Physical mechanism of long-term drying trend over tropical North Africa

Hiroaki Kawase, Manabu Abe, Yukiko Yamada, Toshihiko Takemura, Tokuta Yokohata, Toru Nozawa

    Research output: Contribution to journalArticle

    22 Citations (Scopus)

    Abstract

    Based on an approximated moisture budget equation, we investigate the physical mechanisms of a drying trend observed over tropical North Africa in the boreal summer during the 20th Century by analyzing datasets of several climate-model experiments forced with various combinations of natural and anthropogenic forcings. Increased anthropogenic aerosols thermodynamically induce a drying trend due to a tropospheric cooling and dynamically induce an additional drying trend due to an atmospheric local circulation change stirred up by the strong gradient of a sea surface temperature anomaly over the tropical Atlantic Ocean. Increased greenhouse gases, on the other hand, induce a drying trend through the large-scale dynamic effect, which is canceled out by the thermodynamically induced moistening trend due to tropospheric warming. Therefore, the drying trend observed over tropical North Africa during the 20th Century is strongly affected by the increased anthropogenic aerosols through both the dynamic and thermodynamic effects.

    Original languageEnglish
    Article numberL09706
    JournalGeophysical Research Letters
    Volume37
    Issue number9
    DOIs
    Publication statusPublished - May 1 2010

    Fingerprint

    drying
    trends
    aerosols
    aerosol
    Atlantic Ocean
    climate models
    sea surface temperature
    greenhouses
    moisture
    budgets
    temperature anomaly
    summer
    trend
    North Africa
    climate modeling
    greenhouse gas
    warming
    thermodynamics
    anomalies
    cooling

    All Science Journal Classification (ASJC) codes

    • Geophysics
    • Earth and Planetary Sciences(all)

    Cite this

    Physical mechanism of long-term drying trend over tropical North Africa. / Kawase, Hiroaki; Abe, Manabu; Yamada, Yukiko; Takemura, Toshihiko; Yokohata, Tokuta; Nozawa, Toru.

    In: Geophysical Research Letters, Vol. 37, No. 9, L09706, 01.05.2010.

    Research output: Contribution to journalArticle

    Kawase, Hiroaki ; Abe, Manabu ; Yamada, Yukiko ; Takemura, Toshihiko ; Yokohata, Tokuta ; Nozawa, Toru. / Physical mechanism of long-term drying trend over tropical North Africa. In: Geophysical Research Letters. 2010 ; Vol. 37, No. 9.
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    AU - Nozawa, Toru

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