Abdul Aziz Jemain

The temporal structure of rainfall in Peninsular Malaysia was investigated and characterized by exploring scale-invariant properties in a fractal framework, i.e. by estimating the dimension of rainfall occurrences. This is done using a box-counting method to datasets from 56 selected rain gauge stations in Peninsular Malaysia. The stations were grouped according to four regions, namely northwest, west, southwest and east for a better understanding of the effect of topography and local climatology on the temporal structure of rainfall. Results from box-counting analyses have shown that the distribution of rainfall occurrences in Peninsular Malaysia can be characterized by a fractal behaviour for three different scaling regimes: regime 1 from 15 min to 2 hours, regime 2 from 2 hours to about 2 days and regime 3 over 11 days. The breaks in scaling regimes were found to be closely related to the average of rainfall event and dry period durations. The first regime is characterized by a higher value of fractal dimension compared to the second regime. This implies that the distribution of rainfall within 15 min to 2 hours is densely structured with rainy intervals closely clustered together, while rainfall series in 2 hours-∼2 days regime are sparsely distributed in time. For regimes over than 11 days, the occurrence of rainfall is assumed to be evenly distributed as this regime is characterized by a fractal dimension 1. The analysis of spatial patterns on the fractal behaviour showed that rainfall in Peninsular Malaysia is influenced by topography, seasonal wind flow patterns and local climatology. The northeast monsoon rainfall is clearly having a greater influence on the rainfall distribution of peninsula than the southwest monsoon rainfall as the former monsoon displayed a close resemblance of spatial patterns to those obtained for the total rainfall series. In general, the rainfall occurrences in the east region is characterized by a large fractal dimension in both regimes. This could be reasoned by the flow of wind during northeast monsoon that brings heavy rain for durations from minutes up to 3 days. Meanwhile, stations in the west and southwest regions, particularly the west region which received heavy rainfall and usually in a form of convective rains during the transitional period between southwest and northeast monsoons, displayed large and moderate fractal dimensions in the regime of 15 min to 2 hours but small within regime of 2 hours to about 2 days. The results from this study may help to improve our knowledge about the temporal structure of rainfall in Peninsular Malaysia as well as help us in providing a platform to develop practical tools to produce high-resolution synthetic rainfall for the uses in hydrologic modelling, analysis and design of water resource systems.

Extreme rainfall may cause problems to the social, environmental and ecology. In this paper, we focused on regional frequency analysis of extremes rainfall based on 3-hourly rainfall records by TRMM 3B42 and raingauge data between 1998-2012 at 30 stations of Peninsular Malaysia, Malaysia. Based on the L-Moments method, we developed the regional extreme rainfall frequency analysis in measuring discordancy, regional homogeneity and the goodness-of-fit test to determine the best regional parent distribution. The Wards method is presented to identify the homogenous regions in Peninsular Malaysia and produce 4 acceptably homogeneous regions that had been tested by the L-Moments method. The results show that the L-Moments method is good in term of performance, simplicity and robustness.

This paper aims to estimate Neyman‐Scott rectangular pulse (NSRP) modeling application in representing the storm rainfall that occurred in Peninsular Malaysia. This research utilized hourly rainfall data from 48 rain gauges in Peninsular Malaysia during the period from 1970 to 2008. The raingauge stations are given in four territories, namely northwest, west, southwest, and east. The goodness‐of‐fit test from NSRP model should be done before the other applications of the model. The conclusion of this research revealed that NSRP model is able to show the rainfall data in Peninsular Malaysia.

This paper investigates the persistency properties of ozone concentrations at eight selected air quality monitoring stations situated in uban and suburban area of Peninsular Malaysia. Daily maximum hourly data of ozone concentration in 1998-2009, is used in this study. In describing the persistency, the scaling analysis, namely Detrended Moving Median (DMM) method was used to estimate the degree of persistency, known as Hurst estimator, H. This method is the adaptation of the Detrended Moving Average (DMA) method. The finding showed that there are three different scaling regions separated by a critical time scale, nc₁ and nc₂ which is around 8 month and 2 years. For shorter time scale (n < nc₁) and larger time scale (n > nc₂), the ozone concentration are persist and it remain high which the H values are showed between 0.5 < H < 1 for the most of monitoring stations in urban area. While, in suburban area, the persistency of ozone concentration are as similar as result for urban area. But a weakly persistency of ozone concentration are seen on a middle time scale (nc₁ < n < nc₂). Therefore, these findings provide scaling behaviour and persistence in ozone concentration in the ambient air in urban and suburban area of Peninsular Malaysia.