Occurrence of meridional and easterly surges and their impact on Malaysian rainfall during the northeast monsoon: a climatology study

Abstract

Abstract The cold surge or meridional surge (MS) is known to be one of the main features that contributes to extreme Malaysian rainfall events during the boreal winter or northeast monsoon. This study investigates other factors that contribute to the heavy rainfall, besides the cold surge, as well as their impacts on rainfall in the Malaysian region. Based on known methods, two additional types of surge are identified, namely the easterly surge (ES) and the mixed surge (MES), which is a mixture of both ES and MS. Daily average wind data from the European Centre for Medium‐Range Weather Forecasts Reanalysis ERA‐Interim for 37 seasons of the northeast monsoon (1979–1980 to 2016–2017, October–March) were used to identify the MSs, ESs and MESs. The impact of these surges on rainfall in the Malaysian region was investigated by using the rainfall data from the meteorological stations of the Malaysian Meteorological Department and the Tropical Rainfall Measuring Mission. The results showed that the MS plays an important role in modulating heavy rainfall in the early season over the east coast of Peninsular Malaysia. Meanwhile, the ES dominates the rainfall distribution over Sarawak in the late middle season. The rainfall modulated by the MES shows a higher intensity and concentrates over the southern part of the east coast of Peninsular Malaysia and Sabah. These findings provide a climatological view of the spatial and temporal distribution of heavy rainfall associated with different types of surge, which can be used as a forecasting tool for predicting surges and their impacts.

Keywords

• boreal winter
• cold surge
• easterly surge
• impact on rainfall
• meridional surge
• mixed surge