Improvement of MOM4 by including surface wave-induced vertical mixing

A parameterized surface wave-induced vertical mixing (Bv) is incorporated into the Modular Ocean Model version 4 (MOM4). A comparison of the two numerical experiments with and without Bv shows that Bv can significantly improve the upper-ocean (20–100 m) simulation in summer. The simulated upper-ocean temperature errors are reduced in summer due to the surface wave-induced vertical diffusive heat flux. The non-breaking-wave-induced vertical mixing can increase the probability of the simulated SST biases between −1 °C and 1 °C from 64% to 76% in the Southern Hemisphere (60°S–10°S) in January, and from 66% to 75% in the Northern Hemisphere (10°N–60°N) in July. The averaged mixed layer depth (MLD) simulated by the MOM4 without Bv is 14.4 m shallower than the observations in 10°S–60°S in January, and 7.2 m shallower than the observations in 10°N–60°N in July. Bv can deepen the modeled MLD by 12.4 m in the Southern Hemisphere in January and by 6.3 m in the Northern Hemisphere in July. By including Bv, the corresponding MLD biases from the observations are only 2.0 and 0.9 m in the Southern and Northern hemispheres, respectively. These results clearly demonstrate that the incorporation of Bv can improve the performance of MOM4 significantly in summer.