Small-scale structures in common-volume meteor wind measurements

Observational differences occur when different techniques are used for measuring mesospheric winds because the different instruments observe different physical quantities to infer the wind velocity, and have differing time and space resolution. The AMOR meteor wind radar near Christchurch, New Zealand [Marsh et al., 2000. Journal of Atmospheric and Solar-Terrestrial Physics 62,1129–1133.] has good resolution in time (∼0.1 s) and height (∼1 km) and a narrow beam centred in the geographic N–S meridian. The meteor echoes randomly sample the atmosphere in a region extending over several hundred kilometres to the South of the radar. The volume of data obtained from the one instrument has made it possible to use correlations between measurements made from individual meteor trails to identify the contribution of atmospheric variability to the observational differences. Measurements of the meridional wind component made from May–July 1997 inclusive show that a large part (20–30 m/s r.m.s.) of the atmospheric variation is due to inhomogeneities with small scales, of the order of 10 km and 1 h. There is also a component which has a random time phase over the observation interval but a spatial scale which is coherent over several hundred kilometres, consistent with the behaviour of gravity waves.