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Frédéric Fabry and Juanzhen Sun

about data assimilation in a more conceptual way than usual. In particular, in this work, a greater emphasis will be put on the nature and characteristics of the data to be assimilated or of the model fields to be constrained. Data assimilation is explicitly designed to constrain model variables with noisy measurements. But for data assimilation to succeed, three additional conditions must be met well enough. First, the difference between the assumed atmospheric state x ′ and the true

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Chaojiao Sun, Michele M. Rienecker, Anthony Rosati, Matthew Harrison, Andrew Wittenberg, Christian L. Keppenne, Jossy P. Jacob, and Robin M. Kovach

current depends strongly on the wind forcing product; however, parameterizations in surface layer physics also need to be improved to reduce the uncertainty in surface current estimates. Because of the role of advection in SST variations (e.g., Borovikov et al. 2001 ), it is also of interest whether the assimilation of the temperature profile data impacts the surface current estimate. Unfortunately, few surface current measurements exist. The near-surface estimates from acoustic Doppler current

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Paul J. Neiman, F. Martin Ralph, Allen B. White, David D. Parrish, John S. Holloway, and Diana L. Bartels

Valley cold pool was captured recently by a NOAA/ETL wind profiler and radio acoustic sounding system (RASS; described in section 2 ) at Chowchilla, California (CCL; Fig. 2 ). Shallow cold air formed in situ on 11 December 2004 after the low-level flow weakened to <3.5 m s −1 . The cold air persisted in the stagnant flow for two weeks and was capped by a layer of enhanced static stability whose base ranged in altitude from 300 to 1100 m. The wind shear across the cap was weak, thus preventing the

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Eugene W. McCaul Jr. and Morris L. Weisman

surface vorticity development, a fact that may help explain why mosthurricane-spawned tornadoes are weaker than their Great Plains counterparts.1. Introduction Numerical simulations of convective storms have revealed much about the dynamics of severe storms thatform in typical midlatitude environments. Klemp andWilhelmson (1978) and Wilhelmson and Klemp(1978) describe the effects of vertical shear on simulated storm evolution, particularly the tendency forcells to split laterally with respect to

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X. Zou, Y-H. Kuo, and Y-R. Guo

experiments, we wouldlike to assess the impact of assimilating each individualvariable and its effects on the other fields. All the4DVAR OSSEs used the same IC and LBC as that ofexperiment 3. We also need to assess the impact of refractivity assimilation in an environment with relatively dense measurements of wind and temperature. Experiments 7-9assimilated a combination of observations during the2-h assimilation window: refractivity and wind (experiment 7), temperature and wind (experiment 8

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Dayid R. Fitzjarrald and Michael Garstang

was also equipped to make automatic observations of wet- and dry-bulb air temperatures, sea surface temperature, wind speed anddirection, and incident, reflected and net radiation.The sensors were mounted on a boom extendingfrom the bow of the ship, 8-10 m above the seasurface. The boom system described by Seguin etal. (1977) was designed to obtain measurements inthe surface layer free of the ship effects. Comparisons discussed by Seguin et al. with the Meteorbuoy suggest this objective was

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Georg J. Mayr and Thomas B. McKee

. By comparingda :a from Meeker with Tabernash, we were able tom;tke some deductions about the horizontal extent ofth,: blocked layer. Besides wind, the site in Meeker alsom, insured virtual temperature with RASS (radio acoustic sounding system) during two short periods. Although ihe profiler in Dugway was far enough removed from the Continental Divide to not feel itsblacking influence, the flow there was subject to blockin g effects from the Wasatch Range. During three special observation

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Julie Pullen, James D. Doyle, and Richard P. Signell

; Chelton et al. 2001 ). Similar effects have been observed in the Arabian Sea ( Vecchi et al. 2004 ) and remotely sensed in the Southern Ocean, Kuroshio, and Gulf Stream regions ( O’Neill et al. 2003 ; Nonaka and Xie 2003 ; Park and Cornillon 2002 ). Internal boundary layers (IBLs) typically develop as air moves across a discontinuity in surface properties ( Garratt 1990 ). The dynamical response of the ABL to small-scale temporal and spatial variations in sea surface temperature has been

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C. Warner and G. L. Austin

sensitivity with range. Data withinrange 10 km were not recorded to avoid problems ofsea clutter. Calibration of the radar included power measure ments in the far field and measurements at radio fre quency in the receiver. By comparison with the three ship radars operated during GATE under the auspices of NOAA, and with raingage data, Dr. M. D. Hudlow of the Center for Experimental Design and Data Analysis (NOAA) has Obtained an absolute calibration of the Quadra radar, differing by a few decibels

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Sami Niemelä and Carl Fortelius

forecasts are very important for hydrological applications. Catchment models can employ such forecasts in real-time prediction of river flows ( Montanari and Uhlenbrook 2004 ) and flood events. Hydrological models are also essential tools for planning the optimal management of water resources ( Uhlenbrook et al. 2004 ). In addition, precipitation intensity is a critical parameter for air quality and dispersion modelers in estimation of the scavenging effects of air pollutants, as described in the

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