USP Electronic Research Repository

Influence of Mascarene high and Indian Ocean dipole on East African extreme weather events

Ogwang, Bob and Ongoma, Victor and Xing, Li and Ogou, Faustin (2015) Influence of Mascarene high and Indian Ocean dipole on East African extreme weather events. Geographica Pannonica, 19 (2). pp. 64-72. ISSN 0354-8724

[img]
Preview
PDF (Influence of Mascarene High and Indian Ocean Dipole on East African Extreme Weather Events) - Published Version
Download (661Kb) | Preview

    Abstract

    Extreme weather and climate events such as floods and droughts are common in East Africa, causing huge socio-economic losses. This study links the east African October-December (OND) rainfall, Indian Ocean Dipole (IOD) and Mascarene High (MH).Correlation analysis is applied to quantify the relationship between the index of IOD (Dipole Mode Index (DMI)) and OND rainfall. Results show that there exists a significant correlation between OND rainfall and DMI, with a correlation coefficient of 0.6.During dry years, MH is observed to intensify and align itself in the southeast-northwest orientation, stretching up to the continent, which in turn inhibits the influx of moisture from Indian Ocean into East Africa. During wet years, MH weakens, shifts to the east and aligns itself in the zonal orientation. Moisture from Indian Ocean is freely transported into east Africa during wet years. Analysis of the drought and flood years with respect to the different variables including wind, velocity potential and divergence/convergence revealed that the drought (flood) years were characterized by divergence (convergence) in the lower troposphere and convergence (divergence) at the upper level, implying sinking (rising) motion, especially over the western Indian Ocean and the study area. Convergence at low level gives rise to vertical stretching, whereas divergence results in vertical shrinking, which suppresses convection due to subsidence. Positive IOD (Negative IOD) event results into flood (drought) in the region. The evolution of these phenomena can thus be keenly observed for utilization in the update of seasonal forecasts.

    Item Type: Journal Article
    Subjects: G Geography. Anthropology. Recreation > GB Physical geography
    G Geography. Anthropology. Recreation > GE Environmental Sciences
    Q Science > Q Science (General)
    Divisions: Faculty of Science, Technology and Environment (FSTE) > School of Geography, Earth Science and Environment
    Depositing User: Victor Ongoma
    Date Deposited: 25 Apr 2019 15:56
    Last Modified: 25 Apr 2019 15:56
    URI: http://repository.usp.ac.fj/id/eprint/11505
    UNSPECIFIED

    Actions (login required)

    View Item

    Document Downloads

    More statistics for this item...