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Daniel Leuenberger, Alexander Haefele, Nadja Omanovic, Martin Fengler, Giovanni Martucci, Bertrand Calpini, Oliver Fuhrer, and Andrea Rossa

( Reichardt et al. 2012 ), and the Raman Lidar for Meteorological Observations (RALMO) operated by MeteoSwiss ( Dinoev et al. 2013 ). We consider RALMO representative of state-of-the-art automated Raman lidars and a more detailed description is provided in the following section. Advances in laser technology have paved the way for commercial instruments, which are nowadays available ( Lange et al. 2019 ; Fréville et al. 2015 ). Though operational deployment of such commercial instruments is still very

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Ronald T. H. Collis

In connection with studies of aerial insecticide spraying techniques being carried out by the U. S. Forest Service, Stanford Research Institute personnel have been making lidar observations of smoke and spray material discharged by aircraft flying over forest terrain. The motion of the smoke and suspended spray droplet clouds can be tracked by lidar even when they are not visible to the eye. This makes it possible to study the motion and diffusion of parcels of air caused by micrometeorological factors, such as the insolation of valley slopes. While of primary interest in connection with aerial spraying operations, this research provides new quantitative information regarding atmospheric motion in forest valleys.

The ruby and neodymium lidar instrumentation used is described and the methods of observation explained. Representative results are presented and discussed.

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David Atlas and C. Laurence Korb

The spectrum of weather and climate needs for lidar observations from space is discussed. This paper focuses mainly on the requirements for winds, temperature, moisture, and pressure. Special emphasis is given to the needs for wind observations and it is shown that winds are required to depict realistically all atmospheric scales in the tropics and the smaller scales at higher latitudes, where both temperature and wind profiles are necessary. The need for means to estimate air-sea exchanges of sensible and latent heat also is noted. Lidar can aid here by measurement of the slope of the boundary layer. Recent theoretical feasibility studies concerning the profiling of temperature, pressure, and humidity by differential absorption lidar (DIAL) from space and expected accuracies are reviewed. Initial ground-based trials provide support for these approaches and also indicate their direct applicability to path-average temperature measurements near the surface. An alternative approach to Doppler lidar wind measurements also is presented. The concept involves the measurement of the displacement of the aerosol backscatter pattern, at constant height, between two successive scans of the same area, one ahead of the spacecraft and the other behind it, a few minutes later. Finally, an integrated space lidar system capable of measuring temperature, pressure, humidity, and winds which combines the DIAL methods with the aerosol pattern displacement concept is described briefly.

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Bianca Adler, Alexander Gohm, Norbert Kalthoff, Nevio Babić, Ulrich Corsmeier, Manuela Lehner, Mathias W. Rotach, Maren Haid, Piet Markmann, Eckhard Gast, George Tsaknakis, and George Georgoussis

studies which investigate the spatial structure of the flow in valleys is limited: for cases when the cross-valley component of the large-scale wind is strong, scanning ground-based remote sensing instruments such as Doppler lidars partly in combination with research aircraft measurements have successfully been used to study rotors (e.g., Hill et al. 2010 ; Strauss et al. 2016 ), downslope windstorms (e.g., Adler and Kalthoff 2016 ), and foehn events (e.g., Haid et al. 2020 ). For periods when

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Dino Zardi, Marco Falocchi, Lorenzo Giovannini, Werner Tirler, Elena Tomasi, Gianluca Antonacci, Enrico Ferrero, Stefano Alessandrini, Pedro A. Jimenez, Branko Kosovic, and Luca Delle Monache

valleys, and on phenomena such as formation and evolution of inversions and transport of pollutants around layers trapped in valleys. Similarly, the project Persistent Cold-Air Pool (PCAPS) explored extensively in 2010–11 the persistence of long-lasting cold pools in the Salt Lake Valley and its implications for air quality ( Lareau et al. 2013 ). Also, the project Mountain Terrain Atmospheric Modeling and Observations (MATERHORN) investigated complex-terrain meteorology over a wide range of scales

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R. T. H. Collis

Lidar, using pulsed lasers as energy sources, applies the radar principle at wavelengths in and near the visual spectrum to probe the atmosphere. It can detect particulate matter of much smaller dimensions and sparser concentration than is possible with meteorological radar. Lidar may be used to measure cloud base heights although difficulties arise with diffuse clouds, especially in foggy conditions. Inhomogeneities in turbidity that occur at the heights of temperature inversions in the relatively clear atmosphere are also revealed by lidar. Examples of work in progress that show promise of providing a measurement of visibility are presented.

It is concluded that lidar can already contribute usefully in routine meteorological service, but that its full potential in ceilometry and visibility measurement awaits further developments. For routine unattended use, high pulse-rate low peak-power lidars are advocated on grounds of safety.

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Craig B. Clements, Neil P. Lareau, David E. Kingsmill, Carrie L. Bowers, Chris P. Camacho, Richard Bagley, and Braniff Davis

1990 ; Cunningham et al. 2005 ; Umscheid et al. 2006 ; Seto and Clements 2011 ), whereas detailed quantified observations are not. Banta et al. (1992) , for example, provided direct measurements (with lidar and radar) of counterrotating vortex pairs and whole column rotation, but how these single instance observations compare to the scale and intensity of vortical structures in other fires is not known. Beyond vortical structures, fires are also known to produce strong updrafts and horizontal

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Wayman E. Baker, Robert Atlas, Carla Cardinali, Amy Clement, George D. Emmitt, Bruce M. Gentry, R. Michael Hardesty, Erland Källén, Michael J. Kavaya, Rolf Langland, Zaizhong Ma, Michiko Masutani, Will McCarty, R. Bradley Pierce, Zhaoxia Pu, Lars Peter Riishojgaard, James Ryan, Sara Tucker, Martin Weissmann, and James G. Yoe

per-observation basis for the ECMWF data assimilation system. OSSEs An extensive series of global observing system simulation experiments (OSSEs) has been conducted since the mid-1980s to determine the potential influence of wind profile observations from space and to evaluate trade-offs in the design of a space-based wind lidar. These early experiments showed the great potential for space-based wind profile observations reducing analysis errors and improving numerical forecasts. These studies

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Thomas F. Lee, Richard L. Bankert, and Cristian Mitrescu

Profiles from CloudSat and CALIPSO , atmospheric profilers within the NASA A-Train constellation, offer detailed observations of clouds, providing understanding that neither satellite imagers nor traditional sounders can convey. The potential for training forecasters and educating students is immense using data from the National Aeronautic and Space Administration's (NASA's) two A-Train ( L'Ecuyer and Jiang 2010 ) profilers, CloudSat ( Stephens et al. 2002 ) and Cloud–Aerosol Lidar and

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A. J. Illingworth, D. Cimini, C. Gaffard, M. Haeffelin, V. Lehmann, U. Löhnert, E. J. O’Connor, and D. Ruffieux

lidar to study boundary layer dynamics over London, United Kingdom. Dacre et al. (2010) report on the use of Doppler lidar to study the ash plume of the Icelandic volcano. Westbrook et al. (2010) describe how the properties of ice crystals falling from supercooled clouds can be inferred from Doppler lidar observations. Westbrook and Illingworth (2009) used Doppler lidar to infer the size spectrum of ice crystals in clouds. F ig . 6. Doppler lidar products. Aerosol particles act as reliable

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