A PRECIPITATION CLIMATOLOGY OF THE ALPS FROM HIGH-RESOLUTION RAIN-GAUGE OBSERVATIONS

A new precipitation climatology covering the European Alps is presente d. The analysis covers the entire mountain range including adjacent fo reland areas and exhibits a resolution of about 25 km. It is based on observations at one of the densest rain-gauge networks over complex to pography world-wide, embracing more than 6600 stations from the high-r esolution networks of the Alpine countries. The climatology is determi ned from daily analyses of bias-uncorrected, quality controlled data f or the 20 year period 1971-1990. The daily precipitation fields were p roduced with an advanced distance-weighting scheme commonly adopted fo r the analysis of precipitation on a global scale. The paper describes the baseline seasonal means derived from the daily analysis fields. T he results depict the mesoscale distribution of the Alpine precipitati on climate, its relations to the topography, and its seasonal cycle. G ridded analysis results are also provided in digital form. The most pr ominent Alpine effects include the enhancement of precipitation along the Alpine foothills, and the shielding of the inner-Alpine valleys. A detailed analysis along a section across the Alps also demonstrates t hat a simple precipitation-height relationship does not exist on the A lpine scale, because much of the topographic signal is associated with slope and shielding rather than height effects. Although systematic b iases associated with the rain-gauge measurement and the topographic c lustering of the stations are not corrected for, a qualitative validat ion of the results, using existing national climatologies shows good a greement on the mesoscale. Furthermore a comparison is made between th e present climatology and the Alpine sections of the global climatolog y of Legates and Willmott and the Greater European climatology from th e Climate Research Unit (University of East Anglia). Results indicate that the pattern and magnitude of analysed Alpine precipitation critic ally depend upon the density of available observations and the analysi s procedure adopted. (C) 1998 Royal Meteorological Society.