An interactive graphical system of XBT data quality control and visualization

Abstract

A PC-based system has been developed for quality control and visualization of expendable bathy thermograph (XBT) data archived at the Indian Oceanographic Data Centre. The system, coded in Visual C++, is user interactive and runs on Windows-95 platform. Quality control module of the system incorporates various quality norms/checks and has two levels; inventory and data levels. Inventory level checks are applied for land-sea position, speed of the vessel, invalid date/time, duplicates and station sounding. Station sounding check is performed based on the ETOPO bathymetry file having 5' x 5' spatial resolution. Although the QCS is developed for quality control and visualization of the XBT data, it could be used for inventory level quality checks of any general oceanographic data. Data quality module involves tests for XBT-specific errors such as surface transient, temperature inversions, fall rate and depth reversal. This level also involves visual inspection of the profiles for identifying and correcting/flagging of features caused by wire stretch, wire break, bowing and nub in the mixed layer. Provision is given to compare individual XBT profiles with neighboring stations and also with 1 degree x 1-degree monthly climatologies. Quality flags are assigned for each inventory and depth field. Since data exchange (national and international), under the IODE system, stipulates standard quality flags, the Integrated Global Ocean Observing System recommended flags are applied in the system. Station having data with erroneous or doubtful flags are sent to error bin, which can be accessed by privileged users for possible correction and subsequent modifications in the data base. The data visualization module has options for data queries, selection and graphical presentations, like vertical and horizontal distribution of temperature