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Caldera (Chile) Site History

History Summary

Reference Level

The originators have related the data to tide staff zero which is linked to a fixed set of benchmarks. Specifically, BM #1 (established 1950) is used as a historical datum. However, original data as received from SHOA were adjusted with the SHOA station leveling data as follows.

*Adjustment of shift in reference level deduced from the plot of hourly residuals and from comparison of daily values with Arica and Antofagasta. These adjustments contain uncertainty of a few centimeters.

Data from 1988-1989 were received with the reference level tied to the BM #1(1950) while data for other time periods were received without linking the data to BM #1. Thus, the following level adjustments have been applied to the original data based on SHOA geodetic level records.

The best available channel for the 1993-96 data is from the Bubbler (BUB) as received via satellite at the University of Hawaii. Based on a 3 month (Jan-Mar 1993) overlap with the originators series, (-1949 mm) was added to BUB series to link it to the historical series (BM #1).

Quality Assessment by the UH Sea Level Centre

Comment

The daily and monthly values agree well with the nearest stations, Antofagasta and Arica; however, comparison with redundant sensors that transmit data via satellite shows a level shift of about -5 cm on 16 Jan 1989. The original rolls show a tear in the paper which may have caused the problem. However, the originators accept the data as is and thus no corrections have been applied.

'@' below indicates gaps filled with Encoder data and '#' below is same for Bubbler data received at the TOGA sea level center via satellite. '&' below notes gaps filled with the originator's series.