Climatology of the semidiurnal tide at 52-56 degrees N from ground-based radar wind measurements 1985-1995

Long-term wind measurements carried out at 6 northern midlatitude sites (Sa skatoon, Sheffield, Juliusruh, Collm, Obninsk, Kazan) are investigated to e stablish a climatology of the semidiurnal tide in the mesopause region for the narrow latitudinal range between 52 degrees N and 56 degrees N. Compari son of zonal and meridional components shows that in general the horizontal components are circularly polarized. Intercomparison of amplitudes and pha ses generally shows good agreement between the results from the different m easuring systems. The results are compared with an empirical model of the s emidiurnal tide. The longitudinal variation of the semidiurnal tide is smal l in summer, but the tidal amplitudes in winter are larger at Saskatoon and Kazan, compared with the results from the other sites. The possible influe nce of wave-tidal interaction in the stratosphere on the interannual variab ility of this difference is discussed. (C) 1999 Elsevier Science Ltd. All r ights reserved.