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Lars Wiegand, Arwen Twitchett, Cornelia Schwierz, and Peter Knippertz

section 2b . 3. Synoptic overview On 20 May 2008 a pronounced upper-level disturbance started to penetrate from the midlatitude North Atlantic into the Mediterranean Sea. Figure 1 shows the time evolution of this trough between 21 and 26 May 2008 using UPV. The streamer originates from a PV reservoir over the North Atlantic and northern Europe on 21 May 2008 ( Fig. 1a ). A surface low pressure pattern coincided with this PV reservoir. In the course of the following days a large-scale ridge forms to

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Andrea Schneidereit, Silke Schubert, Pavel Vargin, Frank Lunkeit, Xiuhua Zhu, Dieter H. W. Peters, and Klaus Fraedrich

and ensured moisture transport toward Pakistan (Martius et al. 2012, manuscript submitted to Quart. J. Roy. Meteor. Soc. ; Lau and Kim 2012). Hong et al. (2011) found that La Niña–induced low-level easterly anomalies over South and Southeast Asia led to an enhancement of the moisture transport to the northern Arabian Sea and Pakistan. The predictability of the Pakistan flood is analyzed by Webster et al. (2011) . Large parts of Russia, Belarus, Ukraine, and the Baltic were affected by the long

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Jana Čampa and Heini Wernli

distributed over the whole cyclone area. Field and Wood (2007) composited cyclones according to their intensity (in terms of surface wind speed) and moisture content. They show that for cyclones of the same wind speed intensity, those with more moisture have a slightly higher sea level pressure (SLP) than the drier ones. Therefore the dynamical effect of precipitation processes is also to produce stronger winds in the cyclones that do not have very low SLP. Rudeva and Gulev (2011) found similar

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Yannick Barton, Paraskevi Giannakaki, Harald von Waldow, Clément Chevalier, Stephan Pfahl, and Olivia Martius

air mass is advected in a southerly flow toward the Alpine ridge and then orographically forced to ascend (e.g., Massacand et al. 1998 ; Martius et al. 2006b ). The low-level southerly flow, typically transporting moisture from the Atlantic Ocean and the Mediterranean Sea ( Winschall et al. 2014 ), can be related to the presence of a positive upper-tropospheric potential vorticity (PV) anomaly over western Europe ( Doswell et al. 1998 ; Massacand et al. 1998 ; Martius et al. 2006b ). These

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Hilke S. Lentink, Christian M. Grams, Michael Riemer, and Sarah C. Jones

influence of Sardinia on Corsican rainfall in the western Mediterranean Sea: A numerical sensitivity study . Atmos. Res. , 153 , 451 – 464 , https://doi.org/10.1016/j.atmosres.2014.10.004 . 10.1016/j.atmosres.2014.10.004 Evans , C. , and Coauthors , 2017 : The extratropical transition of tropical cyclones. Part I: Cyclone evolution and direct impacts . Mon. Wea. Rev. , 145 , 4317 – 4344 , https://doi.org/10.1175/MWR-D-17-0027.1 . 10.1175/MWR-D-17-0027.1 Foerster , A. M. , M. M. Bell , P

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Julian F. Quinting and Sarah C. Jones

circulation associated with the inner core of the TC is identified as the relative vorticity within a fixed radius around the TC center, which is defined as the minimum in mean sea level pressure. A successive overrelaxation method enables us to compute the rotational wind induced by the relative vorticity . We tested the results for various radii around the TC center and chose a radius of 600 km for which an adequate distinction between the cyclonic inner core circulation and the surrounding flow

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Julia H. Keller, Sarah C. Jones, and Patrick A. Harr

cutoff cyclone east of the Rocky Mountains. The circulation in the narrowed trough and the cutoff was associated with a temperature drop of about 15–20 K in the western parts of the Great Plains between 21 and 25 September 2009, indicating a significant downstream impact of the transitioning storm. Fig . 3. 500-hPa geopotential height (contours, in gpdm) and mean sea level pressure (shaded, in hPa) from the ECMWF IFS analysis for times indicated in each panel during the extratropical transition of (a

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Julia H. Keller, Christian M. Grams, Michael Riemer, Heather M. Archambault, Lance Bosart, James D. Doyle, Jenni L. Evans, Thomas J. Galarneau Jr., Kyle Griffin, Patrick A. Harr, Naoko Kitabatake, Ron McTaggart-Cowan, Florian Pantillon, Julian F. Quinting, Carolyn A. Reynolds, Elizabeth A. Ritchie, Ryan D. Torn, and Fuqing Zhang

-hPa waveguide as red contour separating high PV air (>3 PVU; orange shading) from lower PV air (<3 PVU; unshaded). Midlevel baroclinic zone as blue tilted surface. Trajectories of rapidly ascending air parcels as blue–red–blue lines, reflecting the diabatic PV modification of the parcels from low to high to low PVU, respectively. Mean sea level pressure (gray contours; every 8 hPa) and equivalent potential temperature (violet contours; 320 and 330 K) are indicated in the lower panel. [Figure 11a

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Olivia Martius and Heini Wernli

.g., sea surface temperatures) on the synoptic variability. In the literature, a distinction is often made between two types of upper-level jet streams: eddy-driven jets and subtropical jets (e.g., Reiter and Whitney 1969 ; Lee and Kim 2003 ). Koch et al. (2006) proposed an alternative jet stream typology with two categories of shallow and deep jets based on the depth of the baroclinic zone associated with the jet. Eddy-driven (“deep”) jets are sustained primarily by baroclinic eddies and they can

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Andreas Schäfler, Andreas Dörnbrack, Christoph Kiemle, Stephan Rahm, and Martin Wirth

vertical levels in the region with maximum transport defined as qυ h > 85 g kg −1 m s −1 (see bold line in Fig. 7 ). In the composed trajectories, the aircraft measurements appear from 38.5 to 41.5 h, as indicated by the gray bar in Fig. 8 . The color grading of the trajectories represents the increasing initial altitude on the cross section at the start time. Generally, the air masses originated from three different geographical regions: one located over the Mediterranean, another over the

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