http://bolin.su.se/data/stockholm-historical-monthly-temperature-3 Anders Moberg Bolin Centre Database 2021 Datafile Atmosphere Weather observations Air temperature Monthly data Early instrumental data Homogenized data Sweden Stockholm Earth science > Atmosphere > Atmospheric temperature > Surface temperature > Air temperature Anders Moberg 2021-01-14T16:03:46+00:00 English 3 Data are provided in three files, one file for each variant of the data. The data are available both as comma-separated values (.csv) and tab-separated values (.tsv) files: 1. stockholm_monthly_mean_temperature_1756_2020_nonhom 2. stockholm_monthly_mean_temperature_1756_2020_homo 3. stockholm_monthly_mean_temperature_1756_2020_adjust Each data file has 18 columns with the following headers: year, jan, feb, mar, may, jun, jul, aug, sep, nov, dec, djf, mam, jja, son, ann. * Column 1: Year * Column 2⁠ ⁠– ⁠13: Monthly mean temperature for January through December * Column 14: December to February mean temperature, assigned to the year in which January falls * Column 15: March⁠ to May mean temperature * Column 16: June to August mean temperature * Column 17: September to November mean temperature * Column 18: Annual mean temperature Temperature unit: °C rounded to one decimal. Code for missing DJF value in year 1756: −999.0 ##### Observation site The observation site is included in the national station network managed by the Swedish Meteorological and Hydrological Institute (SMHI), with station number 98210 (manual station) and 98230 (automatic station). ##### Change from manual to automatic observations in 2013 Data from before 2013 are based on manual observations (SMHI station 98210). Data from 2013 onward are derived from the automatic weather station (SMHI station 98230). Monthly mean temperatures presented here may differ from those that can be obtained directly from the SMHI due to differences in calculation procedures. ##### Three variants of the data The three variants of monthly, seasonal and annual mean air temperatures are derived from the associated dataset with [Daily mean temperatures](https://bolin.su.se/data/stockholm-historical-temps-daily-2). ###### Variant 1: Non-homogenized data The first variant (non-homogenized data, see Moberg et al. 2002) accounts for changes in observation times and also includes the following adjustments: 1. Data for some periods in 1756 and 1763 have been replaced with estimated temperatures derived from contemporaneous observations in Uppsala, to adjust for missing or poor daily observations in Stockholm. 2. Adjustment in 1819 ⁠– 1825 for an incorrectly calibrated thermometer probably being used. *Note:* In the corresponding dataset with [Daily mean temperatures](https://bolin.su.se/data/stockholm-historical-temps-daily-2), these two particular adjustments are not applied to the non-homogenized data, but they are applied there to the homogenized data. The motivation for applying these corrections to the monthly, seasonal and annual non-homogenized data here is to provide a temperature record that represents the actual temperature history, including the urban warming trend, but with corrections made for the supposed unreliable data in short periods in 1756, 1763 and 1819 ⁠– 1825. ###### Variant 2: Homogenized data The second variant (homogenized data, see Moberg et al. 2002) additionally includes an adjustment after 1870 to eliminate an urban warming trend and the effect of other inhomogeneities detected in homogeneity tests against surrounding reference station data. The main purpose of applying this adjustment is to obtain a homogenized record that, throughout its entire length, is approximately respresentative of the rural conditions that prevailed before the mid–19th century. The size of the adjustment changes with time and varies over the year. It causes homogenized temperature data after 1967 being on average 0.8°C colder than non-homogenized temperatures. It should be noted that the current adjustment applied is based on results from a study made in the late 1990s. Thus, there is a need to undertake further analysis of how to better adjust the temperature data for the modern urban heat island effect all the time up to the present. ###### Variant 3: Homogenized data with additional adjustment 1756⁠ – 1858 The third variant (homogenized data, with additional adjustment to data for May – August in the period 1756⁠ – 1858), has been derived as in Moberg et al. (2005) based on conclusions in Moberg et al. (2003). It includes the following additional adjustments, relative to the second variant: * May and August: −0.3 °C. * June and July: −0.7 °C. The motivation for this additional adjustment is based on the available knowledge about the position of the old thermometer in combination with results from homogeneity testing and other statistical modelling, supporting the hypothesis that the old thermometers were insufficiently protected against radiation, which could have caused observed tempertures in the summer season to be to high. However, this should be seen as an ad hoc judgement rather than a result from a strict statistical analysis. Nevertheless, this variant of daily mean temperatures is judged to be the one that currently best represents the true temperature climatology for the May⁠– August season. Further research would be required to better assess the need for adjustments in the early period and to determine their size and how they should be applied. ##### Instrument positions and original data sources Further information about instrument positions and original data sources is available in the comments to the associated dataset with [thermometer observations](https://bolin.su.se/data/stockholm-historical-thermometer). #### Version history ##### Version 3 Data files in version 3 are updated to 2020. Data for 1756⁠ – 2019 are the same as in version 2. Data for 2020 are obtained by calculating the arithmetic averages of the associated [Daily mean air temperatures](https://bolin.su.se/data/stockholm-historical-temps-daily-2). ##### Version 2 Data files in version 2 are updated to 2019, whereas data in version 1 ended in 2018. Monthly, seasonal and annual mean temperature data in version 2 are calculated as arithmetic averages of the associated [Daily mean air temperatures](https://bolin.su.se/data/stockholm-historical-temps-daily-2). Some monthly and annual mean temperatures in version 2 differ by 0.1 °C compared to version 1 because of differences in rounding to one decimal or differences in calculating annual mean temperatures in leap years. Data in version 2 include seasonal mean temperatures, whereas these were not included in version 1. Data in version 2 are provided as csv and tsv files, whereas data in version 1 are provided as tsv and txt files. ##### Version 1 Initial release.