In order to describe the current state of the available UOT information, the World Ocean Atlas 1998 (WOD 98), compiled by the Ocean Climate Laboratory (NODC - NOAA), has been used as a basis to provide general sampling statistics for each XBT SOOP line.

For each line, a subset of the database has been filtered along an average line path, with more or less bandwidth on either side of the path. This bandwidth was defined depending on how spread the actual sampling is in real life, yet the majority of the lines have a 3 degrees latitude bandwidth. This subset is shown on a line-track plot, which indicates all UOT samples taken along the line path since the beginning of the century, regardless of any other characteristics of the sample other than its position (for example no data quality filter has been applied).

Statistics were then compiled out of this subset, shown on the graphs:

• The first graph shows the comparison between the number of drops per year along the whole line given by the WOCE Data Information Unit (i.e. what the operators have reported) and the one from the WOD 98 database. This comparison is relevant only since 1990, as this is the year where WOCE program started to operate.
• The average depth graph shows the average maximum depth of the samples along the line for each year since 1942. The maximum depth was derived for each drop by the depth to which the data quality was acceptable by Levitus' flag.
• The spatial sampling graph shows the average number of samples per month per square box along the line, for the period 1990 till 1996 inclusive. The size of the box was determined by the width used to filter the database. The time period was chosen to allow comparison with WOCE period requirements.
• The temporal sampling graph shows the actual number of drops per month along the whole track since 1975.

The graphs also show a Low Density sampling requirement, which is based on a rate of one sample per 150 km per month, which was the one used to determine the WOCE requirement.
These graphs are stored as an Excel Spreadsheet for each line and can be downloaded from this list or they can be accessed from the line-by-line summaries listed by ocean basin: Atlantic, Indian and Pacific.

Database comparison

In order to assess the relevance of using the WOD 98 database, a few lines have been looked at based on the WOCE CDrom 1998 UOT database. The exact same statistical process has been applied as for the WOD 98 database and the results are plotted on similar graphs to allow for comparison between the two. This is available for lines AX4, IX12, IX22 and PX17.

• Background
• Objectives
• Method
• Atlantic Ocean
• Indian Ocean
• Pacific Ocean
• Workshop