Changing seasonality of moderate and extreme precipitation events in the Alps

Brönnimann, Stefan; Rajczak, Jan; Fischer, Erich M.; Raible, Christoph C.; Rohrer, Marco; Schär, Christoph (2018). Changing seasonality of moderate and extreme precipitation events in the Alps. Natural Hazards and Earth System Sciences, 18(7), pp. 2047-2056. Copernicus Publications 10.5194/nhess-18-2047-2018

[img]
Preview
Text
nhess-18-2047-2018.pdf - Published Version
Available under License Creative Commons: Attribution (CC-BY).

Download (2MB) | Preview

The intensity of precipitation events is expected to increase in the future. The rate of increase depends on the strength or rarity of the events; very strong and rare events tend to follow the Clausius–Clapeyron relation, whereas weaker events or precipitation averages increase at a smaller rate than expected from the Clausius–Clapeyron relation. An often overlooked aspect is seasonal occurrence of such events, which might change in the future. To address the impact of seasonality, we use a large ensemble of regional and global climate model simulations, comprising tens of thousands of model years of daily temperature and precipitation for the past, present, and future. In order to make the data comparable, they are quantile mapped to observation-based time series representative of the Aare catchment in Switzerland. Model simulations show no increase in annual maximum 1-day precipitation events (Rx1day) over the last 400 years and an increase of 10 %–20 % until the end of the century for a strong (RCP8.5) forcing scenario. This fits with a Clausius–Clapeyron scaling of temperature at the event day, which increases less than annual mean temperature. An important reason for this is a shift in seasonality. Rx1day events become less frequent in late summer and more frequent in early summer and early autumn, when it is cooler. The seasonality shift is shown to be related to summer drying. Models with decreasing annual mean or summer mean precipitation show this behaviour more strongly. The highest Rx1day per decade, in contrast, shows no change in seasonality in the future. This discrepancy implies that decadal-scale extremes are thermodynamically limited; conditions conducive to strong events still occur during the hottest time of the year on a decadal scale. In contrast, Rx1day events are also limited by other factors. Conducive conditions are not reached every summer in the present, and even less so in the future. Results suggest that changes in the seasonal cycle need to be accounted for when preparing for moderately extreme precipitation events and assessing their socio-economic impacts.

Item Type:

Journal Article (Original Article)

Division/Institute:

08 Faculty of Science > Institute of Geography > Physical Geography > Unit Climatology
08 Faculty of Science > Physics Institute > Climate and Environmental Physics
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

UniBE Contributor:

Brönnimann, Stefan; Raible, Christoph and Rohrer, Marco

Subjects:

500 Science > 530 Physics
500 Science > 550 Earth sciences & geology

ISSN:

1561-8633

Publisher:

Copernicus Publications

Language:

English

Submitter:

Lukas Simon Meyer

Date Deposited:

08 Aug 2018 14:55

Last Modified:

30 Sep 2021 14:53

Publisher DOI:

10.5194/nhess-18-2047-2018

BORIS DOI:

10.7892/boris.119134

URI:

https://boris.unibe.ch/id/eprint/119134

Actions (login required)

Edit item Edit item
Provide Feedback