Tidal fluctuations as seen in ECMWF data



Diurnal and semi-diurnal fluctuations in the troposphere and lower stratosphere during the 1986 summer and 1986/87 winter, deduced from data of the European Centre for Medium Range Weather Forecasts, are documented. In general, the tidal fluctuations are consistent with the results of previous investigators based on station data. It thus suggests the adequacy of the data generated by the analysis-forecast system for presenting the global structure of tidal fluctuations in the troposphere.

The semi-diurnal fluctuations in ECMWF data are consistent with the predictions of tidal theory. The diurnal fluctuations, which are more sensitive to local factors such as the sea-land contrast and topography, exhibit a complicated geographical dependence. It appears that the current tidal theory, by neglecting the lower boundary effects and zonally varying factors, is incomplete for explaining the diurnal tidal motions in the troposphere.