The study of the long-term climate variability is possible only when we have the long homogeneous data records. In practice we have such climatic series very seldom. Thus, investigations of the detailed information concerning history of the station is very important. The entire documentation connected with the station activity, relocation, methods of observations, instruments and observers is called "metadata". Importance of such data was understood by the Commission of Climatology WMO and the working group on Climate Change Detection. Some proposal was given for Global Climate Observing System Surface Network Sites (WMO 1999). Another example was found in the master station history information file of NOAA (2000) and in the North Atlantic Climatological Dataset (Frich et al., 1996). Broad experience in that matter were presented by I. Auer and R. Boehm (1996), R. Heino (1997), and K. A. Shein (1999).
Meteorological services pay larger attention to the station history documents. The oldest historical information is very dispersed and even sometimes lost and unavailable. Some of them can be obtained from the archival monthly reports from the stations.
There is a lot of proposals for computer metadata-files. This work is an attempt of reconstruction of the metadata files for the Polish climatological stations for the whole period of instrumental observations. For this purposes, the simple data base was constructed using the most common Microsoft Access data base. Apart from the common fields concerning the station identification, number, name, coordinates, altitude, height of instruments, river basin, administrative affiliation, date of the beginning of observations, date of relocation or closing of the station etc., there is the large descriptive field included (Table 1). Information concerning detailed description of all, even small relocation of the station, can be found in this field. It contains the detailed description of station localisation, information concerning the station relocations, instruments used, observation schedule and observation procedures. The most important part is the history of the barometer localisation. Another parts contain: name of observers and short comments concerning quality of observations, changing in procedures of observations, time, calculating of daily means etc. There is also important information about the sources of metadata as well the information about the place of existing original data: archives, yearbooks and other publications, computer data bases. Example of such description is prepared on the basis of the Warsaw and Cracow stations.
Data type are divided on: text, numbers, yes or not (y/n) type, date and the largest memory field (Memo) contains large amount of text for the detailed description of the station. The structure of the table can be easily changed by addition of new fields.

Below you can find some codes for few fields. Another ones can be prepared according to the regional or country needs.

Obst - obstruction within 10 m (WMO 1999):
"blank" - Unknown,
0 - No significant obstructions,
1 - Slightly obstructed,
2 - Mostly obstructed.

LUtype - land use type within 10 square kilometers of the station is described by one-digit integer value (WMO 1999):
"blank" - Unknown,
0 - Forest,
1 - Shrubland,
2 - Savannah,
3 - Grassland,
4 - Permanent Wetland,
5 - Cropland,
6 - Urban (population >10,000),
7 - Snow and Ice,
8 - Barren or Sparsely Vegetated,
9 - Water Bodies.

Traditional historical station exists until today, with thermometer screen on the elevation 12 m above the ground on the northern side of the building, without any changing from the beginning of observations. In 1958 the new, parallel station in Botanical Garden was established for comparison. Coordinates of station: 50° 04'N, 19° 58'E, Hs = 206 m a.s.l.

01.05.1792 - organisation of the station by prof. J. Sniadecki;
1825 - higher level of observation, from this year without any interruptions;
1834 - August psychrometer;
1838 - extreme thermometers;
1849 - starting of rainfall measurements;
1858/59 - rebuilding of the house of Observatory;
20.02.1866 - beginning of the snow cover measurements;
1876! - introduction of metric unit: P in mmHg, temperature in deg. Celsius;
1883 - Campbell-Stokes heliograph (sunshine recorder);
1995 - parallel automatic records of temperature;

1816 - Hb = 211.6 m a.s.l.;
1847 - Hb = about 217.5 m;
1867 - Hb = 217.4 m;
1870 - Hb = 220.3 m;
1951 - Hb = 219.8 m.

01.05.1792: 6-7, 14-15, approx. 21;
01.10.1823: 7-8, 12, 14-15, 19-21;
01.10.1824: 7-8, 12, 14, 19-20;
01.06.1825: 5, 12, 15, 22;
24.07.1825: 7, 12, 15, 21;
01.01.1837: 6, 14, 22;
01.01.1893: 6, 14, 22 CSE (Central European Time of 15 deg. E);
01.01.1903: 7, 14, 21 CSE;
01.01.1912: 7, 14, 21 mean local time (6:40, 12:40, 20:40 CSE);
01.01.1971 (1), 7, 13, 19 CSE - at (1) temperature from thermograph and relative humidity from hygrograph;
01.01.1996 7, 13, 19 CSE.

Original data are available in the Archive of the Department of Climatology of the Jagiellonian University for the periods of: 01.05.1792-18.05.1794, 24-27.12.1798, 1,2,11-20,23,24,30,31.01; 1-28.02;1-31.12.1799, 01.01-31.03.1800, 01.01.-28.02.1803, and 1826-2000. Printed data were prepared for the years 1826-1850. Archive of the Institute of Meteorology and Water Management in Warsaw holds data for the years: 1867-1869, 1870 only I, 1892 only II, 1914 XII, 1915-1917, 1918 IX-XII, 1919-2000. History and results of observations were published in a few papers:
- Hanik J., 1972, Dzieje meteorologii i obserwacji meteorologicznych w Galicji od XVIII do XX wieku (History of meteorology and meteorological observations in Galicia from XVII to XX Century), Wroclaw-Warszawa-Kraków-Gdansk, 216 pp.
- Zeszyty Naukowe UJ "Results of Studies of the Climatological Station of the Jagiellonian University in Cracow":
- Prace Geogr. 55, Prace IGUJ 77, 1982 (raw data),
- Prace Geogr. 69, Prace IGUJ 91, 1986 (raw data),
- Prace Geogr. 75, 1989 (raw data),

01.01.1779 - start of regular observations in Warsaw, elaborated by a royal astronomer. New series of observations started at 20.01.1825 in Astronomical Observatory in the place with coordinates: 52° 13'4.60"N 21° 02'E (1h24m7.245s), Hs=110m, Hb=120.60 m.
Hours of observations:
11.1825-05.1836: 6, 12, 18 local time;
06.1836-12.1840: 4, 10, 16, 22 local time;
01.1841-12.1869: 6, 10, 16, 22 local time;
01.1870-12.1970: 7, 13, 21 local time (6:36, 12:36, 20:36 Central European Time);
01.1971 (1), 7,13,19 Central European Time ((00),06,12,18 GMT).

Auer I., Boehm R., 1996, Data, metadata and the question of homogeneity for the Austrian climatological network, Proceedings of the Seminar for Homogenization of Surface Climatological Data, Budapest, Hungary, 6-12 October 1996, p. 83-95.

Frich P. (et al.), 1996, North Atlantic Climatological dataset (NACD Version 1) - Final Report, Danish Meteorological Institute, Scientific Report 96-1, Copenhagen, pp. 47.

Heino R., 1997, Metadata and their role in homogenization, First Seminar for Homogenization of Surface Climatological Data, Budapest, Hungary Hungarian Meteorological Service, p. 5-8.

NOAA, 2000, NCDC on-line inventories, home page:
ftp://ftp.ncdc.noaa.gov/pub/data/inventories/

Shein K.A., 1999, The role of metadata in climate data homogeneity, [in:] Proceedings of the Second Seminar for Homogenization of Surface Climatological Data (Budapest, Hungary, 9-13 November 1998), WCDMP-No. 41, WMO-TD No. 962, Geneva, p. 195-201.

WMO, 1999, Global Climate Observing System (GCOS), GCOS Surface Network (GSN), Data Format and Supporting Documentation for WMO Members to Use When Providing digital Historical Data for GCOS Surface Network Sites to the National Climatic Data Center, P/GSN
- Annex 4, p. 1-17, home page: 'http://www.wmo.ch/web/gcos/'.