Version of 22 February 2010 Description of the File of PSMSL Monthly Means The file 'psmsl.dat' is composed of 80-byte ASCII records organised as described below. It is about 8 Mbytes in length and should be readable by the job 'psmslrd.f'. For a full understanding of the terminology employed, please consult the file 'PSMSL.doc' on this disk. In particular, it is important to note that only the RLR-adjusted data for each station can be employed for time series work. The data in 'psmsl.dat' are written for one station after another. For each station there are two header records. The first contains: Station Name (40 bytes) PSMSL Country Code (3 bytes) PSMSL Station Code (3 bytes) Latitude (8 bytes) e.g. ' 55 44 N' Longitude (8 bytes) e.g. '123 01 E' Authority Code (2 bytes) Frequency Code (2 bytes) RLR Datum Year (4 bytes) GLOSS code (3 bytes) or blanks if not a GLOSS station Station documentation flag (1 byte) Six blanks (6 bytes) which makes a total of 80 bytes. The authority code (sometimes called 'ACODE' in the documentation) identifies which authority supplied the data - see the file 'indexa.html' for a list of authority codes and addresses. The frequency code (sometimes called 'FCODE' in the documentation) specifies the sea level sampling which has been used for the determination of the mean sea level. Codes are defined as follows: Integer 'n' implies 'n' measurements per day. 'C' implies integration from continuous readings. 'HL' implies a mean of high and low waters (i.e. Mean Tide Level). If the RLR datum year is 9999, this indicates that all data for this station are Metric only i.e. no RLR data exist. (Otherwise the RLR datum year has no special meaning for analysts. For those interested, it is the year of data from which an initial computation of RLR factors for this station was made). The GLOSS code will be blank if the station is not in the GLOSS network. If the station documentation flag is not a blank, it indicates that an entry exists in the documentation for this station. This may point to this record not being as reliable as one would like, but clearly not so unreliable as to have been removed from the dataset entirely. In the second record there are: Number of annual means following (NYEAR) (3 bytes) Number of free-text station comments (NCOMS) (3 bytes) Number of free-text country comments (NCOMC) (3 bytes) Number of free-text authority comments (NCOMA) (3 bytes) Sixty eight blanks (68 bytes) which makes a total of 80 bytes. There are then two 80-byte records for each year of data. The first record is formatted: Year (4 bytes) Six blanks (6 bytes) Missing days word (26 bytes) Four blanks (4 bytes) Documentation flag (1 byte) Thirty nine blanks (39 bytes) which makes a total of 80 bytes. The missing days word contains 2 bytes for each month, then 2 bytes corresponding to the annual mean. For the months, values like '12' indicates 12 days were missing for the month; 'XX' indicates that a gap has been interpolated over to compute the monthly mean. For the 2 bytes corresponding to the annual mean, 'XX' indicates that one month or equivalent of data are missing and that, though an annual mean value is quoted, it may be unreliable; ' -' indicates a missing annual mean. If the documentation flag is not a blank, it indicates that an entry exists in the documentation for this station-year. This may point to this year not being as reliable as one would like, but clearly not so unreliable as to have been removed from the dataset entirely. On the second record there are: Monthly mean values in mm for 12 months of the year (12*5 = 60 bytes) Annual mean value in mm (5 bytes) RLR factor in mm (10 bytes) Five blanks (5 bytes) Monthly or annual mean values of 99999 indicate missing data for this month or year, which will be reflected in the missing days entry on the previous record. An RLR factor of 99999 indicates that this station-year is not RLR. IT IS VERY IMPORTANT TO NOTE NOW that in order to compute the RLR values of mean sea level for this year of data, the 'RLR factor' must be added to each of the 'Metric' monthly values and to the 'Metric' annual mean value. Remember that station-years for which the RLR factor is 99999 must in general NOT be used for time series analysis. To complete the information for this station, there follow: NCOMS 80-byte comments on the station followed by NCOMC comments the relevant country and NCOMA comments on the responsible authority. At latest update the file 'psmsl.dat' contained: - a total of 58420 station-years of data - a total of 9447 station comments - a total of 3210 country comments - a total of 4153 authority comments Subsequent versions of the file will contain larger numbers of records. If problems are found reading the file, or if further information is required, please contact the PSMSL at: Permanent Service for Mean Sea Level Proudman Oceanographic Laboratory Joseph Proudman Building 6 Brownlow Street Liverpool L3 5DA United Kingdom or Telephone: (UK +44) 151-795-4800 or Fax: (UK +44) 151-795-4801 or Email: psmsl@pol.ac.uk