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Hamburg, Germany

Stevens B.,Max Planck Institute For Meteorologie | Giorgetta M.,Max Planck Institute For Meteorologie | Esch M.,Max Planck Institute For Meteorologie | Mauritsen T.,Max Planck Institute For Meteorologie | And 15 more authors.
Journal of Advances in Modeling Earth Systems | Year: 2013

ECHAM6, the sixth generation of the atmospheric general circulation model ECHAM, is described. Major changes with respect to its predecessor affect the representation of shortwave radiative transfer, the height of the model top. Minor changes have been made to model tuning and convective triggering. Several model configurations, differing in horizontal and vertical resolution, are compared. As horizontal resolution is increased beyond T63, the simulated climate improves but changes are incremental; major biases appear to be limited by the parameterization of small-scale physical processes, such as clouds and convection. Higher vertical resolution in the middle atmosphere leads to a systematic reduction in temperature biases in the upper troposphere, and a better representation of the middle atmosphere and its modes of variability. ECHAM6 represents the present climate as well as, or better than, its predecessor. The most marked improvements are evident in the circulation of the extratropics. ECHAM6 continues to have a good representation of tropical variability. A number of biases, however, remain. These include a poor representation of low-level clouds, systematic shifts in major precipitation features, biases in the partitioning of precipitation between land and sea (particularly in the tropics), and midlatitude jets that appear to be insufficiently poleward. The response of ECHAM6 to increasing concentrations of greenhouse gases is similar to that of ECHAM5. The equilibrium climate sensitivity of the mixed-resolution (T63L95) configuration is between 2.9 and 3.4 K and is somewhat larger for the 47 level model. Cloud feedbacks and adjustments contribute positively to warming from increasing greenhouse gases. ©2013. American Geophysical Union. All Rights Reserved.

Guilyardi E.,University of Reading | Lawrence B.,University of Reading | Callaghan S.,Rutherford Appleton Laboratory | Deluca C.,National Oceanic and Atmospheric Administration | And 5 more authors.
Bulletin of the American Meteorological Society | Year: 2013

A project named the Coupled Model Intercomparison Project (CMIP5), that seeks to collect better documentation of climate models and their simulations is reviewed. The (CMIP5), organized by the Working Group on Coupled Modelling (WGCM) on behalf of WMO's World Climate Research Program (WCRP), will generate more than a million individual datasets and several petabytes of data. In early planning stages of CMIP5, the climate modeling community was committed to collecting a comprehensive and standardized set of metadata for the climate model simulations. The various types of metadata of interest were then organized into a new conceptual model, called the CIM (Common Information Model). This conceptual model was applied to the specific needs of CMIP5, and a metadata entry tool was developed to collect the information. Data portals can harvest the information contained in the resulting machine-readable files and render it in a form more usable to humans.

Wagner S.,Helmholtz Center Geesthacht | Fast I.,DKRZ Inc | Kaspar F.,German Weather Service
Climate of the Past | Year: 2012

In this study, we assess how the anthropogenically induced increase in greenhouse gas concentrations affects the climate of central and southern South America. We utilise two regional climate simulations for present day (PD) and pre-industrial (PI) times. These simulations are compared to historical reconstructions in order to investigate the driving processes responsible for climatic changes between the different periods. The regional climate model is validated against observations for both re-analysis data and GCM-driven regional simulations for the second half of the 20th century. Model biases are also taken into account for the interpretation of the model results. The added value of the regional simulation over global-scale modelling relates to a better representation of hydrological processes that are particularly evident in the proximity of the Andes Mountains. Climatic differences between the simulated PD minus PI period agree qualitatively well with proxy-based temperature reconstructions, albeit the regional model overestimates the amplitude of the temperature increase. For precipitation the most important changes between the PD and PI simulation relate to a dipole pattern along the Andes Mountains with increased precipitation over the southern parts and reduced precipitation over the central parts. Here only a few regions show robust similarity with studies based on empirical evidence. However, from a dynamical point-of-view, atmospheric circulation changes related to an increase in high-latitude zonal wind speed simulated by the regional climate model are consistent with numerical modelling studies addressing changes in greenhouse gas concentrations. Our results indicate that besides the direct effect of greenhouse gas changes, large-scale changes in atmospheric circulation and sea surface temperatures also exert an influence on temperature and precipitation changes in southern South America. These combined changes in turn affect the relationship between climate and atmospheric circulation between PD and PI times and should be considered for the statistical reconstruction of climate indices calibrated within present-day climate data. © Author(s) 2012.

Luttgau J.,University of Hamburg | Kunkel J.M.,DKRZ Inc
Proceedings of PDSW 2014: 9th Parallel Data Storage Workshop - Held in Conjunction with SC 2014: The International Conference for High Performance Computing, Networking, Storage and Analysis | Year: 2014

Evaluating I/O performance of an application across different systems is a daunting task because it requires preparation of the software dependencies and required input data. Feign aims to be an extensible trace replay solution for parallel applications that supports arbitrary software and library layers. The tool abstracts and streamlines the replay process while allowing plug-ins to provide, manipulate and interpret trace data. Therewith, the application's behavior can be evaluated without potentially proprietary or confidential software and input data.Even more interesting is the potential of Feign as a virtual laboratory for I/O research: by manipulating trace data, experiments can be conducted; for example, it becomes possible to evaluate the benefit of optimization strategies. Since a plug-in could determine 'future' activities, this enables us to develop optimal strategies as baselines for any run-time heuristics, but also eases testing of a developed strategy on many applications without modifying them.The paper proposes and evaluates a workflow to automatically apply optimization candidates to application traces and approximate potential performance gains. By using Feign's reporting facilities, an automatic optimization engine can then independently conduct experiments by feeding traces and strategies to compare the results. © 2014 IEEE.

Chunpir H.I.,Federal University of Sao Carlos | Chunpir H.I.,University of Hamburg | Chunpir H.I.,DKRZ Inc
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2016

Service desk has been widely deployed to cater user-support in an organisation. However, in the field of e-Research there are only few studies conducted to enhance the user-support services or user-services. Little has been done to improve the motivation of the employees of e-Science infrastructures to service incoming user requests known as incidents. In this paper, User-Support- Worker’s Activity Model (USWAM) is presented that enhances the interactivity of the employees of cyber-infrastructures with the incidents. Furthermore, the model enhances not only the handling of the incoming user requests but also the management of the core activities assigned to the employees via visualization queues and matrices in the UI. Subsequently, USWAM aids the employees to remain interested in supporting users, similar to playing a game. Accomplished tasks can be rewarded in the form of money/gifts or recognitions. Finally, USWAM can be transferred to other service-oriented domains where prioritization or management of tasks is required. © Springer International Publishing Switzerland 2016.

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