Project

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Scaling of space-time precipitation in the Swiss Alps and its impact on basin response

Applicant Molnar Peter
Number 120310
Funding scheme Project funding (Div. I-III)
Research institution Institut für Umweltingenieurwissenschaften ETH Zürich
Institution of higher education ETH Zurich - ETHZ
Main discipline Hydrology, Limnology, Glaciology
Start/End 01.09.2009 - 28.02.2013
Approved amount 156'865.00
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All Disciplines (3)

Discipline
Hydrology, Limnology, Glaciology
Meteorology
Other disciplines of Engineering Sciences

Keywords (10)

precipitation; scaling properties; orographic effects; radar and raingauge; space-time variability; random cascade; disaggregation; Scaling methods; Data analysis; Orography

Lay Summary (English)

Lead
Lay summary
Precipitation in mountain regions is highly variable in space and time due to the complex effects of orography on storm generation and motion. Although these effects are especially visible in high resolution space-time data (m-sec), they propagate to coarser resolutions as well (km-day) in a systematic way which can be studied by scaling methods. In this project we investigate the scaling properties of precipitation in the Swiss Alps and the ways in which they can be utilized for precipitation simulation.Describing the space-time structure of precipitation and its modelling is a particularly challenging problem because a) it involves the physics of the precipitation process, which ultimately guides the development and choice of reasonable models, b) it requires that the precipitation process is accurately monitored in space and time to estimate the parameters of those models, and c) it demands that fundamental statistical properties of precipitation like dependency, stationarity, scaling are properly tested and understood in both data and models. The research hypothesis in this project is that precipitation space-time variability significantly impacts basin runoff response, and in order to quantify these impacts we have to know how the space-time variability in precipitation changes with resolution in an orographically complex environment such as the Swiss Alps. We will use an analysis framework based on scale invariance and multifractality to examine an excellent database of Swiss raingauge and radar data to a) understand the space-time precipitation variability and scaling behaviour from data, b) develop and test a suite of stochastic modelling tools suitable for disaggregating precipitation into the relevant small scales with a special focus on understanding the effects of orography, and c) analyse with simple rainfall-runoff transfer functions the effect of high resolution variability in time on basin response in selected experimental mountain basins.This project will advance the state-of-the-art by producing a robust statistical analysis of space-time precipitation data in the orographically complex environment of the Swiss Alps, by tackling a number of important theoretical issues in scaling-based analyses of precipitation and their modelling with discrete multiplicative random cascades, and by providing guidelines on how to determine the adequate temporal precipitation data resolution needed to capture basin response variability at the appropriate scale.
Direct link to Lay Summary Last update: 21.02.2013

Responsible applicant and co-applicants

Employees

Publications

Publication
Temporal dependence structure in weights in a multiplicative cascade model for precipitation
Paschalis Athanasios, Molnar Peter, Burlando Paolo (2012), Temporal dependence structure in weights in a multiplicative cascade model for precipitation, in Water Resources Research, 48, W01501.

Scientific events



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Title Date Place

Abstract

The identification of the general space-time structure of precipitation and its effect on patterns of land surface processes such as soil moisture and runoff variability is a central issue in hydrological sciences. The research hypothesis in this proposal is that precipitation space-time variability significantly impacts basin runoff response, and a prerequisite to be able to quantify these impacts is to understand how the space-time variability in precipitation changes with resolution or aggregation scale in an orographically complex environment such as the Swiss Alps, and how it can be modelled with appropriate stochastic tools. That is the main focus of this research proposal.We will use an analysis framework based on scale invariance and multifractality to examine an excellent database of Swiss raingauge and radar data to a) comprehensively analyse the space-time precipitation variability and scaling behaviour from data, b) develop and test a suite of stochastic modelling tools suitable for disaggregating precipitation into the relevant small scales with a special focus on understanding the effects of orography, and c) analyse with simple rainfall-runoff transfer functions the effect of high resolution variability in time on basin response in selected experimental basins.The research work will be carried out in two modules “space-time analysis of precipitation” and “scaling models and applications” and five tasks. The analysis of time series of 10-min ANETZ data and other higher resolution sources will be conducted in Task 1 by moment scaling, correlation and spectral methods. Task 2 will look at spatial data from MeteoSwiss radar precipitation fields with 1-2 km resolution and a new X-band radar on Kl. Matterhorn (3’889 m a.s.l.) with similar statistical tools and methods. In particular, Task 2 will examine the self-similarity of spatial fields and the space-time scaling of storm events divided into main storm types as related to the triggering circulation patterns. Task 3 will adapt existing stochastic methods based on the multiplicative discrete random cascade framework by including important features of the space-time precipitation fields found in Tasks 1 and 2. Particular attention will be paid to the empirical breakdown distributions in time and space, ways to treat intermittency, effects of large scale forcing, and the development of methods to include deterministic components in the models to treat orographic effects on precipitation. Task 4 will focus on issues of parameter estimation for the models developed in Task 3 and on testing their general performance. Finally, Task 5 will collect the knowledge gained on time variability in precipitation to analyse its effects on basin response with geomorphologically-driven basin response functions in a Monte Carlo framework. The aim will be to give indications how mean basin reponse time and temporal precipitation resolution influence peak basin response. Spatial effects will be left for a future study. This research proposal is expected to advance the state-of-the-art by a) producing a robust statistical analysis of space-time precipitation data in an orographically complex environment, b) tackling a number of important theoretical issues in scaling-based analyses of precipitation and their modelling with discrete multiplicative random cascades, and c) providing guidelines on how to determine the adequate temporal precipitation data resolution needed to capture basin response variability at the appropriate scale.To the knowledge of the applicants an analysis of the statistical and scaling behaviour of precipitation data in Switzerland, and in orographically complex regions in general, to the extent proposed here has not yet been conducted. Insofar, this study opens new ground and will serve as a benchmark for precipitation data analysis in the Swiss Alps. We expect that the demonstration of orographic effects on space-time precipitation variability will also be of interest to the wider scientific community.
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