Local evaporation controlled by regional atmospheric circulation in the Altiplano of the Atacama Desert

Roco, Felipe Lobos; Hartogensis, Oscar; Arellano, Jordi Vilà‐Guerau de; Fuente, Alberto de la; Muñoz, Ricardo C.; Rutllant, José A.; Suárez, Francisco

doi:10.5194/acp-21-9125-2021

Cited by 18 publications

(24 citation statements)

References 48 publications

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“…8b), this advection comes from the Pacific Ocean. A similar value, −2.36 K h −1 between 1500 and 1800 LT, was reported by Lobos-Roco et al (2021). They estimated advection as a residual term based on Eq.…”

Section: Advectionsupporting

confidence: 77%

“…It has an area of ≈ 1470 km 2 and an average elevation of ≈ 3800 m above sea level (a.s.l). The site is highly heterogeneous with a saline shallow lake at the end of the alluvial system, surrounded by a salt flat of ≈ 60 km 2 and wetlands from which water evaporates (Lobos-Roco et al 2021. However, as observed in Fig.…”

Section: Site Description and Observationsmentioning

confidence: 99%

“…The origin of the temperature decrease, ABL collapse and rise in H is a thermally driven atmospheric flow, caused by the thermal contrast between the Pacific Ocean and the desert land surface, which arrives to the region every afternoon (Muñoz et al 2018;Falvey and Garreaud 2005;Rutllant et al 2003). The advection of this air mass is accompanied by a large increase in the wind and the transport of cold and dry air from the coastal desert into the Altiplano (Lobos-Roco et al 2021;Garreaud et al 2003). These two factors lead to enhanced mechanical turbulence and a rise in the surface-atmosphere temperature gradient, which causes H to increase until its maximum value is reached at 1500 LT, 1.5 h delayed compared to solar noon (see Fig.…”

Section: Introductionmentioning

confidence: 99%

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Midday Boundary-Layer Collapse in the Altiplano Desert: The Combined Effect of Advection and Subsidence

Correa

Arellano

Ronda

et al. 2023

Boundary-Layer Meteorol

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Observations in the Altiplano region of the Atacama Desert show that the atmospheric boundary layer (ABL) suddenly collapses at noon. This rapid decrease occurs simultaneously to the entrance of a thermally driven, regional flow that causes a rise in wind speed and a marked temperature decrease. We identify the main drivers that cause the observed ABL collapse by using a land–atmosphere model. The free atmosphere lapse rate and regional forcings, such as advection of mass and cold air as well as subsidence, are first estimated by combining observations from a comprehensive field campaign and a regional model. Then, to disentangle the ABL collapse, we perform a suite of numerical experiments with increasing level of complexity: from only considering local land–atmosphere interactions, to systematically including the regional contributions of mass advection, cold air advection, and subsidence. Our results show that non-local processes related to the arrival of the regional flow are the main factors explaining the boundary-layer collapse. The advection of a shallower boundary layer ($$\approx -250$$ ≈ - 250 m h$$^{-1}$$ - 1 at noon) causes an immediate decrease in the ABL height (h) at midday. This occurs simultaneously with the arrival of a cold air mass, which reaches a strength of $$\approx -4$$ ≈ - 4 K h$$^{-1}$$ - 1 at 1400 LT. These two external forcings become dominant over entrainment and surface processes that warm the atmosphere and increase h. As a consequence, the ABL growth is capped during the afternoon. Finally, a wind divergence of $$\approx 8 \times 10^{-5}$$ ≈ 8 × 10 - 5 s$$^{-1}$$ - 1 contributes to the collapse by causing subsidence motions over the ABL from 1200 LT onward. Our findings show the relevance of treating large and small-scale processes as a continuum to be able to understand the ABL dynamics.

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Section: Advectionsupporting

confidence: 77%

Section: Site Description and Observationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Midday Boundary-Layer Collapse in the Altiplano Desert: The Combined Effect of Advection and Subsidence

Correa

Arellano

Ronda

et al. 2023

Boundary-Layer Meteorol

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“…These anomalies resulted from the different FLCs average between the selected hour and the five-observation daytimes. In September, we observe higher FLCs presence over the ocean and the first ~ 15 km onshore at night and early morning, when surface temperatures over the ocean do not significantly contrast with the ones at land, generating calm wind conditions (Lobos-Roco et al 2021). Within these conditions facilitating the air condensation and limiting the inland transport, the FLC deck stays steady above the ocean while it causes higher radiative cooling.…”

Section: Seasonal and Diurnal Flcs Presence Cyclesmentioning

confidence: 76%

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

et al. 2021

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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.

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“…The relative importance of wind speed is likely related to its role in turbulent mixing. For example, strong winds in the afternoon have recently been shown to enhance mechanical turbulence and increase evaporation over a lake in the Atacama Desert of Chile [31].…”

Section: Path Analysismentioning

confidence: 99%

Diagnosis of Atmospheric Drivers of High-Latitude Evapotranspiration Using Structural Equation Modeling

et al. 2021

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Evapotranspiration (ET) is a relevant component of the surface moisture budget and is associated with different drivers. The interrelated drivers cause variations at daily to interannual timescales. This study uses structural equation modeling to diagnose the drivers over an ensemble of 45 high-latitude sites, each of which provides at least several years of in situ measurements, including latent heat fluxes derived from eddy covariance flux towers. The sites are grouped by vegetation type (tundra, forest) and the presence or absence of permafrost to determine how the relative importance of different drivers depends on land surface characteristics. Factor analysis is used to quantify the common variance among the variables, while a path analysis procedure is used to assess the independent contributions of different variables. The variability of ET at forest sites generally shows a stronger dependence on relative humidity, while ET at tundra sites is more temperature-limited than moisture-limited. The path analysis shows that ET has a stronger direct correlation with solar radiation than with any other measured variable. Wind speed has the largest independent contribution to ET variability. The independent contribution of solar radiation is smaller because solar radiation also affects ET through various other drivers. The independent contribution of wind speed is especially apparent at forest wetland sites. For both tundra and forest vegetation, temperature loads higher on the first factor when permafrost is present, implying that ET will become less sensitive to temperature as permafrost thaws.

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Local evaporation controlled by regional atmospheric circulation in the Altiplano of the Atacama Desert

Cited by 18 publications

References 48 publications

Midday Boundary-Layer Collapse in the Altiplano Desert: The Combined Effect of Advection and Subsidence

Midday Boundary-Layer Collapse in the Altiplano Desert: The Combined Effect of Advection and Subsidence

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

Diagnosis of Atmospheric Drivers of High-Latitude Evapotranspiration Using Structural Equation Modeling

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