Abstract

Scarce but crucial for hydrological analysis and modelling, near-surface air temperatures (SAT) in mountainous regions are often assumed to match free-air temperature (FAT), despite inherent discrepancies. This study characterizes sub-tropical Andean SAT profiles and compares them with FAT using 3 years of 10 min resolution temperature data from a dense meteorological network located within an Andean Mountain catchment, alongside nearby aircraft operations and radiosonde ascents. Results reveal diurnal and seasonal cycles in the near-surface air temperature lapse rate (STLR) and surface-derived 0 degrees C isotherm altitude (H0(MS)), with marked contrasts between wet and dry conditions. Under wet conditions, FAT and SAT profiles converge, while under dry conditions, aircraft-FAT lapse rates are gentler than STLR, and the derived H0(MS) is lower than aircraft-FAT estimates during the cold season. Radiosonde-H0 simultaneously estimated aligns with H0(MS), but measurements before precipitation events differ by an average of similar to 20%.