Separation of Zonally Elongated Large Cloud Disturbances over the Western Tropical Pacific Separation of Zonally Elongated Large Cloud Disturbances over the Western Tropical Pacific

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Author(s)

    • Atsushi HAMADA HAMADA Atsushi
    • Atmosphere and Ocean Research Institute, The University of Tokyo, Kashiwa, Japan Atmosphere and Ocean Research Institute, The University of Tokyo, Kashiwa, Japan
    • Noriyuki NISHI NISHI Noriyuki
    • Division of Earth and Planetary Sciences, Graduate School of Science, Kyoto University, Kyoto, Japan Division of Earth and Planetary Sciences, Graduate School of Science, Kyoto University, Kyoto, Japan
    • Hideji KIDA KIDA Hideji
    • Division of Earth and Planetary Sciences, Graduate School of Science, Kyoto University, Kyoto, Japan Division of Earth and Planetary Sciences, Graduate School of Science, Kyoto University, Kyoto, Japan

Abstract

 In this study, a data analysis was conducted to describe the common characteristics of “large-scale cloud separations,” in which zonally elongated cloud bands extending a few thousand kilometers over the western tropical Pacific are simultaneously separated into two or three zonally elongated bands. The separated cloud bands maintain their shapes for more than a day. In the present study, a case study was performed on four separation cases observed during the Intensive Obervation Period (IOP) of the Tropical Ocean Global Atmosphere Coupled Ocean Atmosphere Response Experiment (TOGA-COARE).<br> The northern and southern cloud bands consisted of clouds with fine line structures. Their orientations were in good agreement with the horizontal winds near the cloud top, indicating that the northern and southern cloud bands consisted of upper-tropospheric cirriform clouds. After the convective activity in the original cloud band weakened considerably, strong meridional winds remained in the upper troposphere and advected the separated cloud bands northward and southward.<br> All the cloud separations occurred about half a day after the convective activity had peaked, and the onset time of the separations were fixed from evening to midnight. These facts indicate that the typical diurnal convective activity over the western tropical Pacific may play a role in the cloud separations. Westward-propagating cloud clusters were observed to the west of the original cloud band during the separations, which may be related to convectively coupled equatorial waves.

 In this study, a data analysis was conducted to describe the common characteristics of “large-scale cloud separations,” in which zonally elongated cloud bands extending a few thousand kilometers over the western tropical Pacific are simultaneously separated into two or three zonally elongated bands. The separated cloud bands maintain their shapes for more than a day. In the present study, a case study was performed on four separation cases observed during the Intensive Obervation Period (IOP) of the Tropical Ocean Global Atmosphere Coupled Ocean Atmosphere Response Experiment (TOGA-COARE).<br> The northern and southern cloud bands consisted of clouds with fine line structures. Their orientations were in good agreement with the horizontal winds near the cloud top, indicating that the northern and southern cloud bands consisted of upper-tropospheric cirriform clouds. After the convective activity in the original cloud band weakened considerably, strong meridional winds remained in the upper troposphere and advected the separated cloud bands northward and southward.<br> All the cloud separations occurred about half a day after the convective activity had peaked, and the onset time of the separations were fixed from evening to midnight. These facts indicate that the typical diurnal convective activity over the western tropical Pacific may play a role in the cloud separations. Westward-propagating cloud clusters were observed to the west of the original cloud band during the separations, which may be related to convectively coupled equatorial waves.

Journal

  • Journal of the Meteorological Society of Japan. Ser. II

    Journal of the Meteorological Society of Japan. Ser. II 91(3), 375-389, 2013

    Meteorological Society of Japan

Codes

  • NII Article ID (NAID)
    130004788785
  • NII NACSIS-CAT ID (NCID)
    AA00702524
  • Text Lang
    ENG
  • ISSN
    0026-1165
  • NDL Article ID
    024631854
  • NDL Call No.
    Z54-J645
  • Data Source
    NDL  J-STAGE 
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