基于数值模式评估细尺度参数化方案在南大洋背风波生成源地的适用性

验证基于GM(Garret-Munk)大洋内波普适谱的细尺度参数化方案在不同海域的适用性,对于湍流混合研究来说非常重要。包含背景GM内波场的高分辨率数值模式被用于评估细尺度参数化方案在背风波生成源地处的适用性。细尺度参数化方案主要包括基于剪切的G89 (Gregg 1989)方案、基于应变的W93 (Wijesekera 1993)方案、基于剪切和应变的GHP (Gregg-Henyey-Polzin)方案以及对GHP方案中的频率矫正项作出变换的IH (Ijichi-Hibiya)方案。计算结果显示,背风波的生成伴随着海底上方近惯性内波的增强,使得内波场的动能与势能的比值相较于GM内波场偏大。在这种情况下,基于剪切的G89方案会因为高估内波场的总能量而高估耗散率。反之,基于应变的W93方案会因为低估内波场的总能量而低估耗散率。计算结果还显示,已经考虑了内波谱变形的GHP方案仍然会高估耗散率,但IH方案能比较准确地估算耗散率。

NUMERICAL MODEL-BASED ASSESSMENT ON APPLICABILITY OF FINE-SCALE PARAMETERIZATION AT GENERATION SITE OF INTERNAL LEE WAVES IN THE SOUTHERN OCEAN IN NUMERICAL MODEL

Verification of the applicability of fine-scale parameterizations based on the Garret-Munk (GM) universal internal wave spectrum in different regions is important for oceanic turbulent mixing studies. High-resolution numerical model incorporating the background GM wave field was used to assess the applicability of the fine-scale parameterizations at the generation site of internal lee waves. The fine-scale parameterizations include mainly the shear-based Gregg 1989 (G89) parameterization, the strain-based Wijesekera 1993 (W93) parameterization, the shear-strain-based Gregg-Henyey- Polzin (GHP) parameterization, and the Ijichi-Hibiya (IH) parameterization that transforms the frequency correction term in the GHP parameterization. Results show that the generation of internal lee waves is accompanied by the enhancement of near-inertial internal waves above the seafloor topography, which makes the ratio of kinetic energy to potential energy of the internal wave field larger than that of the GM internal wave field. In this case, the shear-based G89 parameterization will overestimate the dissipation rate by overestimating the total energy of the internal wave field. On the contrary, the strain-based W93 parameterization will underestimate the dissipation rate by underestimating the total energy of the internal wave field. The results also show that the GHP parameterization, which has already taken into account the distortion of internal wave spectrum, still overestimates the dissipation rate, while the IH parameterization can evaluate the dissipation rate more accurately.