A STUDY OF GREENHOUSE GASES AND AIR TRAJECTORIES AT PLATEAU-ROSA

The attention paid to changes in atmospheric concentrations of greenho use gases has recently increased, with particular regard to the relati onships between variations of their annual trends and of their shorter -period fluctuations on the one hand, and some geophysical and biologi cal natural processes (like atmospheric transport, volcanic eruptions, ENSO events, seasonal vegetation cycles, and so on) on the other hand . Careful analysis and interpretation of the above relationships, in f act, can often disclose unknown mechanisms acting on modulations of th ese gases and make it possible for us to better understand the contrib utions made to them by natural causes, contrasted with anthropogenic o nes. This paper presents and discusses the results of a series of CO2 air concentration data, measured at Plateau Rosa (3480 m a.s.l. - Ital ian Western Alps) over a period of about four years, and correlated wi th atmospheric transport processes on synoptic scale. These results ha ve shown the leading role played by some kinds of atmospheric circulat ion patterns in creating situations of not fully mixed air streams (an d, as such, not representative of background conditions) and have also suggested a <<meteorological>> selection scheme for CO2 data to be us ed in evaluating more reliable annual trends.