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Daniela Nowak, Dominique Ruffieux, Judith L. Agnew, and Laurent Vuilleumier

information about the meteorological conditions are important for weather forecasters, climate studies, and aviation control. One of the high priority duties of observers is the description of the evolution of clouds, especially within the planetary boundary layer. However, automatic weather reports are becoming important because human observations are becoming more difficult to organize, especially during nighttime ( Aviolat et al. 1998 ). The cloud amount (sky coverage in octas) can be automatically

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Ronny Engelmann, Ulla Wandinger, Albert Ansmann, Detlef Müller, Egidijus Žeromskis, Dietrich Althausen, and Birgit Wehner

1. Introduction The vertical exchange of sensible heat (temperature), latent heat (moisture), particles, and trace gases between the surface and the lower troposphere has a strong influence on weather and climate and atmospheric composition, as well as on smog and haze conditions at the ground. Vertical exchange depends in a complicated way on surface characteristics and meteorological conditions in the planetary boundary layer (PBL). The mechanisms within the PBL and in the entrainment zone

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Rod Frehlich, Yannick Meillier, and Michael L. Jensen

1. Introduction Measuring and modeling of the boundary layer is challenging, especially for the nighttime stable boundary layer (SBL). In particular, high-quality in situ measurements of profiles of mean and turbulent statistics of the nighttime SBL are logistically difficult using instrumented towers or instrumented research aircraft ( Tjernström 1993 ). A suite of fast response turbulence sensors attached to a tethered system can operate effectively under these nighttime conditions. The

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P. C. S. Devara, P. E. Raj, K. K. Dani, G. Pandithurai, M. C. R. Kalapureddy, S. M. Sonbawne, Y. J. Rao, and S. K. Saha

forcing influences the aerosol patterns that are formed because of surface-generated aerosols, especially during the early morning transition from a stable to convective boundary layer and the late evening transition from a convective to a stable boundary layer ( Lenshow et al. 1979 ). Lidars play an important role in these studies because of their capability to make very precise continuous measurements of different aerosol and cloud parameters ( McCormick et al. 1993 ). Detailed knowledge of aerosols

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Laura Bianco, James M. Wilczak, and Allen B. White

probability of that gate being the PBL top was small, and conversely, that if the variance was small, the probability was large. During cloud-free conditions, such as the data used in BW02 , the profile of vertical velocity variance profile generally follows the expected pattern. However, many of the days at Plymouth and Pittsburgh were partly cloudy, especially with fair-weather boundary layer cumulus. When boundary layer clouds are present, the behavior of the profile of vertical velocity variance

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Matthias Grzeschik, Hans-Stefan Bauer, Volker Wulfmeyer, Dirk Engelbart, Ulla Wandinger, Ina Mattis, Dietrich Althausen, Ronny Engelmann, Matthias Tesche, and Andrea Riede

allows the model to be used at kilometer scales; multitasking capability on shared- and distributed-memory machines; different methods for data assimilation [4D data assimilation (FDDA), 3DVAR, and 4DVAR]; and various physics options of different complexity. A detailed overview of the MM5 is given in Grell et al. (1995) . Since MM5 is a regional model, it requires an initial condition as well as lateral boundary conditions to run. To produce lateral boundary condition for a model run, one

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Danny E. Scipión, Phillip B. Chilson, Evgeni Fedorovich, and Robert D. Palmer

) method ( Balsley and Gage 1982 ). BLRs are also sensitive to Rayleigh scatter from hydrometeors and are used to study clouds and precipitation ( Gage et al. 1994 ; Ecklund et al. 1995 ). Thus, the BLR can be used to study the boundary layer under a wide variety of meteorological conditions and has proven invaluable for such investigations (e.g., Rogers et al. 1993 ; Angevine et al. 1994 ; Wilczak et al. 1996 ; Dabberdt et al. 2004 ). Frequency-modulated continuous-wave (FMCW) radar measurements

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Ulrich Löhnert, S. Crewell, O. Krasnov, E. O’Connor, and H. Russchenberg

1. Introduction Continuous profiling of the thermodynamic state of the atmosphere is becoming more and more important in support of mesoscale models, which are increasingly employed for numerical weather prediction (NWP). Especially the development of the boundary layer (BL), for example, its diurnal cycle or its influence on the initiation of convection, is crucial for the correct prediction of regional weather scales, including severe events, such as extreme precipitation. In this context the

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B. L. Cheong, R. D. Palmer, T-Y. Yu, K-F. Yang, M. W. Hoffman, S. J. Frasier, and F. J. Lopez-Dekker

underlying atmospheric characteristics ( Koscielny et al. 1984 ; Strauch et al. 1987 ). Bias of the wind estimates can be caused by a spatial gradient of the wind field, such as nonuniform vertical velocities across the observed region and/or horizontal shear ( Koscielny et al. 1984 ). If any of these conditions occur, of course, the horizontal homogeneity assumption is no longer valid. Koscielny et al. (1984) have shown that the bias increases with increasing zenith angles of the off-vertical beams

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Edwin F. Campos, Wayne Hocking, and Frédéric Fabry

1. Introduction Quantitative measurements of meteorological variables by radar imply the use of the radar equation. This is a relationship that links the radar-received power to the scatterers’ cross sections. Standard forms for this equation assume, most of the time, an average scatterer cross section per unit volume (or radar reflectivity) that is constant within the sampling volume of a given range gate. Under these conditions and neglecting the effect of the convolution of the transmitted

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