Tidal Signals in AOD1B

In total 16 tidal frequencies are estimated and removed from the ECMWF surface pressure fields. This includes the main solar tides S1, S2, and S3 as well as the main semi-diurnal lunar tide M2.

Tidal signals are estimated on a per-year-basis using a least-squares fit and subsequently subtracted.

Additional details on the harmonic analysis and atmospheric tidal signals in ECMWF ERA5 data can be found under:

Figure: Surface pressure signals of atmospheric tides for the constituents π₁, P₁, S₁, K₁, ψ₁, M₂, T₂, S₂, R₂, K₂, T₃, S₃, R₃, S₄, S₅, S₆ removed from AOD1B as estimated over the year 2014.

Periodic changes in atmospheric surface pressure over the oceans pose a time-variable loading to the water column that is not fully compensated isostatically, but excite a periodic motion in the oceans itself that adds to field of lunisolar gravitational ocean tides. The MPIOM simulation used for AOD1B RL07 is forced with atmospheric conditions including atmospheric surface pressure obtained from ECMWF. By doing so, the oceanic response to atmospheric tides is simulated together with the transient non-tidal ocean circulation variability.

All tidal variability from the ocean component of AOD1B has been removed in the same way as for the atmospheric part.