Assessment of climate‐change impacts on alpine discharge regimes with climate model uncertainty (original) (raw)
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Global Circulation Models (GCMs) and Regional Climate Models (RCMs) provide comprehensive physically based information on possible future changes in the global climate system. Their simulations have a coarse spatial resolution and exhibit large deviations from observations, especially for precipitation. Therefore, their output cannot be used directly in impact studies, but needs to be corrected and downscaled to a higher spatial resolution. In the presented study RCM scenarios are downscaled and corrected for the analysis of the hydrological impact of climate change in alpine catchment areas. Bias corrected precipitation and temperature data – with a resolution of 25km for the entire SEE region and a resolution of 1km for the research area in Austria – provided in the framework of the CC-WaterS project were available. Due to the coarse resolution of the RCM data and the observation fields used for the large scale bias correction, differences to local observations remained. While tem...
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Climate Dynamics, 2008
For the fourth assessment report of the Intergovernmental Panel on Climate Change (IPCC), the recent version of the coupled atmosphere/ocean general circulation model (GCM) of the Max Planck Institute for Meteorology has been used to conduct an ensemble of transient climate simulations These simulations comprise three control simulations for the past century covering the period 1860-2000, and nine simulations for the future climate (2001-2100) using greenhouse gas (GHG) and aerosol concentrations according to the three IPCC scenarios B1, A1B and A2. For each scenario three simulations were performed. The global simulations were dynamically downscaled over Europe using the regional climate model (RCM) REMO at 0.44°horizontal resolution (about 50 km), whereas the physics packages of the GCM and RCM largely agree. The regional simulations comprise the three control simulations (1950-2000), the three A1B simulations and one simulation for B1 as well as for A2 (2001-2100). In our study we concentrate on the climate change signals in the hydrological cycle and the 2 m temperature by comparing the mean projected climate at the end of the twenty-first century (2071-2100) to a control period representing current climate (1961-1990). The robustness of the climate change signal projected by the GCM and RCM is analysed focussing on the large European catchments of Baltic Sea (land only), Danube and Rhine. In this respect, a robust climate change signal designates a projected change that sticks out of the noise of natural climate variability. Catchments and seasons are identified where the climate change signal in the components of the hydrological cycle is robust, and where this signal has a larger uncertainty. Notable differences in the robustness of the climate change signals between the GCM and RCM simulations are related to a stronger warming projected by the GCM in the winter over the Baltic Sea catchment and in the summer over the Danube and Rhine catchments. Our results indicate that the main explanation for these differences is that the finer resolution of the RCM leads to a better representation of local scale processes at the surface that feed back to the atmosphere, i.e. an improved representation of the land sea contrast and related moisture transport processes over the Baltic Sea catchment, and an improved representation of soil moisture feedbacks to the atmosphere over the Danube and Rhine catchments. Keywords Regional climate change Á Hydrological cycle Á European catchments Á GCM and RCM ensembles Á Robustness
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Assessment of climate change impacts on the hydrology of the Lech Valley in northern Alps
2010
The objective of this investigation is to assess the impacts of climate change on the hydrology of the Lech Valley (1,000 km 2), a sub-catchment of the Danube River basin located in the northern Alps. An ensemble of nine climate projections is used to simulate the climate of a mid-21stcentury scenario period (2040-2069) and an end-21st-century scenario period (2070-2099). The delta change approach overcame the gap between regional climate models (RCMs) and the hydrological model. An observed 30-year time series (1971-2000) of precipitation and temperature was perturbed according to mean monthly changes between the RCM runs. The hydrological simulations have been employed with the semi-distributed model HQsim in an off-line mode. The climate scenarios show an increase in monthly temperatures and accompanying significant changes in the seasonal precipitation patterns, including an increase in the precipitation during winter and spring and a considerable decrease in the precipitation during summer. The resulting effects on the runoff indicate large, seasonal varying changes. A decrease in monthly runoff during summer and increases in winter minimize the inter-annual disparities between low runoff in winter and high runoff in spring and summer. The overall agreement of RCM runs suggests confidence in the projections.
2019
Climate change is one of the greatest threats to the World's environment. In Norway, the change will strongly affect the pattern, frequency and magnitudes of stream flows. However, it is highly challenging to quantify to what extent it will affect flow patterns and floods from small ungauged rural catchments due to unavailability or inadequacy of hydro-meteorological data for the calibration of hydrological models and tailoring methods to a small-scale level. To provide 15 meaningful climate impact studies at small catchments, it is therefore beneficial to use high spatial and temporal resolution climate projections as input to a high-resolution hydrological model. Here we use such a model chain to assess the impacts of climate change on flow patterns and frequency of floods in small ungauged rural catchments in western Norway using a new high-resolution regional climate projection, with improved performance with regards to the precipitation 20 distribution, and the regionalized hydrological model (Distance Distribution Dynamics) between the reference period (1981-2011) and a future period (2071-2100). The FDCs of all study catchments show there will be more wetter periods in the future than the reference period. The results also show that in the future period, the mean annual flow increases by 16.5% to 33.3%, and there will be an increase in the mean autumn, mean winter and mean spring flows ranging from 25
Impacts of climate change scenarios on runoff regimes in the southern Alps
Hydrology and Earth System Sciences Discussions, 2009
The potential impact of climate change scenarios on the runoff regime in the Italian Alpine area was investigated. A preliminary analysis of the output of three Global Circulation Models (PCM, HADCM, ECHAM) was needed to select IPCC-based scenarios for the 2000-2099 period. Two basins, 1840 and 236 km 2 in size, respectively, and with 5 25 to decrease by about 3% (for the 2050 scenario) and 14% at the end of this century. Also the runoff regime changes are significant, with an increase of spring melt and a decrease of summer and autumn runoff. No clear evidence is found for changes in the 3090 HESSD Abstract Introduction Conclusions References Tables Figures Back Close Full Screen / Esc Printer-friendly Version Interactive Discussion precipitation extremes and in the fraction of rainy days. 15 -Northern Hemisphere snow cover observed by satellite over the 1966 to 2005 period decreased in every month except November and December, with a stepwise drop of 5% in the annual mean in the late 1980s (IPCC, 2007b); glaciers are retreating almost worldwide with a global average annual mass loss of more than half a metre water equivalent during the decade of 1996 to 2005 20 (UNEP-WGMS, 2008), twice the ice loss of the previous decade and over four times the rate of the decade from 1976 to 1985.