[{"title":"Stockholm Historical Weather Observations \u2014 Daily mean air temperatures since 1756","summary":"Weather observations of several meteorological variables have been made continuously at the old astronomical observatory in Stockholm since 1756. As a part of a collection of data for selected variables, the dataset provided here contains daily mean air temperatures for the period 1756\u20132018. Three variants are available: (i) non-homogenized daily mean temperatures, as estimated from the local temperature observations, (ii) homogenized daily mean temperatures, adjusted after 1870 to exclude the urban warming trend in the city, and (iii) homogenized daily mean temperatures having an additional adjustment applied to data for May\u2013August in the period before 1859, to correct for a supposed warm bias of the observed temperatures due to likely poor protection of thermometers against radiation.","citations":"Moberg A, Bergstr\u00f6m H, Ruiz Krigsman J, Svanered O. 2002: Daily air temperature and pressure series for Stockholm (1756\u20131998). Climatic Change 53: 171\u2013212. 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\u20131521. 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\u2013133","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), but data in the current dataset can differ from those in the SMHI database. \r\n\r\n\r\nThe first two variants of daily mean temperatures presented here have been derived from the dataset with thermometer observations as described by Moberg et al. (2002). The first variant (non-homogenized data) consists of daily mean temperatures calculated to account for changes in the actual observation times and number of observations. 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\n1756.04.03\u20131756.10.31:\tThe observed temperatures during this period are judged to be too high, and of poor quality. Therefore, they have been replaced with contemporaneous data extrapolated from Uppsala through linear regression. \r\n\r\n1763.02.25\u20131763.02.28:\tNo observations were made. Daily temperatures have been extrapolated from Uppsala.\r\n\r\n1819.08.01\u20131825.01.13:\tCorrection by \u22120.7\u00b0C because an incorrect thermometer was probably used.\r\n\r\n1870.01.11\u20132018.12.31:\tCorrection 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 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\u00b0C colder than non-homogenized temperatures.\r\n\r\n\r\nThe third variant (with additional adjustment to data for May\u2013August in the period 1756\u20131858), 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\u20134: 0.0\u00b0C, day 5\u20139: \u22120.1\u00b0C, day 10\u201313: \u22120.2\u00b0C, day 14\u201318: \u22120.3\u00b0C, day 19\u201322: \u22120.4\u00b0C, day 23\u201327: \u22120.5\u00b0C, day 28\u201331: \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\u20134: \u22120.6\u00b0C, day 5\u20139: \u22120.5\u00b0C, day 10\u201313: \u22120.4\u00b0C, day 14\u201318: \u22120.3\u00b0C, day 19\u201322: \u22120.2\u00b0C, day 23\u201327: \u22120.1\u00b0C, day 28\u201331: 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 history for the May\u2013August 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. Actually, there is a need also to undertake further analysis of how to better adjust the temperature data for the modern urban heat island effect.\r\n\r\n\r\nThe number of daily observations used to calculate the daily means varies with time. This number is typically: \r\n\r\n1756\u20131760: 2 observations\r\n\r\n1761\u20131858: 3 observations\r\n\r\n1859\u20131946: 3 observations & Tmin in summer months\r\n\r\n1947\u20132018: 3 observations & Tmin & Tmax\r\n\r\n\r\nData from before 2013 are based on manual observations. Data from 2013 onward are based on the automatic weather station (SMHI station 98230).\r\n\r\n\r\nInformation about instrument positions and original data sources is available in the comments to the associated dataset with thermometer observations.\r\n\r\n\r\nFigures that illustrate daily mean air temperatures in each separate year within the period 1756\u20132018 are provided in a related dataset. The daily mean temperatures in this dataset are used to derive the corresponding dataset with monthly mean air temperatures.","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.","publisher":"Bolin Centre Database","version":"1.0","constrains":"None","access":"Free"}]