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

Comment on "Global structure, seasonal and interannual variability of the migrating semidiurnal tide seen in the SABER/TIMED temperatures (2002–2007)" by Pancheva et al. (2009)

“…To conclude this discussion of possible radar biases, we note that a literature/office-search, conducted while in final review of this paper, revealed the recent and highly relevant paper by Jacobi et al (2009). In this, they contemporaneously compare winds (2004)(2005) from Juliusruh (MFR) and Collm ("Low Frequency" radiowave system), which featured in the Jacobi et al (1999) paper, with data from the new Collm-MWR. The proximity of the three systems, and their antenna beam-widths, justifies such comparisons.…”

“…1, the figure also includes the SDTwind contour-plots for Saskatoon, one of the radars within 50-56 • N used by Jacobi et al (1999). For Saskatoon the maximum of the LSEF feature is centred on September, and the vertical phase-gradients are modestly larger, especially above 85 km, than those at 40 • N. Notice also that the tidal-wind phases at both locations are consistent with short vertical SDT-wind "vertical wavelengths" (circa 35 km) in winter-centered months, November to March; with large values (>100 km)/evanescence above 80 km in the late spring and early autumn months; and evanescence above ∼80 km in the summer (June, July, August).…”

“…To complete this section, we comment upon the radars in the 50-60 degree north sector (Jacobi et al, 1999) and then the range of longitudes from which SDT data are available from ground based systems. The radars observing the strong LSEF feature stretched from Saskatoon (107 • W), through Collm (51 • E) to Kazan (49 • E).…”

“…(2,4), (2,6) in the fall, plus (2,5) in the solstices. Jacobi et al (1999) examined the monthly variations of the SDT-wind at heights near 90 km, over the years (1985)(1986)(1987)(1988)(1989)(1990)(1991)(1992)(1993)(1994)(1995), using 6 radars (3 were MWR) at 5 European and Russian locations between 52-56 • N, and including Saskatoon (MFR) in Canada (52 • N, 105 • W). The variations of the SDT-phase and amplitudes, using monthly means at 92.5 km, were quite similar to those at 40 • and 52 • N in North America: winter and late summer-fall maxima of comparable amplitudes; and transitions of vertical phase-gradient between summer and autumn (equivalent to "vertical wavelengths.…”

Longitudinal and latitudinal variations in dynamic characteristics of the MLT (70−95km): a study involving the CUJO network

“…Jacobi et al, (1999) used 6 radars of various types which are mainly in Europe and Russia (4 • W-49 • E) but included one MF Radar (MFR) in Canada (107 • W). The latitude range, for mainly historical reasons, lies from 52-56 • N. The monthly variations of the semi-diurnal tide over the years (1985)(1986)(1987)(1988)(1989)(1990)(1991)(1992)(1993)(1994)(1995) at all 6 locations, at heights near 90 km, were quite similar: amplitudes had winter and late summer-fall maxima, and strong phase transitions occurred during equinoxes.…”