The quantification of long-term atmospheric change via meteor ablation height measurements

Modern meteor radars, with peak pulse powers typically of the order of 10 kW, detect around 5000 meteors per day and determine the spatial coordinates and radial velocity of each meteor trail detected. This information is mainly used to determine horizontal winds at heights between about 80 and 100 km with a time resolution of about 1 h, adequate for the study of tides, planetary waves and prevailing winds. Since the detected meteor trails are accurately located in space, it is also possible to determine their mean height distribution. This height distribution depends on the meteor characteristics, in terms of distributions of size, velocity and entrance angle, and the vertical profile of atmospheric density in the height range in question. For sporadic meteors the meteor characteristics appear to depend only on local time, so the measured height distribution can, in principle, be used to obtain information on atmospheric density and its time variations on scales greater than one day. An analysis of more than 5 years of data acquired with a Skiymet meteor radar, installed at Cachoeira Paulista, Brazil (23°S, 45°W), shows the presence of planetary waves, seasonal and long-term variations in atmospheric density. Of particular interest is the potential of this technique for quantifying long-term changes in the atmosphere via ground-based measurements which should not be difficult to maintain over the long time periods required for global change studies.