| 1. |
- Dunn, Robert J.H., et al.
(författare)
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Reduction in reversal of global stilling arising from correction to encoding of calm periods
- 2022
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Ingår i: Environmental Research Communications. - : IOP Publishing. - 2515-7620. ; 4:6
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Tidskriftsartikel (refereegranskat)abstract
- We describe an undocumented change in how calm periods in near-surface wind speed (and direction) observations have been encoded in a subset of global datasets of sub-daily data after 2013. This has resulted in the under-estimation of the number of calm periods for meteorological stations across much of Asia and Europe. Hence average wind speeds after 2013 have been over-estimated, affecting the assessment of changes in global stilling and reversal phenomena after this date. By addressing this encoding change we show that globally, since 2010, wind speeds have recovered by around 30% less than previously thought.
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| 2. |
- Fang, Keyan, et al.
(författare)
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The potential to use variations in tree-ring geometric center to estimate past wind speed change
- 2022
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Ingår i: Natural Hazards Research. - : Elsevier BV. - 2666-5921. ; 2:2, s. 132-137
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Tidskriftsartikel (refereegranskat)abstract
- Tree radial growth is characterized by not only the annual ring-width increment but also shifts in the tree-ring geometric center (TRGC) if subjected to asymmetric external forcing, such as gravity downslope or prevailing winds. Previous dendrochronological studies have used the asymmetric growth derived from tree-ring widths to reconstruct wind speed changes. Here we propose a novel method that uses quantitative TRGC measurements to estimate wind speed. We investigated TRGC shifts in northeast China, where the prevailing westerly winds are strong and persistent. We found that the TRGC showed significant correlations (r = 0.64, p < 0.01) with wind speed in May–September. The higher tree geometry sensitivity to wind speed obtained with the new method compared to previous ones, suggests the possibility of reconstructing historical wind change and variability in prevailing winds using TRGC. In addition, by correcting tree-ring radius according to their TRGC shifts, the basal area increment (BAI) was calculated. Our new BAI estimation provided stronger correlations with climate than both the standard tree-ring width chronology and a traditional BAI estimation. We suggest that future dendrochronological studies should consider TRGC shifts to increase the accuracy in climate reconstructions.
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| 3. |
- Kaiqiang, Deng, et al.
(författare)
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Changes of Southern Hemisphere westerlies in the future warming climate
- 2022
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Ingår i: Atmospheric Research. - : Elsevier BV. - 0169-8095. ; 270
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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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| 4. |
- Kaiqiang, Deng, et al.
(författare)
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Shifting of summertime weather extremes in Western Europe during the last decade
- 2022
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Ingår i: Advances in Climate Change Research. - : Elsevier BV. - 1674-9278. ; 13:2, s. 218-227
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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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| 5. |
- 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
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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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| 6. |
- 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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| 7. |
- Shen, C., et al.
(författare)
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Does CRA-40 outperform other reanalysis products in evaluating near-surface wind speed changes over China?
- 2022
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Ingår i: Atmospheric Research. - : Elsevier BV. - 0169-8095. ; 266
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Tidskriftsartikel (refereegranskat)abstract
- Global reanalysis products have become essential tools employed towards the understanding of past climates, which are extensively employed by the wind energy industry to assess and develop wind resources. In this study, the terrestrial near-surface wind speed (NSWS) in the 40 year global reanalysis dataset released by China Meteorological Administration (CRA-40) was employed and compared with four state-of-the-art global reanalysis products, namely the European Centre for Medium-Range Weather Forecasts reanalysis version 5 (ERA5), National Centers for Environmental Prediction/National Center for Atmospheric Research reanalysis (NCEP1), National Centers for Environmental Prediction-Department of Energy reanalysis (NCEP2), and the Japanese 55 year reanalysis (JRA55). Large discrepancies were revealed among the reanalysis products in NSWSs across China. CRA-40 captures the climatology, seasonal, interannual, and monthly changes, as well as the terrestrial stilling compared with the recent observed increase. In contrast, NCEP1 and NCEP2 fail to reproduce the climatology and monthly changes in the observed NSWSs. Although JRA55 captures the terrestrial stilling in observations, it underestimates the mean value of NSWS. Therefore, CRA-40 provides the best agreement with stronger and more significant correlations against the observations when compared to other reanalysis products, and reproduces the observed multi-decadal variability. Thus, CRA-40 is the optimal choice to investigate NSWS with high spatial and temporal resolution across China, with a wide array of socioeconomic and environmental impacts. © 2021 The Author(s)
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| 8. |
- Zha, Jin Lin, et al.
(författare)
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Effects of Northern Hemisphere Annular Mode on terrestrial near-surface wind speed over eastern China from 1979 to 2017
- 2022
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Ingår i: Advances in Climate Change Research. - : Elsevier BV. - 1674-9278 .- 2524-1761. ; 13:6, s. 875-83
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Tidskriftsartikel (refereegranskat)abstract
- Large-scale ocean‒atmosphere circulations (LOACs) have a pronounced effect on the near-surface wind speed (NSWS). In this study, we discussed the contributions of zonal and meridional flows to NSWS changes and identify the possible association between the Northern Hemisphere Annular Mode (NAM) and the NSWS changes over eastern China from 1979 to 2017. Results show that the reduction in NSWS over eastern China was mainly dominated by the weakening of the zonal wind component. NAM has a considerable effect on the NSWS over eastern China. When the NAM exhibits positive phases, the zonal-mean westerly weakens at low-to-mid-latitudes (10°–40°N). Meanwhile, descending flows prevail near 40°N, and ascending flows persist near 65°N in the troposphere. In the lower troposphere, there are northerly anomalies at low-to-mid-latitudes and southerly anomalies at mid-to-high latitudes (40°–70°N). The anomalous meridional flows transport heat from low to high latitudes and weaken the north‒south air temperature gradient. The decreased air temperature gradient over East Asia reduces the pressure gradient near the surface, decreasing NSWS in eastern China. NAM variations could dominate (32.0 ± 15.8)% of the changes in the annual mean NSWS. Nevertheless, the contribution of NAM to the interannual changes of the zonal component in NSWS could reach (45.0 ± 12.9)%.
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| 9. |
- Zheng, C. W., et al.
(författare)
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Global trends in oceanic wind speed, wind-sea, swell, and mixed wave heights
- 2022
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Ingår i: Applied Energy. - : Elsevier BV. - 0306-2619. ; 321
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Tidskriftsartikel (refereegranskat)abstract
- The climatic trends of Wind Speed (WS) and wave height play a key role in wind and wave energy assessments, climate change analyses, and air-sea interactions, among many others. Using ERA5 reanalysis, this study reveals the climatic trends of global oceanic WS and wave height for 1979-2018, including the overall trends, regional and seasonal differences of the trends, with a special focus on the differences and similarities between the trends in wind-sea wave height (Hwind) and swell wave height (Hswell), as well as the contributions of climate indices to WS, Hwind, Hswell and Significant Wave Height (Hs) respectively, by employing linear regression and correlation analysis. The results show an overall global oceanic increase for 1979-2018 in WS (+0.47 cm/s/yr), with increases of +0.13, +0.28 and +0.32 cm/yr in Hwind, Hswell and Hs respectively, and a stronger increasing trend in the Southern Hemisphere than in the Northern Hemisphere. There is good agreement between the spatial distribution of annual and seasonal trends in WS and those of Hwind, as well as between Hswell and Hs. Areas with strong increasing trends of WS and Hwind are mainly located in the tropical South Indian Ocean and tropical Pacific Ocean. Hswell and Hs exhibit significant increases in most global oceans. The months with the broadest and strongest increase in Hswell and Hs are June-July-August (JJA). There is a close relationship among the WS, wave height climatology and the modes of climate variability. The wind has the strongest response to climate indices, followed by the wind-sea, with swell having a minimal response.
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| 10. |
- Zhou, F. F., et al.
(författare)
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Teleconnections between large-scale oceanic-atmospheric patterns an interannual surface wind speed variability across China: Regional and seasonal patterns
- 2022
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Ingår i: Science of the Total Environment. - : Elsevier BV. - 0048-9697. ; 838
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Tidskriftsartikel (refereegranskat)abstract
- Great attention has been paid to the long-term decline in terrestrial near-surface wind speed (SWS) in China. However, how the SWS varies with regions and seasons and what modulates these changes remain unclear. Based on quality-controlled and homogenized terrestrial SWS data from 596 stations, the covarying SWS patterns during the Asian Summer Monsoon (ASM) and the Asian Winter Monsoon (AWM) seasons are defined for China using empirical orthogonal function (EOF) analysis for 1961-2016. The dominant SWS features represented by EOF1 patterns in both seasons show a clear decline over most regions of China. The interannual variability of the EOF1 patterns is closely related to the Northeast Asia Low Pressure (NFAIP) and the Arctic Oscillation (AO), respectively. The EOF2 and EOF3 patterns during ASM (AWM) season describe a dipole mode of SWS between Fast Tibetan Plateau and Fast China Plain (between Fast Tibetan Plateau and Northeast China), and between Southeast and Northeast China (between Northeast China and the coastal areas of Southeast China), respectively. These dipole structures of SWS changes arc closely linked with the oceanic-atmospheric oscillations on interannual scale.
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