Scientific Topics & Reports

Underwater sound speed Netcdf calculator

Petros Bitsikokos (a), Ioannis Bitsikokos (b)
(a) Military oceanographer (OF-1), Hellenic Navy Hydrographic Service, 229 Av. Mesogeion TGN 1040, Cholargos,;
(b) Software Engineer, independent researcher, 14 Agnoston Martiron st. Nea Smirni, Athens Greece,

The paper describes and presents preliminary results of a Netcdf Transformer tool, developed under java environment, for calculating and producing underwater Sound Speed Netcdf files. This study has been conducted using E.U. Copernicus Marine Service Information (CMEMS). By combining distinct Salinity and Temperature Netcdf data output from CMEMS, a compatible with low end machines Netcdf calculator is created, suitable for “at sea” calculations of the underwater sound speed. The calculations performed are based on Mackenzie (1981) 9 term formula for underwater sound speed. Products of the calculator are depicted in results. The soundscape / acoustic environment of the area bounded by 36N to 42N and Prime Meridian to 009E is calculated, with the distinct halo-clinic fronts of the area in mind. As input data, monthly mean hind casted average salinity and temperature data are selected for a period of 12 months. The calculator input data are the salinity and temperature Netcdf data outputs of Mediterranean Sea physical reanalysis component (product MEDSEA_REANALYSIS_PHYS_006_004), as made available by CMEMS. The output is a single Netcdf sound speed data file, plotted using NASA’s Panoply software. The use of the calculator, permits the production of Military Oceanography (MILOC) related products, thus allowing the comprehensive and robust identification of the soundscape, therefore directly enhances the Environmental Knowledge and Operational Effectiveness (EKOE) principle for all level commands.

Read the paper HERE

See relevant poster HERE


Validation Of Operational Ocean Circulation Forecast Models of the Aegean Sea

by Panourgias Siderakos

A dissertation submitted in partial fulfilment of the requirements for the degree of M.Sc. (Oceanography) by instructional course


From the ancient years till present, the Aegean Sea has always been a sea with major importance. From famous ancient ship battles to modern trading, it always played an essential role for the whole world. Nowadays, all the above combined with its unique oceanographic conditions and topography, the Aegean Sea has become the field of development for two operational, ocean circulation forecast models, the ALERMO model and the POSEIDON model. In this project, an effort for the validation of both models was originally targeted. However, due to lack of data from the POSEIDON model, the validation was performed only for the ALERMO model. Two months were initially chosen, one in winter and one in summer in order to compare their errors based on the different season. As a result, every forecast of the model was being examined in both resolutions of the model (1/30⁰ and 1/60⁰) for both months. Detailed figures of the forecasts are given, in both months and both resolutions in order for the reader to understand the differences that the model demonstrates in relation to the season. In addition, the Root Mean Square Error is calculated and given for each different case. Finally, from in-situ CTD measurements that took place in the Aegean Sea during 2014 and 2016 from an oceanographic ship of the Greek Navy, vertical temperature and salinity profiles were made in relation to depth in order to see the performance of the model in the water column generally. The most important conclusion of this research project is that the model performs very well with specific defects. Each season has its own defects and the model has permanent errors in specific areas in the Aegean. These areas are the mouth of the Dardanelles Strait and the waters adjacent to the coastline of Greece’s mainland. A significant part of these errors happen probably because of the fact that ALERMO is one-way nested to a larger model that covers the whole Mediterranean Sea and has quite low resolution (1/16⁰). Nevertheless, the development of the model is continuous and the improvements are visible both in its function and its errors. A research with salinity data would be very useful and interesting in the future, as today the daily and monthly data for this region are very poor.


Read the dissertation HERE


ALB Effectiveness in the Aegean Sea

Function of Water Clarity 29/05/2015

An Airborne Lidar Bathymetry (ALB) system has to cope with a number of limitations. Weather conditions (rainfall, humidity and sea state), together with bottom conditions (slope of the seabed, material type, roughness and density) are of great importance. However, the factor that dominates is water clarity. The attenuation of a beam of light by water results from two independent mechanisms; scattering and absorption. Therefore, turbidity, which is controlled by rivers’ runoffs and winds, wind/wave induced sediment re-suspension, the intensity of coastal human activity, the tidal amplitude and the structure of the water column itself, have the potential to significantly influence the maximum surveyable depth.

Lt Georgios Georgopoulos,
Hellenic Navy Hydrographic Service,

Read the article HERE