Abstract
The hyperarid Atacama Desert coast receives scarce moisture inputs mainly from the Pacific Ocean in the form of marine advective fog. The collected moisture supports highly specialized ecosystems, where the bromeliad Tillandsia landbeckii is the dominant species. The fog and low clouds (FLCs) on which these ecosystems depend are affected in their interannual variability and spatial distribution by global phenomena, such as ENSO. Yet, there is a lack of understanding of how ENSO influences recent FLCs spatial changes and their interconnections and how these variations can affect existing Tillandsia stands. In this study, we analyze FLCs occurrence, its trends and the influence of ENSO on the interannual variations of FLCs presence by processing GOES satellite images (1995–2017). Our results show that ENSO exerts a significant influence over FLCs interannual variability in the Atacama at ~ 20°S. Linear regression analyses reveal a relation between ENSO3.4 anomalies and FLCs with opposite seasonal effects depending on the ENSO phase. During summer (winter), the ENSO warm phase is associated with an increase (decrease) of the FLCs occurrence, whereas the opposite occurs during ENSO cool phases. In addition, the ONI Index explains up to ~ 50 and ~ 60% variance of the interannual FLCs presence in the T. landbeckii site during summer and winter, respectively. Finally, weak negative (positive) trends of FLCs presence are observed above (below) 1000 m a. s. l. These results have direct implications for understanding the present and past distribution of Tillandsia ecosystems under the extreme conditions characterizing our study area.
Highlights
The Atacama Desert, located along the western margin of the Andes Cordillera from southern Perú to northern Chile, is one of the oldest and driest places on Earth (Hartley et al 2005; Clarke 2006)
What is the role played by El Niño Southern Oscillation (ENSO) concerning fog and low clouds (FLCs) presence and the vertical variations of the inversion layer? What is the spatial expression of these interannual variations? How do these variations impact fog-water input to Tillandsia ecosystems? To answer these research questions, we (1) characterize and analyze the spatiotemporal distribution of FLCs over recent decades (1995–2017) to detect significant trends and variations; (2) we assess the relationship between interannual variabilities of FLCs and ENSO anomalies; and (3) we describe the relation between recent FLCs spatial changes and the current distribution of Tillandsia landbeckii
We discuss our results regarding the influence of ENSO on FLCs interannual variations
Summary
The Atacama Desert, located along the western margin of the Andes Cordillera from southern Perú to northern Chile, is one of the oldest and driest places on Earth (Hartley et al 2005; Clarke 2006). The large-scale subsidence of warm and dry air masses typical of subtropical regions determines the formation of the Southeast Pacific Anticyclone (SEPA) This phenomenon triggers the formation of a strong thermal inversion layer (TIL) and promotes the presence of a spatial-spread low-clouds deck within the marine boundary layer (MBL) (Serpetzoglou et al 2008; Garreaud et al 2011; Wood et al 2011). An intensification of La Niña years has occurred over the last decades (during the current negative IPO phase) (Meehl et al 2021; Sohn et al 2013) This phenomenon has resulted in cooler sea-surface and air temperatures within the MBL and the intensification of the SEPA (Schulz et al 2011a; Muñoz et al 2016). What is the role played by ENSO concerning FLCs presence and the vertical variations of the inversion layer? What is the spatial expression of these interannual variations? How do these variations impact fog-water input to Tillandsia ecosystems? To answer these research questions, we (1) characterize and analyze the spatiotemporal distribution of FLCs over recent decades (1995–2017) to detect significant trends and variations; (2) we assess the relationship between interannual variabilities of FLCs and ENSO anomalies; and (3) we describe the relation between recent FLCs spatial changes and the current distribution of Tillandsia landbeckii
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