不同边界层稳定性下海气湍流热通量日变化的前沿问题探讨

海气湍流热通量(潜热和感热)是研究海气相互作用和大洋环流的关键要素, 认识其变化机理对理解“海洋动力过程及气候效应”有重要意义。然而, 受观测手段和计算能力两方面的限制, 过去对海气湍流热通量日变化研究存在“特征认识较粗、机制理解较疏”的现象。本文探讨了在不同边界层稳定性下海气湍流热通量日变化研究中的问题与难点, 并讨论了“不同边界层稳定性下海气湍流热通量日变化过程和机理”这一关键科学问题。本文提出, 可基于海洋浮标、平台和波浪滑翔机等综合观测数据和高时空分辨率再分析资料, 利用块体算法和脉动分离方法, 揭示全球海气湍流热通量的精细化日变化特征和决定因素, 以及海气湍流热通量日变化强度(日内小时级变化的标准差)与极端天气过程和气候事件的动力关联。同时, 为更精准认识日变化过程, 在技术上可通过耦合高频海表流速和校正边界层物理参数观测高度等方式提升海气湍流热通量估算的精确度。本文提出可将多时空尺度海气湍流热通量变化维度转换到边界层稳定性上, 以便集中认识其日变化特征和机理, 支撑全球海气能量平衡的科学认识。

On the mechanisms behind diurnal variations in air-sea turbulent heat fluxes under different boundary layer stability

The air-sea turbulent heat fluxes (THFs), including the evaporative latent heat flux and convective sensible heat flux, are key components in air-sea interaction and ocean circulation, which are important for our understanding of the global energy balance, water cycle and climate change. Due to the limitations of observations and numerical simulations, the diurnal variations in THFs are however not accurately known. In this paper, we propose a future research plan toward identifying the mechanisms behind diurnal variations in THFs. With the recent development of traditional buoy observations, new observations (e.g., glider) and newly released atmospheric reanalysis, it is helpful to research the diurnal variations in THFs. Using the combined observations and reanalysis, we investigate the key scientific issues on diurnal variations in THFs under different boundary layer stability based on the bulk formulas and turbulence methods. In the future, we will demonstrate the global basic structures and dominant factors for diurnal variations in THFs, as well as the strength of the diurnal variation associated with the extreme weather processes and climate events. To evaluate accurate magnitudes of THFs for better understanding of diurnal variations, high-frequency surface currents and height-dependent air-sea physical variables will be incorporated into the estimates of THFs in terms of bulk formulas. Innovatively, this study transfers the multi-scale THF variations into the space of boundary layer stability to concentrate on the diurnal variations, which help study the mixed-layer dynamics, upper-ocean ecosystems, energy balance, and climate change.