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Oscar Martínez-Alvarado, Suzanne L. Gray, and John Methven

the set of parameterized diabatic processes in the model. In this work, we consider contributions from four parameterized processes: namely, (i) boundary layer (BL) and turbulent mixing processes, (ii) convection, (iii) cloud microphysics, and (iv) radiation. The term cloud microphysics is used here to refer to two parameterizations: namely, the large-scale cloud parameterization and the large-scale precipitation parameterization. The latter includes the following microphysical processes ( Wilson

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Sam Hardy, David M. Schultz, and Geraint Vaughan

upper-level forcing, or different phasing between the PV anomaly and cyclone, would have produced a higher-impact flooding event across the United Kingdom or whether the verifying solution represented the highest-impact event possible for this synoptic setup. The question is answered by using piecewise PV inversion to design a suite of model simulations with the strength and position of the PV anomaly modified in the initial conditions, following a similar method to previous studies by Huo et al

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Geraint Vaughan, Bogdan Antonescu, David M. Schultz, and Christopher Dearden

the anomaly moves ( Hoskins et al. 1985 ). The mechanism was further clarified by Hoskins et al. (2003) who introduced the concepts of isentropic upglide (the vacuum-cleaner effect) for the motion of air on tilted isentropic surfaces and isentropic displacement for the development of an anomaly over time. In this picture, a cyclonic PV anomaly at tropopause level moving from west to east will be associated with ascending motion, and hence a tendency for clouds and precipitation, on its

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Jeffrey M. Chagnon and Suzanne L. Gray

cloud microphysics scheme of Wilson and Ballard (1999) . The schemes used in this study are configured in the same way as the operational MetUM, version 7.3, which was used by the Met Office. Table 1 summarizes the design of the simulations. Each of the three cases investigated in this study is simulated with the MetUM in three different configurations having horizontal grid spacings of 12, 4, and 1 km. These simulations are hereafter referred to as the 12-, 4-, and 1-km runs, respectively. The 12

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David M. Schultz, Bogdan Antonescu, and Alessandro Chiariello

, doi: 10.1175/MWR-D-10-05003.1 . Keyser , D. , M. J. Reeder , and R. J. Reed , 1988 : A generalization of Petterssen’s frontogenesis function and its relation to the forcing of vertical motion . Mon. Wea. Rev. , 116 , 762 – 780 , doi: 10.1175/1520-0493(1988)116<0762:AGOPFF>2.0.CO;2 . Locatelli , J. D. , and P. V. Hobbs , 1987 : The mesoscale and microscale structure and organization of clouds and precipitation in midlatitude cyclones. XIII: Structure of a warm front . J. Atmos

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Ben Harvey, John Methven, Chloe Eagle, and Humphrey Lean

fluxes in storm-force winds and estimated peak-to-trough ocean wave heights of 6–12 m. The circuit BCDEG was designed to be closed in a frame of reference moving with features on the front, but in practice the circuit was found to be best closed by a point between E and G, labeled F in Fig. 1 (see section 3b ). Subsequently, the aircraft turned to cross the front again before ascending through the cold-sector boundary layer (1635–1705 UTC) and finally crossing the front at high altitude to produce

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Matthew R. Clark and Douglas J. Parker

mean system motion vector. In the two cases analyzed in detail, the observed changes in postfrontal winds and the associated vorticity and stretching increases appeared to be related to the development, or movement along the front, of subtle frontal waves. An open question is whether the waves are a consequence of dynamical processes internal to the frontal rainband, or of external factors, such as a response of the wind field to dynamic forcing in the vicinity of the NCFR (e.g., Browning and

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