Simulations of the 2005, 1910, and 1876 Vb cyclones over the Alps - sensitivity to model physics and cyclonic moisture flux

Stucki, Peter; Froidevaux, Paul; Zamuriano, Marcelo; Isotta, Francesco Alessandro; Messmer, Martina; Martynov, Andrey (2020). Simulations of the 2005, 1910, and 1876 Vb cyclones over the Alps - sensitivity to model physics and cyclonic moisture flux. Natural Hazards and Earth System Sciences, 20(1), pp. 35-57. Copernicus Publications 10.5194/nhess-20-35-2020

[img]
Preview
Text
nhess-20-35-2020.pdf - Published Version
Available under License Creative Commons: Attribution (CC-BY).

Download (23MB) | Preview

In June 1876, June 1910, and August 2005, northern Switzerland was severely impacted by heavy precipitation and extreme floods. Although occurring in different centuries, all three events featured very similar precipitation patterns and an extratropical storm following a cyclonic, so-called Vb (five b of the van Bebber trajectories) trajectory around the Alps. Going back in time from the recent to the historical cases, we explore the potential of dynamical downscaling of a global reanalysis product from a grid size of 220 to 3 km. We investigate sensitivities of the simulated precipitation amounts to a set of differing configurations in the regional weather model. The best-performing model configuration in the evaluation, featuring a 1 d initialization period, is then applied to assess the sensitivity of simulated precipitation totals to cyclonic moisture flux along the downscaling steps. The analyses show that cyclone fields (closed pressure contours) and tracks (minimum pressure trajectories) are well defined in the reanalysis ensemble for the 2005 and 1910 cases, while deviations from the ensemble mean increase for the 1876 case. In the downscaled ensemble, the accuracy of simulated precipitation totals is closely linked to the exact trajectory and stalling position of the cyclone, with slight shifts producing erroneous precipitation, e.g., due to a break-up of the vortex if simulated too close to the Alpine topography. Simulated precipitation totals only reach the observed ones if the simulation includes continuous moisture fluxes of >200 kg m−1 s−1 from northerly directions and high contributions of (embedded) convection. Misplacement of the vortex and concurrent uncertainties in simulating convection, in particular for the 1876 case, point to limitations of downscaling from coarse input for such complex weather situations and for the more distant past. On the upside, single (contrasting) members of the historical cases are well capable of illustrating variants of Vb cyclone dynamics and features along the downscaling steps.

Item Type:

Journal Article (Original Article)

Division/Institute:

08 Faculty of Science > Physics Institute > Climate and Environmental Physics
08 Faculty of Science > Institute of Geography > Physical Geography > Unit Climatology
10 Strategic Research Centers > Oeschger Centre for Climate Change Research (OCCR)
08 Faculty of Science > Institute of Geography
08 Faculty of Science > Institute of Geography > Physical Geography

Graduate School:

Graduate School of Climate Sciences

UniBE Contributor:

Stucki, Peter; Froidevaux, Paul Arnaud; Zamuriano Carbajal, Juan Marcelo; Messmer, Martina Barbara and Martynov, Andrey

Subjects:

500 Science > 530 Physics
500 Science > 550 Earth sciences & geology
900 History > 910 Geography & travel

ISSN:

1561-8633

Publisher:

Copernicus Publications

Funders:

[31] Oeschger Centre for Climate Change Research (OCCR)
[73] Swiss Government Excellence Scholarship

Language:

English

Submitter:

André Hürzeler

Date Deposited:

23 Jan 2020 09:28

Last Modified:

23 Jan 2020 09:28

Publisher DOI:

10.5194/nhess-20-35-2020

Related URLs:

BORIS DOI:

10.7892/boris.138647

URI:

https://boris.unibe.ch/id/eprint/138647

Actions (login required)

Edit item Edit item
Provide Feedback