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K. Yoshimura and M. Kanamitsu

1. Introduction Integration of a regional numerical model requires time-varying forcing fields at the lateral boundaries. These forcing fields are taken from the larger scale model forecasts or analysis, either from a global model or from a coarser resolution regional model that covers the target domain. The latter method is known as a multiple nesting. A regional model that uses some form of spectral nudging to reduce the systematic error of the model ( Kida et al. 1991 ; von Storch et al

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Peter Knippertz and Andreas H. Fink

and the dynamics of an intense and widespread dry-season precipitation event in tropical West Africa in January 2004 and its relation to forcing from the extratropics. The abundant rainfall had large impacts on human activities in several West African countries. The event was accompanied by intense precipitation over the Algerian and Libyan Sahara and by dust storms over northeastern Africa. Besides analysis, satellite, and synoptic station data, high-resolution observations from a field site in

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Linda Schlemmer, Olivia Martius, Michael Sprenger, Cornelia Schwierz, and Arwen Twitchett

; Fuhrer and Schär 2005 ). On the synoptic-scale, high potential vorticity (PV) intrusions over western Europe play an important role in forcing HP along the Alpine south side ( Massacand et al. 1998 , 2001 ; Martius et al. 2006 ; Hoinka and Davies 2007 ). Generally, these intrusions adopt the form of narrow (∼500 km), deep (∼4 km), and meridionally elongated (∼2000 km) filaments of stratospheric air, termed PV streamers ( Appenzeller and Davies 1992 ), and reach from the British Isles southward to

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Heather Dawn Reeves, Yuh-Lang Lin, and Richard Rotunno

, Yuba River, Bear River, Butte Creek, and Eastern Tehama watersheds. An understanding of the underlying dynamical causes for this maximum is important because rainfall runoff from these watersheds ultimately drains into the Sacramento River, which flows through Sacramento, a city with a rather high flood threat and large population. The causes for the precipitation maximum at PNF are explored in this paper. As will be demonstrated, dynamical causes are case dependent, but two important forcings have

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Thomas Spengler and Joseph Egger

P is precipitation rate and E the evaporation rate (kg s −1 m −2 ) at the surface. Acknowledgments We thank P. Knippertz and A. Fink for some clarifying remarks on an earlier version of this comment. REFERENCES Knippertz , P. , and A. H. Fink , 2008 : Dry-season precipitation in tropical West Africa and its relation to forcing from the extratropics. Mon. Wea. Rev. , 136 , 3579 – 3596 . Kong , K-Y. , 2006 : Understanding the genesis of Hurricane Vince through the surface pressure

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Xiaoran Zhuang, Ming Xue, Jinzhong Min, Zhiming Kang, Naigeng Wu, and Fanyou Kong

-scale forcing on convection, and the convective events are often categorized into different regimes, namely, those that are strongly forced and weakly forced. As reported by Keil et al. (2014) , in case of strongly forced convection, large-scale flow dominates error growth, while for weakly forced convection controlled by local instabilities the contributions from both sources are approximately equal. Nielsen and Schumacher (2016) also found that in a case with strong convective to synoptic

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Anthony R. Lupo

1. Introduction Ageostrophic motions, and thus ageostrophic vorticities, have been traditionally viewed as a response to various dynamic and thermodynamic forcing processes, that when applied, perturb the balanced state of the atmosphere. Thus, ageostrophic motions have typically been analyzed in the context of an atmosphere that is initially in geostrophic or near geostrophic balance. Ageostrophic motions or ageostrophic winds have at least been considered to be a component or partition of the

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Joseph Egger

considered. It is an obvious extension of (1.1) to include a forcing term on the right so that is the equation to be analyzed. Periodic boundary conditions are imposed for a domain of length L of periodicity. Such an exercise is certainly far from being academic. One may, for example, interpret f as a source or sink term for a trace substance c. Then (1.2) represents a basic situation found in air pollution modeling as well as in transport calculations for chemical reactants (e.g., Hill 1976

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Xiaosong Yang, Timothy DelSole, and Hua-Lu Pan

wind V , and humidity Q . Because of our physical intuition that it is unwise to upset mass balance, surface pressure was not corrected. The correction terms were incorporated by integrating the GFS for one time step, then adding the product of estimated tendency error and model time step as an extra forcing term. The control experiments were conducted using the original GFS model without empirical correction. One might be tempted assume that correction forcings for wind and temperature should

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Katherine Bell and Peter Sawin Ray

hurricane- force winds will refer to the maximum radius of hurricane-force winds. There is a dearth of meteorological research concerning the systematic documentation of the maximum radii of hurricane-force winds in North Atlantic hurricanes. Schwerdt et al. (1979) examined the interrelationships of parameters that influence the strength and regional variation of hurricane wind fields. The parameters used in their study were central pressure, peripheral pressure, radius of maximum winds, forward

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