The different behavior of anomalous winter monsoon rainfall in northern Malay Peninsula and East Malaysia and its possible link to the LF-BO types of ENSO.
Fredolin T. Tangang (1), Liew Juneng (1)
(1) Natl Univ of Malaysia
This paper investigates the different behavior of anomalous winter monsoon rainfall in northern Malay Peninsula and East Malaysia (Borneo) and its possible links to the low frequency (LF-type) and the biennial oscillation (BO-type) of ENSO. Data used includes local rainfalls during December, January and February (DJF) for a period of 50 years (1951-2000), gridded DJF precipitation of the University of Delaware (UD), version 1.1 of Hadley Centre Global Ice Sea Surface Temperature (HADiSST1) of United Kingdom Meteorological Office (UKMO) and 850mb wind of NCEP reanalysis. A standard cluster analysis is performed for stations regionalization based on DJF rainfalls. Three clusters emerged from this procedure i.e., cluster representing stations in East Malaysia, cluster for stations in northern Malay Peninsula and cluster for stations in southern Malay Peninsula. The discussion in this paper focuses on the behavior of anomalous winter rainfall for stations in northern Malay Peninsula and stations in East Malaysia. Two winter monsoon indices were calculated by averaging the standardized anomalous rainfalls from stations within each region. The East Malaysia winter rainfall index (EMWRI) is dominated by oscillations of about 2-2.5 years period while the northern Malay Peninsula rainfall index (NMPRI) is modulated by oscillations of longer periodicity of about 3.5 to 5 years. The correlation patterns between the indices and sea surface temperature anomaly (SSTA) indicate very distinct patterns between the two regions. For EMWRI, the typical ENSO pattern emerges with the SSTAs in eastern-central Pacific Ocean, South China Sea (SCS) and Indian Ocean are in phase. The correlation pattern for NMPRI appears to have similar pattern in the Pacific and Indian Oceans but with much weaker magnitudes. However, the most notable difference is SSTA in SCS is out of phase to that in eastern-central Pacific Ocean and Indian Ocean. Based on the work by Ose et al. (1997), such different responses in SCS during ENSO may be related to the BO and LF types of ENSO. The BO-type and LF- type SSTA composites also show strong resemblance to the correlation patterns associated with the EMWRI and NMPRI, respectively. Also, the DJF composites of UD rainfall during the BO and LF-types of ENSO correspond to anomalous rainfall in northern Borneo and northern Malay Peninsula, respectively. This leads to a speculation that the different behavior in EMWRI and NMPRI may be associated with these two types of ENSO. The composites of anomalous 850mb wind and moisture convergence flux indicate that the anomalous rainfall during the BO-type of ENSO in northern Borneo is associated with cyclonic / anticyclonic circulation over the southern Philippines and northern Borneo. During the LF-type of ENSO, the anomalous circulation appears to be shifted westward with much weaker cyclonic / anticyclonic circulation over the northern Malay Peninsular and southern Thailand.
Submittal Information
Name :
Date :
Assoc Prof Dr Fredolin Tangang
05-Aug-04-11:12:16
Organization :
Theme :
National University of Malaysia
Theme 3
Address :
Presentation :
Marine Science Program, Schl of Env & Nat Res, Faculty of Sci & Tech, UKM, 43600 Bangi Selangor