Abstract
Abstract. The HD(CP)2 Observational Prototype Experiment (HOPE) was performed as a major 2-month field experiment in Jülich, Germany, in April and May 2013, followed by a smaller campaign in Melpitz, Germany, in September 2013. HOPE has been designed to provide an observational dataset for a critical evaluation of the new German community atmospheric icosahedral non-hydrostatic (ICON) model at the scale of the model simulations and further to provide information on land-surface–atmospheric boundary layer exchange, cloud and precipitation processes, as well as sub-grid variability and microphysical properties that are subject to parameterizations. HOPE focuses on the onset of clouds and precipitation in the convective atmospheric boundary layer. This paper summarizes the instrument set-ups, the intensive observation periods, and example results from both campaigns. HOPE-Jülich instrumentation included a radio sounding station, 4 Doppler lidars, 4 Raman lidars (3 of them provide temperature, 3 of them water vapour, and all of them particle backscatter data), 1 water vapour differential absorption lidar, 3 cloud radars, 5 microwave radiometers, 3 rain radars, 6 sky imagers, 99 pyranometers, and 5 sun photometers operated at different sites, some of them in synergy. The HOPE-Melpitz campaign combined ground-based remote sensing of aerosols and clouds with helicopter- and balloon-based in situ observations in the atmospheric column and at the surface. HOPE provided an unprecedented collection of atmospheric dynamical, thermodynamical, and micro- and macrophysical properties of aerosols, clouds, and precipitation with high spatial and temporal resolution within a cube of approximately 10 × 10 × 10 km3. HOPE data will significantly contribute to our understanding of boundary layer dynamics and the formation of clouds and precipitation. The datasets have been made available through a dedicated data portal. First applications of HOPE data for model evaluation have shown a general agreement between observed and modelled boundary layer height, turbulence characteristics, and cloud coverage, but they also point to significant differences that deserve further investigations from both the observational and the modelling perspective.
Highlights
Clouds and precipitation play a central role in the climate system and were repeatedly identified as the largest problem in a realistic modelling of atmospheric processes, forcings, and feedbacks (IPCC, 2013; Jakob, 2010)
Maurer et al (2016) made use of a triangular set-up of three KITcube Doppler lidar systems deployed approximately 3 km apart from each other. This distance was assumed to be sufficient to ensure that the lidars do not monitor the same convective cells at the same time. They found persistent similar statistical properties of velocity variances measured along the wind direction in contrast to measurements across the wind direction
The HD(CP)2 Observational Prototype Experiment (HOPE) days selected for icosahedral nonhydrostatic model (ICON) runs cover a wide range of meteorological conditions, from clear-sky days for the evaluation of convective processes in the planetary boundary layer to days on which frontal passages accompanied by large-scale precipitation occurred
Summary
Clouds and precipitation play a central role in the climate system and were repeatedly identified as the largest problem in a realistic modelling of atmospheric processes, forcings, and feedbacks (IPCC, 2013; Jakob, 2010). The O module (observations) was defined to provide observational datasets for the initialization and evaluation of the newly developed ICON model and other high-resolved LES models as well as for the development of new parameterizations that are suitable for application in a high-resolution model. The scope of the S module (synthesis) was to provide first improvements of parameterizations from the use of model and observation results The key to this effort was the provision of modelled scenarios at 100-metre grid resolution over thousands of kilometres, which will be used to analyse, improve, or develop parameterizations related to cloud and precipitation development in climate models. The O4 project in the O module of HD(CP) was devoted to HOPE and has been designed to provide a critical model evaluation at the scale of the model simulations and further to provide information on sub-grid variability and microphysical properties that are subject to parameterizations even at high-resolution simulations such as planned with ICON. Individual work performed during HOPE is published in this ACP/AMT HOPE special issue or, in part, in other journals and is cited in the present overview correspondingly
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