TY  - JOUR
A1  - Kormann, Christoph
A1  - Francke, Till
A1  - Bronstert, Axel
T1  - Detection of regional climate change effects on alpine hydrology by daily resolution trend analysis in Tyrol, Austria
JF  - Journal of water and climate change
N2  - Owing to average temperature increases of at least twice the global mean, climate change is expected to have strong impacts on local hydrology and climatology in the Alps. Nevertheless, trend analyses of hydro-climatic station data rarely reveal clear patterns concerning climate change signals except in temperature observations. However, trend research has thus far mostly been based on analysing trends of averaged data such as yearly, seasonal or monthly averages and has therefore often not been able to detect the finer temporal dynamics. For this reason, we derived 30-day moving average trends, providing a daily resolution of the timing and magnitude of trends within the seasons. Results are validated by including different time periods. We studied daily observations of mean temperature, liquid and solid precipitation, snow height and runoff in the relatively dry central Alpine region in Tyrol, Austria. Our results indicate that the vast majority of changes are observed throughout spring to early summer, most likely triggered by the strong temperature increase during this season. Temperature, streamflow and snow trends have clearly amplified during recent decades. The overall results are consistent over the entire investigation area and different time periods.
KW  - Alps
KW  - hydroclimatology
KW  - Mann-Kendall test
KW  - streamflow
KW  - trend detection
Y1  - 2015
U6  - https://doi.org/10.2166/wcc.2014.099
SN  - 2040-2244
VL  - 6
IS  - 1
SP  - 124
EP  - 143
PB  - IWA Publ.
CY  - London
ER  - 
TY  - GEN
A1  - Kormann, Christoph
A1  - Bronstert, Axel
A1  - Francke, Till
A1  - Recknagel, Thomas
A1  - Gräff, Thomas
T1  - Model-Based attribution of high-resolution streamflow trends in two alpine basins of Western Austria
N2  - Several trend studies have shown that hydrological conditions are changing considerably in the Alpine region. However, the reasons for these changes are only partially understood and trend analyses alone are not able to shed much light. Hydrological modelling is one possible way to identify the trend drivers, i.e., to attribute the detected streamflow trends, given that the model captures all important processes causing the trends. We modelled the hydrological conditions for two alpine catchments in western Austria (a large, mostly lower-altitude catchment with wide valley plains and a nested high-altitude, glaciated headwater catchment) with the distributed, physically-oriented WaSiM-ETH model, which includes a dynamical glacier module. The model was calibrated in a transient mode, i.e., not only on several standard goodness measures and glacier extents, but also in such a way that the simulated streamflow trends fit with the observed ones during the investigation period 1980 to 2007. With this approach, it was possible to separate streamflow components, identify the trends of flow components, and study their relation to trends in atmospheric variables. In addition to trends in annual averages, highly resolved trends for each Julian day were derived, since they proved powerful in an earlier, data-based attribution study. We were able to show that annual and highly resolved trends can be modelled sufficiently well. The results provide a holistic, year-round picture of the drivers of alpine streamflow changes: Higher-altitude catchments are strongly affected by earlier firn melt and snowmelt in spring and increased ice melt throughout the ablation season. Changes in lower-altitude areas are mostly caused by earlier and lower snowmelt volumes. All highly resolved trends in streamflow and its components show an explicit similarity to the local temperature trends. Finally, results indicate that evapotranspiration has been increasing in the lower altitudes during the study period.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 364 
KW  - trend attribution
KW  - trend detection
KW  - climate change
KW  - trend drivers
KW  - hydrological modelling
KW  - alpine catchments
KW  - streamflow
KW  - hydroclimatology
Y1  - 2017
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-400641
ER  -