Rainfall and Rain‐on‐Snow Events Over Greenland in Summer: Climatology, Trends, Synoptics

Abstract
Rain‐on‐snow (ROS) events in the Arctic can lead to major impacts on the snow cover, cryosphere and environment. During the last decades, these events have significantly increased, mostly due to climate change. Here, we use outputs from the regional climate model MAR (version 3.14) driven by the ERA5 reanalysis at 10‐km resolution over Greenland, in the period 1940–2023. MAR is used to simulate the climatological properties of summertime ROS events over Greenland, and their long‐term changes over the period. The analyses also focused on the years after 1979, when reanalyses are more reliable. We found that both the spatial extension, the frequency, and rainfall amounts associated with ROS events all strongly increased, especially along the West and East coasts of Greenland. These changes either appeared, or strongly accelerated, during the last 40 yrs. We also analyzed the synoptic configurations conducive to major ROS events (the top 10% in terms of size and amounts). Poleward advection of moisture and heat generally prevails but shows non‐negligible variability in their location, direction and strength of associated centers of action. About 10%–20% of those major ROS events correspond to atmospheric rivers, events that occur 1%–2% of the time but increase the probability of rainfall over Greenland by a factor 10 to nearly 40 locally, with respect to the climatology.