The TOGA Sea Level Center (TSLC) in collaboration with the National Oceanographic Data Center (NODC) has prepared a software package for sea level data processing designed for IBM PC compatible microcomputers under the DOS operating system. The package includes three principle components: 1) tidal analysis and prediction, 2) quality control, and 3) filtering. The software is geared to persons with prior knowledge of the DOS environment as well as a basic understanding of sea level processing. The goal of this software is the establishment of a permanent archive that contains quality-controlled data at hourly, daily, and monthly intervals written in standardized formats suitable for incorporation into international archives, where sea level data are available to the scientific community for exchange and analysis.
The quality control techniques have been well documented (Caldwell and Kilonsky, 1992). The main emphasis is the use of residuals (observed data minus the predicted tides) for detecting suspicious data. An example is shown in (Figure 1).
Several bad data values can be identified in this figure. Individual bad data points or "spikes" can be seen on February 21,23, and 26 as well as May 26. A timing offset is seen over several periods; for instance, December 7-12. The periods with relatively flat signatures indicate good data.
The package also includes a filter for generating daily and monthly values from the hourly sea level heights (Figure 2).
SYSTEM REQUIREMENTS
This package has been developed for use on IBM PC XT, AT, 386, or 486 compatible microcomputers and clones. Because of the plotting subroutines and the complex mathematical algorithms of the tidal analysis program, the execution of the programs will be much faster if the host system has an 8087 math coprocessor or an equivalent. For an indication of the differences in execution time for various host systems, the Tidal Analysis Function takes the following amount of time:
machine execution time
386, 20 Mhz 1.5 minutes
XT with 8087, 4.77 Mhz 14 minutes
XT, no 8087, 4.77 Mhz 2 hours
The plotting subroutines require a display card capable of
supporting graphics in the EGA, CGA, VGA, or Hercules modes,
and support hardcopy output on most IBM and Epson printers
as well as on most HP PC laser and wet ink plotters. The
package works best with at least 512 Kbyte of memory and
assumes the system supports a hard disk drive and either a
1.2 Mbyte or 360 Kbyte 5.25 inch floppy disk drive or a 1.4
Mbyte or 740 Kbyte 3.5 inch disk drive. The batch files of the TSLC/NODC package utilize PC-DOS or MS-DOS operating system versions 3.1 or greater, and the source codes of the programs were compiled with the Micro- Soft FORTRAN Optimizing Compiler version 4.10. The graphics subroutines are provided by PLOTWORKS, INC.
If you desire a copy of this software, please indicate floppy disk specifications for your system including disk size (5.25 or 3.5 inch) and density (high or low). Send request to:
Mr. Patrick Caldwell
TOGA Sea Level Center
University of Hawaii
1000 Pope Road, MSB 316
Honolulu, Hawaii 96822 USA
Internet: caldwell@kapau.soest.hawaii.edu
fax: 808-956-2352 or 808-956-4104
office phone: 808-956-4105
REFERENCE Caldwell, P., and B. Kilonsky, 1992. Data processing and quality control at the TOGA Sea Level Center. Joint IAPSO-IOC Workshop on Sea Level Measurements and Quality Control, Paris, 12-13 October, 1992. IOC Workshop Report No. 81, UNESCO. pp. 122-135.