| 1. |
- Azorin-Molina, Cesar, et al.
(författare)
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Biases in wind speed measurements due to anemometer changes
- 2023
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Ingår i: Atmospheric Research. - 0169-8095. ; 289
-
Tidskriftsartikel (refereegranskat)abstract
- This research presents a case study of the biases and discontinuities that were introduced in observed long-term mean wind-speed and gust data-series due to anemometer changes in a meteorological station in northern Spain, operated by the Spanish State Meteorological Agency: San Sebastian-Igueldo. Field and wind-tunnel experiments with predefined conditions have been presented in the literature, however this research uses a real case study to assess the impact of anemometer changes on wind speed measurements due to three factors being: (i) the 3-cup anemometer model (SEAC vs. THIES companies); (ii) sensor height (∼19.95 m vs. ∼20.45 m) and (iii) sensor age (20-years old vs. new). Our results show (a) substantial biases in the measured wind speed and daily peak wind gusts, with the new THIES anemometer reporting stronger surface winds than the old SEAC anemometer; (b) opposing biases under weak (negative) and moderate-strong (positive) winds; and (c) significant breakpoints in the long-term wind data-series, which highlight the importance of data homogenization. National Weather Services and climate assessment groups will benefit from these findings since errors in wind speed and gust measurements can be minimized by implementing systematic observation protocols. Robust anemometer observations provide a basis for accurate quantification of the magnitude of changes and the variability of surface winds.
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| 2. |
- Azorin-Molina, Cesar, et al.
(författare)
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Evaluating anemometer drift: A statistical approach to correct biases in wind speed measurement
- 2018
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Ingår i: Atmospheric research. - : Elsevier BV. - 0169-8095. ; 203, s. 175-188
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Tidskriftsartikel (refereegranskat)abstract
- Recent studies on observed wind variability have revealed a decline (termed “stilling”) of near-surface wind speed during the last 30–50 years over many mid-latitude terrestrial regions, particularly in the Northern Hemisphere. The well-known impact of cup anemometer drift (i.e., wear on the bearings) on the observed weakening of wind speed has been mentioned as a potential contributor to the declining trend. However, to date, no research has quantified its contribution to stilling based on measurements, which is most likely due to lack of quantification of the ageing effect. In this study, a 3-year field experiment (2014–2016) with 10-minute paired wind speed measurements from one new and one malfunctioned (i.e., old bearings) SEAC SV5 cup anemometer which has been used by the Spanish Meteorological Agency in automatic weather stations since mid-1980s, was developed for assessing for the first time the role of anemometer drift on wind speed measurement. The results showed a statistical significant impact of anemometer drift on wind speed measurements, with the old anemometer measuring lower wind speeds than the new one. Biases show a marked temporal pattern and clear dependency on wind speed, with both weak and strong winds causing significant biases. This pioneering quantification of biases has allowed us to define two regression models that correct up to 37% of the artificial bias in wind speed due to measurement with an old anemometer.
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| 3. |
- Azorin-Molina, Cesar, et al.
(författare)
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Recent trends in wind speed across Saudi Arabia, 1978-2013: a break in the stilling
- 2018
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Ingår i: International Journal of Climatology. - : Wiley. - 0899-8418. ; 38
-
Tidskriftsartikel (refereegranskat)abstract
- We analyse recent trends and variability of observed near-surface wind speed from 19 stations across Saudi Arabia (SA) for 1978-2013. The raw wind speed data set was subject to a robust homogenization protocol, and the stations were then classified under three categories: (1) coast, (2) inland and (3) mountain stations. The results reveal a statistically significant (p<0.05) reduction of wind speed of -0.058m s(-1) dec(-1) at annual scale across SA, with decreases in winter (-0.100m s(-1) dec(-1)) and spring (-0.066m s(-1) dec(-1)) also detected, being non-significant in summer and autumn. The coast, inland and mountain series showed similar magnitude and significance of the declining trends across all SA series, except for summer when a decoupled variability and opposite trends of wind speed between the coast and inland series (significant declines: -0.101m s(-1) dec(-1) and -0.065m s(-1) dec(-1), respectively) and the high-elevation mountain series (significant increase: +0.041m s(-1) dec(-1)) were observed. Even though wind speed declines dominated across much of the country throughout the year, only a small number of stations showed statistically significant negative trends in summer and autumn. Most interestingly, a break in the stilling was observed in the last 12-year (2002-2013) period (+0.057m s(-1) dec(-1); not significant) compared to the significant slowdown detected in the previous 24-year (1978-2001) period (-0.089m s(-1) dec(-1)). This break in the slowdown of winds, even followed by a non-significant recovery trend, occurred in all seasons (and months) except for some winter months. Atmospheric circulation plays a key role in explaining the variability of winds, with the North Atlantic Oscillation positively affecting the annual wind speed, the Southern Oscillation displaying a significant negative relationship with winds in winter, spring and autumn, and the Eastern Atlantic negatively modulating winds in summer.
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| 4. |
- Azorin-Molina, Cesar, et al.
(författare)
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Wind speed variability over the Canary Islands, 1948–2014: focusing on trend differences at the land–ocean interface and below–above the trade-wind inversion layer
- 2018
-
Ingår i: Climate Dynamics. - : Springer Science and Business Media LLC. - 0930-7575 .- 1432-0894. ; 50:11-12, s. 4061-4081
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Tidskriftsartikel (refereegranskat)abstract
- This study simultaneously examines wind speed trends at the land–ocean interface, and below–above the trade-wind inversion layer in the Canary Islands and the surrounding Eastern North Atlantic Ocean: a key region for quantifying the variability of trade-winds and its response to large-scale atmospheric circulation changes. Two homogenized data sources are used: (1) observed wind speed from nine land-based stations (1981–2014), including one mountain weather station (Izaña) located above the trade-wind inversion layer; and (2) simulated wind speed from two atmospheric hindcasts over ocean (i.e., SeaWind I at 30 km for 1948–2014; and SeaWind II at 15 km for 1989–2014). The results revealed a widespread significant negative trend of trade-winds over ocean for 1948–2014, whereas no significant trends were detected for 1989–2014. For this recent period wind speed over land and ocean displayed the same multi-decadal variability and a distinct seasonal trend pattern with a strengthening (late spring and summer; significant in May and August) and weakening (winter–spring–autumn; significant in April and September) of trade-winds. Above the inversion layer at Izaña, we found a predominance of significant positive trends, indicating a decoupled variability and opposite wind speed trends when compared to those reported in boundary layer. The analysis of the Trade Wind Index (TWI), the North Atlantic Oscillation Index (NAOI) and the Eastern Atlantic Index (EAI) demonstrated significant correlations with the wind speed variability, revealing that the correlation patterns of the three indices showed a spatio-temporal complementarity in shaping wind speed trends across the Eastern North Atlantic.
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| 5. |
- Kaiqiang, Deng, et al.
(författare)
-
Changes of Southern Hemisphere westerlies in the future warming climate
- 2022
-
Ingår i: Atmospheric Research. - : Elsevier BV. - 0169-8095. ; 270
-
Tidskriftsartikel (refereegranskat)abstract
- The Southern Hemisphere westerlies (SHWs) play a key role in regulating global climate and ocean circulation, but their future changes under low to high greenhouse gas forcings remain unclear. This study investigates the long-term trends in strength and position of the SHWs and their linkage with human activities, based on the ERA5 reanalysis and model simulations from the Coupled Model Intercomparison Project phase 6 (CMIP6). The results show that the SHWs have intensified and shifted poleward in the recent decades, and are projected to experience divergent trends in strength and position during the 21st century under different Shared Socioeconomic Pathway (SSP) scenarios. Forced by SSP245, 370, and 585, which represent the middle to high greenhouse gas forcings, the SHWs will continue to strengthen and move southward in 2015–2099, with the largest trends induced by SSP585. Nevertheless, forced by SSP126, which implies a low greenhouse gas forcing in the future, the ongoing trends in strength and position of the SHWs will be interrupted and even reversed. Further investigation reveals that the anthropogenic forcing could have affected and will likely influence the SHWs by modulating meridional atmospheric circulation in the Southern Hemisphere. In particular, the Southern Annular Mode and the tropical Pacific convection play crucial roles in the changes of SHWs. This study links human activities to the changes in SHWs, providing important implications for climate change and its mitigation. © 2022 The Authors
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| 6. |
- Kaiqiang, Deng, et al.
(författare)
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Global Near-Surface Wind Speed Changes over the Last Decades Revealed by Reanalyses and CMIP6 Model Simulations
- 2021
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Ingår i: Journal of Climate. - 0894-8755 .- 1520-0442. ; 34:6, s. 2219-2234
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Tidskriftsartikel (refereegranskat)abstract
- Near-surface (10 m) wind speed (NWS) plays a crucial role in many areas, including hydrological cycles, wind energy production, and air pollution, but what drives its multidecadal changes is still unclear. Using reanalysis datasets and model simulations from phase 6 of the Coupled Model Intercomparison Projection (CMIP6), this study investigates recent trends in the annual mean NWS. The results show that the Northern Hemisphere (NH) terrestrial NWS experienced significant (p < 0.1) decreasing trends during 1980–2010, when the Southern Hemisphere (SH) ocean NWS was characterized by significant (p < 0.1) upward trends. However, during 2010–19, global NWS trends shifted in their sign: NWS trends over the NH land became positive, and trends over the SH tended to be negative. We propose that the strengthening of SH NWS during 1980–2010 was associated with an intensified Hadley cell over the SH, while the declining of NH land NWS could have been caused by changes in atmospheric circulation, alteration of vegetation and/or land use, and the accelerating Arctic warming. The CMIP6 model simulations further demonstrate that the greenhouse gas (GHG) warming plays an important role in triggering the NWS trends over the two hemispheres during 1980–2010 through modulating meridional atmospheric circulation. This study also points at the importance of anthropogenic GHG forcing and the natural Pacific decadal oscillation to the long-term trends and multidecadal variability in global NWS, respectively.
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| 7. |
- Kaiqiang, Deng, et al.
(författare)
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Shifting of summertime weather extremes in Western Europe during the last decade
- 2022
-
Ingår i: Advances in Climate Change Research. - : Elsevier BV. - 1674-9278. ; 13:2, s. 218-227
-
Tidskriftsartikel (refereegranskat)abstract
- Over the past decades, droughts and heatwaves frequently appeared in Western Europe (45°–65°N, 10°W–20°E) during boreal summer, causing huge impacts on human society and ecosystems. Although these extremes are projected to increase in both frequency and intensity under a warming climate, our knowledge of their interdecadal variations and causes is relatively limited. Here we show that the droughts and heatwaves in Western Europe have shifted in their trends in the last decade: for 1979–2012, wind speed and precipitation have both strengthened in Western Europe; for 2012–2020, however, Western Europe have experienced declined wind speed, decreased precipitation, and higher air temperature, leading to more frequent droughts and heatwaves there. Recent changes in the WE climate and extremes are related to the variations of the North Atlantic westerly jet stream. In 1979–2012 (2012–2020), the westerly jet stream shifted equatorward (poleward), which enhanced (reduced) transportation of water vapor fluxes from the North Atlantic Ocean to the European land areas, resulting in wetter (drier) surface in Western Europe. Further analysis suggests that phase changes in the Pacific Decadal Oscillation could have played a key role in regulating the position of the jet stream, providing important implications for decadal predictions of the Western Europe summertime climate and weather extremes. © 2022 The Authors
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| 8. |
- Kaiqiang, Deng, et al.
(författare)
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Terrestrial Stilling Projected to Continue in the Northern Hemisphere Mid-Latitudes
- 2022
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Ingår i: Earths Future. - : American Geophysical Union (AGU). - 2328-4277. ; 10:7
-
Tidskriftsartikel (refereegranskat)abstract
- The near-surface wind speed over land has declined in recent decades, a trend known as terrestrial stilling (TS). However, recent studies have indicated a reversal of the TS during the last decade, triggering renovated interest in the future wind speed changes. This study examines the TS over the Northern Hemisphere (NH) land areas and explores its future changes under Model Inter-comparison Projection Phase 6 Shared Socioeconomic Pathways (SSP) scenarios. The results show that the NH mid-latitude TS will likely continue during the whole 21st century under mid-to-high greenhouse warmings (SSPs-245, 370, and 585). Nevertheless, if the world reduces carbon emissions substantially (SSP-126), the TS will be interrupted and likely reversed after the mid-21st century. The projected TS shows seasonal differences, with the largest (smallest) decreasing trends of wind speed in boreal summer (winter). Moreover, the TS reversal during the last decade is suggested as a multi-decadal fluctuation related to the Pacific and Atlantic multi-decadal oscillations. In addition, this study proposes that increased upper-air warming in the future climate could play a key role in reducing the NH mid-latitude surface wind speed. The continuing TS provides strong implications for the near-surface environment and wind energy development, particularly for countries in the NH mid-latitudes.
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| 9. |
- Minola, Lorenzo
(författare)
-
Changes in near-surface winds across Sweden over the past decades - Observations and simulations
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Driven by a combination of anthropogenic activities and climate changes, near- surface terrestrial winds displayed a large decrease in their magnitude in the past decades, named “stilling”, and a recent recovery in their slowdown. Understanding how wind has changed and identifying the factors behind the observed variabilities is crucial so that reasonable future wind scenarios can be constructed. In this way, adaptation strategies can be developed to increase society’s resilience to the plausible future wind climate. This is particularly important for Sweden, which is largely vulnerable to changes in mean wind speed conditions and to the occurrence of extreme winds. Therefore, this thesis investigates past variations in near-surface winds across Sweden and explores the mechanisms behind their variabilities and changes. This is done by using the first homogenized dataset of in-situ observations and by analyzing current simulations of wind gusts. Results show that, during the past decades, both observed mean and gust wind speed underwent nonlinear changes, driven by the dominant winter variability. In particular, consistent with the stilling-reversal phenomena, the significant 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, and the intensity changes of extratropical cyclones passing across Sweden. The comparison with reanalysis outputs reveals that, in addition to the large-scale interannual variability, changes in surface roughness (e.g. changes in forest cover) have most likely contributed to the observed wind change across Sweden. Moreover, this thesis finds that current regional climate models and reanalyses do not have adequate skills in simulating past wind gusts across inland and mountain regions. Major improvements are achieved when the elevation differences are considered in the formulation of the gust parametrization and the convective gust contribution is adjusted according to the observed climatology. The presented work advances the understanding of how surface winds change in a warmer climate at high midlatitudes and improves the model forecasting of wind gustiness over Sweden.
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| 10. |
- Minola, Lorenzo, et al.
(författare)
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Climatology of Near-Surface Daily Peak Wind Gusts Across Scandinavia: Observations and Model Simulations
- 2021
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Ingår i: Journal of Geophysical Research: Atmospheres. - 2169-897X. ; 126:7
-
Tidskriftsartikel (refereegranskat)abstract
- 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. © 2021. The Authors.
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| 11. |
- Minola, Lorenzo, et al.
(författare)
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Climatology of near-surface wind speed from observational, reanalysis and high-resolution regional climate model data over the Tibetan Plateau
- 2023
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Ingår i: Climate Dynamics. - 0930-7575 .- 1432-0894.
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Tidskriftsartikel (refereegranskat)abstract
- As near-surface wind speed plays a role in regulating surface evaporation and thus the hydrological cycle, it is crucial to explore its spatio-temporal characteristics. However, in-situ measurements are scarce over the Tibetan Plateau, limiting the understanding of wind speed climate across this high-elevation region. This study explores the climatology of near-surface wind speed over the Tibetan Plateau by using for the first time homogenized observations together with reanalysis products and regional climate model simulations. Measuring stations across the center and the west of the plateau are at higher elevations and display higher mean and standard deviation, confirming that wind speed increases with increasing altitude. By exploring wind characteristics with a focus on seasonal cycle through cluster analysis, three regions of distinct wind regimes can be identified: (1) the central Tibetan Plateau, characterized by high elevation; (2) the eastern and the peripheral areas of the plateau; and (3) the Qaidam basin, a topographic depression strongly influenced by the blocking effect of the surrounding mountainous terrain. Notably, the ERA5 reanalysis, with its improvements in horizontal, vertical, and temporal spacing, model physics and data assimilation, demonstrates closer agreement to the measured wind conditions than its predecessor ERA-Interim. It successfully reproduces the three identified wind regimes. However, the newest ERA5-Land product does not show improvements compared to ERA5, most likely because they share most of the parametrizations. Furthermore, the two dynamical downscalings of ERA5 analyzed here fail to capture the observed wind statistics and exhibit notable biases and discrepancies also when investigating the diurnal variations. Consequently, these high-resolution downscaling products do not show add value in reproducing the observed climatology of wind speed compared to ERA5 over the Tibetan Plateau.
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| 12. |
- Minola, Lorenzo, et al.
(författare)
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Homogenization and assessment of observed near-surface wind speed trends across Sweden, 1956-2013
- 2016
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Ingår i: Journal of Climate. - 0894-8755. ; 29:20, s. 7397-7415
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Tidskriftsartikel (refereegranskat)abstract
- © 2016 American Meteorological Society.Multidecadal variability of observed near-surface wind speed from 24 stations across Sweden has been analyzed for 1956-2013, with a focus on 1979-2008 (incorporating an additional 9 stations) for comparison with previous studies. Wind speed data have been subjected to a robust data processing protocol, consisting of quality control, reconstruction, and homogenization, by using geostrophic wind speed series as reference. The homogenized dataset displays a significant (at p < 0.05) downward trend for 1956-2013 (-0.06 m s-1 decade-1) and an even larger decreasing trend for 1979-2008 (-0.14 m s-1 decade-1). However, differences have been observed seasonally, with significant decreasing values in spring, summer, and autumn and a small downward trend in winter for 1956-2013. Most interestingly, a nonsignificant wind speed increase has been detected in winter for 1979-2008, which contrasts with the marked "stilling" reported for this season in much of midlatitude regions. The decreasing rate in wind speed is larger for coastal stations and in the southern part of Sweden. Decreasing trends were found at 91.7% of the stations during summer, whereas 58.3% of the stations displayed decreasing trends in winter. On the contrary, increasing trends occurred in 41.7% of the stations for winter and in only 8.3% for summer. The possible impact of the North Atlantic Oscillation (NAO) index has also been investigated, showing evidence that the small increasing trend in winter for 1979-2008 is hypothetically associated with the positive tendency of the NAO index during the last decades. These results reveal the influence of large-scale atmospheric circulation on wind speed variability across Sweden.
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| 13. |
- Minola, Lorenzo, et al.
(författare)
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Near-surface mean and gust wind speeds in ERA5 across Sweden: towards an improved gust parametrization
- 2020
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Ingår i: Climate Dynamics. - : Springer Science and Business Media LLC. - 0930-7575 .- 1432-0894. ; 55:3-4, s. 887-907
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Tidskriftsartikel (refereegranskat)abstract
- The ERA5 reanalysis product has been compared with hourly near-surface wind speed and gust observations across Sweden for 2013-2017. ERA5 shows closer agreement than the previous ERA-Interim reanalysis with regard to both mean wind speed and gust measurements, although significant discrepancies are still found for inland and mountainous regions. Therefore, attempts have been made to improve formulations of the gust parametrization used in ERA5 by adding an elevation-dependency and by adjusting the convective gust contribution. Major improvements, especially over mountain regions, are achieved when the elevation differences among the stations are considered. Closer agreement between the observed and parametrized gusts is reached when the convective gust contribution is also tuned. The newly designed gust parametrization was also tested for Norway, which is characterized by more complex topography. Wind gusts from the selected Norwegian stations are more realistically simulated when both the elevation-dependency and the tuned convective contribution are implemented, although the parametrized gusts are still negatively biased. Such biases are not explained by the different in gust duration in recorded wind gusts between Sweden and Norway.
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| 14. |
- Minola, Lorenzo, et al.
(författare)
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The contribution of large-scale atmospheric circulation to variations of observed near-surface wind speed across Sweden since 1926
- 2023
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Ingår i: Climatic Change. - 0165-0009. ; 176:5
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Tidskriftsartikel (refereegranskat)abstract
- This study investigates the centennial-scale (i.e., since 1926) variability of observed near-surface wind speed across Sweden. Results show that wind speed underwent various phases of change during 1926-2019, i.e., (a) a clear slowdown during 1926-1960; (b) a stabilization from 1960 to 1990; (c) another clear slowdown during 1990-2003; (d) a slight recovery/stabilization period for 2003-2014, which may continue with a possible new slowdown. Furthermore, the performance of three reanalysis products in representing past wind variations is evaluated. The observed low-frequency variability is properly simulated by the selected reanalyses and is linked to the variations of different large-scale atmospheric circulation patterns (e.g., the North Atlantic Oscillation). However, the evident periods of decreasing trend during 1926-1960 and 1990-2003, which drive most of the stilling in the last century, are missing in the reanalyses and cannot be realistically modeled through multiple linear regression by only using indexes of atmospheric circulation. Therefore, this study reveals that changes in large-scale atmospheric circulation mainly drive the low-frequency variability of observed near-surface wind speed, while other factors (e.g., changes in surface roughness) are crucial for explaining the periods of strong terrestrial stilling across Sweden.
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| 15. |
- Minola, Lorenzo, et al.
(författare)
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Wind stilling-reversal across Sweden: The impact of land-use and large-scale atmospheric circulation changes
- 2022
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Ingår i: International Journal of Climatology. - : Wiley. - 0899-8418 .- 1097-0088. ; 42:2, s. 1049-1071
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 16. |
- Pirooz, A. A. S., et al.
(författare)
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Effects of sensor response and moving average filter duration on maximum wind gust measurements
- 2020
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Ingår i: Journal of Wind Engineering and Industrial Aerodynamics. - : Elsevier BV. - 0167-6105. ; 206
-
Tidskriftsartikel (refereegranskat)abstract
- The use of wind speed data recorded using different measuring equipment (i.e. anemometers with different response characteristics) and different signal-processing procedures can introduce errors in the characterisation of surface wind speeds. This study aims to assess the effects of a set of various moving average filter durations and turbulence intensities on the recorded maximum gust wind speeds. For this purpose, a series of wind-tunnel experiments was carried out on the widely-used Vaisala WAA151 cup anemometer. The variations of gust and peak factors, and turbulence intensities measured by the cup anemometer as a function of the averaging duration and turbulence intensity are presented. The wind-tunnel results are compared with values computed from a theoretical approach, namely random process and linear system theory, and the results were also validated against values reported in the literature where possible. The results show that the maximum gust wind speeds measured using large averaging durations (e.g. 3 s or 5 s) lead to up to 25%-30% negative biases compared to high frequency measurements (e.g. 4 Hz unfiltered gust measurements). This result can strongly impact subsequent meteorological, climatological and wind engineering studies, as different gust definitions have been adopted by National Weather Services and institutions around the world. Lastly, a set of correction factors (i.e. gust factor ratios) have been proposed that allows measurements at a specific gust duration to be converted to equivalent measurements at specified particular gust durations of interest.
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| 17. |
- Re, A., et al.
(författare)
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Climate Scenarios for Coastal Flood Vulnerability Assessments: A Case Study for the Ligurian Coastal Region
- 2023
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Ingår i: Climate. - : MDPI AG. - 2225-1154. ; 11:3
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 18. |
- Shen, Cheng, et al.
(författare)
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Evaluation of global terrestrial near-surface wind speed simulated by CMIP6 models and their future projections
- 2022
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Ingår i: Annals of the New York Academy of Sciences. - : Wiley. - 0077-8923 .- 1749-6632. ; 1518:1, s. 249-63
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Tidskriftsartikel (refereegranskat)abstract
- We evaluate the performance of Coupled Model Intercomparison Project Phase 6 (CMIP6) models in simulating the observed global terrestrial near-surface wind speed (NSWS) and project its future changes under three different Shared Socioeconomic Pathways (SSPs). Results show that the CESM2 has the best ability in reproducing the observed NSWS trends, although all models examined are generally not doing well. Based on projections of CESM2, the global NSWS will decrease from 2021 to 2100 under all three SSPs. The projected NSWS declines significantly over the north of 20 degrees N, especially across North America, Europe, and the mid-to-high latitudes of Asia; meanwhile, it increases over the south of 20 degrees N. Under SSP585, there would be more light-windy days and fewer strong-windy days than those under SSP245, which leads to a significant global NSWS decline. Robust hemispheric-asymmetric changes in the NSWS could be due to the temperature gradient in the two hemispheres under global warming, with -1.2%, -3.5%, and -4.1% in the Northern Hemisphere, and 0.8%, 1.0%, and 1.5% in the Southern Hemisphere, for the near-term (2021-2040), mid-term (2041-2060), and long-term (2081-2100), respectively.
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| 19. |
- Shen, Cheng, et al.
(författare)
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March Near-Surface Wind Speed Hiatus Over China Since 2011
- 2023
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Ingår i: Geophysical Research Letters. - 0094-8276. ; 50:15
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Tidskriftsartikel (refereegranskat)abstract
- Previous research has extensively explored the "stilling" and "reversal" phenomena in annual near-surface wind speed (NSWS). However, the variations in the strengths of these phenomena between different months remain unclear. Here the monthly changes in observed NSWS from 769 stations across China during 1979-2020 were analyzed. The analysis reveals a consistent decline in NSWS that ceased around 2011, followed by an increasing trend detected in all months except March, where a distinct hiatus is observed. The hiatus in March NSWS is primarily attributed to a significant reduction in NSWS over North and Northwest China. This reduction can be linked to the southward shift of the East Asian subtropical jet (EASJ), which resulted in a decreased meridional temperature gradient and weakened transient eddy activities across northern China. These findings emphasize the importance of considering changes in the EASJ to gain a comprehensive understanding of NSWS changes at regional scale.
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| 20. |
- Zhang, Gangfeng, et al.
(författare)
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Uneven Warming Likely Contributed to Declining Near-Surface Wind Speeds in Northern China Between 1961 and 2016
- 2021
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Ingår i: Journal of Geophysical Research-Atmospheres. - : American Geophysical Union (AGU). - 2169-897X .- 2169-8996. ; 126:11
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Tidskriftsartikel (refereegranskat)abstract
- 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 < 0.05) decline trend of -0.103 m s(-1 )decade(-1), which stabilized from the 1990s onwards. Similar negative trends are observed for all seasons, with the strongest trends occurring in the central and eastern parts of northern China. Fast warming has occurred at high-latitudes (i.e., >50 degrees N) in recent decades, which has weakened the annual and seasonal meridional air temperature gradient (-0.33 degrees C to -0.12 degrees C dec(-1), p < 0.05, except autumn) between these regions (50 degrees-60 degrees N, 75 degrees-135 degrees E) and the northern China zone (35 degrees-45 degrees N, 75 degrees-135 degrees 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.
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| 21. |
- Zhang, Gangfeng, et al.
(författare)
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Variability of Daily Maximum Wind Speed across China, 1975–2016: An Examination of Likely Causes
- 2020
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Ingår i: Journal of Climate. - 0894-8755 .- 1520-0442. ; 33:7, s. 2793-2816
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Tidskriftsartikel (refereegranskat)abstract
- 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 < 0.05) declining trend of −0.038 m s−1 decade−1 for all China annually, with decreases in winter (−0.355 m s−1 decade−1, p < 0.05) and autumn (−0.108 m s−1 decade−1; p < 0.05) and increases in summer (+0.272 m s−1 decade−1, p < 0.05) along with a weak recovery in spring (+0.032 m s−1 decade−1; 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.
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| 22. |
- Zhou, Chunlue, et al.
(författare)
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HomogWS-se: a century-long homogenized dataset of near-surface wind speed observations since 1925 rescued in Sweden
- 2022
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Ingår i: Earth System Science Data. - : Copernicus GmbH. - 1866-3508 .- 1866-3516. ; 14:5, s. 2167-2177
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Tidskriftsartikel (refereegranskat)abstract
- Creating a century-long homogenized near-surface wind speed observation dataset is essential to improve our current knowledge about the uncertainty and causes of wind speed stilling and recovery. Here, we rescued paper-based records of wind speed measurements dating back to the 1920s at 13 stations in Sweden and established a four-step homogenization procedure to generate the first 10-member centennial homogenized wind speed dataset (HomogWS-se) for community use. Results show that about 38 % of the detected change points were confirmed by the known metadata events, and the average segment length split by the change points is similar to 11.3 years. Compared with the raw wind speed series, the homogenized series is more continuous and lacks significant non-climatic jumps. The homogenized series presents an initial wind speed stilling and subsequent recovery until the 1990s, whereas the raw series fluctuates with no clear trend before the 1970s. The homogenized series shows a 25 % reduction in the wind speed stilling during 1990-2005 than the raw series, and this reduction is significant when considering the homogenization uncertainty. The homogenized wind speed series exhibits a significantly stronger correlation with the North Atlantic oscillation index than that of the raw series (0.54 vs. 0.29). These results highlight the importance of the century-long homogenized series in increasing our ability to detect and attribute multidecadal variability and changes in wind speed. The proposed homogenization procedure enables other countries or regions to rescue their early climate data and jointly build global long-term high-quality datasets. HomogWS-se is publicly available from the Zenodo repository at (Zhou et al., 2022).
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