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Robert S. Ross, T. N. Krishnamurti, S. Pattnaik, and A. Simon

processes represented by the five terms on the right-hand side of the equation: horizontal advection, vertical advection, vertical differential of heating, horizontal differential of heating, and friction. The friction term is not included in the calculations of this study. The total diabatic heating is considered to be the sum of terms 2–4 on the right-hand side of the equation, (i.e., vertical advection, vertical differential of heating, and horizontal differential of heating). The vertical advection

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Ryan D. Torn

analysis in this area (e.g., Tompkins et al. 2005 ). Furthermore, the relationship between diabatic heating, large-scale convection, and AEWs suggests that the formulation of the convective parameterization plays a significant role in the model evolution. Berry et al. (2009, manuscript submitted to Wea. Forecasting ) evaluated the skill of AEW forecasts within four different operational NWP systems during 2007. Although each modeling system’s West Africa analysis has nearly identical errors with

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Anna Agustí-Panareda, Anton Beljaars, Carla Cardinali, Iliana Genkova, and Chris Thorncroft

Thorncroft 2005 ) that is most commonly linked to topography (see Mekonnen et al. 2006 ). Thorncroft et al. (2008) showed, using an idealized dry-adiabatic model, that imposed transient diabatic heating can trigger an AEW downstream as well as increase the overall AEW activity for several days thereafter. This is due to a projection of the perturbation on the most unstable mode for the zonally varying basic state ( Hall et al. 2006 ). The amplitude of the downstream AEW response depends on the

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Peter Knippertz and Andreas H. Fink

activities reaching from greening pastures to flooding and rotting harvests ( Knippertz and Martin 2005 ; Fall et al. 2007 ; KF08 ). KF08 proposed a close link of the unusual tropical rainfalls to the synoptic evolution in the extratropics. They show that extratropical disturbances penetrating into low latitudes support a diabatic pressure fall over West Africa through the anomalous radiative warming under a diagonal cloud band on the eastern flank of a first trough, often referred to as a tropical

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Sen Chiao and Gregory S. Jenkins

22 August 2006 (i.e., 12.0°N, 22.7°W). The line of convection and associated diabatic heating over central Guinea at 0000 UTC 20 August led to the production of potential vorticity (PV) on the 315-K potential temperature surface ( Fig. 8a ). From the morning hours to 1200 UTC 20 August ( Fig. 8b ), the production of PV continued over the Guinea Highlands. Subsequently, it propagated westward to the coast. There was concentrated convection between 0600 and 1400 UTC offshore and over Guinea at

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