Klimatologische Untersuchungen an Hochalpinen Zeitreihen: Ergebnisse aus den Projekten Aloclim und Alpclim : Umweltforschung im Hochgebirge - Ergebnisse von GAW-DACH und verwandten Projekten

1999

S. 14-22

4 Lit. Ang.

Unselbständiges Werk

200086899

One of the strong points of long-term high alpine observatories like that on Sonnblick are their climatic time series, produced above the atmospheric boundarylayer, remote from local disturbancies of the surroundings - in climatic background conditions. We show examoples of results gained by the projects ALOCLIM (Austrian lon-term Climate) and ALPCLIM (Environmental and climate records from high elevation glaciers). Three examples of ALOCLIM concentrate on the opportunity to use the vertical component of climate variability by comparing time series of four high level observatories with low level sites. The first deals with a possible explanation of the regional temperature variability by circulation changes (shown by low level air pressure series) which cause changes in incoming short wave radiation (shown by undisturbed high level sunshine series) which strongly correlate with air temperature both at high and low frequencies. The second ALOCLIM example shows the application of highly homogeneous high- and low level air pressure series to model the air temperature series for an "East Alpine standard air column" - independently of thermometric measurements from low level sites, which are often doubted to be biased by changes of the local environment due to land-use changes, urban development and others. The "barometric air temperature series" are highly corresponding to the directly measured ones, thus supporting the reality of the temperature increase of about 1.8 K since mid 19th century. The last ALOCLIM example discusses an asymmetric behaviour of the low- and high level sunshine and cloudiness series of high- and low levels. High level sunshine increased stronger than the low-level one during more than the last 100 years. The high- and low level cloudiness series do not show the corresponding feature, their difference decreased until the 1940s and show slight increase since then. Together with (shorter) series of direct and scattered short wave radiation this suggests that the steady increase of high-level minus low-level sunshine should be caused by an increase of atmospheric turbidity, specially during the period of strong economic development of the last 50 years. Concerning project ALPCLIM /which still is in progress) some preliminary results show the potential of the gridded ALPCLIM data-set (based on some 90 homogenised temperature time series of the Alps and surroundings) for the calculation of an Alpine proxi data-set based on stable isotope data from high level ice cores at Monte Rosa and Mont Blanc. First attempts to fit the Colle Gnifetti isotope data from Monte Rosa on the instrumental temperatures show encouraging results. Most probably ALPCLIM will produce a some 500 years long proxi series of summer or summer-spring temperatures, representative for large parts of Europe - the latter shown by correlation maps comparing ALPCLIM temperatures with the large scale gridded temperature series of CRU.