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SUMMARY:Towards extended range stream flow drought predictions in Switzerl
 and using reforecast data and snow water equivalent climatologies: Homogen
 isation of a snow water equivalent climatology
DTSTART:20140401T161500
DTEND:20140401T171500
DTSTAMP:20260407T194915Z
UID:cb267482a9067ac4862d806580758670043d3ddb2aaf7971d596782b
CATEGORIES:Conferences - Seminars
DESCRIPTION:Dr Stefanie Jörg-Hess\,  Mountain Hydrology and Mass Movemen
 ts\, WSL Birmensdorf\nAbstract:\nSeveral drought events in recent years ha
 ve highlighted the vulnerability of Switzerland to hydrological droughts. 
 To improve risk management and preparedness we work on forecasts of stream
 -flow droughts. First\, we explored the performance of streamflow simulati
 ons with the hydrological model PREVAH forced with meteorological informat
 ion from numerical weather prediction. The discharge simulations with COSM
 O-LEPS as input performed poorly with focus on low flow. However\, when re
 placing precipitation with observed or bias corrected COSMO-LEPS precipita
 tion and using the other meteorological variables from COSMO-LEPS\, the pe
 rformance of the low-flow simulations was comparable to simulations forced
  with observations of all variables. For operational applications\, a prob
 abilistic reforecast VarEPS from ECMWF was used as meteorological input. T
 hese simulations showed skill up to a lead time of 32 days for the Thur an
 d other catchments. In a second step we wanted to improve the initial cond
 itions for the hydrological model. Runoff was not assimilated because of t
 he presence of hydropower in most catchments in Switzerland. Thus we focus
 ed on the improvement of the snow storage information. We developed a homo
 genised snow water equivalent (SWE) dataset for the period 1971-2009. This
  dataset was used as SWE information at initialisation of the hydrological
  model. The SWE dataset and calibration method will be presented in detail
  in this presentation.\nWhen trying to derive consistent time series for S
 WE products\, changing data availability represents a considerable challen
 ge. In an attempt to improve the product consistency of a gridded SWE data
 set\, we tested the potential of quantile mapping to compensate for mappin
 g errors in a longer SWE product consisting of fewer snow stations\, compa
 red to a shorter SWE product consisting of more snow stations. The SWE cal
 ibration was done with quantile mapping by making seasonal\, regional and 
 altitude-related distinctions. The calibrated SWE maps were accurate when 
 averaged over regions and time periods\, where the mean error was approxim
 ately zero. However\, deviations were observed at single grid cells and ye
 ars. When we looked at three different regions in more detail\, we found t
 hat the calibration had the largest effect in the region with the highest 
 proportion of catchment areas above 2000 m a.s.l. The added value of the c
 alibrated SWE climatology is illustrated with practical examples: the veri
 fication of a hydrological model\, the estimation of snow resources anomal
 ies and the predictability of runoff through SWE.Short biography:\nAfter t
 he master in Environmental sciences at the ETH Zürich I started my PhD at
  the Swiss Federal research institute WSL in the Hydrological Forecasts Gr
 oup. My research interests are the hydrological cycle during drought event
 s and hydrological modelling. The PhD project is part of DROUGHT-CH which 
 is founded by the NRP61.
LOCATION:GR A3 32 http://plan.epfl.ch/?room=GR%20A3%2032
STATUS:CONFIRMED
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