Bivariate joint distribution analysis of the flood characteristics under semiparametric copula distribution framework for the Kelantan River basin in Malaysia

Flood is becoming the severe hydrologic issue at the Kelantan River basin in Malaysia.The joint distribution analysis amongst multiple interacting flood characteristics,i.e.,flood peak discharge flow,volume,and duration series usually provide a comprehensive understanding of the hydrologic risk assessments through visualizing the multivariate exceedance probability or return periods.The traditional copulas-based methodology is frequently employed under parametric settings where parametric family functions are often employed to model univari-ate marginal distribution before capturing their dependence structure.Actually,no universal rules and literature are imposed to model any flood vectors through any fixed or predefined density function,which would follow the different distribution and needs to model by fitting most parsimonious function.Also,the copula function already relaxes the restriction of selecting marginal distributions from the same distribution families.Therefore,incorporation of non-parametric kernel density estimations or KDE would be much stable and less biased smoothing alternatives than the parametric approach.In this literature,the semi-parametric copula-based methodology is incorporated,where the flood marginals are modelled under the kernel functions and applied as a case study for 50 years annual maximum(AM)flood samples of the Kelantan River basin at the Gulliemard Bridge gauge station in Malaysia.The Archimedean families copulas(i.e.,Frank,Gumbel and Clayton)and Elliptical copula(i.e.,Gaussian copula)are tested,and thus best-fitted copulas are employed to model the bivariate joint distribution amongst flood characteristics,and which further employed to derive joint and conditional return periods.

Comparison of photosynthetic pigments and phytoplankton assemblages in two types of coastal regions in Southeast Asia-Indonesian Throughflow and river estuary

Water samples were collected in order to study the spatial variation of photosynthetic pigments and phytoplankton community composition in the Lembeh Strait(Indonesia) and the Kelantan River Estuary(Malaysia)during July and August 2016, respectively. Phytoplankton photosynthetic pigments were detected using high performance liquid chromatography combining with the CHEMTAX software to confirm the Chl a biomass and community composition. The Chl a concentration was low at surface in the Lembeh Strait, which it was 0.580–0.682 μg/L, with the average(0.620±0.039) μg/L. Nevertheless, the Chl a concentration fluctuated violently at surface in the Kelantan River Estuary, in which the biomass was 0.299–3.988 μg/L, with the average(0.922±0.992) μg/L. The biomass at bottom water was higher than at surface in the Kelantan River Estuary, in which the Chl a concentration was 0.704–2.352 μg/L, with the average(1.493±0.571) μg/L. Chl b, zeaxanthin and fucoxanthin were three most abundant pigments in the Lembeh Strait. As a consequence, phytoplankton community composition was different in the two study areas. In the Lembeh Strait, prasinophytes(26.48%±0.83%) and Synechococcus(25.73%±4.13%) occupied ～50% of the Chl a biomass, followed by diatoms(20.49%±2.34%) and haptophytes T8(15.13%±2.42%). At surface water in the Kelantan River Estuary, diatoms(58.53%±18.44%)dominated more than half of the phytoplankton biomass, followed by Synechococcus(27.27%±14.84%) and prasinophytes(7.00%±4.39%). It showed the similar status at the bottom water in the Kelantan River Estuary,where diatoms, Synechococcus and prasinophytes contributed 64.89%±15.29%, 16.23%±9.98% and 8.91%±2.62%,respectively. The different phytoplankton community composition between the two regions implied that the bottom up control affected the phytoplankton biomass in the Lembeh Strait where the oligotrophic water derived from the West Pacific Ocean. The terrigenous nutrients supplied the diatoms growing, and pico-phytoplankton was grazed through top down control in the Kelantan River Estuary.

马来半岛彭亨河和吉兰丹河沉积物稀土元素特征及其物源示踪

通过对马来半岛东部彭亨河28个站位和吉兰丹河22个站位表层沉积物进行稀土元素(REE)测试,对比分析了稀土元素的组成特征和分布规律,探讨了稀土元素组成的控制因素和物源示踪意义。结果表明,彭亨河沉积物稀土元素含量介于24.88~304.29μg/g之间,平均含量为165.22μg/g,吉兰丹河沉积物中稀土元素含量介于126.02~281.40μg/g之间,平均值为181.15μg/g。彭亨河大部分沉积物上陆壳(UCC)标准化模式为重稀土相对轻稀土富集,吉兰丹河沉积物轻重稀土无明显分异。沉积物源岩和矿物组成对两条河流的REE组成起到了重要的控制作用,化学风化对彭亨河REE组成的影响大于吉兰丹河,而彭亨河沉积物粒度组成显著差异也导致了其REE含量变化范围更大。δEuUCC-(Gd/Yb)UCC关系图中彭亨河和吉兰丹河沉积物分区明显,表明其可作为定性判别两条河流来源的有效指标,并可用于海区沉积物来源的示踪和定量识别。