Progress in Simulating the Quasi-Biennial Oscillation in CMIP Models
The Quasi-biennial Oscillation (QBO) is the dominant mode of variability in the tropical stratosphere, however many general circulation models (GCMs) still have a difficult time reproducing this oscillation. We evaluated the simulation of the QBO in historical simulations among the CMIP3, CMIP5, and CMIP6 models.
QBO impacts the variability of the stratosphere and troposphere, and is a source of seasonal predictability. Representing this stratospheric oscillation in GCMs accurately could positively affect the representation of tropospheric variability as well as improve seasonal prediction.
We show that the number of climate models being able to simulate the QBO in CMIP models has increased by a factor of three from CMIP5 to CMIP6. However, the quality of the simulation of the QBO has not improved. Overall, models simulate the period of the QBO well but underestimate the QBO amplitude at all levels below 20 hPa. The deficiency in QBO amplitude in lowermost stratosphere will likely impact the quality of simulated teleconnections