A CRITICAL-EXAMINATION OF THE PRECIPITATION RECORDS AT THE PIC-DU-MIDI-OBSERVATORY, PYRENEES, FRANCE

The set of meteorological data collected from 1882 to 1984 at the Pic du Midi Observatory, a mountain station located at 2862 m MSL in the c entral part of the Pyrenees, includes precipitation measurements. It i s well known that the quality of rain and snow precipitation measureme nts at a mountain station is poor. However, the new interest for all t ypes of meteorological data at high elevation sites in relation with c limatic changes leads to critically examine the precipitation data too . A homogeneity test of the Pic du Midi series, using a regional preci pitation series in the surrounding plain of Aquitaine, confirms a warn ing made by the observers indicating that, since January 1937, the pre cipitation data may not be used. The test also suggests either not to use the data of the years 1923 to 1936, or to use them with a multiply ing factor of 1.17. The data of the 1882-1922 period show that the pre cipitation amount at the Pic du Midi is nearly the same as in the surr ounding valleys from May to November, but that it is about twice durin g the cold months, The seasonal and annual relationships between tempe rature and precipitation suggest that the increase in temperature obse rved from 1882 to 1984 at the Pic du Midi has resulted in a decrease i n the winter and spring precipitation, but in no change in the summer and autumn precipitation.