Introduction

introduction to Mohid, history, some applications, data assimilation importance of data assimilation, improvement on DA for Mohid, our approach. Previews analysis was reported by \cite{Rodrigues2015} 

The HF Radar Data

The HF radar data is provided by the  Sistema de Monitorização Operacional de Correntes Costeiras, it has a large source of data base,
Land-based high-frequency (HF) coastal radars are an important means of acquiring oceanographic information. The "SeaSonde" radar of the "Coastal Ocean Dynamics Application Radar" (CODAR) is a variant of this type of technology.  This monitoring system is composed of two stations, one of which is currently installed in the São Julião da Barra Fort (JLSM) and another in the Cape Espichel lighthouse (EPSM), which allows the measurement of surface currents and sea agitation in an area up to 70 km from the coast. Its operation is based on Doppler variation and back-diffusion of the transmitted signal.  Each station measures the Doppler variation and the intensity of the backscattered signal along each azimuth every 5 ° (000 - 005 - 010 - 015 - ... ..), providing a component of the vector. In the Hydrographic Institute, the central computer joins the two components, one of each station, obtaining the final vector.  After integrating the two components obtained in the stations, this is the final result where we have the intensity of the current represented in two ways (length and color of the arrow) and its direction (arrow direction).

Exploratory analysis at one particular frame

The very first step was to make sure the data was imported properly.  Figure \ref{290607} represent the raw data published by the Hidrografico, resolution of the data come aroun 1.4 km and Figure \ref{359138} is a representation of the same data  for purpose of validation indicating the location of the two monitoring system . The observations are available with frequency of  every hour, for the validation purpose,  May 3, 2018  for this first analysis.