Diurnal mesospheric tidal winds observed simultaneously by meteor radars in Costa Rica (10° N, 86° W) and Brazil (7° S, 37° W)

Abstract. This paper is about a study of diurnal tides on meteor wind observed simultaneously by two meteor radars sited on equatorial region. The radar are located in Santa Cruz (10.3° N, 85.6° W), Costa Rica (hereafter CR) and in Sao Joao do Cariri (7.4° S, 36.5° W), Brazil (hereafter CA). The distance between them is 5800 km. Harmonic analysis was used to get information of amplitude and phase (hour of peak amplitude) of diurnal, semidiurnal and terdiurnal tides between 82 and 98 km of height. The period of observation was from April 2005 to January 2006. The results were compared to GSWM00 model. In general, seasonal agreement between observation and model was satisfactory to zonal and meridional amplitudes. Values of zonal and meridional amplitudes from November to January to CR were very different of GSWM00. Peak of zonal amplitude (~ 25 m/s) to CR was observed in September and December between 90 and 94 km. On the other hand, meridional phase was excellent to both sites and vertical wavelength of 25 km was observed practically every month to CR and CA. The zonal phase presented some difficult to get vertical wavelength according to criteria adopted to calculate it. Considering diurnal zonal amplitude, when we compare CR and CA, we could expect a poor agreement of amplitude between them. That is normal if we believe that this is because the geographical location of both sites are completely different in terms of local climate even if they are close to the equator and effect of heat latent release could lead to different response at high altitudes.