05/02/2024 - Welcome Meng Wang

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The “Meteorological Data Science” group welcomes Meng Wang as a visiting PhD student. Meng is currently doing her PhD at the School of Atmospheric Sciences, Sun Yat-sen University, China with Professor Xiuzhen Li focusing on the interaction of high- and low-latitude Rossby waves leading to extreme cold-wet weather conditions in South China. During her stay, she will specifically investigate to what extent the excitation of these waves is linked to the large-scale circulation over the North Atlantic. Meng Wang successfully applied for scholarship funded by the China Scholarship Council which will allow her to stay with us for 12 months until January 2025. We look forward to learning about her research and wish her a joyful stay at IMKTRO! If you would like to learn more about cold-wet extremes in South China, please meet Meng at Campus North, Building 435, Room 219.

19/01/2024 - New Paper on WCB modulation by the MJO

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Modulation of North Atlantic Weather Regimes stratified according to different MJO phases and (a) normal, (b) low, (c) high WCB activity.

Over the past few decades, research has elucidated the significant role of warm conveyor belts (WCBs), characterized by ascending airstreams within extratropical cyclones, in the dynamics of extratropical atmospheric systems. However, there has been limited investigation into the modulation of WCB occurrence frequency, referred to herein as WCB activity, on subseasonal timescales. Additionally, the potential impact of WCB activity on tropospheric teleconnection patterns, which contribute to predictability on these timescales, remains unclear. A new paper which was now published in the journal Weather and Climate Dynamics utilizes reanalysis data to examine how the Madden–Julian Oscillation (MJO) modulates WCB activity.

A primary discovery is the notable increase in WCB activity over the western North Pacific when MJO convection occurs over the Indian Ocean. This augmented WCB activity, particularly pronounced during La Niña conditions, is attributed to intensified poleward moisture fluxes propelled by the circulation of subtropical Rossby gyres associated with the MJO. Conversely, when MJO convection is situated over the western North Pacific, there is a significant increase in WCB activity over the eastern North Pacific, owing to a southward displacement and eastward elongation of the North Pacific jet stream.

Nevertheless, while overall increases in WCB activity are observed, individual MJO events exhibit considerable variability, with some events displaying anomalously low WCB activity. Events of the same MJO phase with anomalously low WCB activity over the North Pacific tend to be succeeded by canonical teleconnection patterns in the Atlantic–European region. Specifically, the occurrence frequency of the positive phase of the North Atlantic Oscillation (NAO) is increased during MJO convection over the Indian Ocean, and conversely for the negative phase of the NAO during MJO convection over the western North Pacific. However, when individual events of the same MJO phase coincide with anomalously high WCB activity over the North Pacific, these canonical teleconnection patterns are altered, notably weakening the linkage between the MJO and the negative phase of the NAO.

Reanalysis data and experiments employing an idealized general circulation model reveal that this phenomenon is associated with anomalous ridge formation over western North America, facilitated by increased WCB activity. Overall, this study underscores the potential influence of WCBs on tropical–extratropical teleconnection patterns and emphasizes the necessity of accurately representing them in numerical weather prediction models to fully harness the predictability sources emerging from tropical dynamics.

 

Quinting, J. F., Grams, C. M., Chang, E. K.-M., Pfahl, S., and Wernli, H.: Warm conveyor belt activity over the Pacific: modulation by the Madden–Julian Oscillation and impact on tropical–extratropical teleconnections, Weather Clim. Dynam., 5, 65–85, https://doi.org/10.5194/wcd-5-65-2024, 2024.

03/11/2023 - Welcome Bastian Kirsch

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We warmly welcome Bastian Kirsch in the WG „Meteorological Data Science“. Bastian grew up near Hamburg where he studied Meteorology focusing on radar meteorology. In 2022, Bastian completed his PhD under the supervision of Prof. Felix Ament and Cathy Hohenegger entitled “Illuminating convective cold pools with a dense station network”. During his PhD Bastian was heavily involved in the FESSTVaL campaign which took place near the Lindenberg observatory. In the coming years, Bastian will bring in this expertise at IMK-TRO to coordinate the “North Atlantic Waveguide, Dry Intrusion and Downstream Impact Campagin (NAWDIC)”. We are very happy to have Bastian in the NAWDIC team and look forward to the campaign preparation and implementation in winter 2025/2026.

20/09/2023 - Welcome Siyu Li

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We warmly welcome Siyu Li in the WG „Meteorological Data Science“. Siyu Li completed her BSc at Nanjing University of Information Science and Technology (NUIST) in June 2020 where she evaluated the representation of major sudden stratospheric warming events in the CESM-WACCM. Siyu then moved to Karlsruhe to complete her Master's degree at the IMK. For her Master’s thesis, Siyu joined the working group „Atmospheric risks“ where she developed a machine learning model for hail prediction in Germany. The PhD project will also include machine learning. As part of the project "Advancing subseasonal predictions at reduced computational effort", Siyu will address the question of how short-term forecast errors in the tropics affect the reliability of subseasonal predictions in Central Europe.