Separation of zonally elongated large cloud disturbances over the western tropical pacific

In this study,a data analysis was conducted to describe the common characteristics of large-scale cloud separations, in which zonallyelongated cloud bands extending a few thousand kilometers over the western tropical pacific are simultaneouslyseparated into two or three zonallyelongated 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). 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 activityin the original cloud band weakened considerably,strong meridional winds remained in the upper troposphere and advected the separated cloud bands northward and southward. all the cloud separations occurred about half a dayafter the convective activityhad 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 mayplaya role in the cloud separations. westward-propagating cloud clusters were observed to the west of the original cloud band during the separations,which maybe related to convectivelycoupled equatorial waves. © 2013,meteorological society of japan.