Paraglider flight logs as hypsometers: daily temperature profiles of an Alpine valley, its diurnal heating, and the nearly level ceiling of thermals

Jörg Korner 

A paraglider flight recorder stores both pressure and GNSS altitude: together they turn routine flight logs into hypsometric measurements of layer-mean virtual temperature. From 86 369 IGC logs of the Valais, Swiss Alps, quality screening retains 13 520 dedicated-instrument flights on 437 days in 2011–2026; 392 days provide at least one profile layer supported by ten flights. At midday, between about 2200 and 3600 m, the profiles differ from the Payerne radiosonde, 100 km away, by a median of +0.67 K with a scaled median absolute deviation of 1.47 K (1545 layer comparisons on 370 days). Between morning (07–10 UTC) and afternoon (14–18 UTC), temperatures increase by 3.6 K near 2200 m (95 % interval 3.0–4.1 K) and 1.7 K near 3020 m (1.3–2.2 K). Hourly estimates resolve the daytime increase, and pointwise removal of fixes within 300 m of terrain preserves it. On matched observing days, median changes in the humidity contribution at Payerne are only a few tenths of a kelvin, supporting a predominantly thermal interpretation of the multi-kelvin valley signal. The upper envelope of 53 320 observed climbs follows terrain by factors of only 0.2–0.3 at scales of 2.5–10 km. A hydrostatic thought experiment explains how flight geometry can suppress a local warm-slope signal and motivates a comparison of slope-following and slope-leaving climbs. Routine flight archives thus provide a repeatable, vertically resolved record of daytime valley warming without additional airborne sensors.