8 results on '"Xiaoxu Shi"'
Search Results
2. The role of a weakened Atlantic Meridional Overturning Circulation in modulating temperature and precipitation extremes over Europe
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Qiyun Ma, Xiaoxu Shi, Dmitry Sidorenko, Patrick Scholz, Gerrit Lohmann, and Monica Ionita
- Abstract
The Atlantic meridional overturning circulation (AMOC) plays an important role in regulating global and regional climates, especially the European climate, as it affects northward heat transport. Climate model simulations project a decline in the strength of AMOC under future climate change, although high uncertainties exist across models. The potential slowdown of AMOC could cause large and rapid changes in the climate and is therefore regarded as a ‘low probability-high impact’ event. However, how a weakening AMOC affects temperature and precipitation extremes remains poorly understood. Here we use a state-of-the-art global climate model, a new version of the Alfred Wegener Institute Climate Model (AWI-CM3), to quantify these impacts on Europe. We have performed freshwater hosing experiments to weaken the strength of AMOC and to investigate its sensitivity to different freshwater forcing regions. Our results reveal that the largest decline in AMOC generally appears when additional freshwater is put directly at regions of deepwater formation, especially around the Irminger Sea. As atmospheric responses, widespread cooling and less precipitation are found in the Northern Hemisphere mid-latitudes. We further identify the changes in precipitation and temperature extremes on different timescales. Droughts and cold days are very pronounced under AMOC attenuations, and we argue that they may have a stronger impact than the system's mean responses. Our results provide implications for understanding European weather and climate response to a weakening of AMOC in the past, present, and future.
- Published
- 2023
3. Calendar effects on surface air temperature and precipitation based on model-ensemble equilibrium and transient simulations from PMIP4 and PACMEDY
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Xiaoxu Shi, Martin Werner, Carolin Krug, Chris M. Brierley, Anni Zhao, Endurance Igbinosa, Pascale Braconnot, Esther Brady, Jian Cao, Roberta D'Agostino, Johann Jungclaus, Xingxing Liu, Bette Otto-Bliesner, Dmitry Sidorenko, Robert Tomas, Evgeny M. Volodin, Hu Yang, Qiong Zhang, Weipeng Zheng, Gerrit Lohmann, Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Institut Pierre-Simon-Laplace (IPSL (FR_636)), École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), and This research has been supported by the German Federal Ministry of Education and Science (BMBF) PalMod II WP 3.3 (grant no. 01LP1924B) and the PAlaeo-Constraints on Monsoon Evolution and Dynamics (PACMEDY) Belmont Forum project (grant no. 01LP1607A). Xingxing Liu is funded by the open fund of State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, CAS (grant no. SKLLQG1920) and the National Science Foundation for Young Scientists of China (grant no. 41807425). Roberta D’Agostino is funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) under Germany’s Excellence Strategy – EXC 2037 Climate, Climatic Change, and Society (CLICCS) – Cluster of Excellence Hamburg, A4 African and Asian Monsoon Margins (grant no. 390683824). Qiong Zhang is funded by the Swedish Research Council (Vetenskapsrådet, grant nos. 2013-06476 and 2017-04232). Esther Brady and Bette Otto-Bliesner are supported by the National Center for Atmospheric Research, which is a major facility sponsored by the National Science Foundation underCooperative Agreement (grant no. 1852977).
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[SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere ,Global and Planetary Change ,Stratigraphy ,Paleontology ,[SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces, environment - Abstract
Numerical modelling enables a comprehensive understanding not only of the Earth's system today, but also of the past. To date, a significant amount of time and effort has been devoted to paleoclimate modeling and analysis, which involves the latest and most advanced Paleoclimate Modelling Intercomparison Project phase 4 (PMIP4). The definition of seasonality, which is influenced by slow variations in the Earth's orbital parameters, plays a key role in determining the calculated seasonal cycle of the climate. In contrast to the classical calendar used today, where the lengths of the months and seasons are fixed, the angular calendar calculates the lengths of the months and seasons according to a fixed number of degrees along the Earth's orbit. When comparing simulation results for different time intervals, it is essential to account for the angular calendar to ensure that the data for comparison is from the same position along the Earth's orbit. Most models use the classical "fixed-length" calendar, which can lead to strong distortions of the monthly and seasonal values, especially for the climate of the past. Here, by analyzing daily outputs from multiple PMIP4 model simulations, we examine calendar effects on surface air temperature and precipitation under mid-Holocene, last interglacial, and pre-industrial climate conditions. We conclude that: (a) The largest cooling bias occurs in autumn when the classical calendar is applied for the mid-Holocene and last interglacial. (b) The sign of the temperature anomalies between the Last Interglacial and pre-industrial in boreal autumn can be reversed after the switch from classical to angular calendar, particularly over the Northern Hemisphere continents. (c) Precipitation over West Africa is overestimated in boreal summer and underestimated in boreal autumn when the "fixed-length" seasonal cycle is applied. (d) Finally, correcting the calendar based on the monthly model results can reduce the biases to a large extent, but not completely eliminate them. In addition, we examine the calendar effects in 3 transient simulations for 6–0 ka by AWI-ESM, MPI-ESM, and IPSL. We find significant discrepancies between adjusted and unadjusted temperature values over ice-free continents for both hemispheres in boreal autumn. While for other seasons the deviations are relatively small. A drying bias can be found in the summer monsoon precipitation in Africa (in the "fixed-length" calendar), whereby the magnitude of bias becomes smaller over time. Overall, our study underlines the importance of the application of calendar transformation in the analysis of climate simulations. Neglecting the calendar effects could lead to a profound artificial distortion of the calculated seasonal cycle of surface air temperature and precipitation. One important fact to be noted here is that the discrepancy in seasonality under different calendars is an analysis bias and is highly depends on the choice of the reference position/date (usually the vernal equinox, which is set to 31th March) on the Earth's ellipse around the sun. Different model groups may apply different reference dates, so ensuring a consistent reference date and seasonal definition is key when we compare results across multiple models.
- Published
- 2022
4. A new perspective on permafrost boundaries in France during the Last Glacial Maximum
- Author
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Kim Helen Stadelmaier, Patrick Ludwig, Pascal Bertran, Pierre Antoine, Xiaoxu Shi, Gerrit Lohmann, Joaquim G. Pinto, Institute of Meteorology and Climate Research – Atmospheric Environmental Research, Karlsruhe Institute of Technology, Partenaires INRAE, Institut national de recherches archéologiques préventives (Inrap), De la Préhistoire à l'Actuel : Culture, Environnement et Anthropologie (PACEA), Université de Bordeaux (UB)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de géographie physique : Environnements Quaternaires et Actuels (LGP), Université Paris 1 Panthéon-Sorbonne (UP1)-Université Paris-Est Créteil Val-de-Marne - Paris 12 (UPEC UP12)-Centre National de la Recherche Scientifique (CNRS), Alfred Wegener Institute [Potsdam], Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung (AWI), Center for Marine Environmental Sciences [Bremen] (MARUM), Universität Bremen, and Centre National de la Recherche Scientifique (CNRS)-Université de Bordeaux (UB)
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Earth sciences ,ddc:550 ,[SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces, environment - Abstract
During the Last Glacial Maximum (LGM), a very cold and dry period around 26.5–19 kyr BP, permafrost was widespread across Europe. In this work, we explore the possible benefit of using regional climate model data to improve the permafrost representation in France, decipher how the atmospheric circulation affects the permafrost boundaries in the models, and test the role of ground thermal contraction cracking in wedge development during the LGM. With these aims, criteria for possible thermal contraction cracking of the ground are applied to climate model data for the first time. Our results show that the permafrost extent and ground cracking regions deviate from proxy evidence when the simulated large-scale circulation in both global and regional climate models favours prevailing westerly winds. A colder and, with regard to proxy data, more realistic version of the LGM climate is achieved given more frequent easterly winds conditions. Given the appropriate forcing, an added value of the regional climate model simulation can be achieved in representing permafrost and ground thermal contraction cracking. Furthermore, the model data provide evidence that thermal contraction cracking occurred in Europe during the LGM in a wide latitudinal band south of the probable permafrost border, in agreement with field data analysis. This enables the reconsideration of the role of sand-wedge casts to identify past permafrost regions.
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- 2022
5. Reply on RC3
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Xiaoxu Shi
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- 2022
6. Reply on RC1
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Xiaoxu Shi
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- 2022
7. Reply on RC2
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Xiaoxu Shi
- Published
- 2022
8. Supplementary material to 'Calendar effects on surface air temperature and precipitation based on model-ensemble equilibrium and transient simulations from PMIP4 and PACMEDY'
- Author
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Xiaoxu Shi, Martin Werner, Carolin Krug, Chris M. Brierley, Anni Zhao, Endurance Igbinosa, Pascale Braconnot, Esther Brady, Jian Cao, Roberta D'Agostino, Johann Jungclaus, Xingxing Liu, Bette Otto-Bliesner, Dmitry Sidorenko, Robert Tomas, Evgeny M. Volodin, Hu Yang, Qiong Zhang, Weipeng Zheng, and Gerrit Lohmann
- Published
- 2021
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