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Xuefeng Cui, Douglas J. Parker, and Andrew P. Morse

positive feedback from the recirculation of precipitation through the soil moisture reservoir may lead to prolonged persistence of anomalous wet or dry spells ( Betts et al. 1996 ; Taylor and Lebel 1998 ). Understanding the role of the feedback cycle between soil moisture, surface evaporation, and precipitation on continental scales has been featured in all of the Intergovernmental Panel on Climate Change (IPCC) reports, including the most recent (Fourth Assessment Report, AR4), along with the ability

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

is also worth noting that the bias-corrected radiosonde humidity was found to have a moist bias in TCWV with respect to ground-based GPS observations ( Agustí-Panareda et al. 2009c ). Over the Sahel, the model background has a moist bias close to the boundary layer top—around 850 hPa—depicted by a small kink in the observation departures in Fig. 5b . The analysis is able to reduce this bias effectively by reducing the moisture bias that develops in the background ( Fig. 6b ). In the

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Peter Knippertz and Andreas H. Fink

reproduce the details of the convective dynamics. Such a forecast is nevertheless of great value to the local population as discussed in the introduction. The unusual rainfalls are associated with a very pronounced, strongly tilted upper-level trough across northwestern Africa downstream of an equally pronounced upper ridge as indicated by Z500 at 1200 UTC 17 February 1999 ( Fig. 2a ). MSLP is reduced over a large area to the southeast of the trough axis, allowing low-level southerly moisture advection

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O. Bock and M. Nuret

use a 3DVAR system with 28 vertical levels from the surface up to 3 Pa and a spectral truncation of T62 (i.e., horizontal resolution of ∼210 km). Because it has coarser horizontal resolution, fewer surface stations are assimilated in regions of steep topography. There are many differences also in the parameterizations and the treatment of surface variables over land (e.g., the way soil moisture is adjusted from the observations). For what concerns the water cycle, NCEP2 is usually considered to be

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Françoise Guichard, Nicole Asencio, Christophe Peugeot, Olivier Bock, Jean-Luc Redelsperger, Xuefeng Cui, Matthew Garvert, Benjamin Lamptey, Emiliano Orlandi, Julia Sander, Federico Fierli, Miguel Angel Gaertner, Sarah C. Jones, Jean-Philippe Lafore, Andrew Morse, Mathieu Nuret, Aaron Boone, Gianpaolo Balsamo, Patricia de Rosnay, Bertrand Decharme, Philip P. Harris, and J.-C. Bergès

fluctuations during the monsoon than prior to its onset, when moisture advection dominates the water budget. Here, it is the PW variability that seems to be enhanced as the synoptic activity becomes more important during and after the major 28–29 August rainfall sequence. PW remains then higher throughout the Sahel ( Fig. 1a ). Some maxima of PW coincide with rainfall, for instance, on 28 August around 8°E ( Fig. 1e ) and on 26 August at 13°N ( Fig. 1a ). Other local maxima occur the day after rainfall

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Sen Chiao and Gregory S. Jenkins

domain. Grid-scale precipitation was determined from an explicit moisture scheme ( Thompson et al. 2004 ) that includes graupel. The atmospheric model was coupled with the Noah land surface model, which includes four soil layers, and it solves the water and energy balance equations at the land surface. The Grell scheme was adopted for cumulus parameterization for the 25-km domain, while no cumulus parameterization was used in the inner domain. The three numerical experiments [the control run (CTRL

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Adrian M. Tompkins and Laura Feudale

winds, and convection in this region (e.g., Dommenget and Latif 2000 ), coupled models tend to do poorly at predicting these SSTs, with many models exhibiting strong positive temperature biases. Third, while the basic monsoon dynamics in West Africa is reasonably well understood, the intraseasonal and interannual variabilities of the monsoon rains in West Africa depend on a rich array of locally interacting processes, involving deep convection, soil moisture and vegetation properties ( Taylor et al

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Ryan D. Torn

their evolution, the sensitivity of 12- and 48-h MKE forecasts is computed with respect to the analysis of the 700-hPa meridional wind and the equivalent potential temperature ( θ e ) averaged between 3000 and 7000 m (i.e., midtroposphere). Although θ e is not a WRF state variable, this field allows for a quantitative comparison of the role of thermodynamic errors versus kinematic errors. In general, locations that are sensitive to θ e are sensitive to both the temperature and moisture (not

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C. Faccani, F. Rabier, N. Fourrié, A. Agusti-Panareda, F. Karbou, P. Moll, J.-P. Lafore, M. Nuret, F. Hdidou, and O. Bock

the atmosphere, which is extremely important for an accurate description of the monsoon evolution patterns over these regions. In particular, radiosonde data are an important source of moisture data, a crucial piece of information that enables the study of the thermodynamical processes in the atmosphere. For these reasons, several studies have been conducted in order to detect and to quantify the errors associated with the relative humidity from radiosondes. It is well known ( Lorenc et al. 1996

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Fatima Karbou, Elisabeth Gérard, and Florence Rabier

moisture. Many studies have been carried out to improve our understanding of the land emissivity variability ( Choudhury 1993 ; Felde and Pickle 1995 ; Jones and Vonder Haar 1997 ; Karbou et al. 2005 ; Morland et al. 2000 , 2001 ; Prigent et al. 1997 , 2000 ; Mätzler 1994 ; Ruston and Vonder Haar 2004 ; Ruston et al. 2008 , among others), but only a few of them have addressed the issue of land emissivity modeling within the constraints of variational assimilation ( Prigent et al. 2005

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