1.

INTRODUCTIONS

Since 2005, Argo floats have become an important source of observations in the World Ocean and, of course, in the Black Sea. Also, they can be used as Lagrange markers to estimate current speed. [3,4,5] Argo velocity data is only available in netCDF format for all floats on the Argo portal [6] Compared to an online data access and visualization solution, it is less convenient. Therefore, creating a system that allows for data access and current speed visualization is a very real task.

2.

METHOD AND TECHNIQUES

The system was developed based on a client-server architecture. jQuery [7] was used to create the user interface, and Plotly was employed to plot profiles and current rose. The Mapbox GL [8] library provides map service functions. The server part includes a currents database and PHP modules that provide data exchange in JSON format.

The Postgresql DBMS [9] was selected to store data. Data and metadata were intended to be kept apart in the database design. The database consists of a metadata table (trajectories) that is connected to the measurement data table (profiles). (Figure 1, Figure 2) The trajectory tables include the Argo profile ID, cycle number, coordinate fields, the depth of the drift for almost each cycle, and velocity information (speed and direction). Drift information is absent from standard Argo files. A Python script was developed in order to calculate it and insert it into the database table.

Figure 1.

Metadata table example

Figure 2.

Measurement data table

The measurement data table includes the argo platform ID, cycle number, which corresponds to the same trajectories’ table fields, and observed parameters such as pressure, temperature, and salinity. Additionally, some floats have measures for chlorophyll and oxygen. Specially written Python software filled the tables automatically.

The floats’ station positions were indicated by circles, each of which had a different color. They were plotted on the map using the JSON data.

Visualizing velocity vectors on the interactive map was the other task. Recognize that while the Mapbox GL library does not come with arrow markers by default, you may use it to add custom images and icons to your map. Therefore, it was first required to sketch them and add them to the main JavaScript file. The accompanying arrow images were created for intervals of seven speeds. Next, a step expression was created to illustrate the direction and speed of the velocity arrows.

3.

THE USER INTERFACE

You can access the user interface (UI) at http://bod-mhi.ry/ff/.

With the ARGO ID, you can choose the ARGO float trajectories from the appropriate list. The trajectory can be shown as vectors that match the drift speed and direction and can be joined to a line, or as points that match observation cycles.

In addition to trajectories, observations points, profiles plots, and drift velocity at the map, drift rose, and metadata (platform ID, coordinates, date, and time of observations) can all be seen through the user interface. The following criteria can be used to make the queries:

Figure 3.

Selection on Argo ID (profiles)

Figure 4.

Selection on Argo ID (velocity)

Figure 5.

Selection all Argo (velocity)

Figure 6.

Selection by rectangular area

4.

CONCLUSIONS

An online, powerful, and user-friendly instrument for accessing, visualizing, and analyzing currents data—such as Argo float velocity—is made available via WEB GIS tools for visualizing sea current data. Updating data and adding new information is made simple by using Python scripts to automatically fill database tables. In addition to Argo float data, the system can hold other velocity data for the Black Sea and other parts of the World Ocean, such as drifters and ADCP observations.