Modelling implications of MOST departures in marine surface flux estimation

Determine the precise implications of observed departures from Monin–Obukhov Similarity Theory in the marine atmospheric surface layer—specifically non-monotonic wind profiles and large vertical gradients in sensible heat flux—for air–sea surface flux modelling using MOST-based bulk flux algorithms such as COARE, the Global Forecast System (GFS) surface flux scheme, and Weather Research and Forecasting (WRF) flux parameterisations.

Background

Monin–Obukhov Similarity Theory (MOST) underpins nearly all bulk aerodynamic algorithms used to estimate air–sea exchanges of momentum, heat, and moisture in models such as COARE, GFS, and WRF. This paper presents evidence from CLASI-ASIS buoy observations that MOST’s assumptions—monotonic wind profiles and vertically uniform fluxes—frequently break down near the sea surface, especially under offshore winds near coasts, high wave age conditions, and strongly stable thermal stratification.

The authors highlight that these departures may introduce systematic flux errors, but the exact consequences for modelling frameworks remain unresolved. Clarifying the implications for existing parameterisations and bulk algorithms is therefore an explicit open question identified in the discussion, motivating targeted evaluation and potential refinement of MOST-based approaches.