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Chunmei Zhu and Dennis P. Lettenmaier

extremity of the much more pronounced NAMS phenomenon over northwestern Mexico). A key to understanding this predictability is datasets that support analyses of land–atmosphere interactions. The dataset described in this paper arises from this motivation. To date, data that will support land–atmosphere feedback studies within the NAMS region, particularly land surface states and fluxes such as soil moisture and turbulent heat fluxes, have been essentially nonexistent. This is a result mostly of the

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Christopher J. Watts, Russell L. Scott, Jaime Garatuza-Payan, Julio C. Rodriguez, John H. Prueger, William P. Kustas, and Michael Douglas

-Arid Land-Surface-Atmosphere (SALSA) campaign over grassland and shrubland in the San Pedro catchment in 1997–98 ( Chehbouni et al. 2000 ). Neither of these campaigns was specifically designed to study the monsoon system. The intensive observation period (IOP) for NAME took place in the period July–September 2004 and a small network of flux stations ( Fig. 1 ) were set up in the core monsoon region in order to study the exchange of radiation, heat, and water vapor between the surface and the atmosphere

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Alberto M. Mestas-Nuñez, David B. Enfield, and Chidong Zhang

1. Introduction Mestas-Nuñez et al. (2005) have recently evaluated the uncertainties in estimating moisture flux divergences over the Intra-Americas Sea (IAS; composed of the Gulf of Mexico and the Caribbean Sea) using several datasets, which include sounding observations, the National Centers for Environmental Prediction (NCEP) Eta regional analysis ( Black 1994 ), the NCEP–National Center for Atmospheric Research (NCAR) global reanalysis ( Kalnay et al. 1996 ; Kistler et al. 2001 ), and the

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Paquita Zuidema, Chris Fairall, Leslie M. Hartten, Jeffrey E. Hare, and Daniel Wolfe

to the NAME sounding network, helped assess the contribution of the surface fluxes to the regional meteorology and oceanography, documented the mean and diurnally varying wind flow, and provided a surface-based assessment of the cloud field and boundary layer structure. A preliminary analysis is presented here. The observational period included a strong gulf surge around 13 July that coincided with the onset of the summer monsoon in southern Arizona. The surge was associated with Tropical

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Kingtse C. Mo, Eric Rogers, Wesley Ebisuzaki, R. Wayne Higgins, J. Woollen, and M. L. Carrera

precipitation. Areas with negative P anomalies are warmer ( Fig. 6f ). The coarse-resolution CDAS model does not resolve the Gulf of California (GoC) ( Schmitz and Mullen 1996 ). It is interesting to examine whether the assimilation of soundings along the GoC improves the representation of the low-level jet from the Gulf of California (GCLLJ). The vertically integrated moisture fluxes from the operational GDAS ( Fig. 7a ) clearly show two low-level jets: one from the Gulf of Mexico to the Great Plains

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Wayne Higgins and David Gochis

phase with precipitation occurring over the SMO (Lang et al., Zuidema et al.) while precipitation at higher elevations tends to occur several hours earlier in the day (∼1400 LT) compared to precipitation at lower elevations (∼1800 LT). Given the strong dependence on terrain forcing for modulating hydrometeorological fluxes (e.g., precipitation and evapotranspiration) and responses (e.g., infiltration and runoff), and the complexity of terrain, coherent climatic regions in the NAME tier I domain are

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Chunmei Zhu, Tereza Cavazos, and Dennis P. Lettenmaier

capacity). Past studies have been constrained by the lack of long-term, consistent observations of land surface variables that might be predictors of the land surface state, and hence the onset and strength of NAMS. Zhu and Lettenmaier (2007) describe a long-term gridded set of observed surface climate variables, and model-derived [using the Variable Infiltration Capacity (VIC) macroscale hydrological model] land surface states and fluxes for a domain consisting of all of Mexico for the period 1925

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Myong-In Lee, Siegfried D. Schubert, Max J. Suarez, Isaac M. Held, Arun Kumar, Thomas L. Bell, Jae-Kyung E. Schemm, Ngar-Cheung Lau, Jeffrey J. Ploshay, Hyun-Kyung Kim, and Soo-Hyun Yoo

-level jets. This implies that the parameterized precipitation process in the model is rather insensitive to the large-scale wind variations and accompanying moisture flux, regardless of the model resolution. This is apparently a typical problem of buoyancy closure convection schemes ( Lee et al. 2007 ). An increase in the resolution of the GFDL model also induces much stronger diurnal rainfall variability over the mountain region ( Fig. 6 ). One of the notable differences, however, is that the higher

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Enrique R. Vivoni, Hugo A. Gutiérrez-Jurado, Carlos A. Aragón, Luis A. Méndez-Barroso, Alex J. Rinehart, Robert L. Wyckoff, Julio C. Rodríguez, Christopher J. Watts, John D. Bolten, Venkataraman Lakshmi, and Thomas J. Jackson

properties, in particular soil moisture and vegetation, have received much less attention. Theoretically, soil wetness and plant cover can influence the surface energy balance through changes to the albedo, temperature, and partitioning into sensible and latent heat fluxes. Eltahir (1998) hypothesized that variations in surface conditions caused by soil moisture and vegetation dynamics can have a direct impact on the moist static energy in the boundary layer with subsequent effects on rainfall

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Mekonnen Gebremichael, Enrique R. Vivoni, Christopher J. Watts, and Julio C. Rodríguez

rainfall have suggested several mechanisms; however, none of these mechanisms appears, by itself, to explain the majority of the rainfall variability pattern. Berbery (2001) analyzed the Eta Model’s moisture flux at 950 hPa and suggested that the transients rather than the mean flow play a dominant role in bringing moisture flux into this region. Tropical storms are one transient phenomenon that brings abundant rainfall to the region ( Englehart and Douglas 2001 ). Analyzing 9 yr of radiosonde

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