This study starts from a two‐layer 1D Estuary Box Model (EBM), the so called Centro Euro‐Mediterraneo sui Cambiamenti Climatici (CMCC) EBM (Verri et al., 2020, https://doi.org/10.1016/j.ocemod.2020.101587), devised to offer a proper representation of the net river release in a coupled modeling framework with hydrology models and ocean models reaching the mesoscale. Two key advances are proposed in the present study: (I) the estuary length and (II) the horizontal eddy diffusivity coefficient are no longer considered as static parameters to calibrate but two non‐dimensional equations have been introduced in order to make them time‐variable. The Goro branch of the Po river delta is considered as case study of “salt‐wedge estuary” flowing into a microtidal sea. Regarding the estuary length, a non‐dimensional equation has been tested and validated. This equation provides a time dependent estuary box volume which is more realistic choice. This time‐variable estuary length represents the length of the salt wedge intrusion. Regarding the horizontal eddy diffusivity, the static eddy coefficient adopted in the previous version of the model is a coarse assumption. Thus a non‐dimensional equation for this coefficient has been tested and validated. It makes the eddy diffusivity dependent on the velocity shear, the salinity gradient and the estuary geometry. The proposed dynamic formula is found to enhance the model capability to reproduce the salinity at the estuary mouth. Overall the high statistical performance in terms of RMSE and correlation coefficient, the short CPU time and the minimal calibration encourage to use the CMCC EBM in coupled mode with both mesoscale‐resolving ocean and hydrology models to produce operational forecasts and climate scenarios.

中文翻译：

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表示河口动力学的Box模型的最新进展：随时间变化的河口长度和涡流扩散率

这项研究从两层一维河口箱模型（EBM）开始，即所谓的欧洲地中海中部Cambiamenti Climatici（CMCC）EBM（Verri等人，2020年，https：//doi.org/10.1016/j。 ocemod.2020.101587），旨在在耦合模型框架中正确表示河流净释放量，其中水文模型和海洋模型达到中尺度。本研究提出了两个关键进展：（I）河口长度和（II）水平涡流扩散系数不再被视为校准的静态参数，但引入了两个无量纲方程以使其时间多变的。Po河三角洲的五郎支流被认为是流入微潮海的“盐楔河口”的案例研究。关于河口长度，已经测试和验证了无量纲方程。该方程式提供了随时间变化的河口箱容积，这是更现实的选择。随时间变化的河口长度代表盐楔侵入的长度。关于水平涡流扩散率，模型先前版本中采用的静态涡流系数是一个粗略的假设。因此，已经对该系数的无量纲方程进行了测试和验证。它使涡流扩散率取决于速度剪切，盐度梯度和河口几何形状。发现提出的动态公式可增强模型功能，以再现河口口的盐度。总体而言，RMSE和相关系数方面的统计性能很高，