# Stefan Petri's Publications

Contents Data Publications

### Some LaTeX Macros to begin with

• %
% THE \simulan LOGO IS DEFINED HERE.
%
\def\simulan{{\rm s\kern-.06em\raise-.5ex\hbox{i}\kern-.1em\raise-.1ex
\hbox{m}\raise-.3ex\hbox{u}\kern-.10emL\kern-.1667em\lower-.6ex
\hbox{a}\kern-.10emn}}

• %% the \PBeam Logo is defined here
\def\PBeam{{\sc\kern.15emP\kern-.9em\raise.125ex\hbox{$\leftarrow$}\sc\kern-.25emB\sc\kern-.1eme\kern-.1ema\kern-.1emm}}


### Diploma Thesis

• [Petri91] Stefan Petri:
\simulan - Ein Werkzeug zur Simulation lokaler Netze.
Diplomarbeit, TU Braunschweig, 1991 (in german).
Abstract: With decreasing hardware costs and increasing computing power the interconnection of Personal Computers, Workstations and special purpose hardware becomes more and more important. \simulan{} is a tool for efficient and flexible modelling and simulation of such networks. Models for new protocols and applications can be programmed with little effort. The concepts of \simuLan{} are shown, the usage of the program is explained and the possibilities for customizing are discussed.

You might also want look at the companion thesis about modelling with simuLan:
[Schmida91] Ralf Schmidt-Dannert:
\simulan: Modellierung und Simulation lokaler Netzwerke.
Diplomarbeit, TU Braunschweig, 1991 (in german).

### Dissertation

• [Petri97Book] Stefan Petri:
Lastausgleich und Fehlertoleranz in Workstation-Clustern.
PhD Thesis, Institut für Betriebssysteme und Rechnerverbund, TU Braunschweig, Mai 1997 (in german).
Shaker Verlag, Aachen, ISBN 3-8265-2471-3.
Abstract: Networked workstations are commonly used in companies and research institutes to provide users with interactive computing facilities. It was discovered early that the processing capacities of such installations typically show a low utilization. These workstation clusters are an increasingly attractive platform for resource intensive distributed and parallel applications because of their good price-performance ratio.

However, they exhibit problems with unbalanced load, conflicts with interactive users and increased failure probability. Process migration and checkpoint/restart are adequate means to solve these problems. Several of such mechanisms are described in the literature, but they all have certain weaknesses and impose restrictions on the applications they can handle.

In this thesis, a new concept for an application transparent migration and checkpointing mechanism is developed, wich overcomes some substantial of those restrictions. It supports migration and fault transparency for parallel and distributed applications, i.e. groups of communicating processes, on clusters of workstations. Neither the system kernel nor the application programs need to be modified, and applications are not required to be written for a specific runtime environment. However, for better performance the applications can be linked with a modified system library. From this concept, the architecture of the example implementation is derived, and first measured results and experiences with the implementation are reported.

A BiBTeX-File, from my Dissertation.

### Journal Articles

• [PL95] Stefan Petri and Horst Langendörfer:
Load Balancing and Fault Tolerance in Workstation Clusters - Migrating Groups of Communicating Processes.
Operating Systems Review, Vol. 29, No. 4, October 1995, pp. 25-36.
doi:10.1145/219282.219288
Annote:The first publication about the general concept (virtual name space) and very first experiences with the single process checkpointer. Leaves many questions about checkpointing groups of processes open, which are solved in subsequent work.
Abstract: In the past, several process migration facilities for distributed systems have been developed. Due to the complex nature of the subject, all those facilities have limitations that make them usable for only limited classes of applications and environments. We discuss some of the usual limitations and possible solutions. Specifically, we focus on migration of groups of collaborating processes between Unix systems without kernel modifications, and from this we derive the design for a migration system. First experiences with our implementation show that we reach performance figures for the migration that are close to those of real distributed operating systems.
17 citations in ISI Web of Science until August 2021 (although the paper itself is not listed in there).
24 citations counted by ACM Digital Library until August 2021.
79 citations in Google scholar until August 2021.
22 non-self citations in CiteSeerX.
36 citations counted by ResearchGate.
22 citations in US patents shown by lens.org
22 publication citations and 29 patent citations listed by Dimensions in August 2021

• [Petri98] Stefan Petri:
Lastausgleichswerkzeuge für Workstation-Cluster.
Informatik/Informatique -- Zeitschrift der schweizerischen Informatikerorganisationen / Revue des organisations suisses d'informatique, Themenheft Workstations'', No. 3, June 1998, pp. 23-26.
Abstract: Programmierer und Benutzer rechenintensiver verteilter Anwendungen wollen oder gar können Lastausgleich und Fehlertoleranz nicht in ihren Programmen behandeln. Da die verfügbaren Betriebssysteme solche Funktionalitäten nur rudimentär bieten, werden in diesem Artikel zwei anwendungstransparente Migrationssysteme, und CoCheck, vorgestellt und verglichen. Abschließend wird ein Ausblick auf neue Funktionalitäten gegeben, die durch Integration mit interaktiven Werkzeugen erreicht werden können.

• [PRPS13] Vladimir Petoukhov and Stefan Rahmstorf and Stefan Petri and Hans Joachim Schellnhuber:
Quasiresonant amplification of planetary waves and recent Northern Hemisphere weather extremes.
Proceedings of the National Academy of Sciences, Vol. 110, Nr. 14, pp. 5336--5341, April 2013. Published ahead of print March 1, 2013.
doi:10.1073/pnas.1222000110
Abstract: In recent years, the Northern Hemisphere has suffered several devastating regional summer weather extremes, such as the European heat wave in 2003, the Russian heat wave and the Indus river flood in Pakistan in 2010, and the heat wave in the United States in 2011. Here, we propose a common mechanism for the generation of persistent longitudinal planetary-scale high-amplitude patterns of the atmospheric circulation in the Northern Hemisphere midlatitudes. Those patterns -- with zonal wave numbers m = 6, 7, or 8 -- are characteristic of the above extremes. We show that these patterns might result from trapping within midlatitude waveguides of free synoptic waves with zonal wave numbers k ≈ m. Usually, the quasistationary dynamical response with the above wave numbers m to climatological mean thermal and orographic forcing is weak. Such midlatitude waveguides, however, may favor a strong magnification of that response through quasiresonance.
ISI Accession Number: WOS:000318037800032
233 citations in ISI Web of Science until April 2022
326 citations in Google Scholar until December 2021

• [ECCPP13] Alexey V. Eliseev and Dim Coumou and Alexander V. Chernokulsky and Vladimir Petoukhov and Stefan Petri:
Scheme for calculation of multi-layer cloudiness and precipitation for climate models of intermediate complexity.
Geoscientific Model Development, Vol. 6, Nr. 5, pp. 1745--1765, October 2013.
doi:10.5194/gmd-6-1745-2013
ISI Accession Number: WOS:000326601300023
11 citations in ISI Web of Science until February 2022
20 citations in Google Scholar until January 2021

• [CPRPS14] Dim Coumou and Vladimir Petoukhov and Stefan Rahmstorf and Stefan Petri and Hans Joachim Schellnhuber:
Quasi-resonant circulation regimes and hemispheric synchronization of extreme weather in boreal summer.
Proceedings of the National Academy of Sciences, Vol. 111, Nr. 34, pp. 12331--12336, August 2014. Published ahead of print August 11, 2014.
doi:10.1073/pnas.1412797111
Abstract: The recent decade has seen an exceptional number of high-impact summer extremes in the Northern Hemisphere midlatitudes. Many of these events were associated with anomalous jet stream circulation patterns characterized by persistent high-amplitude quasi-stationary Rossby waves. Two mechanisms have recently been proposed that could provoke such patterns: (i) a weakening of the zonal mean jets and (ii) an amplification of quasi-stationary waves by resonance between free and forced waves in midlatitude waveguides. Based upon spectral analysis of the midtroposphere wind field, we show that the persistent jet stream patterns were, in the first place, due to an amplification of quasi-stationary waves with zonal wave numbers 6-8. However, we also detect a weakening of the zonal mean jet during these events; thus both mechanisms appear to be important. Furthermore, we demonstrate that the anomalous circulation regimes lead to persistent surface weather conditions and therefore to midlatitude synchronization of extreme heat and rainfall events on monthly timescales. The recent cluster of resonance events has resulted in a statistically significant increase in the frequency of high-amplitude quasi-stationary waves of wave numbers 7 and 8 in July and August. We show that this is a robust finding that holds for different pressure levels and reanalysis products. We argue that recent rapid warming in the Arctic and associated changes in the zonal mean zonal wind have created favorable conditions for double jet formation in the extratropics, which promotes the development of resonant flow regimes.
ISI Accession Number: WOS:000340780300026
164 citations in ISI Web of Science until April 2022
195 citations in Google Scholar until January 2021

• [SCPPR16] Lisa Stadtherr and Dim Coumou and Vladimir Petoukhov and Stefan Petri and Stefan Rahmstorf:
Record Balkan floods of 2014 linked to planetary wave resonance.
Science Advances, Vol 2, Nr. 4, April 2016.
Abstract: In May 2014, the Balkans were hit by a Vb-type cyclone that brought disastrous flooding and severe damage to Bosnia and Herzegovina, Serbia, and Croatia. Vb cyclones migrate from the Mediterranean, where they absorb warm and moist air, to the north, often causing flooding in central/eastern Europe. Extreme rainfall events are increasing on a global scale, and both thermodynamic and dynamical mechanisms play a role. Where thermodynamic aspects are generally well understood, there is large uncertainty associated with current and future changes in dynamics. We study the climatic and meteorological factors that influenced the catastrophic flooding in the Balkans, where we focus on large-scale circulation. We show that the Vb cyclone was unusually stationary, bringing extreme rainfall for several consecutive days, and that this situation was likely linked to a quasi-stationary circumglobal Rossby wave train. We provide evidence that this quasi-stationary wave was amplified by wave resonance. Statistical analysis of daily spring rainfall over the Balkan region reveals significant upward trends over 1950 - 2014, especially in the high quantiles relevant for flooding events. These changes cannot be explained by simple thermodynamic arguments, and we thus argue that dynamical processes likely played a role in increasing flood risks over the Balkans.
ISI Accession Number: WOS:000380072100020
45 citations in ISI Web of Science until April 2022
50 citations in Google Scholar until January 2021

• [PPRCKS16] Vladimir Petoukhov and Stefan Petri and Stefan Rahmstorf and Dim Coumou and Kai Kornhuber and Hans Joachim Schellnhuber:
Role of quasiresonant planetary wave dynamics in recent boreal spring-to-autumn extreme events.
Proceedings of the National Academy of Sciences, Vol. 113, Nr. 34, pp. 6862--6867, June 2016. Published online before print on June 6, 2016.
doi:10.1073/pnas.1606300113
Abstract: In boreal spring-to-autumn (May-to-September) 2012 and 2013, the Northern Hemisphere (NH) has experienced a large number of severe midlatitude regional weather extremes. Here we show that a considerable part of these extremes were accompanied by highly magnified quasistationary midlatitude planetary waves with zonal wave numbers m = 6, 7, and 8. We further show that resonance conditions for these planetary waves were, in many cases, present before the onset of high-amplitude wave events, with a lead time up to 2 wk, suggesting that quasiresonant amplification (QRA) of these waves had occurred. Our results support earlier findings of an important role of the QRA mechanism in amplifying planetary waves, favoring recent NH weather extremes.
ISI Accession Number: WOS:000378272400034
50 citations in ISI Web of Science until April 2022
51 citations in Google Scholar until January 2021

• [KPPRC16] Kai Kornhuber and Vladimir Petoukhov and Stefan Petri and Stefan Rahmstorf and Dim Coumou:
Evidence for wave resonance as a key mechanism for generating high-amplitude quasi-stationary waves in boreal summer.
Climate Dynamics, Vol. 49, Nr 5--6, pp. 1961-1979, September 2017. First Online: 05 November 2016.
doi:10.1007/s00382-016-3399-6
Abstract: Several recent northern hemisphere summer extremes have been linked to persistent high-amplitude wave patterns (e.g. heat waves in Europe 2003, Russia 2010 and in the US 2011, Floods in Pakistan 2010 and Europe 2013). Recently quasi-resonant amplification (QRA) was proposed as a mechanism that, when certain dynamical conditions are fulfilled, can lead to such high-amplitude wave events. Based on these resonance conditions a detection scheme to scan reanalysis data for QRA events in boreal summer months was implemented. With this objective detection scheme we analyzed the occurrence and duration of QRA events and the associated atmospheric flow patterns in 1979 - 2015 reanalysis data. We detect a total number of 143 events for wave 6, 7 and 8 and find that during roughly one third of all high amplitude events QRA conditions were met for respective waves. Our analysis reveals a significant shift for quasi-stationary waves 6 and 7 towards high amplitudes during QRA events, lagging first QRA-detection by typically one week. The results provide further evidence for the validity of the QRA hypothesis and its important role in generating high amplitude waves in boreal summer.
ISI Accession Number: WOS:000408718200027
47 citations in ISI Web of Science until April 2022
45 citations in Google Scholar until January 2021

• [BFP16] Julia Brugger and Georg Feulner and Stefan Petri:
Baby, it's cold outside: Climate model simulations of the effects of the asteroid impact at the end of the Cretaceous.
Geophysical Research Letters, Vol 44, Nr 1, pp 419--427, January 2017. Accepted manuscript online: 20 December 2016.
doi:10.1002/2016GL072241
Project Information with supplementary movies.
Abstract: 66 million years ago, the end-Cretaceous mass extinction ended the reign of the dinosaurs. Flood-basalt eruptions and an asteroid impact are widely discussed causes, yet their contributions remain debated. Modelling the environmental changes after the Chicxulub impact can shed light on this question. Existing studies, however, focused on the effect of dust or used one-dimensional, non-coupled atmosphere models. Here, we explore the longer-lasting cooling due to sulfate aerosols using a coupled climate model. Depending on aerosol stratospheric residence time, global annual mean surface air temperature decreased by at least 26° C, with 3 to 16 years subfreezing temperatures and a recovery time larger than 30 years. The surface cooling triggered vigorous ocean mixing which could have resulted in a plankton bloom due to upwelling of nutrients. These dramatic environmental changes suggest a pivotal role of the impact in the end-Cretaceous extinction.
ISI Accession Number: WOS:000393954900049
63 citations in ISI Web of Science until April 2022
72 citations in Google Scholar until January 2021

This paper partly inspired the thriller Der Tunnel'' by Hans Leister, ISBN 9783710900532, Benevento, 2019

• [MMPNWC17] Sonja Molnos and Tarek Mamdouh and Stefan Petri and Thomas Nocke and Tino Weinkauf and Dim Coumou:
A network-based detection scheme of the jet stream core.
Earth System Dynamics, Vol 8, Nr 1, pp 75--89, February 2017.
doi:10.5194/esd-8-75-2017
Abstract: The polar and subtropical jet streams are strong upper-level winds with a crucial influence on weather throughout the Northern Hemisphere midlatitudes. In particular, the polar jet is located between cold arctic air to the north and warmer subtropical air to the south. Strongly meandering states therefore often lead to extreme surface weather.
Some algorithms exist which can detect the 2-D (latitude and longitude) jets' core around the hemisphere, but all of them use a minimal threshold to determine the subtropical and polar jet stream. This is particularly problematic for the polar jet stream, whose wind velocities can change rapidly from very weak to very high values and vice versa.
We develop a network-based scheme using Dijkstra's shortest-path algorithm to detect the polar and subtropical jet stream core. This algorithm not only considers the commonly used wind strength for core detection but also takes wind direction and climatological latitudinal position into account. Furthermore, it distinguishes between polar and subtropical jet, and between separate and merged jet states.
The parameter values of the detection scheme are optimized using simulated annealing and a skill function that accounts for the zonal-mean jet stream position (Rikus, 2015). After the successful optimization process, we apply our scheme to reanalysis data covering 1979–2015 and calculate seasonal-mean probabilistic maps and trends in wind strength and position of jet streams.
We present longitudinally defined probability distributions of the positions for both jets for all on the Northern Hemisphere seasons. This shows that winter is characterized by two well-separated jets over Europe and Asia (ca. 20° W to 140° E). In contrast, summer normally has a single merged jet over the western hemisphere but can have both merged and separated jet states in the eastern hemisphere.
With this algorithm it is possible to investigate the position of the jets' cores around the hemisphere and it is therefore very suitable to analyze jet stream patterns in observations and models, enabling more advanced model-validation.

ISI Accession Number: WOS:000395096400001
14 citations in ISI Web of Science until October 2021

• [KPKPRC17] Kai Kornhuber and Vladimir Petoukhov and David J. Karoly and Stefan Petri and Stefan Rahmstorf and Dim Coumou:
Summertime Planetary Wave-Resonance in the Northern and Southern Hemisphere.
Journal of Climate. Vol. 30, Nr. 16, pp. 6133-6150, July 2017. Published Online: 24. April 2017
doi:10.1175/JCLI-D-16-0703.1
Abstract: Slow-moving planetary waves of high amplitudes are often associated with persistent surface weather conditions. This persistence can lead to extreme weather events with potentially serious implications for society and nature. Quasi-resonant amplification of planetary waves (QRA) has been proposed as a mechanism to generate high-amplitude hemisphere-wide patterns of waves 6–8 in the northern Hemisphere (NH) summer. Here we study this mechanism in both hemispheres. Analyzing 1979–2015 reanalysis-data we find evidence for QRA in the SH for waves 4–5. We show that the difference in resonating wavenumbers between hemispheres stems from the different magnitude and latitudinal shape of the respective zonal-mean zonal winds. During resonance events a strong and narrow jet is observed in both hemispheres, while the emergence of a second zonal mean jet at high latitudes (i.e. a double jet'') is seen in the NH only. Strong and narrow jets can form stable, zonally oriented waveguides, which are an essential prerequisite for resonance. Investigating the waves' preferred phase positions during QRA, we identify a bimodal behavior for waves 4–5 in the SH and for wave 6 in the NH, while wave 7 and wave 8 exhibit a single preferred phase position in the NH. Composite plots of meridional wind and temperature anomalies during periods when the resonating wave is in the preferred phase position indicate those regions that are most likely to experience heat extremes. These regions include Western North America, Western Europe and Central Eurasia in the NH and Patagonia and Australia in the SH.
ISI Accession Number: WOS:000406040200005
27 citations in ISI Web of Science until April 2022

• [TEPFCPC18] Sonja Totz and Alexey V. Eliseev and Stefan Petri and Michael Flechsig and Levke Caesar and Vladimir Petoukhov and Dim Coumou:
The dynamical core of the Aeolus 1.0 statistical-dynamical atmosphere model: validation and parameter optimization
Geoscientific Model Development, Vol. 11, Nr. 2, pp. 665--679, February 2018.
doi:10.5194/gmd-11-665-2018
ISI Accession Number: WOS:000425773000001
4 citations in ISI Web of Science until February 2020

• [PPKTCS18] Vladimir Petoukhov and Stefan Petri and Kai Kornhuber and Kirsten Thonicke and Dim Coumou and Hans Joachim Schellnhuber:
Alberta wildfire 2016: Apt contribution from anomalous planetary wave dynamics.
Scientific Reports. Vol. 8, Nr. 1, Article Number 12375, August 2018. Published: 17 August 2018.
doi:10.1038/s41598-018-30812-z
Abstract: In May-June 2016 the Canadian Province of Alberta suffered one of the most devastating wildfires in its history. Here we show that in mid-April to early May 2016 the large-scale circulation in the mid- and high troposphere of the middle and sub-polar latitudes of the northern hemisphere featured a persistent high-amplitude planetary wave structure dominated by the non-dimensional zonal wave number 4. The strongest anticyclonic wing of this structure was located over western Canada. In combination with a very strong El Niño event in winter 2015/2016 this favored highly anomalous, tinder-dry and high-temperature conditions at the surface in that area, entailing an increased fire hazard there. This critically contributed to the ignition of the Alberta Wildfire in May 2016, appearing to be the costliest disaster in Canadian history thus far.
ISI Accession Number: WOS:000441876700078
8 citations in ISI Web of Science until April 2022
9 citations in Google Scholar until April 2022

• [MRKSMPC18] Michael E. Mann and Stefan Rahmstorf and Kai Kornhuber and Byron A. Steinmann and Sonya K. Miller and Stefan Petri and Dim Coumou:
Projected Changes in Persistent Extreme Summer Weather Events: The Role of Quasi-Resonant Amplification.
Science Advances. Vol. 4, Nr. 10, Published: 31 October 2018.
Abstract: Persistent episodes of extreme weather in the Northern Hemisphere summer have been associated with high-amplitude quasi-stationary atmospheric Rossby waves, with zonal wave numbers 6 to 8 resulting from the phenomenon of quasi-resonant amplification (QRA). A fingerprint for the occurrence of QRA can be defined in terms of the zonally averaged surface temperature field. Examining state-of-the-art [Coupled Model Intercomparison Project Phase 5 (CMIP5)] climate model projections, we find that QRA events are likely to increase by ~50% this century under business-as-usual carbon emissions, but there is considerable variation among climate models. Some predict a near tripling of QRA events by the end of the century, while others predict a potential decrease. Models with amplified Arctic warming yield the most pronounced increase in QRA events. The projections are strongly dependent on assumptions regarding the nature of changes in radiative forcing associated with anthropogenic aerosols over the next century. One implication of our findings is that a reduction in midlatitude aerosol loading could actually lead to Arctic de-amplification this century, ameliorating potential increases in persistent extreme weather events.
Digital Material is available at http://www.meteo.psu.edu/holocene/public_html/supplements/SciAdvances2018/
ISI Accession Number: WOS:000449221200015
57 citations in ISI Web of Science until April 2022
78 citations in Google Scholar until December 2021

• [TPLC18] Sonja Totz and Stefan Petri and Jascha Lehmann and Dim Coumou:
Regional changes in the mean position and variability of the tropical edge.
Geophysical Research Letters, Vol 45, Nr 21, pp 12076--12084, November 2018. Accepted manuscript online: 31 October 2018.
doi:10.1029/2018GL079911
Abstract: Recent studies indicate that the tropical belt has been expanding during recent decades, which can significantly influence precipitation in subtropical climates. Often the location of the tropical border is identified using the Hadley cell edge (HCE) or the subtropical jet stream (STJ), but most studies concentrated on the zonal-mean state, thereby missing regional impacts. Here, we detect longitudinal-resolved trends in STJ cores and HCEs over 1979--2016 in both hemispheres at a higher spatial and temporal resolution than previous studies. Besides pronounced regional trend differences in both sign and magnitude, we show that winter HCE and STJ variability increased in the Mediterranean region and decreased over the American and Asian continent. Rainfall variability in these regions changed likewise and that most of those changes can be explained by changes in HCE/STJ variability. This highlights the importance to understand future tropical belt changes both regionally and in terms of variability.
ISI Accession Number: WOS:000451832600062
7 citations in ISI Web of Science until July 2021

• [TPLPC19] Sonja Totz and Stefan Petri and Jascha Lehmann and Erik Peukert and Dim Coumou:
Exploring the sensitivity of Northern Hemisphere atmospheric circulation to different surface temperature forcing using a statistical--dynamical atmospheric model.
Nonlinear Processes in Geophysics, Vol 26, Nr 11, pp 1--12, February 2019.
doi:10.5194/npg-26-1-2019
Abstract: Climate and weather conditions in the mid-latitudes are strongly driven by the large-scale atmosphere circulation. Observational data indicate that important components of the large-scale circulation have changed in recent decades, including the strength and the width of the Hadley cell, jets, storm tracks and planetary waves. Here, we use a new statistical-dynamical atmosphere model (SDAM) to test the individual sensitivities of the large-scale atmospheric circulation to changes in the zonal temperature gradient, meridional temperature gradient and global-mean temperature. We analyze the Northern Hemisphere Hadley circulation, jet streams, storm tracks and planetary waves by systematically altering the zonal temperature asymmetry, the meridional temperature gradient and the global-mean temperature. Our results show that the strength of the Hadley cell, storm tracks and jet streams depend, in terms of relative changes, almost linearly on both the global-mean temperature and the meridional temperature gradient, whereas the zonal temperature asymmetry has little or no influence. The magnitude of planetary waves is affected by all three temperature components, as expected from theoretical dynamical considerations. The width of the Hadley cell behaves nonlinearly with respect to all three temperature components in the SDAM. Moreover, some of these observed large-scale atmospheric changes are expected from dynamical equations and are therefore an important part of model validation.
ISI Accession Number: WOS:000459029000001
1 citation in ISI Web of Science until February 2020
2 citations in Google Scholar until January 2021

• [KOCPPRG19] Kai Kornhuber and Scott Osprey and Dim Coumou and Stefan Petri and Vladimir Petoukhov and Stefan Rahmstorf and Lesley Gray:
Extreme weather events in early summer 2018 connected by a recurrent hemispheric wave-7 pattern.
Environmental Research Letters, Vol 14, Nr. 5, pages 054002, April 2019.
doi:10.1088/1748-9326/ab13bf
Abstract: The summer of 2018 witnessed a number of extreme weather events such as heatwaves in North America, Western Europe and the Caspian Sea region, and rainfall extremes in South-East Europe and Japan that occurred near-simultaneously. Here we show that some of these extremes were connected by an amplified hemisphere-wide wavenumber 7 circulation pattern. We show that this pattern constitutes an important teleconnection in Northern Hemisphere summer associated with prolonged and above-normal temperatures in North America, Western Europe and the Caspian Sea region. This pattern was also observed during the European heatwaves of 2003, 2006 and 2015 among others. We show that the occurrence of this wave 7 pattern has increased over recent decades.
ISI Accession Number: WOS:000466273200002
118 citations in ISI Web of Science until April 2022
139 citations in Google Scholar until December 2021

• [BHPF19] Julia Brugger and Matthias Hofmann and Stefan Petri and Georg Feulner:
On the sensitivity of the Devonian climate to continental configuration, vegetation cover, orbital configuration, CO2 concentration and insolation.
Paleoceanography and Paleoclimatology, Vol 34, Nr 8, pages 1375--1398, August 2019. Accepted manuscript online: 21 July 2019
doi:10.1029/2019PA003562
ISI Accession Number: WOS:000495384600008
5 citations in ISI Web of Science until February 2022
6 citations in Google Scholar until December 2021
Here is the corresponding data publication.

• [LFHP20] Jan Philip Landwehrs and Georg Feulner and Matthias Hofmann and Stefan Petri:
Climatic fluctuations modeled for carbon and sulfur emissions from end-Triassic volcanism.
Earth and Planetary Science Letters Vol 537, article 116174, May 2020. Available online 28 February 2020
doi:10.1016/j.epsl.2020.116174
ISI Accession Number: WOS:000525394700013
13 citations in ISI Web of Science until February 2022

Here is the corresponding data publication.

• [DBSWPCBT21] Markus Drüke and Werner von Bloh and Boris Sakschewski and Nico Wunderling and Stefan Petri and Manoel Cardoso and Henrique M. J. Barbosa and Kisten Thonicke:
Climate-induced hysteresis of the tropical forest in a fire-enabled Earth system model.
European Physical Journal Special Topics Vol 230, pp. 3153-3162, June 2021
doi:10.1140/epjs/s11734-021-00157-2
ISI Accession Number: WOS:000661392300001
1 citation in ISI Web of Science until October 2021

• [LFPSW21] Jan Philip Landwehrs and Georg Feulner and Stefan Petri and Benjamin Sames and Michael Wagreich:
Investigating Mesozoic Climate Trends and Sensitivities with a Large Ensemble of Climate Model Simulations.
Paleoceanography and Paleoclimatology Vol 36 No 6 pages e2020PA004134, June 2021. First published: 20 May 2021
doi:10.1029/2020PA004134
ISI Accession Number: WOS:000665065500005
1 citation in ISI Web of Science until February 2022
Here is the corresponding data publication.

• [KRHPAFW21] Moritz Kreuzer and Ronja Reese and Willem Nicholas Huiskamp and Stefan Petri and Torsten Albrecht and Georg Feulner and Ricarda Winkelmann:
Coupling framework (1.0) for the ice sheet model PISM (1.1.4) and the ocean model MOM5 (5.1.0) via the ice-shelf cavity module PICO in an Antarctic domain
Geoscientific Model Development, Vol 14, Nr 6, pages 3697--3714, June 2021.
doi:10.5194/gmd-14-3697-2021
ISI Accession Number: WOS:000665538700003
3 citation in ISI Web of Science until February 2022

• [BFHP21] Julia Brugger and Georg Feulner and Matthias Hofmann and Stefan Petri:
A pronounced spike in ocean productivity triggered by the Chicxulub impact.
Geophysical Research Letters, Vol 48 Nr 12 pages e2020GL092260, June 2021. First published: 08 June 2021
doi:10.1029/2020GL092260
ISI Accession Number: WOS:000668622800017
1 citation in ISI Web of Science until December 2021
Here is the corresponding data publication.

• [DBPSSFHFT21] Markus Drüke and Werner von Bloh and Stefan Petri and Boris Sakschewski and Sibyll Schaphoff and Matthias Forkel and Willem Huiskamp and Georg Feulner and Kirsten Thonicke:
CM2Mc-LPJmL v1.0: Biophysical coupling of a process-based dynamic vegetation model with managed land to a general circulation model
Geoscientific Model Development, Vol 14, Nr 6, pages 4117--4141, July 2021.
doi:10.5194/gmd-14-4117-2021
Special issue: The Lund-Potsdam-Jena managed Land (LPJmL) dynamic global vegetation, hydrology and crop model - developments, evaluations and documentation.
ISI Accession Number: WOS:000670561700001
Here are the corresponding code and data publications.

### Conference Papers

• [PSL96] Stefan Petri and Bettina Schnor and Horst Langendörfer:
-- Fehlertoleranz für verteilte Anwendungen mittels Migration und Checkpointing.
In Clemens H. Cap (Ed.) Workstations und ihre Anwendungen - Proceedings der Fachtagung SIWORK'96, May 14./15. 1996, vdf Hochschulverlag, Zürich, pages 91-102 (in german).
Abstract: Process migration and checkpointing offer the possibility to achieve load balancing and fault tolerance. We discuss some of the problems and possible solutions for supporting these for distributed applications in workstation clusters. We describe the design for our system and its facility for creating global consistent checkpoints of groups of communication process on networked Unix systems, and present first experiences with our implementation.

• [PSLS96] Stefan Petri and Bettina Schnor and Horst Langendörfer and Jens Steinborn:
Consistent Global Checkpoints for Distributed Applications on Clusters of Workstations.
In Hermann G. Matthies und Josef Schüle (Eds.), Paralleles und Verteiltes Rechnen - Beiträge zum 4. Workshop über Wissenschaftliches Rechnen, pages 77-86, Braunschweig, 9.-11. October 1996. Shaker Verlag.
Annote: Continuation of the SIWORK paper, updated with newer results.
Abstract: Process migration and checkpointing offer the possibility to achieve load balancing and fault tolerance. We give an overview of the design of our system and focus on its facility for creating global consistent checkpoints of groups of communicating processes on networked Unix systems. We present first experiences with our implementation.

• [PL96] Stefan Petri and Horst Langendörfer:
CURE -- Computer Assisted Rehabilitation.
In J. Klaus and E. Auff and W. Kremser and W.L. Zagler (Eds.): Interdisciplinary Aspects on Computers Helping People with Special Needs: 5th International Conference / ICCHP'96, pages 591-598, July, 17.-19. 1996, Linz. Oldenbourg Verlag.
Abstract: Specific training of the disordered functions can yield good success in the treatment of patients with injured central nervous system. To assist this staff-intensive treatment, computers, at which patients work on therapeutic exercises, have been in use for several years. After a brief summary of the experiences with an existing implementation NIXAS-CURE, we focus on the design and implementation of the new CURE (Computerunterstützte Rehabilitation = computer assisted rehabilitation) version 2 system that is developed by Siemens-Nixdorf and TU Braunschweig. This version exploits modern PCs' facilities to create user interfaces that are suited for handicapped persons. Furthermore, it gives the therapist improved support for planning and evaluating the therapy course.

• [PSBHTL97] Stefan Petri and Bettina Schnor and Matthias Becker and Bernd Hinrichs and Titus Tscharntke and Horst Langendörfer:
Evaluation of Multicast Methods to Maintain a Global Name Space for Transparent Process Migration in Workstation Clusters.
In Martina Zitterbart (Ed.), Kommunikation in Verteilten Systemen, GI/ITG Fachtagung KIVS'97, pages 224-234, Braunschweig, 18.-21. February 1997. Springer Verlag.
doi:10.1007/978-3-642-60729-5_16
Abstract: In this paper we examine the performance and fault tolerance of different multicast based methods for maintaining the consistence of distributed data, depending on the network topology and packet loss probability. We present a system model and analytical results. This work is motivated by experiences with our process migration system . There we use a global virtual name space to achieve location transparency for process migration and checkpointing / rollback for distributed applications on clusters of Unix workstations. First measurements have shown that the maintenance of this global name space is critical for the performance of the entire system.

• [PBL98] Stefan Petri and Matthias Bolz and Horst Langendörfer:
Migration and Rollback Transparency for arbitrary Distributed Applications in Workstation Clusters.
In Jose Rolim (Ed.), Parallel and Distributed Processing - 10 IPPS/SDPD'98 Workshops held in conjunction with the 12th International Parallel Processing Symposium and 9th Symposium on Parallel and Distributed Processing, Orlando, Florida, USA; Proceeedings, 30. March 1998, Orlando, Florida. Lecture Notes in Computer Science, Volume 1388, pp. 159-170, Berlin, March 1998. Springer.
2nd Workshop on Runtime Support for Parallel Programming (RTSPP)
DOI:10.1007/3-540-64359-1_686
Extended version published as technical report TU Braunschweig, Informatik-Bericht 98-02.
Abstract: Programmers and users of compute intensive scientific applications often do not want to (or even cannot) code load balancing and fault tolerance into their programs.

The system uses a global virtual name space to provide migration and rollback transparency in user space for distributed groups of processes on workstations. Applications always use the same virtual names for the operating system objects, independent of their current real location. The system calls are interposed and their parameters translated between the name spaces. Unlike other migration mechanisms, does not require the applications to be written for a specific programming model or communication library.

The first approach to execute applications in the virtual name space was to link the programs with a modified system library. Now, in this paper we describe design and implementation of a separate system call interposition process that accesses the application via the debugging interface. The main advantage of this approach is that it can handle even unmodified (e.g. commercially bought) application programs. We compare measured performance figures with previous similar approaches and the modified system library.
ISI Accession Number: WOS:000077612600023
2 citations in ISI Web of Science until August 2013

• [PLGHOB99] Stefan Petri and Gunther Lustig and Claus Grewe and Rainer Hagenau and Wolfgang Obelöer and Marcel Boosten:
Performance Comparison of different High-Speed Networks with a Uniform Efficient Programming Interface.
In: Wolfgang Karl and Geir Horn (Eds), Scalable Coherent Interface -- Proceedings of SCI Europe '99, September 2nd - 3rd, 1999, pages 83 - 90, held as a Conference Stream of Euro-PAR'99, Toulouse, France, 31 Aug. - 3 Sept. 1999.
Annote: Continuation of the CC'99 contribution.
Abstract: The communication network and its interface are an important factor for the performance of modern cluster computing systems. During the last years, several new approaches were developed which yield higher bandwidth and lower latency than traditional alternatives. However, applications often can exploit the performance of the underlying network only by using specially tuned programming interfaces. This dependency makes porting the applications difficult if not impossible. Therefore, with HPCC (High Performance Cluster Communication) we have designed a programming interface which enables applications to use different high speed networks in a uniform and efficient manner. Currently it is implemented for four high speed networks: HIC, SCI, Gigabit Ethernet, and Myrinet. This paper gives a short overview of the HPCC programming interface, and presents comparative figures for the performance of basic operations on four different high speed network technologies.

• [Petri99] Stefan Petri:
A Common Framework for Transparent Checkpointing, Replication and Migration in Clusters.
In: W. Erhard, K.-E. Großpietsch, W. Koch, E. Maehle and E. Zehendner, (Eds.), ARCS'99: Architektur von Rechensystemen, Vorträge der Workshops im Rahmen der 15. GI/ITG-Fachtagung vom 4. bis 7. Oktober 1999 in Jena pp. 79-88, Jena, October 1999.
Workshop Verläßlichkeit und Fehlertoleranz.
Abstract: This paper presents a new approach to unify fault tolerance and load balancing in a common framework, aimed at providing those services (even) to legacy applications, on clusters of off-the-shelf PCs or workstations. Such clusters with high speed networks are attractive due to their price-performance ratio and rising power. However, multi-user operation and high node failure probability necessitate resource management and fault tolerance measures for long running applications, and for applications that require high availability. Now, programmers and users of applications are interested in their algorithms, solutions or services, and expect resource management and fault tolerance as services from the run time environment. Unfortunately, such clusters provide these services only minimally, if at all. A suitable approach to solve this discrepancy is application transparent checkpointing, migration, rollback and replication. It should be implemented as middleware between operating system and application to facilitate implementation and installation. We describe our work to extend our checkpointing and migration system to also provide replication for distributed applications. The approach to achieve these services transparently for the application is the construction of a system-wide virtual name space, which abstracts the running application processes from the actual location and time of their execution. No changes to the system kernel or the application code are required. Checkpointing already is the common base for rollback and for migration, and now we extend the migration to cloning to also achieve replication. With application transparent checkpoint / rollback, can only detect and treat crash faults. With replication it now is also able to detect other faults by comparing the output of the replica, even though it cannot know the meaning of the output contents. The abstraction through the virtual name space is an important prequisite to enable error detection through output comparison on cluster systems. It ensures that no environment specific information can yield differences in the replica outputs during fault-free operation.

### Co-Author of some more Conference Papers

• [SPL94] Jürgen Schönwälder and Stefan Petri and Horst Langendörfer:
Frei erhältliche Software für UNIX Administratoren.
In Offene Systeme -- Unix in Deutschland, GUUG Jahrestagung, Wiesbaden, September 1994, pages 322-329 (in german).
Abstract: The Internet provides a lot of free software for UNIX system administration. This survey of some of the most important programs should help new system administrators to find software that solves their problems. We further would like to motivate an open discussion about experiences with free software for system administration tasks.

• [SLP94] Bettina Schnor and Horst Langendörfer and Stefan Petri:
Einsatz neuronaler Netze zur Lastbalancierung in Workstationclustern.
In: Horst Langendörfer (Ed.), Praxisorientierte Parallelverarbeitung - Beiträge zum 3. Workshop über Wissenschaftliches Rechnen, Hanser, München, October 1994, pages 154-165 (in german).

• [SPL96] Bettina Schnor and Stefan Petri and Horst Langendörfer:
Load Management for Load Balancing on Heterogeneous Platforms: A Comparison of Traditional and Neural Network Based Approaches.
In: Luc Bouge, Pierre Fraigniaud, Anne Mignotte, Yves Robert (Eds.) Euro-Par'96 -- Parallel Processing Proceedings of the Second International Euro-Par Conference, Volume II, Springer Lecture Notes in Computer Science 1124, pages 615-620. ENS Lyon, France, August 27-29, 1996.
doi:10.1007/BFb0024756
Abstract: In this paper we compare simple load metrics with neural networks which have been trained to predict the expected delay of an application from the sampled load informations. The results show that the proposed load metric performs well in heterogeneous environments. Further, neural networks can improve the performance of load balancing facilities.
14 citations listed by Google Scholar until June 2015

• [SPOL96] Bettina Schnor and Stefan Petri and Reinhard Oleyniczak and Horst Langendörfer:
Scheduling of Parallel Applications on Heterogeneous Workstation Clusters.
In: Koukou Yetongnon and Salim Hariri (Ed.), Proceedings of PDCS'96 -- ISCA 9th International Conference on Parallel and Distributed Computing Systems, pages 330-337, Dijon, France, September 1996. ISI Accession Number: WOS:A1996BG69K00055

Abstract: Scheduling and load balancing for parallel applications can be done at application level, or at system level. Application level scheduling is less transparent, because it has to be coded into each program, and can lead to contradicting decisions, when the different applications do not know about each other. Therefore, in this paper we focus on system level load balancing. We discuss the special properties of heterogeneous workstation clusters for scheduling parallel applications. A Shortest-Expected-Delay mapping is presented that assigns the processes of a parallel application to virtually homogeneous'' machines, based upon the current load situation. We present simulation results that show, how and when process migration is beneficial in heterogeneous systems.
12 citations in ISI Web of Science until December 2017.
25 citations listed by Google Scholar until June 2015.
8 non-self citations in CiteSeerX.

• [SPL96b] Bettina Schnor and Stefan Petri and Horst Langendörfer:
A Detailed Comparison of Traditional and Neural Network Based Approaches for Load Metrics on Heterogeneous Platforms.
In: Hermann G. Matthies und Josef Schüle (Eds.), Paralleles und Verteiltes Rechnen -- Beiträge zum 4. Workshop über Wissenschaftliches Rechnen, pages 93-106, Braunschweig, 9.-11. October 1996. Shaker Verlag.
Annote: Extended, continued and updated version of the EuroPar'96 Paper.
Abstract: Adaptive and dynamic load balancing are challenging problems in the field of parallel computing. Therefore, a load management facility is desirable which gives up to date load informations which are also comparable for heterogeneous machines. In this paper we discuss several approaches for load metrics in heterogeneous systems. We compare simple load metrics with neural networks which have been trained to predict the expected delay of an application from the sampled load informations. The results show that the proposed load metric performs well in heterogeneous environments. Further, neural networks can improve the performance of load balancing facilities.

• [SPB98] Bettina Schnor and Stefan Petri and Matthias Becker:
Scalability of Multicast Based Synchronization Methods.
In Proceedings of the 24th EUROMICRO Conference, August 25-27, 1998, Västerås, Sweden, pages 969-975. IEEE Computer Society, August 1998.
10.1109/EURMIC.1998.708129
Abstract: Consistent maintenance of distributed data is important in application areas like groupware and for runtime support for parallel computing. We examine the performance of different multicast based methods for maintaining the consistency of distributed data depending on the network topology and concurrency.

Some amount of data is kept distributed or replicated on some or all nodes of a distributed system. At every moment, each instance that accesses this data must see the same information. Updates must be delivered ordered, reliably, and efficiently.

Our prototype software implements ordered, reliable multicasts on top of the unreliable IP broad- or multicast with three different methods (Master-Slave, Token Exchange on Demand, Totem Single Ring). This paper shows measurement results for the efficiency and scalability of the three methods in different topologies.

The measurements confirm earlier analytical results. Totem behaves well in large networks with many concurrent senders. The overhead of Token on Demand and of the Master-Slave algorithm is almost the same. Also we could not find an indication for the often-read opinion that the Master-Slave approach scales worse because of the central bottleneck.
ISI Accession Number: WOS:000075882900147
2 citations in ISI Web of Science until June 2015

• [GLOP99] Claus Grewe and Gunther Lustig and Wolfgang Obelöer and Stefan Petri:
Leistungsvergleich verschiedener Netzwerke mit einer einheitlichen und effizienten Benutzerschnittstelle.
In: Wolfgang Rehm and Theo Ungerer (Eds.), Cluster Computing -- Tagungsband zum 2. Workshop, Karlsruhe, 25./26. March 1999, pp. 125-134. Chemnitzer Informatik-Berichte CSR-99-02, March 1999 (in german).
Abstract: Ein leistungsbestimmender Faktor moderner Clustersysteme ist das verwendete Kommunikationsnetzwerk. In den letzten Jahren wurden hier eine Reihe neuerer Ansätze entwickelt, die höhere Bandbreiten und niedrigere Latenzzeiten im Vergleich zu klassischen Alternativen aufweisen. Allerdings können Applikationen die höhere Leistungsfähigkeit des zugrundeliegenden Netzwerkes häufig nur durch die Benutzung speziell abgestimmter Schnittstellen erzielen. Dieses mindert aber i.allg. die Portierbarkeit der Anwendungen. Aus diesem Grund wurde eine Benutzerschnittstelle konzipiert, die es aktuell ermöglicht, vier verschiedene Hochgeschwindigkeitsnetzwerke (HIC, SCI, Gigabit Ethernet, Myrinet) einheitlich und effizient zu nutzen. In diesem Beitrag wird ein kurzer Überblick über diese HPCC-Benutzerschnittstelle gegeben und Meßwerte für die vier Hochgeschwindigkeitsnetze vorgestellt.

• [SP99] Bettina Schnor and Stefan Petri:
Using On-line Job Monitoring for Dynamic Load Balancing of Parallel Applications.
In: Hamid R. Arabnia et al. (Eds.), Proceedings of the International Conference on Parallel and Distributed Processing Techniques and Applications, PDPTA'99, pages 2561-2567, Las Vegas, NV, USA, June 28 - July 1, 1999.
Abstract: While the significance of the communication costs for the performance of parallel applications is well known, these costs are hardly considered in the known resource management systems for workstation clusters. In this paper we present the Cluster Search Algorithm (CSA) for dynamic remapping of parallel applications in clusters. The novelty of our approach is that the communication behavior of the application does not have to be known a priori. The decisions are made dynamically at run time according to the actually observed communication behavior of the application and available resources. We present first simulation results and an overview over an actual implementation.
ISI Accession Number: WOS:000167653300383

• [PPG00] Holger Pals, Stefan Petri und Claus Grewe:
FANTOMAS: Fault Tolerance for Mobile Agents in Clusters.
In: J. Rolim et al., (Eds.), Parallel and Distributed Processing -- Proceedings of 15 IPDPS 2000 Workshops, Cancun, Mexico. Lecture Notes in Computer Science, Vol. 1800, pages 1236-1247, Springer, May 2000.
Annual IEEE Workshop on Fault-Tolerant Distributed Systems (FTPDS2000).
doi:10.1007/3-540-45591-4_170
Abstract:
ISI Accession Number: WOS:000171729800155
13 citations in ISI Web of Science until May 2019.
43 citations in Google Scholar until October 2018.
6 non-self citations in CiteSeerX

• [SSP03] Lars Schneidenbach, Bettina Schnor and Stefan Petri:
Architecture and Implementation of the Socket Interface on Top of GAMMA.
In: 28th Annual IEEE Conference on Local Computer Networks (LCN 2003), Workshop on High Speed Local Networks (HSLN 2003), October 21, 2003, Bonn/Königswinter., pages 528-536. IEEE Computer Society.
doi:10.1109/LCN.2003.1243179
Abstract: GAMMA (the Genoa Active Message MAchine) is a lightweight messaging system for Fast and Gigabit Ethernet. It is based on an Active Message-like paradigm and provides a performing, cost-effective alternative to proprietary high-speed networks, e. g. Myrinet, with the combination of low end-to-end latency and high throughput.
GAMMA supports the important class of MPI based-parallel applications via the MPI/GAMMA interface, but up to now support for the also important class of socket based cluster applications is still missing.
This paper describes two different approaches to how the socket interface can be adapted to GAMMA: The first is transparent for both application and GAMMA layer, the second is only transparent for the application. First performance results with the so-called GAMMAsockets are given. They show that the second approach performs almost as good as native GAMMA communication.

ISI Accession Number: WOS:000186828200072
2 citations in ISI Web of Science until June 2015.
9 citations in Google Scholar until June 2015.

• [NHPVWL09] Thomas Nocke, Ursula Heyder, Stefan Petri, Katrin Vohland, Markus Wrobel and Wolfgang Lucht:
Visualization of Biosphere Changes in the Context of Climate Change.
In: Volker Wohlgemuth (Ed.), Information Technology and Climate Change -- 2nd International Conference IT for empowerment (ITCC08), September 26/27th 2008, Berlin., pages 29-36. trafo Wissenschaftsverlag.
See PVV: The Movie

• [RPF09] Claus Rachimow, Stefan Petri and Michael Flechsig:
Manageing Metadata in a Collaborative Earth System Research Environment.
In: Volker Wohlgemuth (Ed.), Information Technology and Climate Change -- 2nd International Conference IT for empowerment (ITCC08), September 26/27th 2008, Berlin., pages 47-54. trafo Wissenschaftsverlag.

### Co-Editor of one Workshop Proceedings

• [ALV98] Arndt Bode and Andreas Ganz and Claudia Gold and Stefan Petri and Niels Reimer and Björn Schiemann and Thomas Schnekenburger (Editors):
Anwendungsbezogene Lastverteilung - ALV'98. SFB-Bericht Nr. 342/01/98 A, TU München, Institut für Informatik, Bericht Nr. TUM-I9806, February 1998.

### Seminarbände

I was involved in supervising several students' seminars, where we have edited collections of the texts and talks. All these are in german.

### Data Publications

Stefan Petri's Homepage