"Spurious internal waves generated during Data Assimilation in ocean model simulations"
Sep 14, 2022, Schedule:
- Nespresso & Teatime ( 417 DSL - Commons )
- 03:00 to 03:30 PM Eastern Time (US and Canada)
- Colloquium - F2F ( 499 DSL ) / Virtual ( Zoom )
- 03:30 to 04:30 PM Eastern Time (US and Canada)
Meeting # 942 7359 5552
Most high-resolution ocean forecast systems assimilate ocean observations using sequential Data Assimilation (DA). The updates to model state during DA act as a non-physical forcing term in the model equations. Following an update, the model has to undergo an adjustment to restore its dynamical balance. This adjustment process usually involves inertial oscillations, unrealistic mixing, and some artificial baroclinic and barotropic adjustments. The reduction of the negative impacts of the model adjustment after assimilation is crucial for the validity of a forecast system. In this talk, we examine the characteristics of a propagating noise in the form of spurious internal waves, generated during the model adjustment after DA in a global ocean model simulation. These spurious waves are in a broad near-inertial frequency band and can propagate far distances from their generation sites in the form of low-mode waves, rendering the data assimilative model unsuitable for studying high-frequency motions. An ad-hoc solution to reduce the generation of spurious internal waves during DA will also be presented.