Sains Malaysiana 48(3)(2019): 509–522

http://dx.doi.org/10.17576/jsm-2019-4803-03

Klimatologi Hujan Diurnal dan Bayu Laut-Darat di Semenanjung Malaysia

(Climatology of Diurnal Rainfall and Land-Sea Breeze in Peninsular Malaysia)

AHMAD FAIRUDZ JAMALUDDIN^1,2, FREDOLIN TANGANG^1*, WAN MAISARAH WAN IBADULLAH^1,2, LIEW JUNENG¹, DIONG JEONG YIK^1,2, ESTER SALIMUN¹, AMBUN DINDANG² & MUHAMMAD HELMI ABDULLAH²

¹Pusat Sains Bumi dan Alam Sekitar, Fakulti Sains dan Teknologi, Universiti Kebangsaan Malaysia, 43600 UKM Bangi, Selangor Darul Ehsan, Malaysia

²Jabatan Meteorologi Malaysia, 46667 Petaling Jaya, Selangor Darul Ehsan, Malaysia

Received: 23 June 2018/Accepted: 19 December 2018

ABSTRAK

Kajian ini bertujuan memahami klimatologi kitaran hujan diurnal dan mekanismanya di Semenanjung Malaysia berdasarkan analisis data cerapan. Analisis jumlah, kekerapan dan keamatan hujan diurnal memperlihatkan 4 peristiwa hujan diurnal yang utama, iaitu: kejadian hujan petang maksimum semasa musim peralihan monsun di kaki bukit Banjaran Titiwangsa adalah lebat dan sering berlaku; kejadian hujan sepanjang hari di pantai timur semenanjung (sub-rantauan PT) semasa monsun timur laut adalah lebat dan sering berlaku; kejadian hujan pada pagi di lembah-pedalaman semenanjung (sub-rantauan LP) semasa monsun timur laut adalah rendah walaupun hujan lebat sering berlaku pada petangnya; dan kejadian hujan pagi maksimum di pantai barat semenanjung (sub-rantauan PB) semasa Jun-Julai-Ogos-September-Oktober-November (JJOSON) merupakan kejadian hujan yang melampau namun kekerapannya adalah rendah. Di sub-rantauan PB, kelajuan angin permukaan yang kuat berbanding lemah pada aras troposfera yang lebih tinggi semasa musim peralihan monsun menyebabkan ricih angin bergerak ke atas. Sebaliknya, kombinasi angin monsun dan bayu laut semasa monsun barat daya menyebabkan ricih angin bergerak ke troposfera bawah. Semasa monsun timur laut, luluran angin sejuk dan bayu laut menyebabkan kelajuan angin adalah kuat pada permukaan sehingga ke aras 2 km tinggi di timur semenanjung. Ini menyebabkan zon perolakan yang tertumpu di sub-rantauan PT pada pagi meluas sehingga ke sub-rantauan LP pada waktu petang.

Kata kunci: Bayu laut-darat; hujan diurnal; Semenanjung Malaysia

ABSTRACT

This study aims to provide a basic understanding of diurnal rainfall climatology and its mechanisms in Peninsular Malaysia by utilising observation data. The analysis of rainfall amount, frequency and intensity showed 4 main diurnal rainfall events: the occurrence of afternoon rainfall maximum at the foothills of Titiwangsa Mountain Range during the inter-monsoon periods was heavy and frequently occurred; the occurrence of rainfall throughout entire day over the east coast of peninsula (PT sub-region) during northeast monsoon was heavy and frequently occurred; the occurrence of entire day rain over the inland-valley (LP sub-region) area during northeast monsoon was low despite heavy rainfall often occurred in the afternoon; and the occurrence of morning rainfall maximum was an extreme rainfall event but with low in frequency over the west coast of peninsula (PB sub-region) during June-July-August-September-October-November (JJASON). During the inter-monsoon periods, stronger surface wind and weaker at higher tropospheric level caused vertical wind shear over the PB sub-region. On the other hand, superimposition of monsoonal flow and sea breeze during southwest monsoon resulted downward shear in the sub-region. During the northeast monsoon, combination of cold surges and sea breezes modulate strong wind from the surface up to 2 km height. This causes a convection zone which was confined over the PT sub-region in the morning to extend into LP sub-region in the afternoon.

Keywords: Diurnal rainfall; land-sea breeze; Peninsular Malaysia

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*Corresponding author; email: tangang@ukm.edu.my