This winter there has been less snow in the mountains than we are us to. This is due to persistent high pressure weather. Last summer, Switzerland was very dry with lots of nice weather, great heat and therefore high evaporation.
Nationwide, there has been less rainfall over the past twelve months than the 1991-2020 norm over the same period. In some regions, a quarter or even half of the average rainfall over the months March-February is missing.
A map showing the deviation of precipitation from the norm in percent. It shows in shades of brown that there was less precipitation throughout Switzerland in the last twelve months than the norm.
Ratio of precipitation for the period from March 1, 2022 to February 22, 2023 to the 1991-2020 norm for the corresponding period (in percent). (MeteoSwiss)
save water
The region most affect by the lack of precipitation is in the Alps, which stretches from Upper Valais through Ticino, northern and central Graubünden to the southern valleys of Graubünden. In view of the current situation, as far as we know, the first municipalities in the Alps are again calling for water conservation, after this was already necessary in many places last summer.
Large rainfall deficit
Some measuring stations show a notable rainfall deficit. In Mosogno, for example, only 1023 mm fell in the last twelve months, which is about half of the normal rainfall for this period (2060 mm). A similar picture can be seen at stations in the Leventina. In Binn in Upper Valais, 494 mm fell (normal: 1177 mm). Upper Engadine and Bergell receiv only slightly more rainfall. There, around 60-80% of the rainfall for the period 1991-2020 was measur over twelve months.
There have been occasional instances of such little rainfall over twelve months in the past. This is especially true if you look beyond the March-February period and look at any 12-month period. panama phone number library Nevertheless, deficits of this magnitude are difficult to make up in the short term. This would require several months of far above-average rainfall in these regions.
extreme drought
Lack of precipitation is only one factor that contributes to dryness or drought. Another key factor is evaporation. The following figures show the Standardiz Precipitation Evapotranspiration Index (SPEI) for long series of measurements from MeteoSwiss. It combines the two factors and describes how much the water balance (difference between precipitation and evaporation) deviates from the long-term average over a certain period of time (here: 12 months, e.g. relevant for the energy industry and water supply). A negative SPEI means drier conditions compar to the long-term average, a positive SPEI means wetter conditions. If the SPEI falls below a value of -2, it is “extremely dry”, and if it is above +2, it is “extremely wet”.
More details about the SPEI:
drought indicators
The SPEI makes it clear that virtually all parts visitors here you will have several ways of the country have been affect by extreme drought over the past 12 months – not only the inner-Alpine region with the largest relative precipitation deficit, but also the Central Plateau, where evaporation was particularly high in the hot summer of 2022.
If the SPEI is calculat over a period of 365 days from February 20, the current year from February 20, 2022 to February 20, 2023 at the measuring location in Geneva/Cointrin ranks first awb directory since measurements began in 1864. In Geneva, it has never been drier over this 12-month period in the past than it is today. This is also the case in the inner Alps in Engelberg and Davos. At the measuring location in Zurich/Fluntern, the current 12-month period ranks second. In Lugano, it has also been extremely dry for 159 years, ranking fourth.
