Abstract. In this paper, we describe the PALM model system 6.0. PALM (formerly an abbreviation for Parallelized Large-eddy Simulation Model and now an independent name) is a Fortran-based code and has been applied for studying a variety of atmospheric and oceanic boundary layers for about 20 years. The model is optimized for use on massively parallel computer architectures. This is a follow-up paper to the PALM 4.0 model description in Maronga et al. (2015). During the last years, PALM has been significantly improved and now offers a variety of new components. In particular, much effort was made to enhance the model with components needed for applications in urban environments, like fully interactive land surface and radiation schemes, chemistry, and an indoor model. This paper serves as an overview paper of the PALM 6.0 model system and we describe its current model core. The individual components for urban applications, case studies, validation runs, and issues with suitable input data are presented and discussed in a series of companion papers in this special issue.

Pulsed Doppler lidars are powerful tools for long-range, high-resolution measurements of radial wind velocities. With the development of commercial Doppler lidars and the reduction of acquisition costs, dualDoppler lidar systems will be become increasingly accessible in upcoming years. This study reviews the most common dual-Doppler techniques, describes the setup of a highly synchronized long-range dual-Doppler lidar system, and discusses extensively the different kinds of errors connected with this complex measurement technique. Sources of errors and their interactions are traced through the retrieval algorithm, including errors from single-Doppler lidar and those occurring from a combination of instruments related to various parameters, such as relative beam angles, time and spatial scales of the scan pattern, and atmospheric conditions.

In this article we present some laboratory experiments on stratified flows over isolated obstacles which were aimed at the simulation of atmospheric rotors as induced by the interaction of mountain waves and the boundary layer. For this purpose we modified the classical tank experiments on mountain waves performed with constant density gradients by introducing an elevated density inversion above the obstacle height. This kind of inversion seems to favour very much the development of mountain-induced rotors as was shown in recent numerical simulations. In fact our experimental set-up was guided by the simulations of Vosper, which provided systematically the upstream conditions under which mountain rotors are expected. We were able to confirm the results from these numerical simulations over a wide range of parameters. Detailed analyses of flow structures for some selected cases, as obtained by particle image velocimeter analysis, are presented.

Abstract. In this paper we describe the PALM model system 6.0. PALM is a Fortran based code and has been applied for studying a variety of atmospheric and oceanic boundary layers for about 20 years. The model is optimized for use on massively parallel computer architectures. This is a follow-up paper to the PALM 4.0 model description in Maronga et al. (2015). During the last years, PALM has been significantly improved and now offers a variety of new components. In particular, much effort was made to enhance the model by components needed for applications in urban environments, like fully interactive land surface and radiation schemes, chemistry, and an indoor model. This paper serves as an overview paper of the PALM 6.0 model system and we describe its current model core. The individual components for urban applications, case studies, validation runs, and issues with suitable input data are presented and discussed in a series of companion papers in this special issue.