| 1. |
- Minola, Lorenzo, et al.
(author)
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Homogenization and assessment of observed near-surface wind speed trends across Sweden, 1956-2013
- 2016
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In: Journal of Climate. - 0894-8755. ; 29:20, s. 7397-7415
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Journal article (peer-reviewed)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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| 2. |
- Vicente-Serrano, S. M., et al.
(author)
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Diverse relationships between forest growth and the Normalized Difference Vegetation Index at a global scale
- 2016
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In: Remote Sensing of Environment. - : Elsevier BV. - 0034-4257. ; 187, s. 14-29
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Journal article (peer-reviewed)abstract
- This study compared the densest available database of tree-ring growth with the longest Normalized Difference Vegetation Index (NDVI) information available at the global scale to quantify the relationship between annual forest growth and the NDVI across different forest types and regions and to characterize the patterns of response of forest growth to NDVI values at different temporal scales. We found a general positive relationship between the inter-annual NDVI variability and the annual tree growth in most of the analyzed forests. Nevertheless, there were strong differences in the tree growth responses to NDVI, given that the annual tree-ring records in each forest responded in a different way to the magnitude, seasonality and accumulation period of the NDVI values. Thus, we found eight main patterns of tree-ring response to the NDVI, which were related to the forest type and climate conditions of each corresponding site. The identified patterns may be useful for determining early-warning signals of changes in forest growth over large areas based on remote sensing information.
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