Objective determination of the winter monsoon onset dates and its interannual variability in Malaysia
Document Type
Article
Publication Date
12-1-2022
Abstract
The northeast/winter monsoon over Malaysia often leads to extreme rainfall events and floods over the windward side of terrain due to the strong northeasterly winds. Comparatively, much less rain falls over the other are sheltered by the mountain ranges. Based on this consideration, the onset of monsoon in the region is best determined operationally using 925 hPa winds. Therefore, we propose the first, simple, single-variable-based method to determine the onset dates of winter monsoon is yet reliable and can be closely monitored for operational purposes. The onset date is defined in the third pentad when the average of three pentads of 925 hPa northerly wind speed is greater than 1 m center dot s(-1), and at least one of three pentads must be greater than 2.5 m center dot s(-1). The study also investigates the relationship between the interannual variability of onset date and El Nino-Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD). Late-onset can be expected when La Nina develops in the boreal fall season. However, a similar association between monsoon onset and El Nino condition was not observed. The lead-lag correlation between the IOD and the onset dates shows that the onset is significantly negatively correlated with the IOD. During negative (positive) IOD events, a delay (early) onset is expected. Results also show that the relationship between the onset and IOD is more robust and linear than the ENSO.
Keywords
Asian winter monsoon, ENSO and monsoon, IOD and monsoon, Monsoon onset, Monsoon onset date, Monsoon season, Northeast monsoon, Northeast monsoon onset
Divisions
ocean
Funders
Ministry of Education, Malaysia LR001-2020,LRGS-MRUN 2016-1,LRGS/1/2016/ UTM/01/1/3
Publication Title
International Journal of Climatology
Volume
42
Issue
16
Publisher
Royal Meteorological Society
Publisher Location
111 RIVER ST, HOBOKEN 07030-5774, NJ USA