インド洋における熱帯低気圧の発生と環境場へのMJOの影響

Abstract

The Madden-Julian Oscillation (MJO) is the most dominant mode of the intra-seasonal variations of the tropical atmosphere. MJO has significant impacts on the weather and climate phenomena not only in the tropics but also in the extra-tropical regions. Moreover, the generation and development of tropical cyclones (TCs) would be affected by MJO. The present study focuses on the influences of MJO on TC genesis in the Indian Ocean and conducts the statistical analysis using the 33-year atmospheric re-analysis dataset. We divide the 33 years into MJO active years and MJO non-active years and compare the characteristics between the two categories. From the comparison, the environmental condition for TC genesis in the active year shows more suitable for the TC genesis than that in the non-active year. The result of the present study indicates that there are significant impacts of MJO activity besides El Nino/La Nina and Southern Oscillation (ENSO) on the inter-annual variation of TC genesis.