报告题目：Diabatic effects on the evolution of storm tracks
时 间：12月7日(周四) ,上午10:00-12:00
Abstract (Feel free to cut where necessary):
The sea surface temperature (SST) distribution in the Kuroshio and Gulf Stream region have been argued to modulate the development and evolution of extratropical cyclones and storm tracks through diabatic heating associated with latent heat release as well as sensible and latent heat fluxes. However, the direct and indirect effects of these surface fluxes on extratropical cyclones are still not well understood. Using reanalysis, idealized modelling, and theory, we show that the direct influence of sensible and latent heating is negligible and not sensitive to the sharpness of the SST front. The dominant factor is the indirect effect of surface latent heat fluxes proportional to absolute SST, providing latent heat for the development of storms. We further pinpoint the role of diabatic processes in the evolution of Northern Hemispheric stormtracks using an isentropic slope framework as a measure of baroclinicity. While diabatic processes act to increase baroclinicity in both the near-surface and free troposphere, the phasing of production and destruction of baroclinicity is in opposite order. In the near-surface troposphere, cold air advection, often associated with cold air outbreaks, first reduces baroclinicity, which is subsequently restored through surface air-sea heat exchange. Baroclinicity in the free troposphere, on the other hand, is first generated by moist diabatic processes before it is reduced associated with the lifecycle of storms.
Bio (feel free to cut where needed):
Thomas Spengler focuses on the combination of theory, observations, and modelling, specialized on scales ranging from meso, synoptic, to large-scale flow and participated and coordinated several field campaigns. He did his PhD at ETH Zurich, Switzerland, followed by a postdoc at Princeton University, USA, before accepting his professorship at the University of Bergen, Norway. Since 2015, he is the director of the Norwegian Research School on Changing Climates in the Coupled Earth System (CHESS). Currently, he is leading research projects focusing on atmosphere-ocean-ice interactions in higher latitudes as well as air-sea interactions and cyclone development in the midlatitude storm tracks. In 2012, he was elected as a member of the International Commission for Dynamic Meteorology (ICDM) and was elected President of ICDM in 2019, re-elected in 2023. From 2015-2019, he was the elected as Chair of the Atmospheric Working Group of the International Arctic Science Committee (IASC), and a member from 2013-2021. Since 2022, he is the elected Leader of the Norwegian Geophysical Society. He was awarded the prize for best lecturer of the academic year 2012/2013 at the Faculty for Mathematics and Natural Sciences at the University of Bergen and nominated for the IAMAS early career scientist medal in 2013.