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Below you'll find information about:

1. Data granularity
2. Update frequency
3. Time stamps and time intervals
4. Column separators, decimal dividers and missing values

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Data granularity

For all types of data MeteoSwiss uses standard granularities. Depending on the application not all granularites are available.

For Ground-based Measurements the lowest granulartiy is usually called 'original data' (Originalwert). Higher granularities are called 'aggregations' or 'aggregated values'. The World Meteorological Organization (WMO) does issue guidelines on how national weather services have to aggregate values and MeteoSwiss does follow these guidelines.

If you need hourly, daily, monthly or yearly values, we strongly recommend that you download the according granularity. Downloading the raw data (10min) and calculating sums or means yourself, will not always lead to the same results! Furthermore for historic data it is possible that manual data corrections have only been applied on higher granularities (like hourly or daily data), which means that historic raw data can still contain errors.

This is the overview of the granularities for Ground-based and Atmosphere Measurements as well as for Homogenous Climate Data Series and Climate Normals used by MeteoSwiss:

Granularity	Name	Description	Used for
t	10min value	At MeteoSwiss this is the standard granularity for realtime data of the automatic measurement network SwissMetNet (SMN) or the model output. Meteorological observations do also use this granularity but only offer values at fixed intervals like 6UTC, 12UTC and 18UTC (called "Terminwerte")!	SMN, OBS
h	Hourly value	Either aggregated from 10min values or provided by the instrument/network	Pollen
d	Daily value	Used throughout the MeteoSwiss measurement network before automatization in 1981 started. Today still used for manual precipitation and snow measurements. For automatic stations daily values are calculated using 10min values according to WMO guidelines.	NIME
m	Monthly value	Usually aggregated from daily values and widely used in climatology for homogenized data and norm values and for seasonal data. For some very old data series (pre 1864) only monthly data exists!	Homogeneous climate data series, Climate normals
y	Yearly value	Usually aggregated from daily values and mostly used in climatology or climate change screnarios.	Climate change scenarios

Update frequency

For Ground-based and Atmosphere Measurements as well as for Homogenous Climate Data Series and Climate Normals MeteoSwiss provides an optimized directory structure separating older historical data, which is not updated regularly, and more recent data, which is updated more often. For realtime data we provide a third "now" directory with a high update frequency.

This is the overview:

Type	Description	Update frequency	Used for
historical	From the start of the measurement until December 31st of last year	Once a year	Granularity m, d, h, t
recent	From January 1st of this year until yesterday	Daily at 12UTC	Granularity m, d, h, t
now	The most recent realtime data from yesterday 12UTC to now	Every 10min	Only Granularity h, t
no type	For certain data types this concept does not apply	varies	varies (e.g. Granularity y)

Time stamps and time intervals

All reference time stamps at MeteoSwiss are in UTC! Depending on the granularity the time stamp does define different intervals:

• t: The sum, mean or max/min of the last 10 minutes (ReferenceTS 16:00 = 15:50:01 to 16:00:00)
• h: The sum, mean or max/min of the last six 10min-values (ReferenceTS 16:00 = 15:10 to 16:00). Please note: Hourly values before 2018 were calculated differently based on the SYNOP schedule (ReferenceTS 16:00 = 14:50 to 15:40)!
• d: For most parameters the sum, mean or max/min from 00:00 to 23:50 of the according date. Exception for precipitation and snow (manual measurement times used for consistency) where the interval is 6:00 UTC until 5:50 UTC tomorrow (ReferenceTS 22.6.2023 = 22.6.2023 6:10 UTC to 23.6.2023 6:00 UTC)
• m: The sum, mean or max/min of the whole month from 1st to last day of month (ReferenceTS 1.6.2023 = 1.6.2023 00:10 UTC to 30.6.2023 24:00 UTC)
• y: The sum, mean or max/min of the whole year (ReferenceTS 1.1.2023 = 1.1.2023 00:10 UTC to 31.12.2023 24:00 UTC)

Accordingly, it follows that:

• for granularity t and h the time stamp defines the end of the measurement interval and
• for higher granularities (d, m and y) the time stamp defines the beginning of the interval!

Column separators, decimal dividers and missing values

Generally, columns are separated with a semicolon (;). The decimal divider is a full stop (.). Missing values (e.g. due to instrument failure) are marked with -1000000, empty columns are used when a parameter is not measured at all at a certain station.