Abstract A year-long Four-Dimensional Variational (4D-Var) data assimilation experiment, formulated on the physical-space statistical analysis system (PSAS) algorithm, has been applied to the Adriatic Sea for the very first time. High-resolution multi-platform observations were assimilated into the Regional Ocean Modeling System (ROMS) forced by mesoscale atmospheric model ALADIN/HR (Aire Limitee Adaptation dynamique Developpement InterNational), including important freshwater river inflows and realistic open boundary conditions for the period between October 2014 and September 2015. The observations included sea surface temperature (SST) measured by satellites, in situ temperature and salinity data measured by various moving (Argo profiling floats, shipborne CTDs, sea glider, towed CTD profiler) and moored platforms, ocean current profiles measured by moored Acoustic Doppler Current Profilers (ADCPs), and 30-minute de-tided surface currents from high-frequency (HF) radars. Three model simulations were integrated: (1) a non-assimilative simulation over a year-long period — baseline simulation; (2) a non-assimilative simulation initiated by the previous assimilation 4-day cycle — background simulation, and (3) a fully assimilative simulation that used all available observations during the 4-day assimilation cycle — analysis simulation. The assimilation significantly improved the modeling system performance, especially in SST, with time average rmse equaling 0.9, 0.7 and 0.5 °C and bias equaling 0.39, 0.15, 0.01 °C for the baseline, background and analysis simulations, respectively. These reductions were mostly achieved during the wintertime outbreaks of a cold and dry bora wind, caused by an underestimation of heat and momentum fluxes by the atmospheric model. Such fine adjustments in the northern and middle Adriatic may be responsible for improved reproduction of dense water generation and the associated Adriatic thermohaline circulation.

中文翻译：

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使用多平台 4D-Var 数据同化改进亚得里亚海动力学建模

摘要 基于物理空间统计分析系统（PSAS）算法制定的为期一年的四维变分（4D-Var）数据同化实验首次应用于亚得里亚海。高分辨率多平台观测被同化到由中尺度大气模型 ALADIN/HR（Aire Limitee Adaptation dynamique Developpement InterNational）强制的区域海洋建模系统（ROMS）中，包括重要的淡水河流流入量和 10 月之间的现实开放边界条件2014 年和 2015 年 9 月。 观测包括卫星测量的海面温度 (SST)、各种移动（Argo 剖面浮标、船载 CTD、海滑翔机、拖曳 CTD 剖面仪）和系泊平台测量的原位温度和盐度数据，由系泊声学多普勒海流剖面仪 (ADCP) 测量的洋流剖面，以及来自高频 (HF) 雷达的 30 分钟去潮汐表面海流。整合了三个模型模拟：(1) 一年期间的非同化模拟——基线模拟；(2) 由前一个 4 天同化周期启动的非同化模拟 - 背景模拟，以及 (3) 完全同化模拟，使用 4 天同化周期期间所有可用的观察结果 - 分析模拟。同化显着提高了建模系统的性能，尤其是在 SST 中，基线、背景和分析模拟的时间平均 rmse 分别等于 0.9、0.7 和 0.5 °C，偏差分别等于 0.39、0.15、0.01 °C。这些减少主要是在冬季爆发寒冷干燥的波拉风期间实现的，这是由于大气模型低估了热量和动量通量。亚得里亚海北部和中部的这种精细调整可能是改善稠密水生成和相关亚得里亚海温盐环流再生的原因。