Browsing by Author "Alfaro, Fernando"

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    Climate and coastal low-cloud dynamic in the hyperarid Atacama fog Desert and the geographic distribution of Tillandsia landbeckii (Bromeliaceae) dune ecosystems
    (Springer, 2021) García B., Juan Luis; Lobos Roco, Felipe Andres; Schween, Jan H.; Río López, Camilo del; Osses, Pablo; Vives Ansted, Raimundo José; Pezoa Jadue, Mariana Ignacia; Siegmund, Alexander; Latorre H., Claudio; Alfaro, Fernando; Koch, Marcus A.; Loehnert, Ulrich
    Despite the extensive area covered by the coastal Atacama fog Desert (18-32 degrees S), there is a lack of understanding of its most notorious characteristics, including fog water potential, frequency of fog presence, spatial fog gradients or fog effect in ecosystems, such as Tillandsia fields. Here we discuss new meteorological data for the foggiest season (July-August-September, JAS) in 2018 and 2019. Our meteorological stations lie between 750 and 1211 m a. s. l. at two sites within the Cordillera de la Costa in the hyperarid Atacama (20 degrees S): Cerro Oyarbide and Alto Patache. The data show steep spatial gradients together with rapid changes in the low atmosphere linked to the advection of contrasting coastal (humid and cold) and continental (dry and warm) air masses. One main implication is that fog presence and fog water yields tend to be negatively related to both distance to the coast and elevation. Strong afternoon SW winds advect moisture inland, which take the form of fog in only about 6% of the JAS at 1211 m a. s. l., but 65% at 750 m a. s. l. on the coastal cliff. Although sporadic, long lasting fog events embrace well-mixed marine boundary layer conditions and thick fog cloud between 750 and 1211 m a. s. l. These fog events are thought to be the main source of water for the Tillandsia ecosystems and relate their geographic distribution to the lowest fog water yields recorded. Future climate trends may leave fog-dependent Tillandsia even less exposed to the already infrequent fog resulting in rapid vegetation decline.
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    Spatial distribution and interannual variability of coastal fog and low clouds cover in the hyperarid Atacama Desert and implications for past and present Tillandsia landbeckii ecosystems
    (SPRINGER WIEN, 2021) del Rio, Camilo; Lobos Roco, Felipe; Latorre, Claudio; Koch, Marcus A.; Garcia, Juan Luis; Osses, Pablo; Lambert, Fabrice; Alfaro, Fernando; Siegmund, Alexander
    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 similar to 20 degrees 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 similar to 50 and similar to 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.