Heat waves in Finland : present and projected summertime extreme temperatures and their associated circulation patterns

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Kim , S , Sinclair , V A , Räisänen , J & Ruuhela , R 2018 , ' Heat waves in Finland : present and projected summertime extreme temperatures and their associated circulation patterns ' , International Journal of Climatology , vol. 38 , no. 3 , pp. 1393–1408 . https://doi.org/10.1002/joc.5253

Title: Heat waves in Finland : present and projected summertime extreme temperatures and their associated circulation patterns
Author: Kim, Sol; Sinclair, Victoria A.; Räisänen, Jouni; Ruuhela, Reija
Contributor organization: Department of Physics
Date: 2018-03-15
Language: eng
Number of pages: 16
Belongs to series: International Journal of Climatology
ISSN: 0899-8418
DOI: https://doi.org/10.1002/joc.5253
URI: http://hdl.handle.net/10138/327668
Abstract: The number and intensity of individual hot days affecting Finland in the current and future climate is investigated together with the circulation patterns associated with the hot days. In addition, the number, length and intensity of heat waves lasting at least 3 days is also considered. ERA-Interim reanalysis data and both direct model output and bias-corrected data for historical and future climate [representative concentration pathway 4.5 (RCP4.5) scenario] simulations from 17 global climate models are analysed. Three intensities of heat waves and hot days are defined based on daily mean temperature thresholds of 20, 24 and 28 °C. The percentage of summertime days which exceed these temperature thresholds is shown to increase in the future. In ERA-Interim, 24% of summertime days in southern Finland exceed the lowest temperature threshold while none exceed the highest temperature threshold. Under the RCP4.5 scenario these values increase to 47 and 1%, respectively. Larger relative changes occur in northern Finland. Heat waves are also longer in the RCP4.5 simulations than in the historical simulations. In southern Finland, the mean length of a heat wave where the 20 °C daily mean temperature is exceeded is 6.1 days in the historical simulations but increases to 9.4 days in the RCP4.5 simulations. The hot days in both northern and southern Finland are associated with a statistically significant positive pressure anomaly over Finland and to the east to Finland and a statistically significant negative pressure anomaly over Russia between 90 and 120°E. These pressure anomalies were evident for all intensities of hot days in the current climate and the future climate. The magnitude of the pressure anomalies increases as the daily mean temperature threshold increases. However, for hot days which exceed the same daily mean temperature threshold, the pressure anomalies are weaker in the RCP4.5 simulations than in the historical or ERA-Interim data.
Subject: 114 Physical sciences
CLIMATE CHANGE
Meteorologia
circulation patterns
climate change
CMIP5
Finland
heat waves
EUROPE
Peer reviewed: Yes
Usage restriction: openAccess
Self-archived version: acceptedVersion


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