**1. Introduction**

River runoff to coastal waters strongly influences local dynamics in several ways, such as, for example, modifying water stratification [1], introducing significant fluctuations in circulation patterns, and modulating the impact of upwelling events [2,3]. In the current context of a global decline of hydrometric networks [4] that were originally designed for purposes other than fulfilling the needs of coastal end-users, it is a challenge in many locations to obtain near real time river runoff values and other associated coastal water

**Citation:** Campuzano, F.; Santos, F.; Simionesei, L.; Oliveira, A.R.; Olmedo, E.; Turiel, A.; Fernandes, R.; Brito, D.; Alba, M.; Novellino, A.; et al. Framework for Improving Land Boundary Conditions in Ocean Regional Products. *J. Mar. Sci. Eng.* **2022**, *10*, 852. https://doi.org/ 10.3390/jmse10070852

Academic Editor: Rodger Tomlinson

Received: 16 April 2022 Accepted: 1 June 2022 Published: 22 June 2022

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properties. For this reason, river climatologies have been commonly used as land boundary conditions in coastal and regional ocean operational models. This type of boundary condition neglects temporal river discharge variability issuing from changes in human managemen<sup>t</sup> that may severely impact the circulating flow. Moreover, generating climatological flows for small or poorly monitored rivers can also be a challenge. On the other hand, watershed models tend to overestimate river flows, especially during dry seasons when drained water is scarce and human managemen<sup>t</sup> activities are more intense through dam retention, irrigation, human consumption, etc. [5].

Once the freshwater fluxes have been characterised, they need to be incorporated into regional ocean models, with a horizontal grid resolution of 5–10 km. The most common method of including river discharges in operational oceanography involves directly adding the river volume with zero salinity into one or more layers of the model [6] or through a rectangular breach in the coastal wall with uniform inflow water properties [1].

Campuzano et al. [5] proposed a methodology for the off-line extraction and analysis of water fluxes and properties extracted from full-scale estuarine models in order to be integrated into regional mesoscale ocean models, such as temporal evolution [7]. In this paper, a method to replace full-scale estuarine models by simple proxy models is proposed. The use of estuarine proxies permits extending the application of the proposed methodology with a low computational cost while including most of the local tidal signal complexity (i.e., tidal prism, range, and phases) and realistic water properties.

The presented research is based on outcomes from the Copernicus Marine Service Evolution LAMBDA (Land-Marine Boundary Development & Analysis; hereafter referred to as LAMBDA) project (http://www.cmems-lambda.eu/, accessed on 15 April 2022) that generated watershed model outputs for two Copernicus Marine Environment Monitoring Service (CMEMS) Monitoring Forecasting Centres (MFCs): the Iberia Biscay Irish (IBI-MFC) and the North West Shelf (NWS-MFC). The impact of LAMBDA watershed model inputs in the IBI-MFC was recently analysed by Sotillo et al. [8]. Here, we evaluate the differences and impacts between using direct discharges and estuarine proxies on a western Iberia regional ocean model.

#### **2. Materials and Methods**

Each section of the water continuum, from the watershed to the open ocean, is reproduced with the different components of the MOHID Water Modelling System (http: //www.mohid.com [9], accessed on 15 April 2022). The MOHID Water Modelling System is an open-source modular finite volume modelling system written in ANSI FORTRAN 95 with an object-oriented programming philosophy integrating several numerical programs accessible via the GitHub repository (https://github.com/Mohid-Water-Modelling-System/Mohid, accessed on 15 April 2022). MOHID Land and MOHID Water are the core numerical models.
