E-DATA: A Comprehensive Field Campaign to Investigate Evaporation Enhanced by Advection in the Hyper-Arid Altiplano

Abstract

In the endorheic basins of the Altiplano, water is crucial for sustaining unique ecological habitats. Here, the wetlands act as highly localized evaporative environments, and little is known about the processes that control evaporation. Understanding evaporation in the Altiplano is challenging because these environments are immersed in a complex topography surrounded by desert and are affected by atmospheric circulations at various spatial scales. Also, these environments may be subject to evaporation enhancement events as the result of dry air advection. To better characterize evaporation processes in the Altiplano, the novel Evaporation caused by Dry Air Transport over the Atacama Desert (E-DATA) field campaign was designed and tested at the Salar del Huasco, Chile. The E-DATA combines surface and airborne measurements to understand the evaporation dynamics over heterogeneous surfaces, with the main emphasis on the open water evaporation. The weather and research forecasting model was used for planning the instruments installation strategy to understand how large-scale air flow affects evaporation. Instrumentation deployed included: meteorological stations, eddy covariance systems, scintillometers, radiosondes and an unmanned aerial vehicle, and fiber-optic distributed temperature sensing. Additional water quality and CO2 fluxes measurements were carried out to identify the link between meteorological conditions and the biochemical dynamics of Salar del Huasco. Our first results show that, in the study site, evaporation is driven by processes occurring at multiple spatial and temporal scales and that, even in the case of available water and energy, evaporation is triggered by mechanical turbulence induced by wind.

Actual Evapotranspiration Estimates in Arid Cold Regions Using Machine Learning Algorithms with In Situ and Remote Sensing Data

“…This fact agrees with the findings of Granata [28], who proved that it is possible to generate accurate and precise estimates of daily ET a through machine learning algorithms only with mean temperature, net solar radiation, and relative humidity data, pointing out that the incorporation of wind speed does not improve the ET a estimations compared to the case when it is not accounted for. However, he analyzed ET a in a subtropical humid climate, where the number of sunshine hours is considered to be the more dominant variable as opposed to arid climates, where wind speed is an important variable [46]. Irmak et al [76] compared 11 ET a models in a crop field in Nebraska, USA, to study their complexity on hourly, daily, and seasonal scales.…”

“…The sampling frequency of the data was 30 min in all sites, which was then integrated into hourly, daily, and monthly timescales. The processing/correction methods of the eddy covariance data of all the sites are described in detail in [5,30,[46][47][48][49][50]. Briefly, the following data filtering methods were applied: (i) only high-quality infilled data were chosen; (ii) ET a data samples collected in rainy periods were removed; and (iii) daytime data were utilized to avoid stable boundary layer conditions.…”

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

“…Vertical profiles of θ , q, U and WD were obtained from the radiosonde to characterize and estimate the ABL height (h), using the surface pressure level of the SDH (∼ 650 hPa). This height was estimated through the maximum vertical gradient of θ (Sullivan et al, 1998). The UAV was flown simultaneously from the same two locations as the balloon launches (described in Sect.…”

Evaporation From Unsaturated Soils as a Function of the Air and Soil Sides of the Land Surface

“…In conclusion, despite the dimensionless number Π = k t ξ / D s and the expression of Equation presented in this article being representative of the links between processes that occur on both sides of the land surface, further analysis is needed to elucidate the actual values of the dimensional variables k t , δ , and D s , particularly under field conditions (Suárez et al, 2020).…”

“…Our motivation for developing the simple expression of Equation 7 for computing the evaporation from unsaturated soils is that it simplifies the dynamic link between large-scale meteorological processes and basin-scale groundwater transport in the closed basins of the Altiplano region in the Andes Mountains of South America (Costelloe et al, 2009;de la Fuente & Meruane, 2017;Johnson et al, 2010;Suárez et al, 2020). In particular, groundwater in these closed basins upwells toward the terminal wetlands (oases in the desert) where it is completely evaporated; however, the amount of water that directly evaporates from the shallow aquifer is uncertain, and understanding how these unique ecosystems would behave in response to changes in the precipitation and the evaporation is necessary.…”