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

Abstract. We investigate the influence of regional atmospheric circulation on the evaporation of a saline lake in the Altiplano region of the Atacama Desert. For that, we conducted a field experiment in the Salar del Huasco (SDH) basin (135 km 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 (~0.5 of net radiation), very low evaporation (LvE   15 m s−1) and a jump in evaporation to > 500 W m−2. While in the morning evaporation is limited by very low turbulence (u*~0.1 m s−1), in the afternoon strong winds (u*~0.65 m s−1) enhance the mechanical turbulence, increasing the 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 extend our understanding of evaporation drivers in arid regions and how large-scale processes affect directly local ones.