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 journalArticlepeer-review

    25 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

    All Science Journal Classification (ASJC) codes

    • Geophysics
    • Earth and Planetary Sciences(all)

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