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

atmospheric variables can be traced along the pathway. LAGRANTO is applied offline on hourly COSMO output data on model levels. This has the advantage that trajectories can be calculated both forward and backward in time. 3. Synoptic overview Typhoon Sinlaku (2008) developed east of the Philippines and quickly strengthened to typhoon intensity before it made landfall on the northern side of Taiwan on 14 September ( Fig. 2 ). Because of the interaction with land and orography, Sinlaku weakened from a

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Volkmar Wirth, Michael Riemer, Edmund K. M. Chang, and Olivia Martius

interactions Although theory provides some guidance, the question remains what makes a jet a good waveguide in the real atmosphere. The issue can be addressed by experimentation with numerical models. It turns out that the ducting property of a jet waveguide in a climate model depends on the strength of the jet stream ( Branstator 2002 ). This result was later corroborated by idealized simulations with a barotropic model, indicating that a jet must be strong and, in particular, narrow in order to make it a

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Maxi Boettcher and Heini Wernli

models were cloud-diabatic heating in a baroclinic background atmosphere producing a positive potential vorticity (PV) anomaly at low-tropospheric levels. The following basic conditions for DRW existence and propagation emerged from these simulations. The vortex of the positive low-level PV anomaly (that is accompanied by a weak SLP minimum) induces a poleward low-level jet of warm moist air at its downstream side. This stream ascends along the poleward-sloping isentropes until condensation occurs

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

, transients, and large-scale modes may contribute to the long-lasting blocking high on different time scales. Therefore, the present study focuses on the analysis of the interannual time scale using the summer mean to indicate the quasi-stationary wave structure, the synoptic time scale analyzing the mean eddy influence, and the intermediate time scale (~10–60 days) to show the wave train evolution. Besides the atmospheric dynamics, the land surface–atmosphere feedback is an additional factor that could

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Jana Čampa and Heini Wernli

Dacre and Gray (2009) showed that most developing cyclones are generated over the sea, which may be because of the availability of a moisture source and of reduced friction compared to land. Their study also showed that the cyclones generated in the eastern North Atlantic have lower SLP and higher relative vorticity in the center at the time of genesis than western North Atlantic cyclones, but the latter start in an environment with a stronger horizontal SST and wet-bulb potential temperature

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Andrea Schneidereit, Dieter H. W. Peters, Christian M. Grams, Julian F. Quinting, Julia H. Keller, Gabriel Wolf, Franziska Teubler, Michael Riemer, and Olivia Martius

1. Introduction During a stratospheric sudden warming (SSW) event, the polar stratospheric temperature increases accompanied by a weakening of the polar night jet. Major SSW events (MSSW) are defined as SSW events with a reversal of the zonal mean zonal wind from westerlies to easterlies at 60°N and a 10-hPa layer. Those events represent the greatest part of intraseasonal variability in the winter middle atmosphere and are associated with low predictive skill at lead times more than 10 days

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Kirstin Kober and George C. Craig

of moisture and temperature in the atmosphere determines the amount of CAPE and is influenced by several processes, especially in the atmospheric boundary layer. Soil type, land use, orography, and elevation are important because they define properties of the interaction between the land surface and the atmosphere. Several processes contribute to create variability in a convective boundary layer. The heating of surfaces with different heat conduction properties by the sun causes turbulent eddies

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

improvements in NWP, the quantitative precipitation forecast (QPF) skill has not changed significantly in recent years. Thus, improving the QPF is one of the main research interests in numerical weather prediction ( Fritsch and Carbone 2004 ; Rotunno and Houze 2007 ; Richard et al. 2007 ; Wulfmeyer et al. 2008 ). The interaction between various synoptic-scale and mesoscale processes, such as large-scale forcing ( Massacand et al. 2001 ; Hoinka and Davies 2007 ), orographic lifting ( Reeves and Rotunno

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Lisa-Ann Quandt, Julia H. Keller, Olivia Martius, and Sarah C. Jones

( ), summer day ( ), and tropical night ( ). 2) Wildfire potential Widespread wildfires were one of the most devastating impacts of the Russian heat wave in 2010 ( Witte et al. 2011 ). For our studies, we used the lower-atmosphere severity index (LASI) for wildlife fires of Haines (1988) . It is separated into four danger classes ( Table 4 ). See appendix B for definitions and additional information about the applications. Table 4. Ranges of the LASI and the associated danger classes adapted from

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