Resumen:
The network of long-term meteorological observations in Southernmost Patagonia is
still sparse but crucial to improve our understanding of climatic variability, in particular
in the more elevated and partially glaciated Southernmost Andes. Here we present a
unique 17-year meteorological record (2000–2016) of four automatic weather stations
(AWS) across the Gran Campo Nevado Ice Cap (53◦S) in the Southernmost Andes
(Chile) and the conventional weather station Jorge Schythe of the Instituto de la
Patagonia in Punta Arenas for comparison. We revisit the relationship between in situ
observations and large-scale climate models as well as mesoscale weather patterns.
For this purpose, a 37-year record of ERA Interim Reanalysis data has been used to
compute a weather type classification based on a hierarchical correlation-based leader
algorithm. The orographic perturbation on the predominantly westerly airflow determines
the hydroclimatic response across the mountain range, leading to significant west-east
gradients of precipitation, air temperature and humidity. Annual precipitation sums heavily
drop within only tens of kilometers from ~7,500 mma−1 to less than 800 mma−1. The
occurrence of high precipitation events of up to 620 mm in 5 days and wet spells of up
to 61 consecutive days underscore the year-around wet conditions in the Southernmost
Andes. Given the strong link between large-scale circulation and orographically controlled
precipitation, the synoptic-scale weather conditions largely determine the precipitation
and temperature variability on all time scales. Major synoptic weather types with distinct
low-pressure cells in the Weddell Sea or Bellingshausen Sea, causing a prevailing
southwesterly, northwesterly or westerly airflow, determine the weather conditions in
Southernmost Patagonia during 68% of the year. At Gran Campo Nevado, more than
80% of extreme precipitation events occur during the persistence of these weather
types. The evolution of the El Niño Southern Oscillation and Antarctic Oscillation impose intra- and inter-annual precipitation and temperature variations. Positive Antarctic
Oscillation phases on average are linked to an intensified westerly airflow and warmer
conditions in Southernmost Patagonia. Circulation patterns with high-pressure influence
leading to colder and dryer conditions in Southernmost Patagonia are more frequent
during negative Antarctic Oscillation phases.