The QBO in two GISS global climate models: 1. Generation of the QBO

Abstract

The adjustment of parameterized gravity waves associated with model convection and finer vertical resolution has made possible the generation of the quasi-biennial oscillation (QBO) in two Goddard Institute for Space Studies (GISS) models, GISS Middle Atmosphere Global Climate Model III and a climate/middle atmosphere version of Model E2. Both extend from the surface to 0.002 hPa, with 2°× 2.5°r esolution and 102 layers. Many realistic features of the QBO are simulated, including magnitude and variability of its period and amplitude. The period itself is affected by the magnitude of parameterized convective gravity wave momentum fluxes and interactive ozone (which also affects the QBO amplitude and variability), among other forcings. Although varying sea surface temperatures affect the parameterized momentum fluxes, neither aspect is responsible for the modeled variation in QBO period. Both the parameterized and resolved waves act to produce the respective easterly and westerly wind descent, although their effect is offset in altitude at each level. The modeled and observed QBO influences on tracers in the stratosphere, such as ozone, methane, and water vapor are also discussed. Due to the link between the gravity wave parameterization and the models' convection, and the dependence on the ozone field, the models may also be used to investigate how the QBO may vary with climate change.

Modeling the QBO—Improvements resulting from higher‐model vertical resolution

“…Earlier works by Scaife et al [2000], Giorgetta et al [2006], among others, and recent works by Rind et al [2014] and Richter et al [2014] have already established the important roles that parameterization of subgrid-scale gravity wave parameterizations and vertical resolution play in modeling a realistic QBO in a self-consistent manner, and the points brought up in the earlier sections of this paper are either explicitly or implicitly contained in those works, but we think it important to stress a few points. One is that sufficient gravity wave momentum flux is required to model the QBO in a self-consistent manner.…”

“…Others [e.g., Giorgetta et al, 2006;Rind et al, 2014] have also noted the sensitivity of the modeled QBO to the magnitude of the gravity wave momentum flux.…”

Overview of experiment design and comparison of models participating in phase 1 of the SPARC Quasi-Biennial Oscillation initiative (QBOi)

“…Takahashi, 1996;Scaife et al, 2000;Hamilton et al, 2001;Giorgetta et al, 2002;Shibata and Deushi, 2005;Anstey et al, 2010;Kawatani et al, 2010;Orr et al, 2010;Lott and Guez, 2013;Richter et al, 2014;Rind et al, 2014;McCormack et al, 2015;Molod et al, 2015). However, common deficiencies exist in all current simulations, notably with QBO winds often being unrealistically weak in the lowermost stratosphere and having unrealistically small cycle-to-cycle variability (e.g.…”

Overview of experiment design and comparison of models participating in phase 1 of the SPARC Quasi-Biennial Oscillation initiative (QBOi)

“…With the advent of non-orographic GWD parameterizations and/or the use of increased vertical resolution in the stratosphere, 25 a growing number of global models have been able to reproduce QBO-like variability in the equatorial stratosphere (e.g., Takahashi, 1996;Scaife et al, 2000;Hamilton et al, 2001;Giorgetta et al, 2002;Shibata and Deushi, 2005;Anstey et al, 2010;Kawatani et al, 2010;Orr et al, 2010;Lott and Guez, 2013;Richter et al, 2014;Rind et al, 2014;McCormack et al, 2015). However, common deficiencies exist in all current simulations, notably with QBO winds often being unrealistically weak in the lowermost stratosphere and having unrealistically small cycle-to-cycle variability (e.g., Schenzinger et al, 2017).…”