The JMA has been operating drifting ocean data buoys. The buoys have cylindrical shape hull with a diameter of 64 centimeters. Sensors for position, air pressure, sea surface temperature and wave height/period are equipped within the hull, at levels close to the sea surface.
The observation is usually carried out every three hours. When wave height exceeds the threshold set beforehand (e.g. 3.0 m), each buoy changes the function automatically to one-hourly observation. The threshold value can be changed anytime via two-way satellite telecommunication system.
Observation data of each buoy are stored on the CD-ROM in a file named "yy-nn.txt", While the chart is stored in a file named "yy-nn.gif". Where yy shows year and nn is a consecutive number assigned in order of deployment in the year.
Explanation of File Format
| Element | Start Position | Field Type | Description of Field |
|---|---|---|---|
| Buoy number | 1 | I5 | WMO station index number. |
| Year | 7 | I4 | |
| Month | 12 | I2 | |
| Day | 15 | I2 | |
| Hour | 18 | I2 | THe Coordinated Universal Time. |
| Latitude | |||
| N or S | 21 | A1 | N:North, S:South. |
| Degrees | 23 | I5 | Latitude in degrees to thousandths. |
| Longitude | |||
| E or W | 29 | A1 | E:East, W:West. |
| Degrees | 30 | I6 | Longitude in degrees to thousandths. |
| Air pressure | 37 | I5 | Air pressure in hPa to tenths. |
| Sea surface temp. | 43 | I3 | Sea surface temperature in degrees centigrade to tenths. |
| Wave height | 47 | I3 | Significant wave height in meter to tenths. |
| Wave period | 51 | I2 | Significant wave period in seconds. |