Comparing the Performance of Turbulent Kinetic Energy and K-Profile Parameterization Vertical Parameterization Schemes over the Tropical Indian Ocean

Abstract

The performance of vertical parameterization schemes, namely, turbulent kinetic energy (TKE) and K-profile parameterization (KPP), is evaluated over the domain [30E-120E; 20S-30N] in the Indian Ocean using the Nucleus for European Modeling of the Ocean (NEMO) regional model. The surface and sub-surface hydrography and mixed layer depth (MLD) of the simulations using TKE and KPP schemes have been compared. The KPP scheme produces higher bias (∼0.5 °C) of sea surface temperature (SST) in monsoon and post-monsoon seasons, which reduces on using the TKE scheme. The maximum surface salinity difference (0.45 psu) between TKE and KPP simulations is obtained over the head Bay of Bengal (BoB) in the post-monsoon months. The KPP scheme also overestimates MLD of the region. Barring highly convective regions as well as regions marked with very low and rapidly changing salinity, the TKE scheme performs better than KPP scheme in simulating the hydrography and MLD of the region. The differences between TKE and KPP simulations in the vertical stability and mixing are studied using buoyancy frequency, vertical shear of horizontal currents and energy required for mixing as quantifiers. The mixed layer heat budget analysis explains seasonal variability of SST and differences in vertical mixing parameterizations.

Key Words:

• Indian Ocean modeling
• TKE and KPP
• vertical parameterization schemes

Acknowledgements

Authors thank WGOMD for providing CORE II forcing data (http://data1.gfdl.noaa.gov). Thanks are also due to three anonymous reviewers whose useful comments and suggestions have helped us to improve the overall quality of the article.

Additional information

Funding

LKP is thankful to the Monsoon Mission, MoES, Government of India for fellowship. SD is thankful to MoES for financial assistance in the form of a research project.