Atmospheric Chemistry and Physics | 2021
Local evaporation controlled by regional atmospheric circulation in the Altiplano of the Atacama Desert
Abstract
Abstract. We investigate the influence of regional atmospheric circulation on the\nevaporation 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\n(SDH) basin (135\u2009 km east of the Pacific Ocean), in November 2018. The\nmeasurements were based on surface energy balance (SEB) stations and airborne\nobservations. Additionally, we simulate the meteorological conditions on a\nregional scale using the Weather Research and Forecasting Model. Our findings\nshow two evaporation regimes: (1) a morning regime controlled by local\nconditions, in which SEB is dominated by the ground heat flux ( ∼0.5 of\nnet radiation), very low evaporation ( LvE W\u2009m−2 ) and wind speed m\u2009s−1 ; and (2) an afternoon regime controlled by\nregional-scale forcing that leads to a sudden increase in wind speed ( >15 m\u2009s−1 ) and a jump in evaporation to >500 W\u2009m−2 . While in the morning evaporation is limited by very\nlow turbulence ( u * ∼ 0.1 m\u2009s−1 ), in the afternoon strong\nwinds ( u * ∼ 0.65 m\u2009s−1 ) enhance mechanical turbulence,\nincreasing evaporation. We find that the strong winds in addition to the\nlocally available radiative energy are the principal drivers of\nevaporation. These winds are the result of a diurnal cyclic circulation\nbetween the Pacific Ocean and the Atacama Desert. Finally, we quantify the\nadvection and entrainment of free-tropospheric air masses driven by\nboundary layer development. Our research contributes to untangling and linking\nlocal- and regional-scale processes driving evaporation across confined saline\nlakes in arid regions.