=========================== FOLLOWING PSMSL DOCUMENTATION ADDED 2001Aug29 :
PSMSL data for Syowa are taken from the reports of the Japanese Antarctic Research Expeditions (JARE).  Data from 1975-87 were from an absolute pressure gauge and are uncorrected for air pressure effects (December 78 value is stated as being unreliable, reference level may be drifting). Data for 1988 onwards are from a differential pressure sensor and are automatically corrected for air pressure. For further information, see the paper:  Odamaki, M., Michida, Y., Noguchi, I.,Iwanaga, Y, Ikeda, S. and Iwamoto, K. 1991. Mean sea level observed at Syowa station, East Antarctica. Proceedings of the National Institute of Polar Research Symposium on Antarctic Geosciences, No.5., pp.19-28. In principle, both periods of recording (i.e. from the absolute and differential sensors) have been referred each January to a benchmark (TGBM 1040) by means of simultaneous tide pole readings. However, the levelling information is very irregular. Again, see the above paper for details. Also, an analysis of data to 1998 was carried out by the PSMSL in 2001 which can be provided if required; Dr Odamaki concurs with the
findings of that analysis.  That suggests that the seasonal cycles for 1990 or so (i.e. since the new sensors were used) have much smaller amplitude than prior to that date (i.e. as used in the Odamaki et al paper). In addition, it suggests that the large rate of sea level fall observed in the 1980s has flattened off considerably. However, the uncertainties about datums precludes definite statements about secular trends.  For people using the data for seasonal cycle studies, they should be aware that data have been usually recorded Feb-Jan because of
the visits to the base each January. Consequently, each year starting Feb sometimes looks off-set from the Jan of that calendar year.
=========================== FOLLOWING PSMSL DOCUMENTATION ADDED 19-SEP-05 :
This is to reiterate that care must be taken with Syowa data, and in particular to treat the year as running from Feb-Jan when computing seasonal cycles as the gauges were usually refurbished at the end of each January.

