Climatology of semidiurnal lunar and solar tides at mid and high latitudes: comparison between hemispheres

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Friday, July 7, 2017

The semidiurnal lunar and solar tides obtained from meteor radar measurements spanning from 2009 until 2013 observed at Davis (69°S) and Rio Grande (54°S) are presented and compared to the northern hemisphere at Andenes (69°N) and Juliusruh (54°N). Mean tidal differences for both intra- and inter-hemispheric scenarios are analyzed.

Mean zonal wind image
Mean zonal wind (U), SW2 and M2 total magnitudes obtained from meteor radar measurements (left) and TIMEGCM/WACCM-X (right) for the year 2009 over Davis, Rio Grande, Andenes and Juliusruh. The vertical black lines indicate the time of the PVW on 23 January. Data gaps are shown in white.

Tidal behavior is also compared against numerical simulations during 2009 and 2013 sudden stratospheric warming (SSW) time periods. Possible influences in the southern hemisphere from the local stratosphere are also investigated using Modern Era Retrospective analysis for Research and Applications, version 2 (MERRA-2) datasets. Mean zonal winds present a similar behavior in both hemispheres, with stronger amplitudes over mid latitude locations and a clear reversal during corresponding summer times. On the other hand, the semidiurnal solar tides observed in the southern hemisphere show clear differences when compared to the northern hemisphere and between same hemisphere mid and high latitude locations. These differences are even larger for the lunar tide, which shows stronger amplitudes from October to March, and March to October, over Davis and Rio Grande, respectively. Our results indicate that the lunar tides over southern hemisphere mid latitudes are more prone to react to the northern hemisphere stratospheric polar vortex influences, in agreement with numerical simulations, particularly for the time of the 2013 SSW.