Meteorology

Overview

IMGW publishes meteorological observations for the Polish weather-station network at daily and monthly resolution, as open data from the public data portal. No authentication is required.

Values are downloaded as zipped CSV archives (decoded as latin-1), with station metadata resolved from the accompanying station-code list. Both daily and monthly summaries are provided.

Status columns

Every measurement in these files is followed by a status column, documented per file in the *_format.txt beside the data. It is read, and carried into quality:

status	meaning	value	quality
blank	the value is a measurement	as published	null
8	brak pomiaru – no measurement	null	8
9	brak zjawiska – the phenomenon did not occur	0	9
Z	opad zbiorczy – a collective total (o_d only)	as published	10

Neither code can be taken from the value column, because the files do not write it the same way twice. Where the status is 8 the value is not left empty but holds a literal zero, which is why the status has to be read at all – snow depth at a rain gauge would otherwise read 0 cm for every day of a Polish January. Where the status is 9 the cell holds a literal zero in some files and nothing at all in others, for the same parameter months apart, so 9 is returned as the zero it means rather than passed through.

8 and 9 are IMGW’s own codes. quality is a numeric column and Z is a letter, so Z is reported as 10, one of two codes here this library assigns itself. An opad zbiorczy is a sum over the preceding days that were not measured, published on the day the reading was taken without saying which days it covers, so the value is kept – it is a real measurement – and the 10 is what says it is not that day’s total alone.

The other is 11. o_d_format.txt adds that brak zjawiska covers a day absent from a month that is itself present (“Brak zjawiska to również brak dnia w istniejącym miesiącu”), and the older o_d files rely on it: o_d_02_2010 carries 14,229 rows for the 26,796 days in its stations’ months, while o_d_07_2024 writes every day out, with status 9 on the dry ones. daily/precipitation returns such a day as 0 mm with quality 11, so that a dry day reads the same whichever year IMGW wrote the file in, and 11 rather than 9 because no status in the file says so. Only precipitation_amount is filled: a day without rain is not a day without snow cover. A month the station has no row in at all is left empty, and daily/climate and daily/synop are read as published, since their format files carry no such sentence.

One thing the status cannot resolve: a 0 in monthly/climate’s snow_depth_max that is not qualified by a status means either that there was no snow cover in the month or that the maximum could not be determined; k_m_d_format.txt says so in as many words. It is common – 96 of the 196 rows of 2024 – and is returned as 0 cm.