Climate scenarios for coastal flood vulnerability assessments: a case study for the Ligurian coastal region

Extreme sea levels and coastal flooding are projected to be among the most uncertain and severe consequences of climate change. In response, a wide development of coastal vulnerability assessment methodologies has been observed in research to support societal resilience to future coastal flood risks. This work aims to explore the scope of application of index-based methodologies for coastal vulnerability assessment, in terms of their suitability to convey information on variations in climate variables potentially leading to sea-level changes and inundation. For this purpose, the InVEST Coastal Vulnerability model was coupled for the first time with the ERA5 reanalysis and used to develop a case study assessment of the biophysical exposure component of vulnerability to coastal flooding for Liguria, an Italian coastal region facing the Mediterranean Sea. Different scenarios of wind speed and wave power were created in order to test the sensitivity of this approach to climate data inputs. The results support the applicability of this approach to provide a preliminary grasp of local vulnerability to coastal inundation. Yet, this work also highlights how the method’s data aggregation and indicator computation processes result in its insensitivity to wind and wave variations, and therefore in its unsuitability to reproduce climate scenarios. The implications of these findings for research methodology and regarding the operationalisation of vulnerability assessment results are discussed

Homogenization of near-surface wind speed and gust series across Sweden

Póster presentado en: EGU General Assembly 2019 celebrada del 7 al 12 de abril en Viena, Austria.Studies which evaluate the impact of wind-related hazards need to have access to reliable and homogeneous measurements. Unfortunately, observed wind series can be affected by several non-climatic artifacts, which may introduce inhomogeneities that mislead the study of climate trends and multi-decadal variability. This study compares different homogenization approaches using the R-package CLIMATOL to identify the best technique for homogenizing near-surface mean wind speed (WS) and daily peak wind gust (DPWG, i.e. the highest near-surface wind gust speed recorded in 24 hours) across Sweden.This work has been supported by the project “Detection and attribution of changes in extreme wind gusts over land” (2017-03780) funded by the Swedish Research Council

Observed and simulated trends of daily peak wind gusts across northern Europe

Póster presentado en: EMS Annual Meeting: European Conference for Applied Meteorology and Climatology celebrado del 4 al 8 de septiembre de 2017 en Dublin, IrlandaExtreme wind hazards have a substantial societal and environmental impact. Due to their complex origins, there are great knowledge gaps about their variations and the associated mechanisms, which makes the prediction challenging. Specifically there is a urgent need to evaluate numerical models’ capability in simulate extreme wind conditions. This study focuses on assessing variabilities and trends of Daily Peak Wind Gust (DPWG) and its extreme (defined as 90th percentile) cross Northern Europe, based on observation during 1996-2016 and Regional Climate Model (RCM) simulations for 1970-2016. The aim is to evaluate RCMs’ ability in simulating past changes of the DPWG and its extreme as reflected in the observations. RCMs are the key tools available for the prediction of wind conditions. An improved understanding about how these models perform can help identify eventual deficiencies in the models, which may enhance our prediction ability

How well do Regional Climate Models simulate and parametrize surface wind speed and wind gust across Scandinavia?

Presentación realizada para el: EMS Annual Meeting - European Conference for Applied Meteorology and Climatology 2018, celebrado en Budapest del 3 al 7 de septiembre de 2018.This work has been also supported by the project “Detection and attribution of changes in extreme wind gusts over land” (2017-03780) funded by the Swedish Research Council

Climatology of near‐surface daily peak wind gusts across Scandinavia: observations and model simulations

An observed daily peak wind gusts (DPWG) dataset over Scandinavia, consisting of time series from 127 meteorological stations across Finland, Norway and Sweden, has been created. This dataset provides high-quality and homogenized near-surface DPWG series for Scandinavia, spanning the longest available time period (1996–2016). The aim of this study is to evaluate the ability of two regional climate models (RCMs) in simulating DPWG winds. According to the observed DPWG climatology, meteorological stations are classified into three regions for which wind conditions are influenced by similar physical processes: coast, inland and mountain. Smaller-scale DPWG features of the three regions are only captured when coarser general circulation models or reanalyses are downscaled by a RCM. Dynamic downscaling is thus needed to achieve more realistic simulations of DPWG when compared to their driving models. The performances of the RCMs are found to be more dependent on model dynamics and physics (such as gust parametrization) than on the boundary conditions provided by the driving models. We also found that the RCMs cannot accurately simulate observed DPWG in inland and mountainous areas, suggesting the need for higher horizontal resolution and/or better representation of relevant boundary-layer processes.It is supported by Swedish Research Council (2017-03780) and Spanish Ministry of Science, Innovation and Universities (RTI2018-095749-A-I00)

Wind stilling-reversal across Sweden: the impact of land-use and large-scale atmospheric circulation changes

This study analyses for the first time the break in the stilling detected by previous research around 2010, with focus in Sweden using homogenized near-surface mean and gust wind speed observations for 1997–2019. During the recent past two decades, both mean and gust wind magnitude and frequency (exceeding the 90th percentile) underwent nonlinear changes, driven by the dominant winter variability. In particular, consistent with previous studies, the significant (p < .05) stilling ceased in 2003, followed by no clear trend afterwards. The detected stilling-reversal is linked to large-scale atmospheric circulation changes, in particular to the North Atlantic Oscillation for both mean and gust wind changes, and the intensity changes of extratropical cyclones passing across Sweden especially for wind gusts. Furthermore, in different wind change phases, the observed wind distribution did not vary uniformly for the various wind speed ranges; instead, strong winds drove most of the changes. In the same way, increases in gust winds are greater compared to changes in mean wind speed conditions. The stilling-reversal is also identified by the ERA5 reanalysis, where large-scale atmospheric circulation changes are captured. But the background slowdown detected in most stations does not appear in the ERA5 data as the observed increase in forest cover is not considered in the reanalysis. This study reveals that, in addition to the large-scale interannual variability, changes in surface roughness (e.g., changes in forest cover) contribute to the observed wind variability across Sweden.Ministry of Oceans and Fisheries of Korea, Grant/Award Number: 20210427; Ramon y Cajal, Grant/Award Number: RYC2017-22830; Spanish Ministry of Science and Innovation, Grant/Award Number: RTI2018-095749-A-I00; Swedish Research Council, Grant/Award Number: 2017-0378

Trends of daily peak wind gusts in Australia, 1948-2016

Póster presentado en: EGU General Assembly 2019 celebrada del 7 al 12 de abril en Viena, Austria.Daily Peak Wind Gust (DPWG) time series are important for the evaluation of wind-related hazard risks to different socioeconomic and environmental sectors. Yet wind time series analyses can be impacted by several artefacts, such as anemometer changes and site location changes, both temporally and spatially, that may introduce inhomogeneities that mislead the study of their decadal variability and trends. A previous study (EGU2018-14546 and Azorin-Molina et al. 2019. Int. J. Climatol. 39(4), 2260-2277) presented a strategy in the homogenization of this challenging climate extreme such as the DPWG. The automatic homogenization of this DPWG dataset was implemented in the recently developed version 3.1 of the R package Climatol which: (i) represents an advance in homogenization of this extreme climate record; and (ii) produced the first homogenized DPWG dataset to assess and attribute long-term variability of extreme winds across Australia. Given the inconsistencies of wind gust trends under the widespread decline in near-surface wind speed (stilling), the aim of this poster presentation is to show DPWG trends in 35 Bureau of Meteorology operated stations for 1948-2016, with particular focus on the spatiotemporal magnitude (wind speed maxima) of DPWG at annual, seasonal and monthly timescales.This work has been supported by the project “Detection and attribution of changes in extreme wind gusts over land” (2017-03780) funded by the Swedish Research Council

Stilling project: advances in the compilation and homogenization of historical wind speed data for the assessment of the stilling phenomenon

Póster presentado en: EGU General Assembly 2018 celebrada del 8 al 13 de abril en Viena, Austria.During the last decade scientists have reported a terrestrial slowdown in wind speed across the world. This weakening in wind speed has been recently termed the “stilling” phenomenon, with a worldwide average trend of -0.140 m s-1 decade-1 reported since the 1960s. The precise causes of this “stilling” remain largely uncertain and have been hypothetically attributed to several factors, mainly related to an increase in surface roughness (i.e. forest growth, land use changes, and urbanization) with little attention paid to changes in atmospheric circulation. Unlike this “stilling” over land, satellite measurements have revealed that wind speed has increased over ocean surfaces, which introduces uncertainty to the “stilling” debate. Therefore, scientists are currently debating if global warming has and will impact on changes in wind speed.The uncertainty on the causes driving the “stilling” over land is mainly due to short availability (i.e. since the 1960s) and low quality of observed wind speed records as stated by the Fifth Assessment Report (AR5) of the Intergovernmental Panel on Climate Change (IPCC) and the recent report “State of the Climate in 2015” . The main objective of the ongoing EU funded project STILLING (MSCAIF-2015 GA-703733) is to fill the key gap of short availability and low quality of wind speed datasets, and improve the limited knowledge on the causes driving the “stilling” in a climate change scenario. This has not yet been addressed by the scientific community due to (i) scientists have traditionally paid little attention on variability of wind speed; (ii) digitization of climate series at National Weather Services (NWS) systematically started in the 1960s, however, some longer but isolated past wind speed records are available for scientists to be rescued and analyzed; and (iii) efforts on advances in homogenization algorithms to improve quality of wind speed series have been scarce. The STILLING project covers a novel research niche on the “stilling” debate, and this contribution will present the advances in the compilation and homogenization of historical wind speed data (prior to the 1960s) to better assess trends/cycles and causes on multidecadal time periods and reliable datasets than previous studies.This research has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No. 703733 (STILLING project)

Variability of daily maximum wind speed across China, 1975–2016: an examination of likely causes

Assessing change in daily maximum wind speed and its likely causes is crucial for many applications such as wind power generation and wind disaster risk governance. Multidecadal variability of observed near-surface daily maximum wind speed (DMWS) from 778 stations over China is analyzed for 1975–2016. A robust homogenization protocol using the R package Climatol was applied to the DMWS observations. The homogenized dataset displayed a significant (p 0.10); that is, DMWS declined during the cold semester (October–March) and increased during the warm semester (April–September). Correlation analysis of the Arctic Oscillation, the Southern Oscillation, and the west Pacific modes exhibited significant correlation with DMWS variability, unveiling their complementarity in modulating DMWS. Further, we explored potential physical processes relating to the atmospheric circulation changes and their impacts on DMWS and found that 1) overall weakened horizontal airflow [large-scale mean horizontal pressure gradient (from −0.24 to +0.02 hPa decade−1) and geostrophic wind speed (from −0.6 to +0.6 m s−1 decade−1)], 2) widely decreased atmospheric vertical momentum transport [atmospheric stratification thermal instability (from −3 to +1.5 decade−1) and vertical wind shear (from −0.4 to +0.2 m s−1 decade−1)], and 3) decreased extratropical cyclones frequency (from −0.3 to 0 month decade−1) are likely causes of DMWS change.This study was supported by the National Natural Science Foundation of China (Grant 41621061), the National Key Research and Development Program–Global Change and Mitigation Project (Grant 2016YFA0602404), funding from STINT (CH2015-6226), and the European Union’s Horizon 2020 research and innovation program under the Marie Skłodowska-Curie grant agreement 703733 (STILLING project). This work has been also supported by the VR project (2017-03780) funded by the Swedish Research Council and Ramon y Cajal fellowship (RYC-2017-22830) and Grant RTI2018-095749-A-I00 (MCIU/AEI/FEDER, UE)

Uneven warming likely contributed to declining near-surface wind speeds in Northern China between 1961 and 2016

A decline in mean near-surface (10 m) wind speed has been widely reported for many land regions over recent decades, yet the underlying cause(s) remains uncertain. This study investigates changes in near-surface wind speed over northern China from 1961 to 2016, and analyzes the associated physical mechanisms using station observations, reanalysis products and model simulations from the Community Atmosphere Model version 5.1 (CAM5). The homogenized near-surface wind speed shows a significantly (p 50°N) in recent decades, which has weakened the annual and seasonal meridional air temperature gradient (−0.33°C to −0.12°C dec−1, p < 0.05, except autumn) between these regions (50°–60°N, 75°–135°E) and the northern China zone (35°–45°N, 75°–135°E). This caused a significant (p < 0.05) decrease in annual and seasonal pressure gradient (−0.43 to −0.20 hPa dec−1) between the two zones, which contributed to the slowdown of winds. CAM5 simulations demonstrate that spatially uneven air temperature increases and near-surface wind speed decreases over northern China can be realistically reproduced using the so-called “all forcing” simulation, while the “natural only forcing” simulation fails to realistically simulate the uneven warming patterns and declines in near-surface wind speed over most of northern China, except for summer.This study was supported by the Second Tibetan Plateau Scientific Expedition and Research Program (STEP, Grant No. 2019QZKK0606), the National Natural Science Foundation of China (Grant No. 41621061), and by the National Key Research and Development Program—Global Change and Mitigation Project (Grant No. 2016YFA0602404). This work was also supported by a Swedish Research Council (2017-03780) and a Swedish Research Council for Sustainable Development (2019-00509) grant, and by the IBER-STILLING project, funded by the Spanish Ministry of Science, Innovation and Universities (RTI2018-095749-A-I00; MCIU/AEI/FEDER, UE)