ENVIRONMENT AND ENERGY

Clouds and precipitation are the major source of uncertainty in numerical predictions of weather and climate. A common analysis of polarimetric radar observations and synthetic radar data from numerical simulations provides new methods to evaluate models. Using the Terrestrial Systems Modeling Platform, researchers conducted ensemble simulations for multiple summertime storms over north-western Germany. The simulated cloud processes were compared in the radar space using a forward operator with the measurements from X-band polarimetric radars. In addition, sensitivity studies were conducted using different background aerosol states and land cover types in the model to better understand land-aerosol-cloud-precipitation interactions.

The African Continent will be severely hit by climate change. A necessary building brick for counteraction are reliable projections of the African climate of our century. The CORDEX CORE initiative is designed to provide such information for the CORDEX CORE regions, among them CORDEX CORE Africa. IMK-TRO contributed to this with an ensemble of presently ten regional climate simulations performed on the Hazel Hen at HLRS Stuttgart. Results indicate dramatic changes especially in precipitation. The simulations presented here will be part of the IPCC AR6 atlas of regional climate change and the CORDEX data repository. They will be freely available for impact, adaptation and mitigation studies.

Hydrometeorological extremes, such as droughts and floods are one of the grand challenges of our future and pose great interest and concern for water management and public safety. Hence, the ClimEx project disaggregates the response of the climate system into changing anthropogenic forcing and natural variability by analyzing a novel large-ensemble of climate simulations, operated using High-Performance Computing. The comprehensive new dataset (CRCM5-LE) generated 50 transient independent and evenly likely realizations of the past and the future climate (1950-2099) over two large domains (Europe, Eastern North America) in high spatial (12km) and temporal (1h-1d) resolution. The resulting 7500 model years allow for a thorough analysis of…

Using the Model for Prediction Across Scales (MPAS), four years of climate simulations at convection-permitting resolutions where carried out using a variable 30-3km resolution mesh, transitioning the so-called gray zone of convection around 5-10km. The comprehensive data set generated following the protocol of the CORDEX Flagship Pilot Study (FPS) on convection-permitting climate simulations will allow the CORDEX-FPS community to study the added value of global, variable-resolution simulations down to convective scales over traditional approaches employing regional climate models and/or coarse horizontal resolutions.

The planetary boundary layer (PBL) is the lower layer of the troposphere, the layer that directly feels surface effects on time scales smaller than a day. Planetary boundary layers are important in climatology—modulating the fluxes between atmosphere, land and ocean—, and in meteorology—influencing weather conditions—, but key properties remain poorly understood, largely because the PBL is turbulent, and understanding and characterizing the multi-scale nature of turbulence remains challenging. High-performance computing and direct numerical simulations are decisively contributing to advance our understanding of PBL properties.

Modelling of the regional present day as well as future climate is of great interest both scientifically as well as for applications. The “Regional Climate and Water Cycle Group” at KIT Karlsruhe uses the COSMO-CLM regional climate model for detailed climate simulations in various parts of the world. Many of these quite expensive and storage intensive runs are performed on Hazel Hen at HLRS. After giving a motivation for high resolution climate modelling, the scientists briefly describe some technical aspects like nesting and ensemble building and then go to a short presentation of some results concerning the future climate in Baden-Württemberg.

The SMOC (SubMesoscale Ocean Modelling for Climate) project aimed to shed light on the role of submesoscale turbulent processes in the overall functioning of the ocean. Leveraging HPC power, the researchers in particular tried to get answers to: A) how deep do submesoscale fronts penetrate and can they be a significant source of dissipation for the ocean circulation away from the surface?, and B) to which extent do submesoscale fronts participate in the transfer into the deep ocean of the near-inertial energy injected by the wind at the ocean surface?

The dynamic behavior of the atmosphere is driven by processes on a wide range of spatial and temporal scales. In a project run by scientists of the Heidelberg University, those parts of model systems which describe the fluid dynamics and the temperature evolution were investigated. The models are formulated in terms of the velocity, temperature, pressure, and density. The researchers employ a hierarchy of different physical models with an increasing degree of complexity. The task of predicting the evolution of tropical cyclones is a typical challenging example.

Exploiting the computing power and memory capacities of HPC system SuperMUC, scientists of the Technische Universität München aimed at providing a global high resolution gravity field model with hitherto unprecedented accuracy and resolution. The model can be now be used by the scientific community as a surface reference for climate studies and it serves e.g. as main input for geophysical analyses and for the determination of the ocean circulation patterns.

Predicting weather and climate and its impacts on the environment, including hazards such as floods, droughts and landslides, continues to be one of the main challenges of the 21st century – in particular for the European region as it is exposed to intense Atlantic synoptic perturbations. Scientists performed for the first time long climate simulations over the European domain at a very fine cloud-permitting resolution of about 4 km with explicitly resolved convection and a sharp representation of orography, thanks to the possibility of running very computationally and data storage demanding simulations on SuperMUC.

Thanks to the availability of HLRS’s petascale HPC system Hornet, researchers of the Institute of Physics and Meteorology of the University of Hohenheim were able to run a highly complex climate simulation for a time period long enough to cover various extreme weather events on the Northern hemisphere at a previously unmatched spatial resolution. Deploying the highly scalable Weather Research and Forecasting (WRF) model on 84,000 compute cores of Hornet, the achieved results confirm an extraordinary quality with respect to the simulation of fine scale meteorological processes and extreme events.

Scientists from the University of Hohenheim (Stuttgart/Germany) aim to investigate and to improve the performance of regional climate simulations in Europe with the Weather Research and Forecast (WRF) model. The model is operated from 12 km down to the convection permitting scale of 3 km, for advancing process understanding.

Using the computing capabilities of HLRS system Hermit, a team of scientists used the Community Earth System Model (CESM) with a strongly eddying ocean submodel to study the presence of ocean eddies on the sensitivity of the Meridional Overturning Circulation (MOC) in the Atlantic Ocean to the Greenland Ice Sheet (GrIS) freshwater anomalies.

In past decades, high performance computing has become a valuable tool in many fields of environmental science and technology to utilize computational power for better characterization of the complexity of environmental systems as well as predicting their evolution in time. The challenge is to develop efficient numerical schemes and software implementations which can take full advantage of today’s supercomputing hardware (i.e. PetaFlop platforms). The JUQUEEN project „Massive parallel computation of non-linear multi-field problems in terrestrial systems“ strives to meet this challenge for the solution of thermo-hydro-mechanical-chemical problems in fractured porous media with applications in hydrology, geotechnical engineering and renewable…

Atmospheric processes and climate change take place on all spatial scales: global, continental down to regional or local scales. Not only do processes on the different scales differ from each other but also regions exhibit various characteristics. Regional and local climate as such depends on small-scale structures such as urbanisation, land use, soil types, water surfaces, orography and vegetation.

Whenever we travel by plane, we often experience that the flight becomes bumpy quite suddenly during the descent. This phenomenon causes not only discomfort to the passengers, but also a few headaches to climate scientists, whose models depend critically on properties associated with this phenomenon.