A new study pinpoints the seasonal and interannual variability of windthrows.
Windthrows (gaps of uprooted or broken trees) are a recurrent disturbance in Amazonia that affects the persistence of woody biomass, which, in turn, affects patterns of productivity and biomass, floristic composition, and soil composition in the basin. Windthrows are produced by severe convective events that are expected to become more frequent with climate change. Yet the variability of windthrows over time has not been investigated. Studying the frequency of their occurrence is key to understanding the atmospheric conditions that produce these events.
The study’s findings show that windthrows occurred every year and were more frequent from September through February. One driver of windthrows are southerly squall lines (that form in southern Amazonia and move to northeast Amazonia). These squall lines were found to be more frequent than their previously reported ~50-year interval. These results will improve representations of tree mortality in Earth system models and, in particular, the Accelerated Climate Modeling for Energy (ACME) Land Model (ALM).
Windthrows are a recurrent disturbance in Amazonia and are an important driver of forest dynamics and carbon storage. In this study, researchers present, for the first time, the seasonal and interannual variability of windthrows, focusing on central Amazonia, and discuss the potential meteorological factors associated with this variability. Landsat images from 1998 through 2010 were used to detect the occurrence of windthrows, which were identified based on their spectral characteristics and shape. They were found to occur every year, but were more frequent between September and February. Organized convective activity associated with multicell storms embedded in mesoscale convective systems—such as northerly squall lines (that move from northeast to southwest), and southerly squall lines (that move from southwest to northeast)—can cause windthrows. The researchers also found that southerly squall lines occurred more frequently than their previously reported ~50-year interval. At the interannual scale, the study did not find an association between El Niño-Southern Oscillation and windthrows.
Contacts (BER PM)
Renu Joseph and Dan Stover
Renu.Joseph@science.doe.gov (301-903-9237), and Daniel.Stover@science.doe.gov (301-903-0289)
William J. Riley
Lawrence Berkeley National Laboratory
This research was funded by the U.S. Department of Energy, Office of Science, Office of Biological and Environmental Research under contract DE-AC02-05CH11231 as part of the Next-Generation Ecosystem Experiments-Tropics project and Regional and Global Climate Modeling program.
R. I. Negron-Juarez, H. S. Jenkins, C. F. M. Raupp, W. J. Riley, L. M. Kueppers, D. Magnabosco Marra, G. H. P. Ribeiro, M. T. Monterio, L. A. Candido, J. Q. Chambers, and N. Higuch, “Windthrow Variability in Central Amazonia.” Atmosphere 8(2), 28 (2017). DOI:10.3390/atmos8020028. (Reference link)
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