Mountain regions have been recognized to be more sensitive to climate and environmental changes, and in particular to global warming. Several studies report on elevation-dependent warming (EDW), i.e., when warming rates are different in different altitude ranges, particularly focusing on the enhancement of warming rates with elevation. The Andean chain proved to be a relevant climate change hot-spot with positive temperature trends and a widespread glacier retreat over the recent decades. To assess and to better understand elevation dependent warming in this mountain region and to identify its possible dependence on latitude, the Andean Cordillera was split into five domains, three pertaining to the tropical zone and two pertaining to the Subtropics. Further, for each area the eastern and western faces of the mountain range were separately analyzed. An ensemble of regional climate model (RCM) simulations participating in the Coordinated Regional Climate Downscaling Experiment (CORDEX), consisting of one RCM nested into eight different global climate models from the CMIP5 ensemble was considered in this study. EDW was assessed by calculating the temperature difference between the end of the century (2071–2100) and the period 1976–2005 and relating it to the elevation. Future projections refer to the RCP 8.5 high-emission scenario. Possible differences in EDW mechanisms were identified using correlation analyses between temperature changes and all the variables identified as possible EDW drivers. For the maximum temperatures, a positive EDW signal (i.e. enhancement of warming rates with elevation) was identified in each side of both the tropical and subtropical Andes and in all seasons. For the minimum temperatures, on the contrary, while a positive EDW was identified in the Subtropics (particularly evident in the western side of the chain), the Tropics are characterized by a negative EDW throughout the year. Therefore, the tropical boundary marks a transition between discordant EDW behaviours in the minimum temperature. In the Tropics and particularly in the inner Tropics, different EDW drivers were identified for the minimum temperature, whose changes are mostly associated with changes in downward longwave radiation, and for the maximum temperature, whose changes are mainly driven by changes in downward shortwave radiation. This might explain the opposite EDW signal found in the tropical Andes during daytime and nighttime. Changes in albedo are an ubiquitous driver for positive EDW in the Subtropics, for both the minimum and the maximum temperature. Changes in longwave radiation and humidity are also EDW drivers in the Subtropics but with different relevance throughout the seasons and during daytime and nighttime. Also, the western and eastern sides of the Cordillera might be influenced by different EDW drivers.

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Two models for footprint calculations are compared employing flux measurements in the planetary boundary layer. The calculationsare based on the analytical models by Kormann e Meixner (2001) [An analytical footprint model for non-neutral stratification.Boundary-Layer Meteorology 99, 207–224] and by Schuepp et al. (1990) [Footprint prediction of scalar fluxes from analytical solutions of the difussion equation. Boundary-Layer Meteorology 50, 355-373]. The footprint density functions of a flux sensor are determined using eddy-covariance data. Those functions are integrated over surfaces given by quadrangular rectangles, in this case an agricultural field. This work ilustrates the features of each footprint model employing flux measurements with an eddy-covariance system of the SULFLUX network, installed on a agricultural field. Finally, it is presented the model that describes in a better way the flux measurements in small fields.

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<p>Several studies report on elevation-dependent warming (EDW), i.e., when warming rates change with elevation. This study assesses future EDW in the Andes, using an ensemble of regional climate model simulations belonging to the CORDEX experiment. EDW was assessed by calculating the (minimum and maximum) temperature difference between the end of the century (2071-2100) and the period 1976-2005 and relating it to the elevation. For the maximum temperatures, a positive EDW (enhancement of warming rates with elevation) was identified in both the western and eastern side of the tropical and subtropical Andes and in all seasons. For the minimum temperature, while a positive EDW was identified in the Subtropics (particularly in the western side of the chain), the Tropics are characterized by a negative EDW throughout the year. The tropical boundary marks a transition between discordant EDW behaviours in the minimum temperature. In the Tropics, EDW drivers were found to be different for the minimum temperature (Tmin) and for the maximum temperature (Tmax). Changes in Tmin  are mostly associated with changes in downward longwave radiation, while changes in Tmax are mainly driven by changes in downward shortwave radiation. This might explain the opposite EDW signal found in the tropical Andes during daytime and nighttime. Changes in albedo are an ubiquitous driver for positive EDW in the Subtropics, for both the minimum and the maximum temperature. Changes in longwave radiation and humidity are also EDW drivers in the Subtropics but with different relevance throughout the seasons and during daytime and nighttime. Besides the dependence on the latitude, we found that the western and eastern sides of the Cordillera might be influenced by different EDW drivers.</p>