Influence of Climate Change on the Water Cycle in Alpine Environments: A Plausibility Analysis
Problem Statement
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Davos, a research site
Photo: W. Schönenberger (WSL)
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Simulations of the effects from changing environmental conditions on water cycles and hydrological processes often base on incomplete existing input- and model-parameters. In this context comprehensive sensitivity analyses are important, which allow to assess the influence of deviations and initial conditions on the results. Within the project, we investigate the spatial and temporal development of water cycles in the Swiss Alps for the next decades as influenced by climate change. In addition, we implement error propagation and sensitivity analysis of the models used, in particular the cross-scaling problems influencing the model resolution's accuracy and precision. We will use innovative methods to verify and assess Daymet for the complex terrain of Switzerland as well as to evaluate Biome-BGC for the simulations of ecosystem developments with respect to water cycles. Scenarios are afflicted with uncertainties; to quantify the dimension of these errors and to assess the quality of the deployed models for scenarios we implement a sensitivity analysis.
Objectives
The main goal of this project is to assess the impact of climatic change on the water cycle in forest ecosystems as a function of abiotic site factors, by evaluating the reliability and plausibility of different approaches to model the hydrological cycle in space and time. This goal can be further divided into the following sub-goals:
- Objective A
Developments and changes of the hydrological state will be estimated, depending on the forest ecosystem, the climate, and the topographical unique characteristics of the Swiss Alps.
- Objective B
Quantification of implicit uncertainties by sensitivity analysis and error propagation in the simulation process.
- Objective C
Assessment of uncertainties of digital data representation (e.g. digital terrain surface) by means of suitable mathematical methods in different scales (cross-scaling).
Methods
The figure showed below gives an overview over the planed approach. The spedific models as well as the methods are illustrated in more detail later.
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Figure 1: Model approach for simulation and sensitivity analysis of water balance in forest ecosystems. Click on image to enlarge.
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The three models and methods a) Daymet for generation of climatic surfaces, b) the terrestrial ecosystem process model Biome-BGC and c) Generalised Likelihood Uncertainty Estimation techniques and Global Sensitivity Analysis will be employed.
Research Plan
The Project will investigate the spatial and temporal development of forest ecosystems in the Swiss Alps as influenced by a changing climate during the next five decades. The following models and methods will be employed:
- Daymet to generate climatological surfaces
- Biome-BGC a process model for terrestrial ecosystems
- GLUE and GSA
The objective is not to develop new, or to enhance existing models but to evaluate the quality, the reliability and the uncertainties using error simulations and predictions. Following steps will be conducted:
- Validation of a verified and calibrated model: We will simulate the daily minimum and maximum temperatures and the daily total precipitation (snow and water separately) for the Swiss Alps from 1961 until 2000.
- Plausibility analysis of future water cylces: With the second step, we will model the influence of changing climate (temperature and precipitation) on the water cycle in the Swiss Alps.
- Sensitivity analysis and error simulation: With this step we implement a stochastic procedure to study the sensitivity of daily minimum and maximum temperatures, daily total precipitation, and the DTM.
- Cross-scaling: Cross-scaling will be used to demonstrate the scale dependencies and limitations of the used models.
Participants
- Luzi Bernhard
- Britta Allgöwer
- Niklaus Zimmermann
Contact
