| 1. |
- Dance, Sarah L., et al.
(författare)
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Improvements in Forecasting Intense Rainfall : Results from the FRANC (Forecasting Rainfall Exploiting New Data Assimilation Techniques and Novel Observations of Convection) Project
- 2019
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Ingår i: Atmosphere. - : MDPI. - 2073-4433. ; 10:3
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Forskningsöversikt (refereegranskat)abstract
- The FRANC project (Forecasting Rainfall exploiting new data Assimilation techniques and Novel observations of Convection) has researched improvements in numerical weather prediction of convective rainfall via the reduction of initial condition uncertainty. This article provides an overview of the project's achievements. We highlight new radar techniques: correcting for attenuation of the radar return; correction for beams that are over 90% blocked by trees or towers close to the radar; and direct assimilation of radar reflectivity and refractivity. We discuss the treatment of uncertainty in data assimilation: new methods for estimation of observation uncertainties with novel applications to Doppler radar winds, Atmospheric Motion Vectors, and satellite radiances; a new algorithm for implementation of spatially-correlated observation error statistics in operational data assimilation; and innovative treatment of moist processes in the background error covariance model. We present results indicating a link between the spatial predictability of convection and convective regimes, with potential to allow improved forecast interpretation. The research was carried out as a partnership between University researchers and the Met Office (UK). We discuss the benefits of this approach and the impact of our research, which has helped to improve operational forecasts for convective rainfall events.
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| 2. |
- Emerton, R., et al.
(författare)
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Predicting the unprecedented : forecasting the June 2021 Pacific Northwest heatwave
- 2022
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Ingår i: Weather. - : John Wiley & Sons. - 0043-1656 .- 1477-8696. ; 77:8, s. 272-279
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Tidskriftsartikel (refereegranskat)abstract
- In June 2021, an unprecedented extreme heatwave impacted the Pacific Northwest of North America, resulting in more than 1000 excess deaths and affecting infrastructure and wildlife. Predicting such extreme events is key for preparedness and early action, and beyond temperature, it is important to consider biometeorological forecasts, accounting for the effects of the environment on the human body. The performance of ECMWF's (the European Centre for Medium-Range Weather Forecasts) temperature and heat stress (Humidex and the Universal Thermal Climate Index) forecasts during this heatwave is explored, and highlights that several days in advance, an event surpassing the maximum of climatology was predicted with extremely high confidence (100% of ensemble members) – successfully predicting the unprecedented.
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| 3. |
- Mason, David C., et al.
(författare)
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Floodwater detection in urban areas using Sentinel-1 and WorldDEM data
- 2021
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Ingår i: Journal of Applied Remote Sensing. - : SPIE-SOC PHOTO-OPTICAL INSTRUMENTATION ENGINEERS. - 1931-3195. ; 15:3
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Tidskriftsartikel (refereegranskat)abstract
- Remote sensing using synthetic aperture radar (SAR) is an important tool for emergency flood incident management. At present, operational services are mainly aimed at flood mapping in rural areas, as mapping in urban areas is hampered by the complicated backscattering mechanisms occurring there. A method for detecting flooding at high resolution in urban areas that may contain dense housing is presented. This largely uses remotely sensed data sets that are readily available on a global basis, including open-access Sentinel-1 SAR data, the WorldDEM digital surface model (DSM), and open-accessWorld Settlement Footprint data to identify urban areas. The method is a change detection technique that locally estimates flood levels in urban areas. It searches for increased SAR backscatter in the post-flood image due to double scattering between water (rather than unflooded ground) and adjacent buildings, and reduced SAR backscatter in areas away from high slopes. Areas of urban flooding are detected by comparing an interpolated flood level surface to the DSM. The method was tested on two flood events that occurred in the UK during the storms of Winter 2019-2020. High urban flood detection accuracies were achieved for the event in moderate density housing. The accuracy was reduced for the event in dense housing, when street widths became comparable to the DSM resolution, though it would still be useful for incident management. The method has potential for operational use for detecting urban flooding in near real-time on a global basis. (C) The Authors. Published by SPIE under a Creative Commons Attribution 4.0 Unported License.
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| 4. |
- Mason, David C., et al.
(författare)
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Improving Urban Flood Mapping by Merging Synthetic Aperture Radar-Derived Flood Footprints with Flood Hazard Maps
- 2021
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Ingår i: Water. - : MDPI. - 2073-4441. ; 13:11
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Tidskriftsartikel (refereegranskat)abstract
- Remotely sensed flood extents obtained in near real-time can be used for emergency flood incident management and as observations for assimilation into flood forecasting models. High-resolution synthetic aperture radar (SAR) sensors have the potential to detect flood extents in urban areas through clouds during both day- and night-time. This paper considers a method for detecting flooding in urban areas by merging near real-time SAR flood extents with model-derived flood hazard maps. This allows a two-way symbiosis, whereby currently available SAR urban flood extent improves future model flood predictions, while flood hazard maps obtained after the SAR overpasses improve the SAR estimate of urban flood extents. The method estimates urban flooding using SAR backscatter only in rural areas adjacent to urban ones. It was compared to an existing method using SAR returns in both rural and urban areas. The method using SAR solely in rural areas gave an average flood detection accuracy of 94% and a false positive rate of 9% in the urban areas and was more accurate than the existing method.
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| 5. |
- Mason, David C., et al.
(författare)
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Robust algorithm for detecting floodwater in urban areas using synthetic aperture radar images
- 2018
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Ingår i: Journal of Applied Remote Sensing. - : SPIE-SOC PHOTO-OPTICAL INSTRUMENTATION ENGINEERS. - 1931-3195. ; 12:4
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Tidskriftsartikel (refereegranskat)abstract
- Flooding is a major hazard in both rural and urban areas worldwide, but it is in urban areas that the impacts are most severe. High-resolution synthetic aperture radar (SAR) sensors are able to detect flood extents in urban areas during both day- and night-time. If obtained in near real time, these flood extents can be used for emergency flood relief management or as observations for assimilation into flood forecasting models. A method for detecting flooding in urban areas using near real-time SAR data is developed and extensively tested under a variety of scenarios involving different flood events and different images. The method uses an SAR simulator in conjunction with LiDAR data of the urban area to predict areas of radar shadow and layover in the image caused by buildings and taller vegetation. Of the urban water pixels visible to the SAR, the flood detection accuracy averaged over the test examples is 83%, with a false alarm rate of 9%. The results indicate that flooding can be detected in the urban area to reasonable accuracy but that this accuracy is limited partly by the SAR's poor visibility of the urban ground surface due to shadow and layover. (C) The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License.
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| 6. |
- Mason, David C., et al.
(författare)
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Toward improved urban flood detection using Sentinel-1 : dependence of the ratio of post- to preflood double scattering cross sections on building orientation
- 2023
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Ingår i: Journal of Applied Remote Sensing. - : SPIE-SOC PHOTO-OPTICAL INSTRUMENTATION ENGINEERS. - 1931-3195. ; 17:1
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Tidskriftsartikel (refereegranskat)abstract
- High-resolution synthetic aperture radar (SAR) sensors are now commonly used for flood detection. Automated detection tends to be limited to rural areas owing to the complicated backscattering mechanisms occurring in urban areas. Flooding can be identified in urban areas by searching for increased SAR backscatter in a postflood image due to double scattering between water and adjacent buildings, compared with a preflood image where double scattering is between unflooded ground and buildings. For co-polarized data, if f is the angle between the building wall and the satellite direction of travel, double scattering is strongest for f = 0 deg and falls off as f increases. Theoretical studies estimating the ratio of flooded-to-unflooded double scatterer (DS) radar cross section (RCS) using X-band SAR data, found that the ratio was high at f = 0 deg but only small at f > 10 deg. Ostensibly, this implies that few DSs might be detected in an urban area. However, experiments on real images have called into question the veracity of the modeling. We describe an empirical study to examine the relationship between the flooded-to-unflooded DS RCS ratio and f in Sentinel-1 (S-1) C-band data. We use high-resolution light detection and ranging and aerial photographs so that f can be measured accurately and is based on S-1 images from flood events that occurred in the United Kingdom during the storms of winter 2019 to 2020. Results indicate that vertical-vertical polarization is better than vertical-horizontal at distinguishing flooded from unflooded DS; that the theoretical model used underestimates the number of DS with high RCS ratios in the f range 10 deg to 30 deg; and that sufficient DS ground heights can be determined to estimate an accurate local average flood level, although in high density housing there are less of these due to the presence of adjacent buildings.
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| 7. |
- Matthews, Gwyneth, et al.
(författare)
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Evaluating the impact of post-processing medium-range ensemble streamflow forecasts from the European Flood Awareness System
- 2022
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Ingår i: Hydrology and Earth System Sciences. - : Copernicus Publications. - 1027-5606 .- 1607-7938. ; 26:11, s. 2939-2968
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Tidskriftsartikel (refereegranskat)abstract
- Streamflow forecasts provide vital information to aid emergency response preparedness and disaster risk reduction. Medium-range forecasts are created by forcing a hydrological model with output from numerical weather prediction systems. Uncertainties are unavoidably introduced throughout the system and can reduce the skill of the streamflow forecasts. Post-processing is a method used to quantify and reduce the overall uncertainties in order to improve the usefulness of the forecasts. The post-processing method that is used within the operational European Flood Awareness System is based on the model conditional processor and the ensemble model output statistics method. Using 2 years of reforecasts with daily timesteps, this method is evaluated for 522 stations across Europe. Post-processing was found to increase the skill of the forecasts at the majority of stations in terms of both the accuracy of the forecast median and the reliability of the forecast probability distribution. This improvement is seen at all lead times (up to 15 d) but is largest at short lead times. The greatest improvement was seen in low-lying, large catchments with long response times, whereas for catchments at high elevation and with very short response times the forecasts often failed to capture the magnitude of peak flows. Additionally, the quality and length of the observational time series used in the offline calibration of the method were found to be important. This evaluation of the post-processing method, and specifically the new information provided on characteristics that affect the performance of the method, will aid end users in making more informed decisions. It also highlights the potential issues that may be encountered when developing new post-processing methods.
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| 8. |
- Titley, Helen A., et al.
(författare)
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A global evaluation of multi-model ensemble tropical cyclone track probability forecasts
- 2020
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Ingår i: Quarterly Journal of the Royal Meteorological Society. - : Wiley. - 0035-9009 .- 1477-870X. ; 146:726, s. 531-545
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Tidskriftsartikel (refereegranskat)abstract
- At the Met Office, dynamic ensemble forecasts from the Met Office Global and Regional Ensemble Prediction System (MOGREPS-G), the European Centre for Medium-Range Weather Forecasts Ensemble (ECMWFENS) and National Centers for Environmental Prediction Global Ensemble Forecast System (NCEP GEFS) global ensemble forecast models are post-processed to identify and track tropical cyclones. The ensemble members from each model are also combined into a 108-member multi-model ensemble. Track probability forecasts are produced for named tropical cyclones showing the probability of a location being within 120 km of a named tropical cyclone at any point in the next 7 days, and also broken down into each 24-hour forecast period. This study presents the verification of these named-storm track probabilities over a two-year period across all global tropical cyclone basins, and compares the results from basin to basin. The combined multi-model ensemble is found to increase the skill and value of the track probability forecasts over the best-performing individual ensemble (ECMWF ENS), for both overall 7-day track probability forecasts and 24-hour track probabilities. Basin-based and storm-based verification illustrates that the best performing individual ensemble can change from basin to basin and from storm to storm, but that the multi-model ensemble adds skill in every basin, and is also able to match the best performing individual ensemble in terms of overall probabilistic forecast skill in several high-profile case-studies. This study helps to illustrate the potential value and skill to be gained if operational tropical cyclone forecasting can continue to migrate away from a deterministic-focused forecasting environment to one where the probabilistic situation-based uncertainty information provided by the dynamic multi-model ensembles can be incorporated into operational forecasts and warnings.
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| 9. |
- Wagener, Thorsten, et al.
(författare)
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Knowledge gaps in our perceptual model of Great Britain's hydrology
- 2021
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Ingår i: Hydrological Processes. - : John Wiley & Sons. - 0885-6087 .- 1099-1085. ; 35:7
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Tidskriftsartikel (refereegranskat)abstract
- There is a no lack of significant open questions in the field of hydrology. How will hydrological connectivity between freshwater bodies be altered by future human alterations to the hydrological cycle? Where does water go when it rains? Or what is the future space-time variability of flood and drought events? However, the answers to these questions will vary with location due to the specific and often poorly understood local boundary conditions and system properties that control the functional behaviour of a catchment or any other hydrologic control volume. We suggest that an open, shared and evolving perceptual model of a region's hydrology is critical to tailor our science questions, as it would be for any other study domain from the plot to the continental scale. In this opinion piece, we begin to discuss the elements of and point out some knowledge gaps in the perceptual model of the terrestrial water cycle of Great Britain. We discuss six major knowledge gaps and propose four key ways to reduce them. While the specific knowledge gaps in our perceptual model do not necessarily transfer to other places, we believe that the development of such perceptual models should be at the core of the debate for all hydrologic communities, and we encourage others to have a similar debate for their hydrologic domain.
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| 10. |
- Arnal, Louise, et al.
(författare)
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Skilful seasonal forecasts of streamflow over Europe?
- 2018
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Ingår i: Hydrology and Earth System Sciences. - : Copernicus GmbH. - 1027-5606 .- 1607-7938. ; 22:4, s. 2057-2072
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Tidskriftsartikel (refereegranskat)abstract
- This paper considers whether there is any added value in using seasonal climate forecasts instead of historical meteorological observations for forecasting streamflow on seasonal timescales over Europe. A Europe-wide analysis of the skill of the newly operational EFAS (European Flood Awareness System) seasonal streamflow forecasts (produced by forcing the Lisflood model with the ECMWF System 4 seasonal climate forecasts), benchmarked against the ensemble streamflow prediction (ESP) forecasting approach (produced by forcing the Lisflood model with historical meteorological observations), is undertaken. The results suggest that, on average, the System 4 seasonal climate forecasts improve the streamflow predictability over historical meteorological observations for the first month of lead time only (in terms of hindcast accuracy, sharpness and overall performance). However, the predictability varies in space and time and is greater in winter and autumn. Parts of Europe additionally exhibit a longer predictability, up to 7 months of lead time, for certain months within a season. In terms of hindcast reliability, the EFAS seasonal streamflow hindcasts are on average less skilful than the ESP for all lead times. The results also highlight the potential usefulness of the EFAS seasonal streamflow forecasts for decision-making (measured in terms of the hindcast discrimination for the lower and upper terciles of the simulated streamflow). Although the ESP is the most potentially useful forecasting approach in Europe, the EFAS seasonal streamflow forecasts appear more potentially useful than the ESP in some regions and for certain seasons, especially in winter for almost 40 % of Europe. Patterns in the EFAS seasonal streamflow hindcast skill are however not mirrored in the System 4 seasonal climate hindcasts, hinting at the need for a better understanding of the link between hydrological and meteorological variables on seasonal timescales, with the aim of improving climate-model-based seasonal streamflow forecasting.
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| 11. |
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| 12. |
- Boelee, Leonore, et al.
(författare)
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Estimation of uncertainty in flood forecasts—A comparison of methods
- 2019
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Ingår i: Journal of Flood Risk Management. - : Wiley. - 1753-318X. ; 12:Supplement: 1
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Tidskriftsartikel (refereegranskat)abstract
- The scientific literature has many methods for estimating uncertainty, however, there is a lack of information about the characteristics, merits, and limitations of the individual methods, particularly for making decisions in practice. This paper provides an overview of the different uncertainty methods for flood forecasting that are reported in literature, concentrating on two established approaches defined as the ensemble and the statistical approach. Owing to the variety of flood forecasting and warning systems in operation, the question "which uncertainty method is most suitable for which application" is difficult to answer readily. The paper aims to assist practitioners in understanding how to match an uncertainty quantification method to their particular application using two flood forecasting system case studies in Belgium and Canada. These two specific applications of uncertainty estimation from the literature are compared, illustrating statistical and ensemble methods, and indicating the information and output that these two types of methods offer. The advantages, disadvantages and application of the two different types of method are identified. Although there is no one "best" uncertainty method to fit all forecasting systems, this review helps to explain the current commonly used methods from the available literature for the non-specialist.
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| 13. |
- Brimicombe, Chloe, et al.
(författare)
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Borderless Heat Hazards With Bordered Impacts
- 2021
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Ingår i: Earth's Future. - : American Geophysical Union (AGU). - 2328-4277. ; 9:9
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Tidskriftsartikel (refereegranskat)abstract
- Heatwaves are increasing in frequency, duration, and intensity due to climate change. They are associated with high mortality rates and cross-sectional impacts including a reduction in crop yield and power outages. Here we demonstrate that there are large deficiencies in reporting of heatwave impacts in international disasters databases, international organization reports, and climate bulletins. We characterize the distribution of heat stress across the world focusing on August in the Northern Hemisphere, when notably heatwaves have taken place (i.e., 2003, 2010, and 2020) for the last 20 years using the ERA5-HEAT reanalysis of the Universal Thermal Comfort Index and establish heat stress has grown larger in extent, more so during a heatwave. Comparison of heat stress against the emergency events impacts database and climate reports reveals underreporting of heatwave-related impacts. This work suggests an internationally agreed protocol should be put in place for impact reporting by organizations and national government, facilitating implementation of preparedness measures, and early warning systems.
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| 14. |
- Brimicombe, Chloe, et al.
(författare)
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Heatwaves : An invisible risk in UK policy and research
- 2021
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Ingår i: Environmental Science and Policy. - : Elsevier. - 1462-9011 .- 1873-6416. ; 116, s. 1-7
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Tidskriftsartikel (refereegranskat)abstract
- In 2019, a heatwave - an unusual extended period of hot weather - broke the UK's highest recorded temperature of 38.7 degrees C set in 2003. Of concern is that for summer 2019, this resulted in 892 excess deaths. With the intensity and frequency of UK heatwaves projected to increase, and summer temperatures predicted to be 5 degrees C hotter by 2070, urgent action is needed to prepare for, and adapt to, the changes now and to come. Yet it remains unclear what actions are needed and by whom. In response, a systematic literature review of UK heatwaves peer reviewed publications, inclusive of keyword criteria (total papers returned = 183), was conducted to understand what lessons have been learnt and what needs to happen next. Our research shows that heatwaves remain largely an invisible risk in the UK. Communication over what UK residents should do, the support needed to make changes, and their capacity to enact those changes, is often lacking. In turn, there is an inherent bias where research focuses too narrowly on the health and building sectors over other critical sectors, such as agriculture. An increased amount of action and leadership is therefore necessary from the UK government to address this.
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| 15. |
- Brimicombe, Chloe, et al.
(författare)
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Thermofeel : A python thermal comfort indices library
- 2022
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Ingår i: SoftwareX. - : Elsevier. - 2352-7110. ; 18
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Tidskriftsartikel (refereegranskat)abstract
- Here the development of the python library thermofeel is described. thermofeel was developed so that prominent internationally used thermal indices (i.e. Universal Thermal Climate Index and Wet Bulb Globe Temperature) could be implemented into operational weather forecasting systems (i.e. the European Centre for Medium Range Weather Forecasts) whilst also adhering to open research practices. This library will be of benefit to many sectors including meteorology, sport, health and social care, hygiene, agriculture and building. In addition, it could be used in heat early warning systems which, with the right preparedness measures, has the potential to save lives from thermal extremes.
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| 16. |
- Brimicombe, Chloe, et al.
(författare)
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Wet Bulb Globe Temperature : Indicating Extreme Heat Risk on a Global Grid
- 2023
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Ingår i: GeoHealth. - : American Geophysical Union (AGU). - 2471-1403. ; 7:2
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Tidskriftsartikel (refereegranskat)abstract
- The Wet Bulb Globe Temperature (WBGT) is an international standard heat index used by the health, industrial, sports, and climate sectors to assess thermal comfort during heat extremes. Observations of its components, the globe and the wet bulb temperature (WBT), are however sparse. Therefore WBGT is difficult to derive, making it common to rely on approximations, such as the ones developed by Liljegren et al. and by the American College of Sports Medicine (WBGT(ACSM87)). In this study, a global data set is created by implementing an updated WBGT method using ECMWF ERA5 gridded meteorological variables and is evaluated against existing WBGT methods. The new method, WBGT(Brimicombe), uses globe temperature calculated using mean radiant temperature and is found to be accurate in comparison to WBGT(Liljegren) across three heatwave case studies. In addition, it is found that WBGT(ACSM87) is not an adequate approximation of WBGT. Our new method is a candidate for a global forecasting early warning system.
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| 17. |
- Di Napoli, Claudia, et al.
(författare)
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Assessing heat-related health risk in Europe via the Universal Thermal Climate Index (UTCI)
- 2018
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Ingår i: International journal of biometeorology. - : SPRINGER. - 0020-7128 .- 1432-1254. ; 62:7, s. 1155-1165
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Tidskriftsartikel (refereegranskat)abstract
- In this work, the potential of the Universal Thermal Climate Index (UTCI) as a heat-related health risk indicator in Europe is demonstrated. The UTCI is a bioclimate index that uses a multi-node human heat balance model to represent the heat stress induced by meteorological conditions to the human body. Using 38 years of meteorological reanalysis data, UTCI maps were computed to assess the thermal bioclimate of Europe for the summer season. Patterns of heat stress conditions and non-thermal stress regions are identified across Europe. An increase in heat stress up to 1 A degrees C is observed during recent decades. Correlation with mortality data from 17 European countries revealed that the relationship between the UTCI and death counts depends on the bioclimate of the country, and death counts increase in conditions of moderate and strong stress, i.e., when UTCI is above 26 and 32 A degrees C. The UTCI's ability to represent mortality patterns is demonstrated for the 2003 European heatwave. These findings confirm the importance of UTCI as a bioclimatic index that is able to both capture the thermal bioclimatic variability of Europe, and relate such variability with the effects it has on human health.
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| 18. |
- Di Napoli, Claudia, et al.
(författare)
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ERA5-HEAT : A global gridded historical dataset of human thermal comfort indices from climate reanalysis
- 2021
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Ingår i: Geoscience Data Journal. - : John Wiley & Sons. - 2049-6060. ; 8:1, s. 2-10
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Tidskriftsartikel (refereegranskat)abstract
- The mean radiant temperature (MRT) and the Universal Thermal Climate Index (UTCI) are widely used as human biometeorology parameters to assess the linkages between outdoor environment and human well-being. Historically computed from meteorological station measurements, we here present ERA5-HEAT (Human thErmAl comforT), the first historical dataset of MRT and UTCI as spatially gridded records at the global scale. Derived using climate variables from ERA5, a quality-controlled reanalysis produced by the European Centre for Medium-Range Weather Forecasts (ECMWF) within the Copernicus Climate Change Service (C3S), ERA5-HEAT consists of hourly gridded maps of MRT and UTCI at 0.25 degrees x 0.25 degrees spatial resolution. It currently spans from 1979 to present, and it will be extended in time as updates of ERA5 are made available. ERA5-HEAT provides two streams, a consolidated and an intermediate one, that are released at 2 or 3 months and 5 days behind real time, respectively. Data are publicly and freely available for download at the Climate Data Store which has been developed as part of C3S. Being the only existing global historical gridded time series of MRT and UTCI to date, ERA5-HEAT is aimed at a wide range of end users, from scientists to policymakers, with an interest in environment-health applications at any spatial and temporal scale.
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| 19. |
- Di Napoli, Claudia, et al.
(författare)
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Verification of Heat Stress Thresholds for a Health-Based Heat-Wave Definition
- 2019
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Ingår i: Journal of Applied Meteorology and Climatology. - : AMER METEOROLOGICAL SOC. - 1558-8424 .- 1558-8432. ; 58:6, s. 1177-1194
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Tidskriftsartikel (refereegranskat)abstract
- Heat waves represent a threat to human health and excess mortality is one of the associated negative effects. A health-based definition for heat waves is therefore relevant, especially for early warning purposes, and it is here investigated via the universal thermal climate index (UTCI). The UTCI is a bioclimate index elaborated via an advanced model of human thermoregulation that estimates the thermal stress induced by air temperature, wind speed, moisture, and radiation on the human physiology. Using France as a test bed, the UTCI was computed from meteorological reanalysis data to assess the thermal stress conditions associated with heat-attributable excess mortality in five cities. UTCI values at different climatological percentiles were defined and evaluated in their ability to identify periods of excess mortality (PEMs) over 24 years. Using verification metrics such as the probability of detection (POD), the false alarm ratio (FAR), and the frequency bias (FB), daily minimum and maximum heat stress levels equal to or above corresponding UTCI 95th percentiles (15 degrees +/- 2 degrees C and 34.5 degrees +/- 1.5 degrees C, respectively) for 3 consecutive days are demonstrated to correlate to PEMs with the highest sensitivity and specificity (0.69 <= POD <= 1, 0.19 <= FAR <= 0.46, 1 <= FB <= 1.48) than minimum, maximum, and mean heat stress level singularly and other bioclimatological percentiles. This finding confirms the detrimental effect of prolonged, unusually high heat stress at day- and nighttime and suggests the UTCI 95th percentile as a health-meaningful threshold for a potential heat-health watch warning system.
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| 20. |
- Emerton, Rebecca, et al.
(författare)
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Developing a global operational seasonal hydro-meteorological forecasting system : G1oFAS-Seasonal v1.0
- 2018
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Ingår i: Geoscientific Model Development. - : COPERNICUS GESELLSCHAFT MBH. - 1991-959X .- 1991-9603. ; 11:8, s. 3327-3346
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Tidskriftsartikel (refereegranskat)abstract
- Global overviews of upcoming flood and drought events are key for many applications, including disaster risk reduction initiatives. Seasonal forecasts are designed to provide early indications of such events weeks or even months in advance, but seasonal forecasts for hydrological variables at large or global scales are few and far between. Here, we present the first operational global-scale seasonal hydrometeorological forecasting system: G1oFAS-Seasonal. Developed as an extension of the Global Flood Awareness System (G1oFAS), G1oFAS-Seasonal couples seasonal meteorological forecasts from ECMWF with a hydrological model to provide openly available probabilistic forecasts of river flow out to 4 months ahead for the global river network. This system has potential benefits not only for disaster risk reduction through early awareness of floods and droughts, but also for water-related sectors such as agriculture and water resources management, in particular for regions where no other forecasting system exists. We describe the key hydrometeorological components and computational framework of G1oFAS-Seasonal, alongside the forecast products available, before discussing initial evaluation results and next steps.
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| 21. |
- Emerton, Rebecca E., et al.
(författare)
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What is the most useful approach for forecasting hydrological extremes during El Niño?
- 2019
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Ingår i: Environmental Research Communications (ERC). - : IOP PUBLISHING LTD. - 2515-7620. ; 1:3
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Tidskriftsartikel (refereegranskat)abstract
- In the past, efforts to prepare for the impacts of El Nino-driven flood and drought hazards have often relied on seasonal precipitation forecasts as a proxy for hydrological extremes, due to a lack of hydrologically relevant information. However, precipitation forecasts are not the best indicator of hydrological extremes. Now, two different global scale hydro-meteorological approaches for predicting river flow extremes are available to support flood and drought preparedness. These approaches are statistical forecasts based on large-scale climate variability and teleconnections, and resource-intensive dynamical forecasts using coupled ocean-atmosphere general circulation models. Both have the potential to provide early warning information, and both are used to prepare for El Nino impacts, but which approach provides the most useful forecasts? This study uses river flow observations to assess and compare the ability of two recently-developed forecasts to predict high and low river flow during El Nino: statistical historical probabilities of ENSO-driven hydrological extremes, and the dynamical seasonal river flow outlook of the Global Flood Awareness System (GloFAS-seasonal). Our findings highlight regions of the globe where each forecast is (or is not) skilful compared to a forecast of climatology, and the advantages and disadvantages of each forecasting approach. We conclude that in regions where extreme river flow is predominantly driven by El Nino, or in regions where GloFAS-seasonal currently lacks skill, the historical probabilities generally provide a more useful forecast. In areas where other teleconnections also impact river flow, with the effect of strengthening, mitigating or even reversing the influence of El Nino, GloFAS-seasonal forecasts are typically more useful.
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| 22. |
- Emerton, Rebecca, et al.
(författare)
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Emergency flood bulletins for Cyclones Idai and Kenneth : A critical evaluation of the use of global flood forecasts for international humanitarian preparedness and response
- 2020
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Ingår i: International Journal of Disaster Risk Reduction. - : ELSEVIER. - 2212-4209. ; 50
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Tidskriftsartikel (refereegranskat)abstract
- Humanitarian disasters such as Typhoon Haiyan (SE Asia, 2013) and the Horn of Africa drought (2011-2012) are examples of natural hazards that were predicted, but where forecasts were not sufficiently acted upon, leading to considerable loss of life. These events, alongside international adoption of the Sendai Framework for Disaster Risk Reduction, have motivated efforts to enable early action from early warnings. Through initiatives such as Forecast-based Financing (FbF) and the Science for Humanitarian Emergencies and Resilience (SHEAR) programme, progress is being made towards the use of science and forecasts to support international humanitarian organisations and governments in taking early action and improving disaster resilience. However, many challenges remain in using forecasts systematically for preparedness and response. The research community in place through SHEAR enabled the UK government's Department for International Development to task a collaborative group of scientists to produce probabilistic real-time flood forecast and risk bulletins, aimed at humanitarian decision-makers, for Cyclones Idai and Kenneth, which impacted Mozambique in 2019. The process of bulletin creation during Idai and Kenneth is reviewed and critically evaluated, including evaluation of the forecast information alongside evidence for how useful the bulletins were. In this context, this work seeks to navigate the "murky landscape" of national and international mandates, capacities, and collaborations for forecasting, early warning and anticipatory action, with the ultimate aim of finding out what can be done better in the future. Lessons learnt and future recommendations are discussed to enable better collaboration between producers and users of forecast information.
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| 23. |
- Harrigan, Shaun, et al.
(författare)
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Daily ensemble river discharge reforecasts and real-time forecasts from the operational Global Flood Awareness System
- 2023
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Ingår i: Hydrology and Earth System Sciences. - : European Geosciences Union (EGU). - 1027-5606 .- 1607-7938. ; 27:1, s. 1-19
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Tidskriftsartikel (refereegranskat)abstract
- Operational global-scale hydrological forecasting systems are usedto help manage hydrological extremes such as floods and droughts. The vastamounts of raw data that underpin forecast systems and the ability togenerate information on forecast skill have, until now, not been publiclyavailable. As part of the Global Flood Awareness System (GloFAS; https://www.globalfloods.eu/, last access: 3 December 2022) service evolution, in this paper daily ensemble river discharge reforecasts and real-time forecast datasets are made free and openly available through the Copernicus Climate Change Service (C3S) Climate Data Store (CDS). They include real-time forecast data starting on 1 January 2020 updated operationally every day and a 20-year set of reforecasts and associated metadata. This paper describes the model components and configuration used to generate the real-time river discharge forecasts and the reforecasts. An evaluation of ensemble forecast skill using the continuous ranked probability skill score (CRPSS) was also undertaken for river points around the globe. Results show that GloFAS is skilful in over 93 % of catchments in the short (1 to 3 d) and medium range (5 to 15 d) against a persistence benchmark forecast and skilful in over 80 % of catchments out to the extended range (16 to 30 d) against a climatological benchmark forecast. However, the strength of skill varies considerably by location with GloFAS found to have no or negative skill at longer lead times in broad hydroclimatic regions in tropical Africa, western coast of South America, and catchments dominated by snow and ice in high northern latitudes. Forecast skill is summarised as a new headline skill score available as a new layer on the GloFAS forecast Web Map Viewer to aid user interpretation and understanding of forecast quality.
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| 24. |
- Harrigan, Shaun, et al.
(författare)
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GloFAS-ERA5 operational global river discharge reanalysis 1979-present
- 2020
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Ingår i: Earth System Science Data. - : Copernicus GmbH. - 1866-3508 .- 1866-3516. ; 12:3, s. 2043-2060
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Tidskriftsartikel (refereegranskat)abstract
- Estimating how much water is flowing through rivers at the global scale is challenging due to a lack of observations in space and time. A way forward is to optimally combine the global network of earth system observations with advanced numerical weather prediction (NWP) models to generate consistent spatio-temporal maps of land, ocean, and atmospheric variables of interest, which is known as a reanalysis. While the current generation of NWP models output runoff at each grid cell, they currently do not produce river discharge at catchment scales directly and thus have limited utility in hydrological applications such as flood and drought monitoring and forecasting. This is overcome in the Global Flood Awareness System (GloFAS; http://www.globalfloods.eu/, last access: 28 June 2020) by coupling surface and sub-surface runoff from the Hydrology Tiled ECMWF Scheme for Surface Exchanges over Land (HTESSEL) land surface model used within ECMWF's latest global atmospheric reanalysis (ERA5) with the LISFLOOD hydrological and channel routing model. The aim of this paper is to describe and evaluate the GloFAS-ERA5 global river discharge reanalysis dataset launched on 5 November 2019 (version 2.1 release). The river discharge reanalysis is a global gridded dataset with a horizontal resolution of 0.1 degrees at a daily time step. An innovative feature is that it is produced in an operational environment so is available to users from 1 January 1979 until near real time (2 to 5 d behind real time). The reanalysis was evaluated against a global network of 1801 daily river discharge observation stations. Results found that the GloFAS-ERA5 reanalysis was skilful against a mean flow benchmark in 86% of catchments according to the modified Kling-Gupta efficiency skill score, although the strength of skill varied considerably with location. The global median Pearson correlation coefficient was 0.61 with an interquartile range of 0.44 to 0.74. The long-term and operational nature of the GloFAS-ERA5 reanalysis dataset provides a valuable dataset to the user community for applications ranging from monitoring global flood and drought conditions to the identification of hydroclimatic variability and change and as raw input for post-processing and machine learning methods that can add further value. The dataset is openly available from the Copernicus Climate Change Service Climate Data Store: https://cds.climate.copernicus.eu/cdsapp#!/dataset/cems-glofas-historical?tab=overview (last access: 28 June 2020) with the following DOI: https://doi.org/10.24381/cds.a4fdd6b9 (C3S, 2019).
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| 25. |
- Kauffeldt, Anna, et al.
(författare)
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Imbalanced land surface water budgets in a numerical weather prediction system
- 2015
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Ingår i: Geophysical Research Letters. - 0094-8276 .- 1944-8007. ; 42:11, s. 4411-4417
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Tidskriftsartikel (refereegranskat)abstract
- There has been a significant increase in the skill and resolution of numerical weather prediction models (NWPs) in recent decades, extending the time scales of useful weather predictions. The land surface models (LSMs) of NWPs are often employed in hydrological applications, which raises the question of how hydrologically representative LSMs really are. In this paper, precipitation (P), evaporation (E), and runoff (R) from the European Centre for Medium-Range Weather Forecasts global models were evaluated against observational products. The forecasts differ substantially from observed data for key hydrological variables. In addition, imbalanced surface water budgets, mostly caused by data assimilation, were found on both global (P-E) and basin scales (P-E-R), with the latter being more important. Modeled surface fluxes should be used with care in hydrological applications, and further improvement in LSMs in terms of process descriptions, resolution, and estimation of uncertainties is needed to accurately describe the land surface water budgets.
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