Weather-regime Based Stochastic Weather Generation for Process-informed Climate Vulnerability Assessments of Water Systems
Abstract
There is a growing trend towards vulnerability-based frameworks to better understand water system performance under deeply uncertain climate change. Under these frameworks, stochastic weather generators are often fit to historic data, and then model parameters are systematically altered to produce synthetic weather records with a wide range of distributional characteristics that can be used to force hydrologic and water systems models. This approach can reveal important vulnerabilities that might not be captured when using GCM ensembles, but it has largely been confined to exploratory analyses that focus on changes in the statistical properties of weather. Notably, an explicit link to thermodynamic and dynamic pathways in the climate system that control these features is missing. Therefore, these analyses can highlight potential vulnerabilities of water systems to nuanced climate change, but cannot provide a clear indication of whether those climate scenarios are physical plausible, let alone likely to occur in the future.
This work advances the use of weather-regime based stochastic weather generators that link weather events to the larger-scale weather regimes that cause them. Weather regimes are recurring, large-scale atmospheric flow patterns with fixed geographic locations and subseasonal (days-weeks) residence times that organize high-frequency weather systems. In a weather-regime based stochastic weather generator, simulated daily weather is conditioned on the weather regime, which is modeled as a Markovian process that can be conditioned on large-scale climate features. Projections of these regional- to global-scale features, which are often the most credibly simulated by GCMs, can then be used to constrain scenario development. Similarly, projected changes to the moisture holding capacity of the atmosphere can be modeled directly by altering precipitation distributions within a weather regime. In this way, the proposed model can be used to create a more direct link between emerging hypotheses of change in climate dynamics and thermodynamics and their impacts on water systems. This approach is demonstrated in a vulnerability assessment of the Hetch Hetchy system in California, which is significantly impacted by climate in the Pacific-North American sector during the cold season.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFMPA11A..04S
- Keywords:
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- 1630 Impacts of global change;
- GLOBAL CHANGEDE: 1637 Regional climate change;
- GLOBAL CHANGEDE: 6304 Benefit-cost analysis;
- POLICY SCIENCESDE: 6309 Decision making under uncertainty;
- POLICY SCIENCES