Tropical cyclone formation and motion in the Mozambique Channel

摘要

Although tropical cyclones (TCs) forming in the Mozambique Channel are relatively close to land and have affected vulnerable populations, few studies specifically examine these storms. This study analysed formation frequency and location and storm motion during 1948-2010. A geographic information system was employed to calculate storm trajectory and determine whether or not landfall occurred. Reanalysis data from NCEP/NCAR were examined to identify environmental conditions such as 500hPa geopotential heights and precipitable water. Nonparametric statistical tests explored relationships between these conditions, TC attributes, and four teleconnections known to influence circulation patterns in the greater Southwest Indian Ocean: the El Nino Southern Oscillation (ENSO), Indian Ocean Subtropical Dipole (IOSD), Madden-Julian Oscillation (MJO), and Southern Annular Mode (SAM). Results show that 94 TCs formed in the channel, with approximately 50% making landfall. Formation frequency varied under different phases of the SAM, IOSD, and MJO. Findings differed when the study period was divided into half, suggesting that inclusion of data prior to 1979 be interpreted cautiously. During the second period, formation tended to occur in the northern (southern) portion of the channel when the IOSD and SAM were negative (positive). The MJO and SAM were associated with differences in precipitable water values, while the MJO and IOSD were associated with track curvature. Geopotential height anomalies at 500hPa varied under the three phases of ENSO.