Convection-permitting regional climate simulations for representing floods in small- and medium-sized catchments in the Eastern Alps
<p>Small-scale floods are a consequence of high precipitation rates in small areas that can occur along frontal activity and convective storms. This situation is expected to become more severe due to a warming climate, when single precipitation events resulting from deep convection become m...
| Main Authors: | , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2018-10-01
|
| Series: | Natural Hazards and Earth System Sciences |
| Online Access: | https://www.nat-hazards-earth-syst-sci.net/18/2653/2018/nhess-18-2653-2018.pdf |
| Summary: | <p>Small-scale floods are a consequence of high precipitation rates in small
areas that can occur along frontal activity and convective storms. This
situation is expected to become more severe due to a warming climate, when
single precipitation events resulting from deep convection become more
intense (super Clausius–Clapeyron effect). Regional climate model (RCM)
evaluations and inter-comparisons have shown that there is evidence that an
increase in RCM resolution and, in particular, at the convection-permitting
scale will lead to a better representation of the spatial and temporal
characteristics of heavy precipitation at small and medium scales. In this
paper, the benefits of grid size reduction and bias correction in climate
models are evaluated in their ability to properly represent flood generation
in small- and medium-sized catchments. The climate models are sequentially
coupled with a distributed hydrological model. The study area is the Eastern
Alps, where small-scale storms often occur along with heterogeneous rainfall
distributions leading to a very local flash flood generation. The work is
carried out in a small multi-model framework using two different RCMs (CCLM
and WRF) in different grid sizes. Bias correction is performed by the use of
the novel scaled distribution mapping (SDM), which is similar to the usual quantile
mapping (QM) method. The results show that, in the investigated RCM ensemble, no
clear added value of the usage of convection-permitting RCMs for the purpose
of flood modelling can be found. This is based on the fact that flood events
are the consequence of an interplay between the total precipitation amount
per event and the temporal distribution of rainfall intensities on a
sub-daily scale. The RCM ensemble is lacking in one and/or the other. In
the small catchment ( < 100 km<sup>2</sup>), a favourable superposition of the
errors leads to seemingly good CCLM 3 km results both for flood statistics and
seasonal occurrence. This is, however, not systematic across the catchments.
The applied bias correction only corrects total event rainfall amounts in an
attempt to reduce systematic errors on a seasonal basis. It does not account
for errors in the temporal dynamics and deteriorates the results in the small
catchment. Therefore, it cannot be recommended for flood modelling.</p> |
|---|---|
| ISSN: | 1561-8633 1684-9981 |