TY - JOUR A1 - Kornhuber, Kai A1 - Petoukhov, Vladimir A1 - Karoly, D. A1 - Petri, Stefan A1 - Rahmstorf, Stefan A1 - Coumou, Dim T1 - Summertime Planetary Wave Resonance in the Northern and Southern Hemispheres JF - Journal of climate Y1 - 2017 U6 - https://doi.org/10.1175/JCLI-D-16-0703.1 SN - 0894-8755 SN - 1520-0442 VL - 30 SP - 6133 EP - 6150 PB - American Meteorological Soc. CY - Boston ER - TY - JOUR A1 - Molnos, Sonja A1 - Mamdouh, Tarek A1 - Petri, Stefan A1 - Nocke, Thomas A1 - Weinkauf, Tino A1 - Coumou, Dim T1 - A network-based detection scheme for the jet stream core JF - Earth system dynamics N2 - 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. 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 degrees W to 140 degrees 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. Y1 - 2017 U6 - https://doi.org/10.5194/esd-8-75-2017 SN - 2190-4979 SN - 2190-4987 VL - 8 IS - 1 SP - 75 EP - 89 PB - Copernicus CY - Göttingen ER - TY - JOUR A1 - Totz, Sonja Juliana A1 - Petri, Stefan A1 - Lehmann, Jascha A1 - Coumou, Dim T1 - Regional Changes in the Mean Position and Variability of the Tropical Edge JF - Geophysical research letters N2 - 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 continents. Rainfall variability in these regions changed likewise, and most of those changes can be explained by changes in HCE/STJ variability. This highlights the importance of understanding future tropical belt changes both regionally and in terms of variability. Plain Language Summary We applied a new network-based method to detect motion of the tropical climate border with longitudinal resolution. Depending on the longitudinal position, there are differences in both direction and magnitude of the border motion. In addition, we demonstrate that the rainfall variability is increasing in the Mediterranean region and decreasing over the American and Asian continents, which can be explained by the variability of the tropical belt location. Y1 - 2018 U6 - https://doi.org/10.1029/2018GL079911 SN - 0094-8276 SN - 1944-8007 VL - 45 IS - 21 SP - 12076 EP - 12084 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Totz, Sonja Juliana A1 - Petri, Stefan A1 - Lehmann, Jascha A1 - Peukert, Erik A1 - Coumou, Dim T1 - Exploring the sensitivity of Northern Hemisphere atmospheric circulation to different surface temperature forcing using a statistical-dynamical atmospheric model JF - Nonlinear processes in geophysics N2 - 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. Y1 - 2019 U6 - https://doi.org/10.5194/npg-26-1-2019 SN - 1023-5809 SN - 1607-7946 VL - 26 IS - 1 SP - 1 EP - 12 PB - Copernicus CY - Göttingen ER -