Browsing by Author "Hartogensis, Oscar"
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- ItemEvaporation 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
- ItemEvaporation Driven by Atmospheric Boundary Layer Processes over a Shallow Saltwater Lagoon in the Altiplano(2024) Aguirre-Correa, Francisca; De Arellano, Jordi Vila-Guerau; Ronda, Reinder; Lobos-Roco, Felipe; Suarez, Francisco; Hartogensis, OscarObservations over a saltwater lagoon in the Altiplano show that evaporation E is triggered at noon, concurrent to the transition of a shallow, stable atmospheric boundary layer (ABL) into a deep mixed layer. We investigate the coupling between the ABL and E drivers using a land-atmosphere conceptual model, observations, and a regional model. Additionally, we analyze the ABL interaction with the aerodynamic and radiative components of evaporation using the Penman equation adapted to saltwater. Our results demonstrate that nonlocal processes are dominant in driving E. In the morning, the ABL is controlled by the local advection of warm air (similar to 5 K h(-1)), which results in a shallow (<350 m), stable ABL, with virtually no mixing and no E (<50 W m(-2)). The warm-air advection ultimately connects the ABL with the residual layer above, increasing the ABL height h by similar to 1 km. At midday, a thermally driven regional flow arrives to the lagoon, which first advects a deeper ABL from the surrounding desert (similar to 1500 m h(-1)) that leads to an extra similar to 700-m h increase. The regional flow also causes an increase in wind (similar to 12 m s(-1)) and an ABL collapse due to the entrance of cold air (similar to-2 K h(-1)) with a shallower ABL (similar to-350 m h(-1)). The turbulence produced by the wind decreases the aerodynamic resistance and mixes the water body releasing the energy previously stored in the lake. The ABL feedback on E through vapor pressure enables high evaporation values (similar to 450 W m(-2) at 1430 LT). These results contribute to the understanding of E of water bodies in semiarid conditions and emphasize the importance of understanding ABL processes when describing evaporation drivers.
- ItemEvaporation Driven by Atmospheric Boundary Layer Processes over a Shallow Saltwater Lagoon in the AltiplanoAguirre Correa, Francisca; Vilà-Guerau de Arellano, Jordi; Ronda, Reinder; Lobos Roco, Felipe; Suárez, Francisco; Hartogensis, OscarObservations over a saltwater lagoon in the Altiplano show that evaporation E is triggered at noon, concurrent to the transition of a shallow, stable atmospheric boundary layer (ABL) into a deep mixed layer. We investigate the coupling between the ABL and E drivers using a land–atmosphere conceptual model, observations, and a regional model. Additionally, we analyze the ABL interaction with the aerodynamic and radiative components of evaporation using the Penman equation adapted to saltwater. Our results demonstrate that nonlocal processes are dominant in driving E. In the morning, the ABL is controlled by the local advection of warm air (∼5 K h−1), which results in a shallow (<350 m), stable ABL, with virtually no mixing and no E (<50 W m−2). The warm-air advection ultimately connects the ABL with the residual layer above, increasing the ABL height h by ∼1 km. At midday, a thermally driven regional flow arrives to the lagoon, which first advects a deeper ABL from the surrounding desert (∼1500 m h−1) that leads to an extra ∼700-m h increase. The regional flow also causes an increase in wind (∼12 m s−1) and an ABL collapse due to the entrance of cold air (∼−2 K h−1) with a shallower ABL (∼−350 m h−1). The turbulence produced by the wind decreases the aerodynamic resistance and mixes the water body releasing the energy previously stored in the lake. The ABL feedback on E through vapor pressure enables high evaporation values (∼450 W m−2 at 1430 LT). These results contribute to the understanding of E of water bodies in semiarid conditions and emphasize the importance of understanding ABL processes when describing evaporation drivers.
- ItemMidday 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.
- ItemMulti-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 %.
- ItemOptical 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)
- ItemWater balance in the Chilean Altiplano: exploring the spatiotemporal scales of coupled atmospheric-hydrogeological processes(2025) Aguirre Correa, Francisca; Suárez Poch, Francisco Ignacio; Hartogensis, Oscar; Bollasina, Massimo; Pontificia Universidad Católica de Chile. Escuela de IngenieríaEsta investigación estudia los procesos multi-escala que gobiernan el balance hídrico en el Altiplano chileno, una región árida y de gran altitud compuesta por múltiples cuencas endorreicas. Mediante el uso de observaciones in situ, datos de teledetección y modelos numéricos, se analiza cómo la precipitación, la evaporación y el agua subterránea interactúan en escalas continental, regional y de cuenca. A gran escala, se muestra que ∼60% de la variabilidad intraestacional de la precipitación proviene de oscilaciones de alta frecuencia (<20 días) del Monzón de Sudamérica, desencadenadas por ondas de Rossby originadas en la Zona de Convergencia del Pacífico Sur. Estas oscilaciones provocan cambios abruptos entre fases monzónicas activas e inactivas, definiendo cuándo y dónde ocurre la precipitación. A escala regional, una circulación térmicamente impulsada genera un colapso de la capa límite atmosférica al mediodía sobre el desierto y transporta aire más frío y seco hacia humedales y lagunas adyacentes, creando peaks pronunciados de evaporación. Esta interacción pone de manifiesto cómo la dinámica de la capa límite regula la pérdida de agua a la atmósfera en un entorno heterogéneo. Por último, a nivel de cuenca, se observa que la recarga de agua subterránea ocurre en zonas de gran altitud donde la precipitación excede la evaporación. Por el contrario, el agua subterránea aflora en humedales, lagunas y zonas ribereñas de baja altitud que actúan como vías preferenciales para la evaporación, siendo los principales puntos de descarga del sistema endorreico. En conjunto, se demuestra que la precipitación establece el marco de la disponibilidad de agua, los procesos en la capa límite atmosférica rigen las tasas de evaporación y el agua subterránea media los flujos a escala de cuenca. Reconocer estos acoplamientos multiescala es esencial para estimar con precisión el balance hídrico y elaborar estrategias de gestión sostenible ante la variabilidad climática y la creciente demanda de recursos hídricos.