Browsing by Author "Hartogensis, Oscar"

Now showing 1 - 4 of 4
  • Thumbnail Image
    Item
    Evaporation driven by Atmospheric Boundary Layer Processes over a Shallow Salt-Water Lagoon in the Altiplano
    (2024) Hartogensis, Oscar; Aguirre Correa, Francisca; Suárez Poch, Francisco Ignacio; Lobos Roco, Felipe Andrés; Ronda, Reinder; Vilà-Guerau de Arellano, Jordi
  • Thumbnail Image
    Item
    Midday Boundary-Layer Collapse in the Altiplano Desert: The Combined Effect of Advection and Subsidence
    (2023) Aguirre Correa, Francisca; De Arellano, Jordi Vila-Guerau; Ronda, Reinder; Lobos Roco, Felipe Andrés; Suárez Poch, Francisco Ignacio; Hartogensis, Oscar; CEDEUS (Chile)
    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 (approximate to -250 m h(-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 approximate to -4 Kh(-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 approximate to 8 x 10(-5) s(-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.
  • Thumbnail Image
    Item
    Multi-scale temporal analysis of evaporation on a saline lake in the Atacama Desert
    (2022) Lobos Roco, Felipe Andres; Hartogensis, Oscar; Suarez Poch, Francisco Ignacio; Huerta-Viso, Ariadna; Benedict, Imme; de la Fuente, Alberto; Vila-Guerau de Arellano, Jordi; CEDEUS (Chile)
    We investigate how evaporation changes depending on the scales in the Altiplano region of the Atacama Desert. More specifically, we focus on the temporal evolution from the climatological to the sub-diurnal scales on a high-altitude saline lake ecosystem. We analyze the evaporation trends over 70 years (1950–2020) at a high-spatial resolution. The method is based on the downscaling of 30 km ERA5 reanalysis data at hourly resolution to 0.1 km spatial resolution data, using artificial neural networks to analyze the main drivers of evaporation. To this end, we use the Penman open-water evaporation equation, modified to compensate for the energy balance non-closure and the ice cover formation on the lake during the night. Our estimation of the hourly climatology of evaporation shows a consistent agreement with eddy-covariance (EC) measurements and reveals that evaporation is controlled by different drivers depending on the time scale. At the sub-diurnal scale, mechanical turbulence is the primary driver of evaporation, and at this scale, it is not radiation-limited. At the seasonal scale, more than 70 % of the evaporation variability is explained by the radiative contribution term. At the same scale, and using a large-scale moisture tracking model, we identify the main sources of moisture to the Chilean Altiplano. In all cases, our regime of precipitation is controlled by large-scale weather patterns closely linked to climatological fluctuations. Moreover, seasonal evaporation significantly influences the saline lake surface spatial changes. From an interannual scale perspective, evaporation increased by 2.1 mm yr−1 during the entire study period, according to global temperature increases. Finally, we find that yearly evaporation depends on the El Niño–Southern Oscillation (ENSO), where warm and cool ENSO phases are associated with higher evaporation and precipitation rates, respectively. Our results show that warm ENSO phases increase evaporation rates by 15 %, whereas cold phases decrease it by 2 %.
  • Thumbnail Image
    Item
    Optical Microwave Scintillometer Evaporation Measurements over a Saline Lake in a Heterogeneous Setting in the Atacama Desert
    (2022) Lobos-Roco, Felipe; Hartogensis, Oscar; De Arellano, Jordi Vila-Guerau; Aguirre, Francisca; de la Fuente, Alberto; Suarez Poch, Francisco; CEDEUS (Chile)