The maps reachable here show the density of air pressure observations at sea level carried out by marine stations (buoys and ships). In each Marsden square (10 x 10 degrees), two numbers are shown.

• The top number is an index which is representative of how the requirements (WWW, WCRP, or GOOS) are met: An index of 100 means that an average of 8 observations per day per 500 km x 500 km area has been received from the square during the month.
• The bottom number represents the percentage of BUOY reports from the total of SHIP plus BUOY reports received. In order not to give too much weight to drifting buoys reporting very often every day, BUOY reports in excess of 8 per day per buoy are not counted.