Observation of an Extremely Dry Atmospheric Air Column above Bern

The water vapour column density or vertically integrated (IWV) ranges from about 8 mm in winter to 25 summer Bern, Switzerland. However, there can be day episodes when IWV drops 2 even less so that the atmosphere is extremely dry. We selected an event February 2021 tropospheric radiometer TROWARA measured a mean value of 1.5 ± 0.2 for time interval one Bern. ECMWF reanalysis ERA5 indicated slightly higher 2.2 0.4 where uncertainty standard deviation during depression. profiles relative humidity and specific this episode are reduced by 50% more compared monthly profiles. On global map, it seen Bern within mesoscale dry region on with descending wind. Back trajectory analysis gives result air masses came North trajectories altitude mid troposphere into lower troposphere. These explain minimum observed 13–14 2021. surface climate Switzerland was dominated cold wave at time. At same time, severe waves occurred Greece Northern America.