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

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

We investigate the influence of regional atmospheric circulation on the evaporation of a saline lake in the Altiplano (also known as the Andean Plateau) region of the Atacama Desert. For that, we conducted a field experiment in the Salar del Huasco (SDH) basin (135 inline-formulakm east of the Pacific Ocean), in November 2018. The measurements were based on surface energy balance (SEB) stations and airborne observations. Additionally, we simulate the meteorological conditions on a regional scale using the Weather Research and Forecasting Model. Our findings show two evaporation regimes: (1) a morning regime controlled by local conditions, in which SEB is dominated by the ground heat flux (inline-formula∼0.5 of net radiation), very low evaporation (inline-formulaLvE<30inline-formulaW m−2) and wind speed inline-formula<1inline-formulam s−1; and (2) an afternoon regime controlled by regional-scale forcing that leads to a sudden increase in wind speed (inline-formula>15inline-formulam s−1) and a jump in evaporation to inline-formula>500inline-formulaW m−2. While in the morning evaporation is limited by very low turbulence (inline-formula M11inlinescrollmathml u * normal 0.1 40pt11ptsvg-formulamathimg8e070312c3b1887bd0a2e14c5e273ff9 acp-21-9125-2021-ie00001.svg40pt11ptacp-21-9125-2021-ie00001.png inline-formulam s−1), in the afternoon strong winds (inline-formula M13inlinescrollmathml u * normal 0.65 46pt11ptsvg-formulamathimga4765698574557daa47492956badf195 acp-21-9125-2021-ie00002.svg46pt11ptacp-21-9125-2021-ie00002.png inline-formulam s−1) enhance mechanical turbulence, increasing evaporation. We find that the strong winds in addition to the locally available radiative energy are the principal drivers of evaporation. These winds are the result of a diurnal cyclic circulation between the Pacific Ocean and the Atacama Desert. Finally, we quantify the advection and entrainment of free-tropospheric air masses driven by boundary layer development. Our research contributes to untangling and linking local- and regional-scale processes driving evaporation across confined saline lakes in arid regions.

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Lobos-Roco, Felipe / Hartogensis, Oscar / Vilà-Guerau de Arellano, Jordi / et al: Local evaporation controlled by regional atmospheric circulation in the Altiplano of the Atacama Desert. 2021. Copernicus Publications.

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