Non-migrating tides

Recently, two interesting advancements in the study of non-migrating tides have occurred. There are currently two distinct approaches to this subject. One. based on mechanistic models that consider heating due to non-uniform global distribution of water vapour or heating only over lands, solves the primitive equations. One model of this approach that shows insolution absorption of the non-uniformly distributed water vapour produces non-migrating tides with 15% of the migrating ones in the lower thermosphere. The planetary boundary layer heating can explain very enhanced tides over land masses and those with short vertical wavelengths in the stratosphere. The other approach uses a general circulation model (GCM) simulation. This model can produce tides globally and in many details. The model predicts enhancement of the non-migrating modes as eastwards traveling modes with a wave number 3 and westwards traveling modes with a wave number 5 that is in a surprisingly good agreement with observation at sea-level, at 700 mb and at 300 mb.Whilst the GCM simulation is to be developed so as to include thermospheric tides, the mechanistic model should consider more realistic situations so as to include winds. Observation of tides at many heights and locations is essential in future studies.