QBO-composite mean meridional circulation: ERA5 and MIPAS tracer-derived residual velocities

This study focuses on analyzing the Quasi-Biennial Oscillation (QBO)-composite mean meridional circulation during the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) measurement period 2002 to 2012, using both ERA5 reanalysis and MIPAS tracer-derived velocities. The investigation employs the approach described in the S-RIP report: We have  deseasonalized QBO-W onsets at 20 hPa and have compared zonal-mean vertical and meridional velocities extracted from MIPAS tracer measurements with reanalysis data from ERA5.

 

To infer the effective transport velocities and mixing coefficients of the 2-D atmosphere, we employ a direct inversion technique utilizing tracer measurements from MIPAS (Clarmann and Grabowski 2016). This method involves the integration of the continuity equation over time and determines those vertical and meridional mean velocities that best reproduce the measured trace gas distributions. The advantage of the method is that it does not involve a dynamic model; instead it provides independent observation-based information on the mean meridional circulation.

 

This inversion method is applied to MIPAS monthly zonal mean tracer measurements of the years 2002 to 2012.  This study reveals QBO patterns in tracer-retrieved velocities within the mean circulation. Observed structures compare favourably with S-RIP reanalysis results. Quantitative comparisons reveal differences that have the potential to pinpoint certain processes that might not be adequately represented in the models or deficiencies in the tracer-based inversion of the continuity equation.

 

These results underscore the utility of MIPAS tracer measurements for enhancing the understanding and modeling of mean-meridional circulation in Earth's atmosphere.

 

Reference

von Clarmann, T. and Grabowski, U.: Direct inversion of circulation and mixing from tracer measurements – Part 1: Method, Atmos. Chem. Phys., 16, 14563–14584,  https://doi.org/10.5194/acp-16-14563-2016, 2016.