The Mid‐ to High‐Latitude Migrating Semidiurnal Tide: Results From a Mechanistic Tide Model and SuperDARN Observations

Abstract

AbstractSimulations of the solar thermal migrating semidiurnal (SW2) tide in the mesosphere‐lower‐thermosphere (MLT) are compared against meteor wind observations from a longitudinal chain of high‐latitude Super Dual Auroral Radar Network radars. The simulations span the year 2015 and are performed using a mechanistic primitive equation model. The model employs a whole‐atmosphere tide forcing based on temperature tendency fields from the Specified Dynamics Whole Atmosphere Community Climate Model with Thermosphere and Ionosphere Extension, and a background atmospheric specification based on zonal wind and temperature data from the Navy Global Environmental Model‐High Altitude meteorological analysis system. Results show that the model accurately reproduces the observed seasonal variability of the SW2 tide in both the amplitude and phase. Numerical experiments are performed to investigate how the tidal forcing, dissipation terms, and seasonal variations in the background atmosphere shape the seasonal variations of the simulated SW2 tide. Notable results are that the background atmosphere most strongly impacts the SW2 tide forced in the troposphere, and that the specification of a narrow surface friction profile enhances the net SW2 amplitude in the MLT between April and October. Eddy diffusion is found to damp the simulated tide predominantly around summer solstice and in December.