• 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 ...
    • 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 ...
    • Factors affecting extreme rainfall events in the South Pacific 

      Pariyar, Sunil Kumar; Keenlyside, Noel; Sorteberg, Asgeir; Spengler, Thomas; Bhatt, Bhuwan Chandra; Ogawa, Fumiaki (Journal article; Peer reviewed, 2020)
      Extreme rainfall events in the South Pacific are widespread and affected by various factors on different time scales. We use daily rainfall data from 20 stations over the South Pacific to investigate the characteristics ...
    • Impact of Arctic sea ice variations on winter temperature anomalies in northern hemispheric land areas 

      Köenigk, Torben; Gao, Yongqi; Gastineau, Guillaume; Keenlyside, Noel; Nakamura, Tetsu; Ogawa, Fumiaki; Orsolini, Yvan; Semenov, Vladimir A.; Suo, Lingling; Tian, Tian; Wang, Tao; Wettstein, Justin; Yang, Shuting (Peer reviewed; Journal article, 2018-07-30)
      Coordinated numerical ensemble experiments with six different state-of-the-art atmosphere models have been used in order to evaluate the respective impact of the observed Arctic sea ice and sea surface temperature (SST) ...
    • Impact of ocean and sea ice initialisation on seasonal prediction skill in the Arctic 

      Kimmritz, Madlen; Counillon, Francois; Smedsrud, Lars H.; Bethke, Ingo; Keenlyside, Noel; Ogawa, Fumiaki; Wang, Yiguo (Peer reviewed; Journal article, 2019)
      There is a growing demand for skillful prediction systems in the Arctic. Using the Norwegian Climate Prediction Model (NorCPM) that combines the fully-coupled Norwegian Earth System Model and the Ensemble Kalman filter, ...
    • 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 ...
    • Mitigating climate biases in the midlatitude North Atlantic by increasing model resolution: SST gradients and their relation to blocking and the jet 

      Athanasiadis, Panos J.; Ogawa, Fumiaki; Omrani, Nour-Eddine; Keenlyside, Noel Sebastian; Schiemann, Reinhard; Baker, Alexander J.; Vidale, Pier Luigi; Bellucci, Alessio; Ruggieri, Paolo; Haarsma, Rein; Roberts, Malcolm J.; Roberts, Chris; Novak, Lenka; Gualdi, Silvio (Journal article; Peer reviewed, 2022)
      Starting to resolve the oceanic mesoscale in climate models is a step change in model fidelity. This study examines how certain obstinate biases in the midlatitude North Atlantic respond to increasing resolution (from 1° ...
    • Oceanic forcing of the global warming slowdown in multi-model simulations 

      Xu, Xinping; He, Shengping; Furevik, Tore; Gao, Yongqi; Wang, Huijun; Li, Fei; Ogawa, Fumiaki (Journal article; Peer reviewed, 2020)
      Abstract Concurrent with the slowdown of global warming during 2002–2013, the wintertime land surface air temperatures over Eurasia, North America, Africa, Australia, South America, and Greenland experienced notable ...
    • 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 oceanic front amplifies the impact of Atlantic oceanic front on North Atlantic blocking 

      Cheung, Ho Nam; Omrani, Nour-Eddine; Ogawa, Fumiaki; Keenlyside, Noel Sebastian; Nakamura, Hisashi; Zhou, Wen (Journal article; Peer reviewed, 2023)
      Atmospheric blocking is a crucial driver of extreme weather events, but its climatological frequency is largely underestimated in state-of-the-art climate models, especially around the North Atlantic. While air-sea interaction ...
    • Prevailing Surface Wind Direction during Air-Sea Heat Exchange 

      Ogawa, Fumiaki; Spengler, Thomas (Peer reviewed; Journal article, 2019)
      While the climatological-mean sensible and latent heat fluxes are remarkably well described using climatological-mean fields in the bulk flux formulas, this study shows that a significant fraction of the climatological-mean ...