57 research outputs found
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The 2013/14 Thames basin floods: do improved meteorological forecasts lead to more skilful hydrological forecasts at seasonal timescales?
The Thames basin experienced 12 major Atlantic depressions in winter 2013/14 leading to extensive and prolonged fluvial and groundwater flooding. This exceptional weather coincided with highly anomalous meteorological conditions across the globe. Atmospheric relaxation experiments, whereby conditions within specified regions are relaxed towards a reanalysis, have been used to investigate teleconnection patterns. However, no studies have examined whether improvements to seasonal meteorological forecasts translate into more skilful seasonal hydrological forecasts. This study applied relaxation experiments to reforecast the 2013/14 floods for three Thames basin catchments with different hydrogeological characteristics. The tropics played an important role in the development of extreme conditions over the Thames basin. Greatest hydrological forecasting skill was associated with the tropical Atlantic and less with the tropical Pacific, although both captured seasonal meteorological flow anomalies. Relaxation applied over the north-eastern Atlantic produced confident ensemble forecasts, but hydrological extremes were under-predicted; this was unexpected with relaxation applied so close to the UK. Streamflow was most skilfully forecast for the catchment representing a large drainage area with high peak flow. Permeable lithology and antecedent conditions were important for skilfully forecasting groundwater levels. Atmospheric relaxation experiments can improve our understanding of extratropical anomalies and the potential predictability of extreme events such as the Thames 2013/14 floods. Seasonal hydrological forecasts differed to what was expected from the meteorology alone, thus knowledge is gained by considering both components. In the densely populated Thames basin, considering local hydrogeological context can provide an effective early alert of potential high-impact events, allowing for better preparedness
Domino: A new framework for the automated identification of weather event precursors, demonstrated for European extreme rainfall
A number of studies have investigated the large-scale drivers and
upstream-precursors of extreme weather events, making it clear that the
earliest warning signs of extreme events can be remote in both time and space
from the impacted region. Integrating and leveraging our understanding of
dynamical precursors provides a new perspective on ensemble forecasting for
extreme events, focused on building story-lines of possible event evolution.
This then acts as a tool for raising awareness of the conditions conducive to
high-impact weather, and providing early warning of their possible development.
However, operational applications of this developing knowledge-base is limited
so far, perhaps for want of a clear framework for doing so. Here, we present
such a framework, supported by open software tools, designed for identifying
large-scale precursors of categorical weather events in an automated fashion,
and for reducing them to scalar indices suitable for statistical prediction,
forecast interpretation, and model validation. We demonstrate this framework by
systematically analysing the precursor circulations of daily rainfall extremes
across 18 regional- to national-scale European domains. We discuss the
precursor rainfall dynamics for three disparate regions, and show our findings
are consistent with, and extend, previous work. We provide an estimate of the
predictive utility of these precursors across Europe based on logistic
regression, and show that large-scale precursors can usefully predict heavy
rainfall between two and six days ahead, depending on region and season. We
further show how for more continental-scale applications the
regionally-specific precursors can be synthesised into a minimal set of indices
that drive heavy precipitation. We then provide comments and guidance for
generalisation and application of our demonstrated approach to new variables,
timescales and regions.Comment: 3 figure SI, 22 manuscript pages, 10 figures, submitted to QJRM
Year-round sub-seasonal forecast skill for Atlantic-European weather regimes
Weather regime forecasts are a prominent use case of subâseasonal prediction in the midlatitudes. A systematic evaluation and understanding of yearâround subâseasonal regime forecast performance is still missing, however. Here we evaluate the representation of and forecast skill for seven yearâround AtlanticâEuropean weather regimes in subâseasonal reforecasts from the European Centre for MediumâRange Weather Forecasts. Forecast calibration improves regime frequency biases and forecast skill most strongly in summer, but scarcely in winter, due to considerable largeâscale flow biases in summer. The average regime skill horizon in winter is about 5âdays longer than in summer and spring, and 3âdays longer than in autumn. The Zonal Regime and Greenland Blocking tend to have the longest yearâround skill horizon, which is driven by their high persistence in winter. The yearâround skill is lowest for the European Blocking, which is common for all seasons but most pronounced in winter and spring. For the related, more northern Scandinavian Blocking, the skill is similarly low in winter and spring but higher in summer and autumn. We further show that the winter average regime skill horizon tends to be enhanced following a strong stratospheric polar vortex (SPV), but reduced following a weak SPV. Likewise, the yearâround average regime skill horizon tends to be enhanced following phases 4 and 7 of the MaddenâJulian Oscillation (MJO) but reduced following phase 2, driven by winter but also autumn and spring. Our study thus reveals promising potential for yearâround subâseasonal regime predictions. Further model improvements can be achieved by reduction of the considerable largeâscale flow biases in summer, better understanding and modeling of blocking in the European region, and better exploitation of the potential predictability provided by weak SPV states and specific MJO phases in winter and the transition seasons.The overall subâseasonal forecast performance (biases and skill) for predicting seven yearâround AtlanticâEuropean weather regimes is highest in winter and lowest in summer. The yearâround skill horizon is shortest for the European Blocking and longest for the Zonal Regime and Greenland Blocking (see figure). Furthermore, the winter skill horizon tends to be enhanced following a strong stratospheric polar vortex but reduced following a weak one. MaddenâJulian Oscillation phases 4 and 7 tend to increase and phase 2 to decrease the yearâround skill horizon.HelmholtzâGemeinschaft
http://dx.doi.org/10.13039/50110000165
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A vision for hydrological prediction
IMproving PRedictions and management of hydrological EXtremes (IMPREX) was a European Union Horizon 2020 project that ran from September 2015 to September 2019. Its aim was to improve societyâs ability to anticipate and respond to future extreme hydrological events in Europe across a variety of uses in the water-related sectors (flood forecasting, drought risk assessment, agriculture, navigation, hydropower, and water supply utilities). Through the engagement with stakeholders and continuous feedback between model outputs and water applications, progress was achieved in better understanding the way hydrological predictions can be useful to (and operationally incorporated into) problem solving in the water sector. The work and discussions carried out during the project nurtured further reflections towards a common vision for hydrological prediction. In this article, we summarize the main findings of the IMPREX project within a broader overview of hydrological prediction, providing a vision for improving such predictions. In so doing, we firstly present a synopsis of hydrological and weather forecasting, with a focus on medium-range to seasonal scales of prediction for increased preparedness. Second, the lessons learnt from IMPREX are discussed. The key findings are the gaps highlighted in the global observing system of the hydrological cycle, the degree of accuracy of hydrological models and the techniques of post-processing to correct biases, the origin of seasonal hydrological skill in Europe, and user requirements of hydrometeorological forecasts to ensure their appropriate use in decision-making models and practices. Lastly, a vision for how to improve these forecast systems/products in the future is expounded and these include advancing numerical weather and hydrological models, improved earth monitoring, and more frequent interaction between forecasters and users to tailor the forecasts to applications. We conclude that if these improvements can be implemented in the coming years, earth system and hydrological modelling will become more skilful, thus leading to socioeconomic benefits for the citizens of Europe and beyond
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A stratospheric prognostic ozone for seamless Earth system models: performance, impacts and future
We have implemented a new stratospheric ozone model in the European Centre for Medium-Range Weather Forecasts (ECMWF) system and tested its performance for different timescales to assess the impact of stratospheric ozone on meteorological fields. We have used the new ozone model to provide prognostic ozone in medium-range and long-range (seasonal) experiments, showing the feasibility of this ozone scheme for a seamless numerical weather prediction (NWP) modelling approach. We find that the stratospheric ozone distribution provided by the new scheme in ECMWF forecast experiments is in very good agreement with observations, even for unusual meteorological conditions such as Arctic stratospheric sudden warmings (SSWs) and Antarctic polar vortex events like the vortex split of year 2002. To assess the impact it has on meteorological variables, we have performed experiments in which the prognostic ozone is interactive with radiation. The new scheme provides a realistic ozone field able to improve the description of the stratosphere in the ECMWF system, as we find clear reductions of biases in the stratospheric forecast temperature. The seasonality of the Southern Hemisphere polar vortex is also significantly improved when using the new ozone model. In medium-range simulations we also find improvements in high-latitude tropospheric winds during the SSW event considered in this study. In long-range simulations, the use of the new ozone model leads to an increase in the correlation of the winter North Atlantic Oscillation (NAO) index with respect to ERA-Interim and an increase in the signal-to-noise ratio over the North Atlantic sector. In our study we show that by improving the description of the stratospheric ozone in the ECMWF system, the stratosphereâtroposphere coupling improves. This highlights the potential benefits of this new ozone model to exploit stratospheric sources of predictability and improve weather predictions over Europe on a range of timescales
The North Atlantic Waveguide and Downstream Impact Experiment
The North Atlantic Waveguide and Downstream Impact Experiment (NAWDEX) explored the impact of diabatic processes on disturbances of the jet stream and their influence on downstream high-impact weather through the deployment of four research aircraft, each with a sophisticated set of remote sensing and in situ instruments, and coordinated with a suite of ground-based measurements. A total of 49 research flights were performed, including, for the first time, coordinated flights of the four aircraft: the German High Altitude and Long Range Research Aircraft (HALO), the Deutsches Zentrum fĂŒr Luft- und Raumfahrt (DLR) Dassault Falcon 20, the French Service des Avions Français InstrumentĂ©s pour la Recherche en Environnement (SAFIRE) Falcon 20, and the British Facility for Airborne Atmospheric Measurements (FAAM) BAe 146. The observation period from 17 September to 22 October 2016 with frequently occurring extratropical and tropical cyclones was ideal for investigating midlatitude weather over the North Atlantic. NAWDEX featured three sequences of upstream triggers of waveguide disturbances, as well as their dynamic interaction with the jet stream, subsequent development, and eventual downstream weather impact on Europe. Examples are presented to highlight the wealth of phenomena that were sampled, the comprehensive coverage, and the multifaceted nature of the measurements. This unique dataset forms the basis for future case studies and detailed evaluations of weather and climate predictions to improve our understanding of diabatic influences on Rossby waves and the downstream impacts of weather systems affecting Europe
The open innovation research landscape: established perspectives and emerging themes across different levels of analysis
This paper provides an overview of the main perspectives and themes emerging in research on open innovation (OI). The paper is the result of a collaborative process among several OI scholars â having a common basis in the recurrent Professional Development Workshop on âResearching Open Innovationâ at the Annual Meeting of the Academy of Management. In this paper, we present opportunities for future research on OI, organised at different levels of analysis. We discuss some of the contingencies at these different levels, and argue that future research needs to study OI â originally an organisational-level phenomenon â across multiple levels of analysis. While our integrative framework allows comparing, contrasting and integrating various perspectives at different levels of analysis, further theorising will be needed to advance OI research. On this basis, we propose some new research categories as well as questions for future research â particularly those that span across research domains that have so far developed in isolation
En JÀmförelse av Olika Studier pÄ Visus- och K-vÀrdeförÀndringar vid Ortokeratologibehandling
Bakgrund: Ortokeratologi Ă€r en teknik dĂ€r man genom specialdesignade RGP-linser kan reducera eller helt eliminera lĂ„g och mĂ„ttlig myopi och Ă€ven lĂ„ggradig hyperopi och astigmatism. Man sover med linserna under natten, tar ut dem pĂ„ morgonen och kan sedan gĂ„ utan glasögon och kontaktlinser hela dagen med bra visus. I denna studie tas en del fakta upp om hur ortokeratologi fungerar och pĂ„ vilka tekniken fungerar. Syfte: Syftet vara att ta reda pĂ„ mera om ortokeratologi dĂ„ detta Ă€r en teknik pĂ„ framfart. Ăven att jĂ€mföra undertecknads prövotid med redan gjorda studier. Metod: I studien jĂ€mfördes en försöksperson med tidigare gjorda studier, försökspersonen anvĂ€nde ortokeratologilinser under 45 dagar och mĂ€tningar som togs och jĂ€mfördes var k-vĂ€rde (corneas kurvatur) och fri visus (synskĂ€rpa). MĂ€tningarna utfördes dag 1, 3, 7 och 14, sedan togs visus 1 gĂ„ng i veckan för att kontrollera att den hölls stabil. Resultat: visade att samtliga studier hade ungefĂ€r samma resultat dĂ€r nĂ€stan alla försökspersoner fick bra visus under behandlingen. PĂ„ försökspersonen i denna studie fungerade det ocksĂ„ bra förutom lite inducerad astigmatism av linserna och halofenomen. Slutsats: ortokeratologi Ă€r en vĂ€l fungerande metod om endast rĂ€tt patienter som ligger inom grĂ€nserna av synfel anvĂ€nds. Den krĂ€ver dock mer arbete Ă€n en vanlig linstillpassning, bĂ„de frĂ„n tillpassaren genom tĂ€ta Ă„terbesök och frĂ„n patienten genom att compliance och linsskötsel Ă€r vĂ€ldigt viktigt. 2008:O2
Utveckling och utvĂ€rdering av en ny âMass-Consistent Modelâ med terrĂ€nginfluerat koordinatsystem
Simulations of the wind climate in complex terrain may be useful in many cases, e.g. for wind energy mapping. In this study a new mass-consistent model (MCM), the λ-model, was developed and the ability of the model was examined. In the model an initial wind field is adjusted to fulfill the requirement of being non-divergent at all points. The advance of the λ- model compared with previous MCM:s is the use of a terrain-influenced coordinate system. Except the wind field, the model parameters include constants α, one for each direction. Those constants have no obvious physical meaning and have to be determined empirically. To determine the ability and quality of the λ-model, the results were compared with results from the mesoscale MIUU-model. Firstly, comparisons were made for a Gauss-shaped hill, to find situations which are not caught by the λ-model, e.g. wakes and thermal effects. During daytime the results from the λ-model were good but the model fails during nighttime. From the comparisons between the models the importance of the α-constants were studied. Secondly, comparisons between the models were made for real terrain. Wind data from the MIUU-model with resolution 5 km was used as input data and was interpolated to a 1 km grid and made non-divergent by the λ-model. To study the quality of the results, they were compared with simulations from the MIUU-model with resolution 1 km. The results are quite accurate, after adjusting for a difference in mean wind speed between MIUU-model runs on 1km and 5 km resolution. Good results from the λ-model were reached if a climate average wind speed was calculated from several simulations with different wind directions. Especially if the mean wind speed for the domain in the λ-model was modified to the same level as in the MIUU 1 km. The λ-model may be a useful tool as the results were found to be reasonable good for many cases. But the user must be aware of situations when the model fails. Future studies could be done to investigate if the λ-model is useable for resolutions down to 100 meters.Modellering av vindklimat i komplex terrÀng Àr anvÀndbart i mÄnga sammanhang, t ex vid vindkartering för vindenergi. I den hÀr studien utvecklas och undersöks anvÀndbarheten av en sk. Mass-Consistent Model, λ-modellen. Modellen bygger pÄ att ett initialt vindfÀlt justeras för att uppfylla kontinuitetsekvationen i alla punkter. För att göra vindfÀltet divergensfritt anvÀnds en metod som bygger pÄ variationskalkyl. Fördelen med denna nya modell jÀmfört med tidigare Àr anvÀndandet av ett terrÀnginfluerat koordinatsystem. I teorin för λ-modellen införs en parameter α. DÄ denna inte har nÄgon sjÀlvklar fysikalisk betydelse behöver den bestÀmmas empiriskt.  För att undersöka kvalitén hos λ-modellen gjordes jÀmförelser med den mesoskaliga MIUU-modellen. Det första steget var att jÀmföra körningar över en Gaussformad kulle, detta för att jÀmföra modellerna och finna situationer som λ-modellen inte löser upp. Exempel pÄ sÄdana Àr termiska effekter och vakar. Resultaten under dagtid var bra medan under nattetid var det stora skillnader mellan modellerna. UtifrÄn resultaten kunde betydelsen av α-parametern studeras.  NÀsta steg var att jÀmföra med verklig terrÀng. Detta gjordes för ett omrÄde i Norrbotten. HÀr anvÀndes vinddata frÄn MIUU-modellen med upplösning 5 km som indata för att berÀkna vinden pÄ en skala 1 km. För att undersöka kvalitén hos λ-modellen anvÀndes data frÄn MIUU-modellen med upplösning 1 km som jÀmförelse. Resultaten avseende vindvariationerna i terrÀngen Àr tillfredstÀllande, dock med nÄgot för höga vindhastigheter i λ-modellen. Detta visade sig bero pÄ för högre medelvind i MIUU 5 km Àn i MIUU 1 km. JÀmförelse mellan modellerna gjordes Àven för Suorva-dalen i Lappland vilken omges av bergig terrÀng. Resultaten hÀr var sÀmre avseende medelvindarna, men med bÀttre resultat avseende vindriktningarna.  Bra resultat för λ-modellen nÄddes dÄ resultat frÄn flera simuleringar slogs samman till ett medelvÀrde. Framförallt blev resultatet bra dÄ medelvinden justerades till samma nivÄ som MIUU 1 km.  Sammanfattningsvis kan sÀgas att resultaten frÄn λ-modellen Àr rimliga i mÄnga situationer men att det Àr viktigt att veta i vilka situationer den inte fungerar. Framtida undersökningar bör göras för att undersöka om modellen Àr anvÀndbar för upplösningar ner till ca 100 meter
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