NOTE: AUGUST 1996 - The SLP-PAC pressure corrected sea level data set has been updated with a "new improved" NWS atmospheric pressure data set. When we received the new pressure corrections, we were able to reprocess the anomaly data from 1979 through the present. Beginning in 1997, the mean sea level and annual cycle are referenced to the period 1975 - 1995. Data from previous years have been updated using the new reference means. Joint WMO/IOC Technical Commission for Oceanography and Marine Meteorology (JCOMM) Sea Level Program in the Pacific (SLP-Pac) The JCOMM Sea Level Program in the Pacific was established for the purpose of making monthly mean sea level data available to a wide circle of users in a timely fashion, and to generate products that would be valuable for scientific analysis of climate-related processes. A pilot project started in June, 1984 and a permanent program was established in 1988. During the pilot project and in the first year of the permanent program, maps of the sea level deviations from the mean sea level have been produced without fail since June, 1984. In January, 1988 we began producing maps of the anomaly of sea level from the 1975 to 1986 mean annual cycle of sea level. This anomaly is also corrected for the inverted barometer effect using the atmospheric pressure fields computed at the National Meteorological Center. In addition to these basic products, we developed additional products during the pilot project. These products include time series of the volume of the tropical Pacific Ocean (published quarterly) and indices of the equatorial current system (published annually). The volume time series has received much attention because of its importance for El Nino prediction and analysis. A major goal in the past year was the development of a system for distributing digital versions of our JCOMM products using the modern computer networks now available. This "anonymous ftp" system on the INTERNET computer network will help us to reach this goal. We ask that you help us to monitor the success of this effort to enhance the access to our JCOMM products. To do this, please let us know what data you have copied, and make comments or suggestions for improvement. You can send mail messages to Mark Merrifield (Internet mail at markm@.soest.hawaii.edu), or to Shikiko Nakahara (nakahara@kia.soest.hawaii.edu on the INTERNET mail system). We thank you in advance for your cooperation. Mark A. Merrifield and Klaus Wyrtki SLPP.DEVIATIONS This file contains the time series of the deviations of sea level from the 1975 through 1995 mean sea level value computed at each station. The time series cover the period 1975 through 1997. Large linear trends were found at five stations and are corrected for in this data set. The seven stations affected are Davao in the Philippines, La Libertad in Ecuador, Kushiro in Japan, Suva in Fiji and Seldovia, Unalaska, Yakutat in Alaska. Units for the sea level deviations are millimeters, and missing data points are set to a value of 9999. The format gives the complete time series for a station, followed by a separator record, then by the time series for the next station, etc. The time series at each station is preceded by one header record, which includes the station name (columns 1-20), the country name (columns 21-40), the latitude (columns 41-46), and the longitude (columns 48-54). This header is followed by a series of data records, each of which contains data for one year. These data records contain the station name (columns 1-10), the year (columns 12-15), and the 12 monthly values of the sea level deviations (January value in columns 16-20, February value in columns 21-25, ... , and December value in columns 71-75). The time series are separated by one record of dashes. SLPP.ANOMALIES This file contains the anomalies of sea level corrected for the atmospheric pressure. Anomalies of sea level are computed by subtracting the mean annual cycle of the sea level variation that is estimated using data from 1975 through 1995. Atmospheric pressure corrections for the period 1979 to present are derived from the fields computed at the National Meteorological Center. Atmospheric pressure corrections for the earlier period are from historical meteorological station data. The time series of the pressure-corrected sea level anomaly cover the period 1975 through 1997. Large linear trends were found at five stations and are corrected for in this data set. The five stations affected are Davao in the Philippines, La Libertad in Ecuacor, Kushiko in Japan, Suva in Fiji and Seldovia, Unalaska, Yakutat in Alaska. Units are millimeters and missing values are marked with values of 9999. The format gives the complete time series for a station, followed by a separator record, then by the time series for the next station, etc. The time series at each station is preceded by one header record, which includes the station name (columns 1-20), the country name (columns 21-40), the latitude (columns 41-46), and the longitude (columns 48-54). This header is followed by a series of data records, each of which contains data for one year. These data records contain the station name (columns 1-10), the year (columns 12-15), and the 12 monthly values of the sea level anomalies (January value in columns 16-20, February value in columns 21-25, ... , and December value in columns 71-75). The time series are separated by one record of dashes. SLPP.PC_DEVIATIONS This file contains the time series of the pressure-corrected deviations of sea level from the 1975 through 1995 mean sea level value computed at each station. The time series cover the period 1975 through 1997. Large linear trends were found at five stations and are corrected for in this data set. The five stations affected are Davao in the Philippines, Kushiro in Japan Suva in Fiji and Seldovia, Yakutat in Alaska. Units for the pressure-corrected sea level deviations are millimeters, and missing data points are set to a value of 9999. The format gives the complete time series for a station, followed by a separator record, then by the time series for the next station, etc. The time series at each station is preceded by one header record, which includes the station name (columns 1-20), the country name (columns 21-40), the latitude (columns 41-46), and the longitude (columns 48-54). This header is followed by a series of data records, each of which contains data for one year. These data records contain the station name (columns 1-10), the year (columns 12-15), and the 12 monthly values of the sea level deviations (January value in columns 16-20, February value in columns 21-25, ... , and December value in columns 71-75). The time series are separated by one record of dashes. SLPP.CURRENTS and SLPP.TOPOGRAPHY These files contain indices of the equatorial Pacific currents (SLPP.CURRENTS) and estimates of the equatorial ridge and trough topography (SLPP.TOPOGRAPHY) that are used to derive the current indices. Current indices are provided for the North Equatorial Countercurrent, the North Equatorial Current, and for the portions of the South Equatorial Current lying north and south of the equator. The current indices are computed by perturbing the meridional profile of mean surface dynamic height with the monthly mean time series of the sea level variations and calculating the appropriate ridge to trough difference for each current for each month. The mean values of the indices have not been removed from the time series. The calculation of these indices is discussed in greater detail in a paper by Wyrtki in the Journal of Physical Oceanography (1974, Volume 4, pp. 372-380). The time series of each index is preceded by one header record that identifies the index. This header record is followed by data records, each of which contains one year of monthly values. Specifically, the data records contain an ID value (columns 1-3), the year (columns 5- 8), and the 12 monthly values (January value in columns 9-14, February value in columns 15-20, ... , and December value in columns 75-80). The units are millimeters. Missing values are marked by a value of 9999. The time series for the various indices are separated by a record containing dashes. SLPP.VOLUME This file contains the monthly time series of the variations in the upper layer volume of the tropical Pacific between 15N and 15S. The volume is computed from a gridded field of the sea level deviations via a one and a half layer approximation for the vertical structure of the tropical Pacific. Further details of the calculation are given by Wyrtki in a paper in the Journal of Geophysical Research (1987, Volume 90, pp. 7129-7132). The units for the volume changes are 10 to the 12th cubic meters, and the variations are relative to mean value of about 7000 of these units. The annual cycle has not been removed from the volume deviation time series. The first record of this file contains identification information. This header record if followed by a series of data records, each of which contains one year of the time series. Specifically, the data records contain an ID value (columns 1-9), the year (columns 11-14), and the 12 monthly values (January value in columns 15-19, February value in columns 20-24, ... , and December value in columns 70-74). (12*5 bytes). Missing data points are marked with a value of 9999.