Enhancing model temperature estimations in shallow, turbid, coastal regions: Mobile Bay, Alabama

Abstract

Accurate estimation of water column temperature is vital for modeling physical and biogeochemical processes. A key process in the thermal dynamics of the upper ocean is the attenuation of solar radiation. In shallow-turbid coastal systems, spatially and temporally varying optical characteristics present challenges for commonly used attenuation parameterization schemes. This study investigates the dependency of temperature with a ROMS model of Mobile Bay, a shallow, turbid estuary, using six different attenuation approaches including three base cases: Conventional approach PS77 based on water type-9; Novel approach SAL relating in situ PAR attenuation to salinity; and Surface trapped irradiance method ST. In addition, these base cases are also tested with surface atmospheric heat flux correction (QC). Simulations were validated against observations from various sources to identify the optimal approach at annual and synoptic scales. While all simulations showed effective temperature performance over an annual cycle, monthly analysis revealed some seasonality, with winter months typically performing better than summer months. The influence of QC notably enhanced temperature performance in both annual and synoptic scales, given that surface heat flux primarily drove temperature changes in this shallow system. The best overall performance was determined to be the ST approach incorporating QC. Conversely, PS77 without QC demonstrated the poorest performance. The SAL model with QC, notably improved performance over PS77 with QC, yet demonstrated comparable yet weaker performance compared to the ST model with QC. The study also implies that neglecting subseasonal validation in long-term regional climate modeling could introduce uncertainty into analyzing events tied to subseasonal temperatures.