Multi-year cloud and precipitation statistics observed with remote sensors at the high-altitude Environmental Research Station Schneefernerhaus in the German Alps

Kurzfassung

Clouds and precipitation over mountainous terrain are a challenge for models and observations alike. In this study, we exploit a unique, nearly one decade long dataset of collocated microwave radiometer, radar, ceilometer, and auxiliary observations collected at the Environmental Research Station Schneefernerhaus (UFS). Located at 2650 m a.s.l. just 300 m below the summit of Zugspitze, Germany's highest mountain, this dataset allows a combined view on water vapor, clouds, and precipitation. Annual and diurnal cycles of water vapor, cloud liquid water, cloud ice, rainfall, and snowfall rate are investigated. Strong diurnal cycles during summer in several observables indicate a strong coupling with the surface and convective transport of air from the surrounding valleys to the level of UFS resulting in maximum amounts in integrated water vapor (IWV), cloud liquid water path (LWP) and rain during the afternoon. In contrast, no diurnal cycle is found during winter, which points to the predominance of advection of cloud systems associated with large scale dynamics during winter. Daily precipitation estimates for snowfall and rainfall derived from a vertically pointing, low-cost micro rain radar (MRR) are found to be in good agreement with manual observations from the German Weather Service at the summit. Exploiting the synergy of MRR and microwave radiometer measurements revealed that almost 90 % of the snow clouds contained significant amounts of super-cooled LWP but only a weak correlation between snowfall rate and LWP is found. The still growing data set at this very particular location, also in combination with further observations, such as trace gases and aerosols, has a unique potential for many applications, e.g. to investigate cloud processes, evaluate high resolution models, and to validate satellite products.