCB outflow region shows that B85 performs better in the representation of the double jet structure at 1 d lead time than the other two simulations. That can be attributed to the more active WCB at upper levels. However, this effect is too strong and that simulation becomes less realistic than the other ones at forecast ranges beyond 1.5 d. The simulation with the PCMT scheme has an intermediate behaviour between the one with the B85 scheme and without parameterized deep convection, but its impact on the jet stream is closer to the latter one. Finally, additional numerical experiments show that main differences in the impact on the jet between PCMT and B85 largely come from the chosen closure, with the former being based on CAPE and the latter on moisture convergence.

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“…Uncertainty in the representation of latent heat released during cloud formation can represent a dominant source of initial error growth (Baumgart et al, 2019). In general, WCBs influence the large-scale flow through both direct PV modification in the lower and upper troposphere (e.g., Rossa et al, 2000;Pomroy and Thorpe, 2000;Joos and Forbes, 2016;Oertel et al, 2020;Mazoyer et al, 2021) and their related divergent outflow in the upper troposphere (e.g., Grams and Archambault, 2016;Steinfeld and Pfahl, 2019;Teubler and Riemer, 2021).…”

mentioning

confidence: 99%

“…The WCB ascent strength and its isentropic outflow level, which are tightly related to latent heat release, strongly impact the upper-level divergent wind field. It has been shown that uncertainty in the representation of latent heating substantially influences the WCB's cross-isentropic ascent strength (e.g., Martínez-Alvarado et al, 2014;Joos and Forbes, 2016;Mazoyer et al, 2021) and the frequency of WCB ascent (Pickl et al, 2022). A misrepresentation of WCB ascent, and its isentropic outflow level, can influence the jet stream wind speed (Schäfler and Harnisch, 2015) and also lead to forecast busts through underestimation of the downstream ridge amplitude (Grams et al, 2018).…”

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confidence: 99%

Interaction of microphysics and dynamics in a warm conveyor belt simulated with the ICON model

Oertel¹,

Miltenberger²,

Grams³

et al. 2023

Preprint

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Abstract. The representation of warm conveyor belts (WCBs) in numerical weather prediction (NWP) models is important, as they are responsible for the major precipitation in extratropical cyclones and modulate the large-scale flow evolution. Their cross-isentropic ascent into the upper troposphere is influenced by latent heat release mostly, but not exclusively, from cloud formation whose representation in NWP models is associated with large uncertainties. The diabatic heating additionally modifies the potential vorticity (PV) distribution which influences the circulation. We analyse diabatic heating and associated PV rates from all physics processes, including microphysics, turbulence, convection, and radiation, in a case study of a WCB that occurred during the North Atlantic Waveguide and Downstream Impact Experiment (NAWDEX) campaign using the Icosahedral Nonhydrostatic (ICON) modelling framework. In particular, we consider all individual microphysical process rates that are implemented in ICON's two-moment microphysics scheme, which sheds light on (i) which microphysical processes dominate the diabatic heating and PV structure in the WCB, and thus, potentially influence the large-scale flow, and (ii) which microphysical processes are most active during the ascent and influence cloud formation and characteristics. For this purpose, diabatic heating and PV rates are integrated along online WCB trajectories. Our convection-permitting simulation setup also takes the reduced aerosol concentrations over the North Atlantic into account. Complementary Lagrangian and Eulerian perspectives on diabatic heating and PV modification confirm that microphysical processes are the dominant diabatic heating contribution during ascent. Near cloud top longwave radiation cools WCB air parcels. Due to the longevity of the WCB cloud band, the diabatic heating contributions from radiation, and corresponding PV modification in the upper troposphere, are non-negligible. The turbulence scheme is active in the WCB ascent region, despite large gradient Richardson numbers, and process rates from turbulence and microphysics partially counteract each other. From all microphysical processes condensational growth of cloud droplets and vapor deposition on frozen hydrometeors most strongly influence diabatic heating and PV, while below-cloud evaporation strongly cools WCB air parcels prior to their ascent and increases their PV value. PV production is strongest near surface, and extends up to 4 km height with substantial contributions from condensation, melting, evaporation, and vapor deposition. In the upper troposphere, PV is reduced by diabatic heating from vapor deposition, condensation, and radiation. Activation of cloud droplets as well as homogeneous and heterogeneous freezing processes have a negligible diabatic heating contribution due to small overall mass conversion, but their detailed representation is likely important as the hydrometeor size distributions influence other microphysical processes. Generally, faster ascending WCB trajectories are heated markedly more than more slowly ascending WCB trajectories, which is linked to larger initial specific humidity content of fast WCB trajectories providing a thermodynamic constraint on total microphysical heating. Yet, the total diabatic heating contribution of convectively ascending trajectories is relatively small due to their small fraction in this case study.

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Microphysics Impacts on the Warm Conveyor Belt and Ridge Building of the NAWDEX IOP6 Cyclone

Cited by 13 publications

References 76 publications

Visual analysis of model parameter sensitivities along warm conveyor belt trajectories using Met.3D (1.6.0-multivar0)

Visual analysis of model parameter sensitivities along warm conveyor belt trajectories using Met.3D (1.6.0-multivar0)

The impact of deep convection representation in a global atmospheric model on the warm conveyor belt and jet stream during NAWDEX IOP6

Interaction of microphysics and dynamics in a warm conveyor belt simulated with the ICON model

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