Comparison between satellite-derived rainfall and rain gauge observation over Peninsular Malaysia

Validation of the bias-corrected product of National Oceanic and Atmospheric Administration (NOAA) Climate Prediction Centre Morphing Technique CMORPH-CRT was conducted using gridded rain gauge dataset of Wong et al. (2011) and rain gauge data from meteorological stations throughout Peninsular Malaysia. The CMORPH-CRT was compared for four contrasting topographic sub-regions of Peninsular Malaysia, i.e. west coast (WC), foothills of Titiwangsa range (FT), inland-valley (IN) and east coast (EC). CMORPH-CRT product with grid resolution of 8 km × 8 km at temporal resolution of 1-hour from 00Z January 1998 to 23Z December 2018 was utilized. The results show that CMORPH-CRT are in agreement with the rain gauge data. The CMORPH-CRT performed best over coastal sub-regions but it underestimated over FT sub-region and overestimated at IN. CMORPH-CRT tend to perform better in moderate rather than heavy rainfall events. For extreme weather events, the CMORPH-CRT had shown capability in observing the formation and decay of low-pressure system in Penang during 4th November 2017 and it is in agreement with rain gauge based SPI index i.e. drought conditions over Peninsular Malaysia

Practical predictability of the 17 December 2014 heavy rainfall event over East Coast of Peninsular Malaysia using WRF model

An investigation on the practical predictability aspects of heavy rainfall event in the east coast states of Peninsular Malaysia was carried out by simulating the 17 December 2014 episode using the Weather Research and Forecasting (WRF). The WRF model was configured with three nested domains of 36 km, 12 km, and 4 km horizontal resolution for 36 h simulations. It was found that the cumulative rainfall amount and the location of the heavy rainfall centre are sensitive to the choices of Cumulus Parameterisation Scheme (CPS). The experiment with a resolution of 4 km that used the multiscale Kain-Fritsch for the outer domains and no cumulus scheme in the inner domain reasonably well simulated the case. Further analysis suggests that the CPS and initialisation gave larger impact to the forecast quality compared to boundary conditions. Grid resolution contributed the least error

Klimatologi hujan diurnal dan bayu laut-darat di Semenanjung Malaysia

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 (subrantauan 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-OgosSeptember-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