B128-06
Divergence in eco-hydrological responses to 2015-2016 El Nino-induced drought over tropical South America

Thursday, 17 December 2020: 05:50
Virtual
Yelin Jiang, University of Connecticut, Department of Civil and Environmental Engineering, Groton, CT, United States, Guiling Wang, University of Connecticut, Civil and Environmental Engineering & Center for Environmental Sciences and Engineering, Groton, CT, United States, Qing Peng, NUIST Nanjing University of Information Science and Technology, Nanjing, China, Meijian Yang, University of Connecticut, Civil and Environmental Engineering, Groton, CT, United States and Weiguang Liu, Nanjing University of Information Science and Technology, Nanjing, China
Recorded Presentation
Abstract:
Extreme drought and heat associated with the 2015-2016 El Nino event have impacted water, energy, and carbon cycles over tropical South America. It remains unclear how vegetation in different subregions responded to the unprecedented drought event and what mechanisms may have driven the ecological and climatic variables to return to normal conditions. Here, we examine the recovery of the regional eco-hydrological system through analyzing precipitation and drought index data (GPCC), satellite-based terrestrial water storage (GRACE), land surface model and data assimilation products of soil moisture (GLDAS) and evapotranspiration (GLEAM), and three different vegetation indices (MODIS-GPP, MODIS-LAI, and GOME2-SIF). In addition, GHCN temperature, FLASHFlux solar insolation, as well as GPCC precipitation were used to evaluate the limitations on vegetations in different parts of tropical South America and understand the eco-hydrological processes during the drought development and recovery stages. Our results indicated that soil moisture and terrestrial water storage in the Amazon region returned to normal hydrological conditions at the beginning of 2017, but Nordeste region did not recover till 2018. During the severe drought, GPP and LAI increased in Amazon and decreased in Nordeste, suggesting that vegetation was energy limited in the wet region and water limited in the dry region. However, the SIF response diverged from the responses of GPP and LAI, especially in northern Amazon. This disparity indicates a high degree of uncertainty in the productivity response to drought, and casts doubt on the reliability of some of the satellite data. The seeming decoupling between LAI and SIF during the drought suggests that forest photosynthesis could still be suppressed despite the recovery of canopy greenness. In Nordeste where water is clearly a limiting factor for vegetation growth, all three vegetation indices showed that vegetation didn’t recover from the drought until the middle of 2017, indicating that woodlands and shrublands are more vulnerable to drought than forest ecosystems.
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