• The 11 year solar cycle UV irradiance effect and its dependency on the Pacific Decadal Oscillation 

      Guttu, Sigmund; Orsolini, Yvan J.; Stordal, Frode; Otterå, Odd Helge; Omrani, Nour-Eddine (Journal article; Peer reviewed, 2021)
      The stratospheric, tropospheric and surface impacts from the 11 year ultraviolet solar spectral irradiance (SSI) variability have been extensively studied using climate models and observations. Here, we demonstrate using ...
    • Assessing the influence of sea surface temperature and arctic sea ice cover on the uncertainty in the boreal winter future climate projections 

      Cheung, Ho-Nam; Keenlyside, Noel Sebastian; Koenigk, Torben; Yang, Shuting; Tian, Tian; Xu, Zhiqing; Gao, Yongqi; Ogawa, Fumiaki; Omrani, Nour-Eddine; Qiao, Shaobo; Zhou, Wen (Journal article; Peer reviewed, 2022)
      We investigate the uncertainty (i.e., inter-model spread) in future projections of the boreal winter climate, based on the forced response of ten models from the CMIP5 following the RCP8.5 scenario. The uncertainty in the ...
    • The Dominant Patterns of Intraseasonal Rainfall Variability in May–October and November–April over the Tropical Western Pacific 

      Pariyar, Sunil Kumar; Keenlyside, Noel; Bhatt, Bhuwan Chandra; Omrani, Nour-Eddine (Journal article, 2019)
      The space–time structure of intraseasonal (10–90 day) rainfall variability in the western tropical Pacific is studied using daily 3B42 TRMM and ERA-Interim reanalysis data for the period 1998–2014. Empirical orthogonal ...
    • Evaluating Impacts of Recent Arctic Sea Ice Loss on the Northern Hemisphere Winter Climate Change 

      Ogawa, Fumiaki; Keenlyside, Noel; Gao, Yongqi; Koenigk, Torben; Yang, Shuting; Suo, Lingling; Wang, Tao; Gastineau, Guillaume; Nakamura, Tetsu; Cheung, Ho Nam; Omrani, Nour-Eddine; Ukita, Jinro; Semenov, Vladimir (Journal article; Peer reviewed, 2018)
      Wide disagreement among individual modeling studies has contributed to a debate on the role of recent sea ice loss in the Arctic amplification of global warming and the Siberian wintertime cooling trend. We perform coordinated ...
    • Has a warm North Atlantic contributed to recent European cold winters? 

      Keenlyside, Noel; Omrani, Nour-Eddine (Peer reviewed; Journal article, 2014-06-02)
      The rise of global surface temperature waned during the last decade, despite increasing greenhouse gas concentrations. The temperature changes were most pronounced over northern hemisphere land masses during winter (Cohen ...
    • Impacts of UV Irradiance and Medium-Energy Electron Precipitation on the North Atlantic Oscillation during the 11-Year Solar Cycle 

      Guttu, Sigmund; Orsolini, Yvan; Stordal, Frode; Otterå, Odd Helge; Omrani, Nour-Eddine; Tartaglione, Nazario; Verronen, Pekka T.; Rodger, Craig J.; Clilverd, Mark A. (Journal article; Peer reviewed, 2021)
      Observational studies suggest that part of the North Atlantic Oscillation (NAO) variability may be attributed to the spectral ultra-violet (UV) irradiance variations associated to the 11-year solar cycle. The observed ...
    • Inconsistent Wind Speed Trends in Current Twentieth Century Reanalyses 

      Wohland, Jan; Omrani, Nour-Eddine; Witthaut, Dirk; Keenlyside, Noel (Peer reviewed; Journal article, 2019)
      Reanalysis data underpin much research in atmospheric and related sciences. While most reanalysis only cover the last couple of decades, National Oceanic and Atmospheric Administration (20CR) and European Centre for ...
    • Key Role of the Ocean Western Boundary currents in shaping the Northern Hemisphere climate 

      Omrani, Nour-Eddine; Ogawa, Fumiaki; Nakamura, Hisashi; Keenlyside, Noel; Lubis, Sandro W.; Matthes, Katja (Peer reviewed; Journal article, 2019)
      The individual impact of North Atlantic and Pacific Ocean Western Boundary Currents (OWBCs) on the tropospheric circulation has recently been studied in depth. However, their simultaneous role in shaping the hemisphere-scale ...
    • North Atlantic multi-decadal variability - mechanisms and predictability 

      Keenlyside, Noel; Ba, Jin; Mecking, Jennifer V.; Omrani, Nour-Eddine; Latif, Mojib; Zhang, Rong; Msadek, Rym (World Scientific Series on Asia-Pacific Weather and Climate, Chapter; Peer reviewed, 2015-10)
      The North Atlantic Ocean undergoes pronounced basin-wide, multi-decadal variations. The corresponding fluctuations in sea surface temperature (SST) have become known as the Atlantic Multi-decadal Oscillation (AMO) or ...
    • Ozone-induced climate change propped up by the Southern Hemisphere oceanic front 

      Ogawa, Fumiaki; Omrani, Nour-Eddine; Nishii, Kazuaki; Nakamura, Hisashi; Keenlyside, Noel (Peer reviewed; Journal article, 2015-11-23)
      The late twentieth century was marked by a significant summertime trend in the Southern Annular Mode (SAM), the dominant mode of tropospheric variability in the extratropical Southern Hemisphere (SH). This trend with ...
    • Pacific contribution to decadal surface temperature trends in the Arctic during the twentieth century 

      Svendsen, Lea; Keenlyside, Noel; Muilwijk, Morven; Bethke, Ingo; Omrani, Nour-Eddine; Gao, Yongqi (Journal article; Peer reviewed, 2021)
      Instrumental records suggest multidecadal variability in Arctic surface temperature throughout the twentieth century. This variability is caused by a combination of external forcing and internal variability, but their ...
    • Pacific contribution to the early twentieth-century warming in the Arctic 

      Svendsen, Lea; Keenlyside, Noel; Bethke, Ingo; Gao, Yongqi; Omrani, Nour-Eddine (Journal article; Peer reviewed, 2018)
      Arctic surface temperature warmed more than twice as fast as global temperature during the early twentieth century, similar to that during the recent global warming. This Arctic warming has been attributed to both external ...
    • Remarkable link between projected uncertainties of Arctic sea-ice decline and winter Eurasian climate 

      Cheung, Ho Nam; Keenlyside, Noel; Omrani, Nour-Eddine; Zhou, Wen (Journal article; Peer reviewed, 2018)
      We identify that the projected uncertainty of the pan-Arctic sea-ice concentration (SIC) is strongly coupled with the Eurasian circulation in the boreal winter (December–March; DJFM), based on a singular value decomposition ...
    • Significant multidecadal variability in German wind energy generation 

      Wohland, Jan; Omrani, Nour-Eddine; Keenlyside, Noel; Witthaut, Dirk (Peer reviewed; Journal article, 2019-09-12)
      Wind energy has seen large deployment and substantial cost reductions over the last decades. Further ambitious upscaling is urgently needed to keep the goals of the Paris Agreement within reach. While the variability in ...
    • Solar forcing synchronizes decadal North Atlantic climate variability 

      Thiéblemont, Rémi; Matthes, Katja; Omrani, Nour-Eddine; Kodera, Kunihiko; Hansen, Felicitas (Peer reviewed; Journal article, 2015-09-15)
      Quasi-decadal variability in solar irradiance has been suggested to exert a substantial effect on Earth’s regional climate. In the North Atlantic sector, the 11-year solar signal has been proposed to project onto a pattern ...