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Articles by T. Lihan
Total Records ( 5 ) for T. Lihan
  T. Lihan , M.A. Mustapha , S.A. Rahim , S. Saitoh and K. Iida
  Freshwater discharge from rivers into the ocean is an important element of the dynamics in coastal areas. River discharge from land that includes chlorophyll a, nutrients, sediments and pollutants have been identified as one of the major causes of deterioration of the coastal water. The objective of this study was to examine the relationship between river discharge and variability of chlorophyll a concentration in plume area using satellite imagery. Satellite ocean color and Sea Surface Temperature (SST) imagery were used to present the synoptic quantification of chlorophyll a variability on seasonal and interannual timescales for the plume area of Tokachi River, Japan. Five years (1998 to 2002) of SeaWiFS local area coverage, AVHRR imagery and surface wind were analyzed using default NASA coefficients and community-standard algorithms as implemented by SeaDAS. The chlorophyll a climatology seasonal pattern showed seasonal cycles, first peak in spring and second peak in late summer to early autumn. Elevated chlorophyll a concentration demonstrates seasonal cycles and interannual variability are present around plume area associated with variation of river discharge. Elevated chlorophyll a concentration in offshore area was seen to be influenced by low sea surface temperature and wind stress.
  A. Jabbar , T. Lihan , M.A. Mustapha , Z.A. Rahman and S.A. Rahim
  Estuarine outflow associated with suspended matter concentrations and pollutants have a major impact on marine ecosystems. Understanding the dynamics and dispersal pattern of suspended matter from river water are important for management of coastal water quality and biological productivity. This study aimed to determine the variability of Pahang River plume signature at the coastal area. One km spatial-resolution normalized water-leaving radiance, (nLw 551) obtained from the Moderate Resolution Imaging Spectroradiometer (MODIS) on Aqua satellite were analyzed from the period of 2005-2010. The plume spectral signature estimated of the backscattering coefficient nLw 551 (proxy for suspended matter) was strongly correlated with the amount of monthly average rainfall over the study period. The plume signature distributions during 2005-2010 based on nLw 551 was highly variable. During northeast monsoon, the plume tends to propagate to the south and shows the strongest plume signature of nLw 551 value (>2.0 mW cm-2 μm-1 sr-1) meanwhile during southwest monsoon the plume dispersion to the north and exhibit weakest plume signature value (<1.5 mW cm-2 μm-1 sr-1). The variability of plume signature was determined by the backscattering characteristics of surface waters in the region of the river mouth as a result of rainfall, wind stress and surface current event.
  Z.A. Rahman , J.Y.Y. Lee , S.A. Rahim , T. Lihan and W.M.R. Idris
  The demand for land in conjunction to infrastructure development is become crucial and expensive. In the near future, a problematic soil such as peat is becoming a final alternative. In crucial cases, peat land cannot be avoided and has been hosted for engineering structures (e.g., road, highway, railway and bridge). Peat soil is well established of its downgraded characteristics, highly compressibility and low in shear strength. This study aimed to investigate effect of fly ash and gypsum on the mechanical properties of peat soil. Fly Ash (FA) is a by-product material that is generated from the burning of coal in thermal power plants. In this study, gypsum was prepared chemically in the laboratory to simulate residue from Neutralization Underflow Process (NUF). For the first batch of samples, the peat samples were initially treated with Synthetic Gypsum (SG) in the ranges between 0 and 20% of sample dried weight (SG treated soil). In a second batch, the peat samples were prepared with 10% FA and then mixed thoroughly with different amounts of SG contents (0, 5, 10 and 20%) (10FA-SG treated soil). The results showed that soil treated with mixture of 10% FA and SG indicated lower liquid limit values than the SG treated soil. In compaction tests, the maximum dry density of both increased in both SG treated soil and FA-SG treated soil. The permeability of SG treated soil increased with the increases in SG contents. Similarly, occurred to permeability of FA-SG treated soil however, its values are lower than the soil treated without FA. Shear strength of SG treated showed decreased with increasing amount of SG content. In contrast, the FA-SG treated soil exhibited higher strength if compared to that of SG treated soil. The result suggested that the application of FA and SG mixture is more effective in stabilization in mechanical strength and densification of peat soil than the use of SG only.
  M.N. Sumardi , A.M. Mustapha , T. Lihan and F. Tangang
  The east coast of Malaysian waters is of importance because it harbors the country’s fisheries resources. Determination of its spatial and temporal variations enables understanding of the coastal waters dynamics and physical processes affecting the region. Aqua MODIS satellite data of normalized water-leaving radiance (nLw at 412, 443 and 551 nm) from January 2006 to December 2010 were processed to determine variability using the classification approach. Five spectrally defined classes were obtained to represent the coastal water characteristics based on false color images. Variability was influenced by the outflow of terrestrial water which carries the load of suspended materials into the ocean and it moved according to the northeast and southwest wind and current propagation. Empirical Orthogonal Function (EOF) analysis of nLw 551 imagery explained the variability in temporal and spatial scale. The first mode of the EOF analysis (77.38% of variance) indicated the seasonal cycle. The second mode (4.96% of variance) explained the inter-monsoon period indicating the variability between the two periods of the Northeast and Southwest monsoon in this area. The third mode (3.17% of variance) indicated the Northeast monsoon which showed high variability toward the coastal water region associated with strong wind. The fourth mode (1.91% of variance) explained the Southwest monsoon associated with weakened wind and showed spreading surface pattern further from the coastline. Understanding of this variability would greatly contribute to coastal fisheries management and planning that could provide benefits to the coastal area as well as the productivity of this region.
  A.M. Mustapha , T. Lihan and S. Saitoh
  In management of the Japanese scallop Mizuhopecten yessoensis culture, it is important to understand the phytoplankton bloom development in the coastal region of the Okhotsk Sea. Variations in food available to this benthic bivalve are a primary environmental factor affecting growth in nature. This paper determined the seasonal variability of Chlorophyll a (Chl a) at the scallop farming region in the Okhotsk Sea from 1998 to 2004 using satellite imageries. Satellite images were processed using default NASA coefficients and community-standard algorithms as implemented by Sea DAS. Spatial and temporal variation of Chl a was determined by EOF analysis. The Chl a concentration showed high seasonal and interannual variability. Peak of Chl a concentration occurred in spring followed by autumn and summer. This was evident in the Empirical Orthogonal Function (EOF) analysis. The spatial pattern of the first mode of EOF analysis of Chl a revealed intensified Chl a at the shelf and offshore areas in spring and autumn (51.8% of variance). The second mode explained 14.2% of the variance indicating enhancement of spring (April-May) Chl a pattern in the frontal area along the coast. Meanwhile, the third mode captured 9.0% of the variability demonstrating high Chl a extending seaward from the shelf area during late autumn. These seasonal variability of Chl a resulted from the variability in occurrences of physical processes associated with retreat of sea ice in spring, advection of Soya Warm Current in summer and intrusion of East Sakhalin Current in autumn.
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