Monthly mean air temperatures from Tarfala Research Station, Kebnekaise Mountains, Northern Sweden

Tarfala Research Station staff

This dataset contains monthly mean air temperatures from Tarfala Research Station, acquired since 1965 and updated annually.

Tarfala Research Station (TRS), located at 1135 m a.s.l. in the Tarfala Valley, Kebnekaise Mountains, Northern Sweden, is Stockholm University’s centre for glaciological and alpine research. Here, meteorological observations have been carried out regularly since the first glaciological field campaign to the Tarfala Valley in May 1946, already before TRS was inaugurated in 1961. These data provide important climatological information in itself and also give context for a wide range of other climate system components in the Tarfala Valley, such as glaciers, streams, permafrost, etc., and their dynamic change over time.

Up until 1965, air temperature measurements were made manually, and only during the summer season. Thus, for the years 1946 – 1964, monthly mean air temperatures are reported only for June, July and August. From 1965 to 1987, automated data collection was carried out during all months of the year. In 1987 the first digital logger based automatic weather station (AWS) was established and operated until 2013 when it was replaced by a more modern equivalent (referred to as TRS-AWS). The dataset presented here is compiled from some previously published separate datasets containing data until 2022. The current version includes data until 2024.

Citation

Tarfala Research Station staff (2025) Monthly mean air temperatures from Tarfala Research Station, Kebnekaise Mountains, Northern Sweden. Dataset version 2. Bolin Centre Database. https://doi.org/10.17043/tarfala-monthly-temperature-2

References

Grudd H, Schneider T (1996) Air Temperature at Tarfala Research Station 1946-1995. Geografiska Annaler Series A, Physical Geography 78:115. https://doi.org/10.2307/520973

Jonsell U, Hock R, Duguay M (2013) Recent air and ground temperature increases at Tarfala Research Station, Sweden. Polar Research 32:19807. https://doi.org/10.3402/polar.v32i0.19807

Tarfala Research Station staff (2012) Data from Tarfala Research Station, Kebnekaise Mountains, Northern Sweden. Dataset version 1. Bolin Centre Database. https://doi.org/10.17043/tarfala-1

Tarfala Research Station (2021) Meteorological data from Tarfala Research Station, 2015-01-01–2021-03-31. SITES Data Portal. https://hdl.handle.net/11676.1/RjPJiNY2PM5BteTUhS1QFH1g

Kirchner N, Barnett B, TRS staff (2023) Monthly mean air temperatures from Tarfala Research Station, Kebnekaise Mountains, 1965 – 2022. Dataset version 1. Bolin Centre Database. https://doi.org/10.17043/tarfala-kirchner-2023-monthly-temperature-1

Data description

The dataset is provided in two comma-separated values (csv) files. Both files contain the same temperature data, but they are given in two different forms:

Time series form

The data file tarfala-monthly-temperature-2-vector.csv provides the monthly temperatures as a time series vector. This file has three columns:

• time Time (YYYY-MM)
• temperature Monthly mean temperature (°C)
• source A digit between 1 and 5 depending on the original source, where
  • 1 = manual observations from TRS
  • 2 = old automatic temperature recording equipment at TRS
  • 3 = current automatic weather station at TRS (TRS-AWS)
  • 4 = data measured with TRS-AWS, published at SITES Data Portal
  • 5 = SMHI station Tarfala A

Table form

The data file tarfala-monthly-temperature-2-table.csv provides the monthly temperatures in the form of a table. This file has 13 columns:

• time Time (YYYY)
• t_jan January mean temperature (°C)
• t_feb February mean temperature (°C)
• ...
• t_dec December mean temperature (°C)

Missing values occur for the years 1946 – 1964, in all months except June, July, and August. They are indicated by NaN.

No data was available from TRS-AWS for February 2009, and November 2022 to March 2023. For these months, data is instead taken from the SMHI Tarfala A weather station also located at TRS, as mentioned under Comments.

Comments

Dataset compilation

The dataset is an extension in time of the dataset Monthly mean air temperatures from Tarfala Research Station, Kebnekaise Mountains, 1965 – 2022. The above mentioned dataset was compiled from the following public data sources:

• Monthly mean data for June, July, August 1946 – 1964

  • Data from Tarfala Research Station, Kebnekaise Mountains, Northern Sweden (version 1), Tarfala Data — Climate, Monthly mean air temperature at Tarfala 1946–2012.

• Monthly mean data 1965 – 2012

  • Data from Tarfala Research Station, Kebnekaise Mountains, Northern Sweden (version 1), Tarfala Data — Climate, Monthly mean air temperature at Tarfala 1946–2012.

• Daily mean data for 2013

  • Data from Tarfala Research Station, Kebnekaise Mountains, Northern Sweden (version 1), Tarfala Data — Climate, Temperature data for 2013.

• Daily mean data for 2014

  • Air temperatures at Tarfala Research Station acquired by a HC2S3 temperature and relative humidity sensor manufactured by Rotronic as part of the TRS-AWS instrumentation.

• Daily mean data for 2015 – 2020

  • Meteorological data from Tarfala Research Station, 2015-01-01–2021-03-31. SITES Data Portal

• Daily mean data for 2021 – 2022

  • Air temperatures at Tarfala Research Station acquired by a HC2S3 temperature and relative humidity sensor manufactured by Rotronic as part of the TRS-AWS instrumentation.

Data from 2023 onward are appended here. They were collected in the same way as mentioned above for 2021 – 2022.

Instrumentation

Since 2013, air temperatures at Tarfala Research Station are acquired by a HC2S3 temperature and relative humidity sensor manufactured by Rotronic as part of the TRS-AWS instrumentation. Measurements are reported as 10 minute averages, from which daily and further, monthly, averages were computed. The sensor is mounted approximately 2 m above ground, at an elevation of 1143 m a.s.l., and at geographical coordinates N 7537422, E 651517 (SWEREF99 TM coordinate system).

Dataset creators

The dataset builds on data that was over the years collected and managed by various members of TRS staff. The compilation of the various data sources listed here, to derive the current dataset, was made by Nina Kirchner and Jamie Barnett for the dataset Monthly mean air temperatures from Tarfala Research Station, Kebnekaise Mountains, 1965 – 2022. Data for 2023 and onward was appended by Nina Kirchner.

Climatological summary

This dataset allows for the calculation of annual and seasonal averages, along with other climate trends. The following notable values are mentioned:

• lowest annual average temperature: −5.9 °C (1966)
• highest annual average temperature: −1.3 °C (2024)
• lowest summer (June, July, August) average temperature: +3.3 °C (1975)
• highest summer (June, July, August) average temperature: +9.0 °C (2024)
• Mean July temperatures have been above +10 °C in the years 2003 (+11.7 °C), 2014 (+12.6 °C), 2018 (+12.8 °C), 2021 (+10.2 °C), and 2024 (+10.2 °C). This is especially of interest as one of the definitions of “Arctic” is that July average temperatures do not exceed 10 °C.
• Since 1965, monthly averaged air temperatures have never been higher in May and June than in 2024 (+2.8 °C in May, +7.6 °C in June).
• In 2024, monthly averaged air temperatures for all months except April have been higher than the average for each month over the period 1965⁠ – ⁠2023. For instance, the average air temperature in May 2024 (+2.8 °C) is 4 °C higher than the average of all May temperatures during 1965⁠ – ⁠2023 (−1.2 °C).

Note

In July 1995, the Swedish Meteorological and Hydrological Institute (SMHI) installed a separate automatic weather station at Tarfala (station 178970, Tarfala A) as part of their national weather observation network. These data are available from the SMHI open data resource.

Version history

Version 2

Data from 1946 to 2024.

Version 1

Initial release. Data from 1946 to 2023.