[{"title":"Stockholm Historical Weather Observations \u2014 Daily mean air temperatures since 1756","summary":"Data for daily mean air temperatures at the old astronomical observatory in Stockholm since 1756 are provided.\r\n\r\nThree variants of the data are available: (i) non-homogenized daily mean temperatures, as estimated from the local temperature observations, (ii) homogenized daily mean temperatures, adjusted after 1870 to remove the urban warming effect on the observed temperatures, and (iii) homogenized daily mean temperatures with an additional adjustment applied to data for May\u2060\u200a\u2013\u200aAugust in the period before 1859, to eliminate a supposed warm bias of the observed temperatures due to exposure of thermometers to radiation.\r\n\r\nIn the 18th century, the weather observations were made by astronomers as a part of their studies of the universe. Today, the observation site in Stockholm is a weather station within the national station network managed by the Swedish Meteorological and Hydrological Institute (SMHI).","citations":"Moberg A, Bergstr\u00f6m H, Ruiz Krigsman J, Svanered O. 2002: Daily air temperature and pressure series for Stockholm (1756\u2060\u200a\u2013\u2060\u200a1998). Climatic Change 53: 171\u2060\u200a\u2013\u2060\u200a212. DOI:10.1023\/A:1014966724670\r\n\r\nMoberg A, Alexandersson H, Bergstr\u00f6m H, Jones PD. 2003: Were Southern Swedish summer temperatures before 1860 as warm as measured? Int. J. Climatol. 23: 1495\u2060\u200a\u2013\u2060\u200a1521. DOI:10.1002\/joc.945\r\n\r\nMoberg A, Tuomenvirta H, Nordli \u00d8. 2005: Recent climatic trends. In: Physical Geography of Fennoscandia. (Ed: Sepp\u00e4l\u00e4 M). Oxford Regional Environments Series, Oxford University Press, Oxford: 113\u2060\u200a\u2013\u2060\u200a133","comments":"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). Data in the current dataset can differ from those in the SMHI database before 2013.\r\n\r\n\r\nData until 2012\u201312\u201331 are the same as in an earlier version of this dataset. Data after 2013\u201301\u201301 are obtained by automated daily download of daily mean temperatures for station 98230 in the SMHI resource \u00d6ppna Data. These data from the SMHI are used for column 2 in the data file here. Data in columns 3 and 4 have been adjusted as described below.\r\n\r\n\r\nThe first two variants of daily mean temperatures (columns 2 and 3 in the data file) have been calculated as described by Moberg et al. (2002).\r\n\r\n\r\nThe first variant (non-homogenized data) consists of daily mean temperatures calculated to account for changes in the observation times and the number of observations per day. Thus, they are estimates of daily mean temperatures obtained directly from the observations without any further corrections.\r\n\r\n\r\nThe second variant (homogenized data) includes the following adjustments, relative to the first variant:\r\n\r\n\r\n1756\u201304\u201303\u2060\u2013\u200a1756\u201310\u201331: The observed temperatures in Stockholm during this period are judged to be too high, and of poor quality. Therefore, daily means for this period have been replaced with temperatures estimated from contemporaneous observations in Uppsala through a linear regression model. \r\n\r\n1763\u201302\u201325\u200a\u2013\u200a1763\u201302\u201328: No observations were made. Daily temperatures have been extrapolated from Uppsala.\r\n\r\n1819\u201308\u201301\u200a\u2013\u200a1825\u201301\u201313: Correction by \u22120.7 \u00b0C because an incorrect thermometer was probably used.\r\n\r\n1870\u201301\u201311\u2060\u2013\u200apresent: Adjustment for urban heat island trend and other inhomogeneities.\r\n\r\n\r\nThe adjustment for the urban warming trend, and the effect of other inhomogeneities detected in homogeneity tests against surrounding reference station data, is applied such that the most recent homogenized temperatures are made somewhat colder than the non-homogenized temperatures in order to make the entire series being respresentative of rural conditions that prevailed before the mid-19th century. The size of the adjustment changes with time from 1870 until 1967 and is thereafter held at a constant level until the present, although the adjustment has an annual cycle and therefore varies between the dates in each year. This adjustment causes homogenized temperature data after 1967 to be on average 0.8 \u00b0C colder than non-homogenized temperatures.\r\n\r\n\r\nThe third variant (with additional adjustment to data for May\u2060\u200a\u2013\u200aAugust in the period 1756\u2060\u200a\u2013\u200a1858), 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:\r\n\r\n\r\nMay: day 1\u2060\u2013\u200a4: 0.0 \u00b0C, day 5\u2060\u2013\u200a9: \u22120.1 \u00b0C, day 10\u2060\u2013\u200a13: \u22120.2 \u00b0C, day 14\u2060\u2013\u200a18: \u22120.3 \u00b0C, day 19\u2060\u2013\u200a22: \u22120.4 \u00b0C, day 23\u2060\u2013\u200a27: \u22120.5 \u00b0C, day 28\u2060\u2013\u200a31: \u22120.6 \u00b0C.\r\n\r\nJune: day 1\u201330: \u22120.7 \u00b0C.\r\n\r\nJuly: day 1\u201331: \u22120.7 \u00b0C.\r\n\r\nAugust: day 1\u2060\u2013\u200a4: \u22120.6 \u00b0C, day 5\u2060\u2013\u200a9: \u22120.5 \u00b0C, day 10\u2060\u2013\u200a13: \u22120.4 \u00b0C, day 14\u2060\u2013\u200a18: \u22120.3 \u00b0C, day 19\u2060\u2013\u200a22: \u22120.2 \u00b0C, day 23\u2060\u2013\u200a27: \u22120.1 \u00b0C, day 28\u2060\u2013\u200a31: 0.0 \u00b0C.\r\n\r\n\r\nThis gives an average adjustment by \u22120.3 \u00b0C for May and August and \u22120.7 \u00b0C for June and July. 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. However, it 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\u2060\u2013\u200aAugust season. Further research would be needed to better assess the need for adjustments in the early period and to determine their size and how they should be applied. There is a need also to undertake further analysis of how to better adjust the temperature data for the modern urban heat island effect, because the current adjustment is based on results from a study made in the late 1990s.\r\n\r\n\r\nThe number of daily observations used to calculate the daily means has varied with time, as described in the comments to an earlier version of this dataset. Information about instrument positions and original data sources is available in the comments to an associated dataset with thermometer observations.\n\n\n\nVersion history\nVersion 2.0\n\nData in version 2.0 is updated daily to the present, whereas data in version 1.0 ended in 2018-12-31. Data in version 2.0 are the same as in version 1.0 until 2012-12-31. From 2013-01-01 onward daily mean temperatures for SMHI station 98230 are downloaded automatically from the SMHI resource \u00d6ppna Data and used without any changes in the data column labeled \u2018raw\u2019. Data in the columns labeled \u2018homo\u2019 and \u2018adjust\u2019 are corrected in the same way as in version 1.0 but one or two daily mean temperatures each year may differ by 0.1 \u00b0C compared to version 1.0 because of differences in rounding to one decimal. \n\nVersion 1.0\n\nInitial release.","category":"Atmosphere","subcategory":"Weather observations","keywords":"Air temperature; Daily data; Early instrumental data; Homogenized data; Sweden; Stockholm","scientist":"Anders Moberg","firstname":"Anders","lastname":"Moberg","address":"Department of Physical Geography, Stockholm University","postalcode":"SE-106 91 ","city":"Stockholm","province":"","country":"Sweden","parameters":"Earth science > Atmosphere > Atmospheric temperature > Surface temperature > Air temperature","location":"Continent > Europe > Northern Europe > Scandinavia > Sweden","progress":"Completed","language":"English","project":"Digitization, quality control and development of daily and monthly air temperature and pressure data series until 1998 was undertaken as part of the project IMPROVE \u2014 Improved Understanding of Past Climatic Variability from Early Daily European Instrumental Sources. Project funding: EU 4th Framework Programme, 1998\u20131999. Contract: ENV4-CT97-0511. Co-ordinator: Dario Camuffo, Consiglio Nazionale delle Ricerche, Istituto di Scienze dell'Atmosfera e del Clima, Padova, Italy. PI at Stockholm University: Anders Moberg. Later updates of the data have been made by Anders Moberg without any further dedicated funding.","publisher":"Bolin Centre Database","version":"2.0","constrains":"None","access":"Free"}]