Instruments:cof

From CedarWiki
Jump to: navigation, search

Collm LF Radar

Collm.gif

Collm Geophysical Observatory

Contents


Contact Persons

Web Sites

Acknowledgments

The Collm LF windprofiler is operated by the University of Leipzig (Institute of Meteorology, Collm Geophysical Observatory).

Data Description

The Collm Geophysical Observatory (51.31 N 13.003 E) uses the closely spaced receiver method at 177, 225, and 270 kHz. Two receivers are used to the geographic north and east of the radar so the center of the reflection point triangle is near (52 N, 15 E). The measurements of the nighttime neutral winds and virtual heights are averaged over half-hour intervals from measurements of about 3/minute for winds and about 300/minute for virtual heights.

The virtual height of the half-hour means is converted to true height using an empirical relation with linear height reduction (Kurschner et al, 1987). Then the half-hour means of the zonal and meridional winds are put through a multiple regression analysis to determine the altitude dependance of the prevailing and semi-diurnal tidal winds. To improve the spectral sensitivity, it proved useful to assume a circularly polarized tidal wind, which is acceptable for mid-latitudes. Therefor, the amplitude of the zonal and meridional semi-diurnal tidal wind is equal, and the phase of the meridional wind is 3 hours earlier than that of the zonal wind. Similarly, the amplitude of the zonal and meridional diurnal tidal wind is equal, and the phase of the meridional wind is 6 hours earlier than that of the zonal wind. However, the 24 hour component is normally only computed for the height of 95 km where the signal is a maximum. The result should be treated with some caution considering the fact that the observations are nighttime only.

The phases are in mean local solar time (SLT). There is 1 hour between SLT and UT since the measurements are near 15E. Most of the calculations are for the period of a month. Extra information of interest such as seasonal transitions and the quasi two-day wave are in catalogue records. The data in the CEDAR Data Base are from January 1993 to January 1997, with selected Lower Thermosphere Coupling Study (LTCS) periods earlier.

References

D. Kurschner, Ein beitrag zur statistischen analyse hochatmospharisher winddaten aus bodengebundenen messungen, Z. Meteorologie, 41, pp 262-266, 1991.
R. Schminder and D. Kurschner, Permanent monitoring of the upper mesosphere and lower thermosphere wind fields (prevailing and semidiurnal tidal components) obtained from LF D1 measurements in 1991 at the Collm Geophysical Observatory, J. Atmos. Terr. Phys., 56, pp 1263-1269, 1994.
R. Schminder and D. Kurschner, Permanent monitoring of the upper atmosphere wind field over Central Europe by LF windprofiler and MF radar measurements at Collm and Juliusruh (Germany), submitted to J. Geophys. Res., 1995.
R. Schminder, W. Singer, D. Kurschner, P. Hoffmann and D. Keuer, Permanent monitoring of the upper atmosphere wind field over Central Europe by a joint analysis of LF windprofiler and MF measurements at Collm and Juliusruh (Germany), Z. Meteorologie, 44, pp 297-300, 1994.
W. Singer, P. Hoffmann, A. Hl Manson, C. E. Meek, R. Schminder, D. Kurschner, G. A. Kokin, A. K. Knyazev, Yu. I. Portnyagin, N. A. Makarov, A. N. Fakhrutdinova, V. V. Sidorov, G. Cevolani, H. G. Muller, E. S. Kazimirovsky, V. A. Gaidukov, R. R. Clark, R. P. Chebotarev, and Y. Karadjaev, The wind regime of the mesosphere and lower thermosphere during the DYANA campaign - I. Prevailing winds, J. Atmos. Terr. Phys., 56, pp 1717-1729, 1994.

Summary Plots for Collm LF Radar Tidal Components

Summary plots of the prevailing, diurnal and semidiurnal amplitudes and phases are shown as a function of height for the horizontal winds.


-Revised 11 Jun 2007 by Barbara Emery