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Vinodkumar, A. Chandrasekar, K. Alapaty, and Dev Niyogi

improve the atmospheric boundary layer (ABL) simulations using improved surface boundary conditions in atmospheric models. The surface fluxes, and to some extent the entrainment fluxes at the top of the ABL, determine ABL structure and evolution. Improved surface fluxes over land require, in addition to surface observations of temperature and humidity, detailed observations of soil moisture and soil temperature. Soil moisture (and soil temperature) is not available from most routine meteorological

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Young-Kwon Lim, Ming Cai, Eugenia Kalnay, and Liming Zhou

NNR because the surface temperature observations are used in the initialization of soil temperature and moisture ( Simmons et al. 2004 ). Evaluation of reanalyzed tropical temperature time series archived from ERA-40 ( Palmer et al. 1990 ; Betts et al. 2003 ; Simmons et al. 2004 ) and NNR ( Kalnay et al. 1996 ; Kistler et al. 2001 ) indicates that the climatic trend derived from reanalysis data capture the upward surface temperature trends but that the trend is not identical to that of observed

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M. Baldi, G. A. Dalu, and R. A. Pielke Sr.

1. Introduction It is well known that mesoscale processes can act to provide adequate moisture and instability for convection to initiate, and surface processes such as those driven by surface heterogeneity or soil moisture gradients can play a fundamental role in the development of convection. Once initiated, the interaction of convection with shear can enhance storm evolution and lead to severe weather ( Chang and Wetzel 1991 ). In this perspective, the surface conditions (dry versus wet soil

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K. W. Oleson, G. B. Bonan, J. Feddema, M. Vertenstein, and C. S. B. Grimmond

[roofs: storage of liquid and solid precipitation (ponding and dew), evaporation, surface runoff; walls: hydrologically inactive; impervious road: storage of liquid and solid precipitation (ponding and dew), evaporation, surface runoff; pervious road: evaporation, infiltration, surface runoff, subsurface drainage, redistribution of water within the column]. The heat and moisture fluxes from each surface interact with each other through a bulk air mass that represents air in the UCL for which specific

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K. W. Oleson, G. B. Bonan, J. Feddema, and M. Vertenstein

1. Introduction Urban ecosystems can significantly alter the radiative, thermal, moisture, and aerodynamic characteristics of the land surface ( Landsberg 1981 ; Oke 1987 ; Bonan 2002 ; Arnfield 2003 ). As a consequence of these changes, urban climates can differ significantly from surrounding natural ecosystems, often resulting in urban heat islands (e.g., Landsberg 1981 ). The simulation of urban climate impacts requires two major components: 1) the representation of the physical

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