1. Unit of Marine Technology and Engineering, Technical Univ. of Lisbon, Inst. Superior Téchnico, Av. Rovisco Pais, 1049-001 Lisboa, Portugal.
2. Puertos del Estado, Avda. del Partenon No. 10, 28042 Madrid, Spain.
3. Unit of Marine Technology and Engineering, Technical Univ. of Lisbon, Inst. Superior Téchnico, Av. Rovisco Pais, 1049-001 Lisboa, Portugal (corresponding author).
4. Dept. de Física, Univ. de Las Palmas de Gran Canaria, Campus Universitario de Tafira, 35017 Las Palmas de Gran Canaria, Spain.