The Key Role of Diabatic Outflow in Amplifying the Midlatitude Flow: a Representative Case Study of Weather Systems Surrounding Western North Pacific Extratropical Transition
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...If the outflow layer is higher, the negative PV anomaly is stronger and more of the air mass enters the anticyclonic branch of the WCB flowing into the downstream ridge (Grams and Archambault 2016)....
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75 citations
Cites background from "The Key Role of Diabatic Outflow in..."
...and reinforcement of blocking patterns through diabatic latent heat release [Pfahl et al., 2015; Grams and Archambault, 2016; O’Reilly et al., 2016], and thus there may be mutually reinforcing dynamical linkages between cyclonic Rossby wave breaking, extratropical cyclones, ARs, and Greenland blocking, ultimately modulating GrIS mass loss....
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65 citations
Cites background from "The Key Role of Diabatic Outflow in..."
...This amplification of the near-tropopause wave pattern can trigger downstream development of baroclinic Rossby wave packets (compare with Grams and Archambault, 2016)....
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...A similar impact of WCB outflow on an upstream cut-off formation occurred during the extratropical transition of Hurricane Hanna (2008: Grams et al. 2011). A more detailed investigation of this evolution showed that formation of the PV filament and its reabsorption were key in reconfiguring the lower troposphere and modulating WCB activity. In essence, a low-level baroclinic zone was strengthened and strong advection of warm moist air occurred ahead of the PV filament, which favoured vigorous poleward WCB ascent and outflow. In contrast, the baroclinic zone was weaker and more zonally oriented in the ensemble, resulting in an erroneous strengthening of the southern WCB branch. We conclude that, for the severe forecast bust in March 2016, WCB activity can be regarded as the dynamical link that amplifies initial condition error of the midlatitude flow strongly and propagates it into downstream regions. This is due to the three-dimensional structure of a WCB and its sensitivity to cloud diabatic processes. WCB ascent is highly sensitive to low-level baroclinicity, facilitating slantwise ascent, and to the availability of moisture in the inflow region (for example, Schäfler and Harnisch, 2015). Once condensation occurs, latent heat release triggers a nonlinear feedback that enhances WCB ascent and associated air-mass transport into the upper troposphere further. In turn, WCB outflow near the tropopause modifies the upper-level Rossby wave pattern and thus reconfigures the large-scale midlatitude flow. Hence, WCB activity can be regarded as an important physical–dynamical process that contributes to upscale error growth during the second stage of the conceptual error growth model by Zhang et al. (2007). The studies by Joos and Wernli (2012) and Joos and Forbes (2016) showed that WCB outflow is sensitive to the details of microphysical parametrizations. Selz and Craig (2015) reported that a misrepresentation of diabatic heating in convective parametrization schemes might lead to overconfident ensembles, as was the case for evolution of the southern WCB outflow branch in the study at hand....
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...A similar impact of WCB outflow on an upstream cut-off formation occurred during the extratropical transition of Hurricane Hanna (2008: Grams et al. 2011). A more detailed investigation of this evolution showed that formation of the PV filament and its reabsorption were key in reconfiguring the lower troposphere and modulating WCB activity. In essence, a low-level baroclinic zone was strengthened and strong advection of warm moist air occurred ahead of the PV filament, which favoured vigorous poleward WCB ascent and outflow. In contrast, the baroclinic zone was weaker and more zonally oriented in the ensemble, resulting in an erroneous strengthening of the southern WCB branch. We conclude that, for the severe forecast bust in March 2016, WCB activity can be regarded as the dynamical link that amplifies initial condition error of the midlatitude flow strongly and propagates it into downstream regions. This is due to the three-dimensional structure of a WCB and its sensitivity to cloud diabatic processes. WCB ascent is highly sensitive to low-level baroclinicity, facilitating slantwise ascent, and to the availability of moisture in the inflow region (for example, Schäfler and Harnisch, 2015). Once condensation occurs, latent heat release triggers a nonlinear feedback that enhances WCB ascent and associated air-mass transport into the upper troposphere further. In turn, WCB outflow near the tropopause modifies the upper-level Rossby wave pattern and thus reconfigures the large-scale midlatitude flow. Hence, WCB activity can be regarded as an important physical–dynamical process that contributes to upscale error growth during the second stage of the conceptual error growth model by Zhang et al. (2007). The studies by Joos and Wernli (2012) and Joos and Forbes (2016) showed that WCB outflow is sensitive to the details of microphysical parametrizations....
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58 citations
References
22,055 citations
"The Key Role of Diabatic Outflow in..." refers methods in this paper
...For surface parameters not available from CFSR in the layers needed for COSMO (skin and sea surface temperature, soil temperature, soil moisture, snow depth, snow layer temperature), ERAInterim (Dee et al. 2011) data for monthly means at the synoptic times are used....
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4,520 citations
"The Key Role of Diabatic Outflow in..." refers methods in this paper
...This study is based on 6-hourly NCEP Climate Forecast System Reanalysis (CFSR; Saha et al. 2010) data, which are used to construct composites of selected recurving western North Pacific strong interaction ET cases and which serve as the initial and boundary condition data for numerical simulations…...
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3,296 citations
"The Key Role of Diabatic Outflow in..." refers methods in this paper
...The additional simulations are run: a control simulation using a Tiedtke mass flux scheme (Tiedtke 1989) for the representation of moist convection (control Tiedtke), one using the Tiedtke scheme for shallow clouds only (control shallow), one with convective parameterization completely…...
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1,789 citations
"The Key Role of Diabatic Outflow in..." refers methods in this paper
...In adaptation to the investigation of ET on large domains we use a Kain–Fritsch scheme (Kain and Fritsch 1993) for the representation of moist convection and a Kessler-type bulk microphysics scheme (Kessler 1969) with six categories of water includingwater vapor, cloudwater, rain, snow, cloud ice, and graupel....
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...In adaptation to the investigation of ET on large domains we use a Kain–Fritsch scheme (Kain and Fritsch 1993) for the representation of moist convection and a Kessler-type bulk microphysics scheme (Kessler 1969) with six categories of water includingwater vapor, cloudwater, rain, snow, cloud ice,…...
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1,572 citations
"The Key Role of Diabatic Outflow in..." refers methods in this paper
...In adaptation to the investigation of ET on large domains we use a Kain–Fritsch scheme (Kain and Fritsch 1993) for the representation of moist convection and a Kessler-type bulk microphysics scheme (Kessler 1969) with six categories of water includingwater vapor, cloudwater, rain, snow, cloud ice, and graupel....
[...]
...…to the investigation of ET on large domains we use a Kain–Fritsch scheme (Kain and Fritsch 1993) for the representation of moist convection and a Kessler-type bulk microphysics scheme (Kessler 1969) with six categories of water includingwater vapor, cloudwater, rain, snow, cloud ice, and graupel....
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