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F. Couvreux, F. Guichard, P. H. Austin, and F. Chen

1. Introduction Water vapor variability was the main focus of the International H 2 O Project (IHOP_2002), which took place in May–June 2002 over the southern Great Plains of the United States ( Weckwerth et al. 2004 ). This field project gathered together most of the techniques for measuring water vapor. We address water vapor variability at the mesoscale (scales larger than thermals, ranging from tens to a few hundreds of kilometers). Comparatively few investigations have considered this

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Lindsay J. Bennett, Tammy M. Weckwerth, Alan M. Blyth, Bart Geerts, Qun Miao, and Yvette P. Richardson

. Pelon , 2001 : Airborne lidar LEANDRE II for water-vapor profiling in the troposphere. Appl. Opt. , 40 , 3450 – 3475 . Cohn , S. A. , and W. M. Angevine , 2000 : Boundary-layer height and entrainment zone thickness measured by lidars and wind profiling radars. J. Appl. Meteor. , 39 , 1233 – 1247 . Couvreux , F. , F. Guichard , J. L. Redelsperger , C. Kiemle , V. Masson , J. P. Lafore , and C. Flamant , 2005 : Water-vapour variability within a convective boundary

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Robin L. Tanamachi, Wayne F. Feltz, and Ming Xue

1. Introduction During the intensive observation period (IOP) from 13 May to 25 June 2002 of the International H 2 O Project (IHOP_2002), a large array of in situ, mobile, and aircraft-mounted water vapor sensing instruments from many institutions took collaborative water vapor measurements over the central United States ( Weckwerth et al. 2004 ; Weckwerth and Parsons 2006 ). One of the specified objectives of IHOP_2002 was “improved characterization of the four-dimensional (4-D) distribution

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S. B. Trier, F. Chen, K. W. Manning, M. A. LeMone, and C. A. Davis

studies have emphasized the hydrological importance of horizontal transport of water vapor from remote regions (e.g., Trenberth 1999 ; Dirmeyer and Brubaker 1999 ). The 1993 summer regional-scale precipitation anomaly that led to widespread flooding over the upper Mississippi River basin of the central United States presents an example that has been widely investigated using both global (e.g., Trenberth and Guillemot 1996 ; Beljaars et al. 1996 ; Viterbo and Betts 1999 ) and regional ( Paegle et

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Diane Strassberg, Margaret A. LeMone, Thomas T. Warner, and Joseph G. Alfieri

computed relative to half-hour averages, using 5-min block averages that were quality-checked and postprocessed by the Integrated Surface Flux Facilities (ISFF) of NCAR using a standard suite of corrections that are summarized at http://www.eol.ucar.edu/rtf/projects/ihop_2002/isff/ . The water vapor flux was estimated from the water vapor concentration and sonic anemometer vertical velocity. The temperature flux was calculated from the vertical sonic-temperature flux using the specific humidity flux

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Roger M. Wakimoto and Hanne V. Murphey

our ability to forecasts these events, it has been suggested that further gains in predictability would occur if high-resolution water vapor measurements in the boundary layer could be obtained (e.g., Emanuel et al. 1995 ; Dabberdt and Schlatter 1996 ; Weckwerth et al. 2004 ). Several recent studies have shown that inclusion of detailed water vapor measurements has improved our understanding of storm initiation (e.g., Sun 2005 ; Murphey et al. 2006 ; Fabry 2006 ; Roberts et al. 2008

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Steven E. Koch, Wayne Feltz, Frédéric Fabry, Mariusz Pagowski, Bart Geerts, Kristopher M. Bedka, David O. Miller, and James W. Wilson

1. Introduction One of the coordinated research objectives of the International H 2 O Project (IHOP), which occurred from 13 May to 25 June 2002 in the southern Great Plains of the United States, was to seek to improve understanding of the relationship between water vapor and processes occurring in the surface and boundary layers that might have a bearing on convective initiation ( Weckwerth et al. 2004 ). Density currents and bores are lower-tropospheric phenomena that have a proven capability

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Edward I. Tollerud, Fernando Caracena, Steven E. Koch, Brian D. Jamison, R. Michael Hardesty, Brandi J. McCarty, Christoph Kiemle, Randall S. Collander, Diana L. Bartels, Steven Albers, Brent Shaw, Daniel L. Birkenheuer, and W. Alan Brewer

installation in the Falcon adjacent to the DLR DIAL system. DIAL is an appropriate technique for the remote sensing of atmospheric trace gases such as water vapor. A DIAL emits short light pulses into the atmosphere at two distinct wavelengths. The online wavelength is tuned to the center of a molecular water vapor absorption line (around 927 nm in IHOP_2002). The offline wavelength is the reference and contains information about the aerosol load and cloud cover of the probed atmosphere. Combining both

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Margaret A. LeMone, Fei Chen, Mukul Tewari, Jimy Dudhia, Bart Geerts, Qun Miao, Richard L. Coulter, and Robert L. Grossman

; Chen et al. 2007 ), and coupled to the Noah land surface model (LSM; Ek et al. 2003 ). The goal of IHOP_2002 is to improve prediction of continental warm-season precipitation in numerical weather prediction models by improving the measurement and use of water vapor data, and by improving representation of the evolution of water vapor in numerical weather prediction models. Land surface processes are emphasized because of their importance in the initiation and evolution of precipitating

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Margaret A. LeMone, Mukul Tewari, Fei Chen, Joseph G. Alfieri, and Dev Niyogi

the air. Aircraft H and LE estimates are based on vertical velocity determined from the Rosemount 858AJ/1332 differential gust-probe system and a Honeywell Laseref SM inertial navigation system, with temperature from a reverse-flow thermometer developed at the University of Wyoming. Water vapor fluctuations are sampled using a Li-Cor-6262 gas analyzer and a Lyman- α instrument from NCAR. The Li-Cor measures infrared absorption by water vapor; while the Lyman- α measures absorption of

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