Decadal variability of clouds, solar radiation and temperature at a high-latitude coastal site in Norway
The observed variability of shortwave (SW) irradiance, clouds and temperature and the potential connections between them is studied for the subarctic site Bergen (60.4°N, 5.3°E), located on the Norwegian west coast. Focusing on the quality and spatial representativity of the data, we compare observa...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
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Stockholm University Press
2014-12-01
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| Series: | Tellus: Series B, Chemical and Physical Meteorology |
| Subjects: | |
| Online Access: | http://www.tellusb.net/index.php/tellusb/article/view/25897/pdf_3 |
| _version_ | 1818246912166330368 |
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| author | Kajsa Parding Jan A. Olseth Knut F. Dagestad Beate G. Liepert |
| author_facet | Kajsa Parding Jan A. Olseth Knut F. Dagestad Beate G. Liepert |
| author_sort | Kajsa Parding |
| collection | DOAJ |
| description | The observed variability of shortwave (SW) irradiance, clouds and temperature and the potential connections between them is studied for the subarctic site Bergen (60.4°N, 5.3°E), located on the Norwegian west coast. Focusing on the quality and spatial representativity of the data, we compare observations from independent instruments and neighbouring measurement sites. The observations indicate that the decrease of sunshine duration and SW irradiance during the 1970s and 80s in Bergen is associated with the increasing frequency of clouds, in particular clouds of low base heights. We argue that the observed cloud changes are indicative of increased frequencies of storms in northern Europe. The annual mean observational time series show an increase in SW irradiance since 1990, which is not accompanied by a cloud cover (NN) decrease. This implies the influence of factors other than clouds, for example, decreasing aerosol emissions. Calculations of the aerosol optical depth (AOD) based on irradiance observations for hours when the sun is unobscured by clouds confirm a decreasing aerosol load after 1990, from 0.15 to 0.10 AOD which corresponds to 2–6 Wm−2 of brightening. At the same time, a seasonal analysis reveals opposite changes in SW irradiance and NN during the months of strongest changes – March, April and August – also during the recent period of increasing SW irradiance. We conclude that the seasonally decreasing NN also contributes to the recent changes in SW irradiance. Finally, we address the relationship between temperature, SW irradiance and clouds. In winter (December–February), the surface air temperature in Bergen is statistically linked to the warming influence of clouds. In all other seasons, the North Atlantic sea surface temperature variability has a more dominant influence on the air temperature in Bergen compared to local cloud and SW irradiance variability. |
| first_indexed | 2024-12-12T14:56:20Z |
| format | Article |
| id | doaj.art-9917036a5c0f4704bf112fd56ce790b8 |
| institution | Directory Open Access Journal |
| issn | 1600-0889 |
| language | English |
| last_indexed | 2024-12-12T14:56:20Z |
| publishDate | 2014-12-01 |
| publisher | Stockholm University Press |
| record_format | Article |
| series | Tellus: Series B, Chemical and Physical Meteorology |
| spelling | doaj.art-9917036a5c0f4704bf112fd56ce790b82022-12-22T00:20:54ZengStockholm University PressTellus: Series B, Chemical and Physical Meteorology1600-08892014-12-0166011710.3402/tellusb.v66.2589725897Decadal variability of clouds, solar radiation and temperature at a high-latitude coastal site in NorwayKajsa Parding0Jan A. Olseth1Knut F. Dagestad2Beate G. Liepert3 Geophysical Institute, University of Bergen, Bergen, Norway Geophysical Institute, University of Bergen, Bergen, Norway Norwegian Meteorological Institute, Bergen, Norway NorthWest Research Associates, Redmond, WA, USAThe observed variability of shortwave (SW) irradiance, clouds and temperature and the potential connections between them is studied for the subarctic site Bergen (60.4°N, 5.3°E), located on the Norwegian west coast. Focusing on the quality and spatial representativity of the data, we compare observations from independent instruments and neighbouring measurement sites. The observations indicate that the decrease of sunshine duration and SW irradiance during the 1970s and 80s in Bergen is associated with the increasing frequency of clouds, in particular clouds of low base heights. We argue that the observed cloud changes are indicative of increased frequencies of storms in northern Europe. The annual mean observational time series show an increase in SW irradiance since 1990, which is not accompanied by a cloud cover (NN) decrease. This implies the influence of factors other than clouds, for example, decreasing aerosol emissions. Calculations of the aerosol optical depth (AOD) based on irradiance observations for hours when the sun is unobscured by clouds confirm a decreasing aerosol load after 1990, from 0.15 to 0.10 AOD which corresponds to 2–6 Wm−2 of brightening. At the same time, a seasonal analysis reveals opposite changes in SW irradiance and NN during the months of strongest changes – March, April and August – also during the recent period of increasing SW irradiance. We conclude that the seasonally decreasing NN also contributes to the recent changes in SW irradiance. Finally, we address the relationship between temperature, SW irradiance and clouds. In winter (December–February), the surface air temperature in Bergen is statistically linked to the warming influence of clouds. In all other seasons, the North Atlantic sea surface temperature variability has a more dominant influence on the air temperature in Bergen compared to local cloud and SW irradiance variability.http://www.tellusb.net/index.php/tellusb/article/view/25897/pdf_3cloudssolar irradianceglobal dimming and brightening |
| spellingShingle | Kajsa Parding Jan A. Olseth Knut F. Dagestad Beate G. Liepert Decadal variability of clouds, solar radiation and temperature at a high-latitude coastal site in Norway Tellus: Series B, Chemical and Physical Meteorology clouds solar irradiance global dimming and brightening |
| title | Decadal variability of clouds, solar radiation and temperature at a high-latitude coastal site in Norway |
| title_full | Decadal variability of clouds, solar radiation and temperature at a high-latitude coastal site in Norway |
| title_fullStr | Decadal variability of clouds, solar radiation and temperature at a high-latitude coastal site in Norway |
| title_full_unstemmed | Decadal variability of clouds, solar radiation and temperature at a high-latitude coastal site in Norway |
| title_short | Decadal variability of clouds, solar radiation and temperature at a high-latitude coastal site in Norway |
| title_sort | decadal variability of clouds solar radiation and temperature at a high latitude coastal site in norway |
| topic | clouds solar irradiance global dimming and brightening |
| url | http://www.tellusb.net/index.php/tellusb/article/view/25897/pdf_3 |
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