Land Surface Temperature — Accumulation Season
Seasonal mean LST maps for the accumulation period reveal a progressive warming trend across all elevation zones. Maximum accumulation-season LST increased from approximately 6.11°C in 2018 to 7.57°C in 2025. Zone I mean LST increased from −2.09°C in 2018 to approximately +0.39°C in 2025, representing a warming of ~2.5°C and crossing the freezing threshold. Zone II exhibited a mean LST increase from −3.82°C to −1.30°C; Zone III from −6.62°C to −4.26°C; and Zone IV from −10.07°C to −7.89°C. A temporary reduction in peak LST was recorded in 2021 (~3.47°C), coinciding with a slight recovery in snow extent.
Land Surface Temperature — Depletion Season
Depletion-season LST maps confirm a consistent warming pattern. Maximum LST values exceeded 21°C in all years, reaching above 22°C by 2024–2025. In Zone I, minimum temperatures stabilized above 0°C during the depletion window in the latter half of the study period (2022–2025), substantially reducing the nighttime refreezing capacity of the snowpack. At the highest elevations (Zone IV), a subtle but consistent upward shift in mean temperatures (approximately 2–3°C over 2018–2025) suggests that even the highest portions of the park are not immune to the regional warming trend.
Temperature and Precipitation
The SPARTACUS temperature record demonstrates a strong seasonal cycle characteristic of high-altitude alpine environments, with mean annual temperatures close to 0°C. Winter months (December–February) are consistently sub-zero, establishing the thermal prerequisite for sustained snowpack accumulation. Precipitation exhibits a bimodal seasonal distribution, with a primary maximum during summer months associated with convective activity, and a secondary maximum in autumn linked to frontal systems. The correlation between seasonal temperature and precipitation was weak and positive (r ≈ 0.2–0.35), indicating that precipitation phase rather than total amount is the critical determinant of snowpack development.
Temperature vs. Dry Snow Area by Elevation Class
The negative relationship between temperature and dry snow cover exhibits considerable variability across elevation zones. In the lowest elevation band (<1500 m), the scatterplot shows substantial dispersion and a negligible R², reflecting the episodic nature of dry snow occurrence at lower elevations. The 1500–2000 m band shows a slightly stronger negative signal, consistent with this range straddling the climatological rain–snow transition zone. In the 2000–3000 m and >3000 m bands, the dry snow signal remains small in absolute area and shows little systematic temperature dependence, reinforcing that these high-altitude zones maintain cold enough conditions throughout the accumulation season that mean temperature variability does not meaningfully perturb dry snow extent.
Temperature vs. Wet Snow Area by Elevation Class
In the <1500 m and 1500–2000 m elevation bands, wet snow area shows moderate negative correlations with temperature, indicating that warmer conditions at lower elevations enhance snowmelt processes and increase the likelihood of rain-on-snow events. In contrast, the 2000–3000 m band — which dominates the total wet snow signal with values between approximately 1,150 and 1,270 km² — shows a relatively flat regression with high scatter, suggesting insensitivity to mean temperature variability within the observed range. The >3000 m band similarly shows minimal temperature sensitivity. These results suggest that a warming threshold exists somewhere in the 1500–2000 m range at which point temperature begins to meaningfully erode wet snow area.
Precipitation vs. Dry Snow Area by Elevation Class
The elevation-dependent scatterplots demonstrate that the weak basin-scale negative correlation between precipitation and dry snow cover is not uniform across altitudinal zones. In the <1500 m band, data points are widely scattered with no evident trend. The 1500–2000 m band shows a slightly more negative slope. The 2000–3000 m and >3000 m bands exhibit near-flat regression lines with very low R² values, confirming that precipitation amount has little impact on whether snow is classified as dry at these altitudes — the consistently cold temperatures ensure all precipitation falls as snow and maintains dry snow characteristics regardless of precipitation intensity.
Precipitation vs. Wet Snow Area by Elevation Class
The strong positive precipitation–wet snow relationship identified at the basin scale is most clearly expressed in the 2000–3000 m elevation band, which shows the strongest positive correlation and the tightest clustering of data points among all four panels. This confirms that the dominant wet snow reservoir in HTNP — residing in the broad 2000–3000 m zone — is primarily precipitation-driven, with higher snowfall inputs directly expanding the areal extent of wet snow. Precipitation is thus the master variable controlling wet snow distribution in Hohe Tauern, with profound implications for alpine water storage: maintaining adequate winter precipitation is critical to sustaining the wet snowpack that drives spring and early summer streamflow.