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  • Springer  (2)
  • Nature Publishing Group (NPG)  (1)
  • Cambridge Univ. Press
  • PANGAEA
  • 2015-2019  (3)
  • 1
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    Atmospheric feedbacks in North Africa from an irrigated, afforested Sahara (2018)
    Springer
    In:  Climate Dynamics, 50 (11-12). pp. 4561-4581.
    Details
    Publication Date: 2021-02-08
    Description: Afforestation of the Sahara has been proposed as a climate engineering method to sequester a substantial amount of carbon dioxide, potentially effective to mitigate climate change. Earlier studies predicted changes in the atmospheric circulation system. These atmospheric feedbacks raise questions about the self-sustainability of such an intervention, but have not been investigated in detail. Here, we investigate changes in precipitation and circulation in response to Saharan large-scale afforestation and irrigation with NCAR’s CESM-WACCM Earth system model. Our model results show a Saharan temperature reduction by 6 K and weak precipitation enhancement by 267 mm/year over the Sahara. Only 26% of the evapotranspirated water re-precipitates over the Saharan Desert, considerably large amounts are advected southward to the Sahel zone and enhance the West African monsoon (WAM). Different processes cause circulation and precipitation changes over North Africa. The increase in atmospheric moisture leads to radiative cooling above the Sahara and increased high-level cloud coverage as well as atmospheric warming above the Sahel zone. Both lead to a circulation anomaly with descending air over the Sahara and ascending air over the Sahel zone. Together with changes in the meridional temperature gradient, this results in a southward shift of the inner-tropical front. The strengthening of the Tropical easterly jet and the northward displacement of the African easterly jet is associated with a northward displacement and strengthening of the WAM precipitation. Our results suggest complex atmospheric circulation feedbacks, which reduce the precipitation potential over an afforested Sahara and enhance WAM precipitation.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1007/s00382-017-3890-8
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 2
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    Uncertainty in twenty-first century projections of the Atlantic Meridional Overturning Circulation in CMIP3 and CMIP5 models (2017)
    Springer
    In:  Climate Dynamics, 49 (5-6). pp. 1495-1511.
    Details
    Publication Date: 2020-02-06
    Description: Uncertainty in the strength of the Atlantic Meridional Overturning Circulation (AMOC) is analyzed in the Coupled Model Intercomparison Project Phase 3 (CMIP3) and Phase 5 (CMIP5) projections for the twenty-first century; and the different sources of uncertainty (scenario, internal and model) are quantified. Although the uncertainty in future projections of the AMOC index at 30°N is larger in CMIP5 than in CMIP3, the signal-to-noise ratio is comparable during the second half of the century and even larger in CMIP5 during the first half. This is due to a stronger AMOC reduction in CMIP5. At lead times longer than a few decades, model uncertainty dominates uncertainty in future projections of AMOC strength in both the CMIP3 and CMIP5 model ensembles. Internal variability significantly contributes only during the first few decades, while scenario uncertainty is relatively small at all lead times. Model uncertainty in future changes in AMOC strength arises mostly from uncertainty in density, as uncertainty arising from wind stress (Ekman transport) is negligible. Finally, the uncertainty in changes in the density originates mostly from the simulation of salinity, rather than temperature. High-latitude freshwater flux and the subpolar gyre projections were also analyzed, because these quantities are thought to play an important role for the future AMOC changes. The freshwater input in high latitudes is projected to increase and the subpolar gyre is projected to weaken. Both the freshening and the gyre weakening likely influence the AMOC by causing anomalous salinity advection into the regions of deep water formation. While the high model uncertainty in both parameters may explain the uncertainty in the AMOC projection, deeper insight into the mechanisms for AMOC is required to reach a more quantitative conclusion.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
    Format: text
    Format: text
    Format: text
    DOI: 10.1007/s00382-016-3180-x
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 3
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    Analysis of immunoglobulin transcripts and hypermutation following SHIVAD8 infection and protein-plus-adjuvant immunization (2015)
    Nature Publishing Group (NPG)
    Details
    Publication Date: 2015-04-12
    Description: Article HIV vaccine development will be facilitated by having animal models that are predictive for translation to humans. Here, the authors use two nonhuman primate models to compare the effects of natural infection and different adjuvants on antigen persistence, diversity and humoral immunity. Nature Communications doi: 10.1038/ncomms7565 Authors: Joseph R. Francica, Zizhang Sheng, Zhenhai Zhang, Yoshiaki Nishimura, Masashi Shingai, Akshaya Ramesh, Brandon F. Keele, Stephen D. Schmidt, Barbara J. Flynn, Sam Darko, Rebecca M. Lynch, Takuya Yamamoto, Rodrigo Matus-Nicodemos, David Wolinsky, Martha Nason, Nicholas M. Valiante, Padma Malyala, Ennio De Gregorio, Susan W. Barnett, Manmohan Singh, Derek T. O’Hagan, Richard A. Koup, John R. Mascola, Malcolm A. Martin, Thomas B. Kepler, Daniel C. Douek, Lawrence Shapiro, Robert A. Seder
    Electronic ISSN: 2041-1723
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General , Physics
    Published by Nature Publishing Group (NPG)
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