Arnis Asmat

Retrievals of Aerosol Optical Depth and Angstrom Exponent for Identification of Aerosols at Kuching, Sarawak

Anthropogenic and natural aerosols are important atmospheric constituents that significantly contribute to the Earth’s radiation budget but remain uncertainties due to the poor understanding of aerosol properties and its direct effects on scattering and absoprtion of solar radiation and the ability of aerosols to stay in atmosphere for a very short time. Different types of aerosols, representing biomass burning, urban or continental aerosols, maritime aerosols and dust particles will give different characterization and classification of aerosol properties. The data used in this study was obtained from Aerosol Robotic Network (AERONET).Two parameters were used for aerosol analysis which are Aerosol Optical Depth (AOD) at four wavelengths (440, 500, 675 and 870nm) and Angstrom exponent (α) derived from a multispectral log linear.

Identification of initial drift in semiconductor gas sensors caused by temperature variation

Metal-oxide (MOX) gas sensors are well-known with their high sensitivity in detecting gases. Despite of this quality, the responses of gas sensor are inclined to substantial drift effects caused by the environmental variable of the surrounding atmosphere such as temperature. The variation of temperature introduced shifts in the dynamic features of sensor resistance, and nonlinearly modified the original unique patterns of acquired response. In this paper, the initial drift in MOX gas sensors were identified from the responses of gas sensors that shifted over temperature variation. This initial drift identification is important for further analyses on drift compensation.

Rainfall Trend Analysis and Geospatial Mapping of the Kelantan River Basin

Trend analysis was widely used as a tool to detect changes in climatic and hydrologic time series data such as rainfall. Fourteen rainfall stations in the Kelantan River Basin were used to detect trends for each of the sub-basin areas. Two objectives of the study are (i) to quantify the changing trends of rainfall of Kelantan River using statistical tests (i.e., Mann-Kendall test and Sen’s slope test) based on monthly, seasonal, and annual time series, and secondly, (ii) to map rainfall trend according to Mann-Kendall test result. Analysis for these two tests revealed that several stations indicated significant increasing and decreasing trends for monthly, seasonal, and annual rainfall time series. The study found that rainfall varies in different months, seasons, and annually as evidenced by the graph and trend maps. Therefore, this information will benefit especially for flood preparation and responses in Kelantan River Basin which annually experiences monsoon flooding.

Land Use Change Effects on Extreme Flood in the Kelantan Basin Using Hydrological Model

Land use and land cover (LULC) change results in increased of flood frequency and severity. The increase of annual runoff which is caused by urban development, heavy deforestation, or other anthropogenic activities occurs within the catchment areas. Therefore, accurate and continuous LULC change information is vital in quantifying flood hydrograph for any given time. Many studies showed the effect of land use change on flood based on hydrological response (i.e., peak discharge and runoff volume). In this study, a distributed hydrological modeling and GIS approach were applied for the assessment of land use impact in the Kelantan Basin. The assessment focuses on the runoff contributions from different land use classes and the potential impact of land use changes on runoff generation. The results showed that the direct runoff from developmental area, agricultural area, and grassland region is dominant for a flood event compared with runoff from other land-covered areas in the study area. The urban areas or lower planting density areas tend to increase for runoff and for the monsoon season floods, whereas the inter-flow from forested and secondary jungle areas contributes to the normal flow.

Seasonal wind speed distribution analysis in west coast of Malaysia

Wind in Malaysia varies according to the Northeast and Southwest monsoon. The transition period of the two monsoons, April and October intermonsoon also influence the wind in Malaysia. The determination of the fit wind speed distribution has become a vital process in wind energy estimation and coastal engineering application. However, previous study focuses only on the fit annual distribution instead of the fit seasonal distribution of wind speed. The fit seasonal distribution of wind can leads to the proper installation of wind energy technology devices, the wind power generation and the pattern of the wind itself. Thus, this paper aims to determine the best fir distribution of monsoon and inter-monsoon occurred in Malaysia every year. The distribution that was tested is the Gamma, Log-normal and Weibull distribution model hence, the fit distribution was determined using Kolmogorov-Smirnov goodness-of-fit test. It was found that the Log-normal distribution fits best with all monsoon and inter-monsoon in Malaysia.

Variability of optical properties for atmospheric aerosol in Kuching city using AERONET Sunphotometer

The knowledge of aerosol optical properties is important for estimation of radiative balance effect to the Earths system. Aerosol can have directly effect to the radiation by scattering and absorption process depending on their chemical and physical properties. Uncertainties in estimation of radiative effect are cause by lack of knowledge for aerosol properties. AERONET Sun photometer had been used to measure the AOD, linear regressions to calculate Angstrom exponent and inversion algorithm to retrieve single scattering albedo and refractive index over Kuching, Sarawak from August 2011 until October 2011. The mean values of AOD for August was (0.4014±0.3126), for September was reported as (0.3158±0.1877) and (0.1689±0.0813) for October 2011. The minimum value for Angstrom is 0.3233 and the maximum value is 1.9325 which indicates a presence of fine mode aerosol and coarse mode aerosol. The averaged SSA for August at 440nm was 0.8997 and 0.7604 for 1020nm meanwhile for September SSA value was 0.9586 for 440nm and 0.9239 for 1020nm. It shows an increasing of urban pollution and biomass burning aerosol. The refractive index for real part and imaginary part measurement suggest that absorbing aerosols are more dominant in Kuching, Sarawak.

Derivation of aerosol loading from visibility range in Penang Island using atmospheric model

Atmospheric aerosol has influenced many atmospheric processes including cloud formation, visibility variation and solar radiation transfer. Atmospheric aerosol plays as an important indicator of visibility distance range because it will obscure the objects that can be seen. Visibility degradation has become an environmental topic of community concern in most urban areas because of low visibility range will lead to the deterioration of air quality. In this study, the atmospheric aerosol loading from the image was retrieved by using urban and maritime with visibility range at the distance of 10 km up to 50 km which are later converted into (%) reflectance. Later the works is established the relationship between aerosol loading and visibility was produced using urban and maritime models. To accommodate with the intention research works, Penang Island has been chosen. This is because of the strategic location of Penang Island which located close to the sea and recognized as one of main urbanized city in Malaysia. Results were indicated that visibility was inversely correlated with aerosol loading, the farthest the visibility range, the lower the aerosol loading. Result also showed that the urban aerosol loading estimated is higher than maritime aerosol. This may influence by meteorological factor such as the higher temperatures in urban could lead to higher rate of smog formation. Lower wind speeds will contribute which it may tend to keep pollutants concentrated over urban areas. Atmospheric urban model can derive the estimated minimum aerosol loading (12.1%) when the visibility range is about 30 km can be used to determine the minimum.

Deriving Optimum Visibility Range and Aerosol Loading from Urban Atmospheric Model in Malaysia

Visibility, aerosol optical thickness and water vapor are important atmospheric parameters that vary in space and time. Using radiative transfer algorithm to derive surface reflectance from imaging these values would be critical to be assigned. This study will investigate the optimum range of visibility and aerosol loading in Malaysia deriving from atmospheric model. Urban atmospheric model was performed into two major cities in Malaysia to represent for ideal tropical climate. The study found that the farthest visibility range at 50km,the aerosol loading was low and the shortest range at 10 km was contain high aerosol loading. Relatively, aerosol loading estimation is higher at close-shore city (Penang) than inland city (Kuala Lumpur).

Aerosol Properties over Kuching, Sarawak from Satellite and Ground-Based Measurements

The effect of aerosols on the global and regional climate can be understood through an insight into the properties of aerosols. In this article, the optical properties of aerosols were analyzed through the ground-based Aerosol Robotic Network (AERONET) and MODIS satellite data over Kuching city in northwestern Sarawak. This study deals with the optical properties of aerosols: aerosol optical depth (AOD), Angstrom exponent (α), single scattering albedo (SSA), and the asymmetry factor (ASY) during 2011–2012 over Kuching city, Sarawak, Malaysia. The results show that the variability in optical properties of aerosols can be determined by the type of aerosol or the source of the aerosol. In the study area, higher concentrations are encountered due to the presence of aerosol from urban activities, especially during the dry season. While monsoonal rainfall tends to reduce aerosol concentrations by washing aerosols out of the atmosphere, their effect is still significant during the wet season.

Impact of land cover change on the environmental hydrology characteristics in Kelantan river basin, Malaysia

Changing the land cover/ land use has serious environmental impacts affecting the ecosystem in Malaysia. The impact of land cover changes on the environmental functions such as surface water, loss water, and soil moisture is considered in this paper on the Kelantan river basin. The study area at the east coast of the peninsular Malaysia has suffered significant land cover changes in the recent years. The current research tried to assess the impact of land cover changes in the study area focused on the surface water, loss water, and soil moisture from different land use classes and the potential impact of land cover changes on the ecosystem of Kelantan river basin. To simulate the impact of land cover changes on the environmental hydrology characteristics, a deterministic regional modeling were employed in this study based on five approaches, i.e. (1) Land cover classification based on Landsat images; (2) assessment of land cover changes during last three decades; (3) Calculation the rate of water Loss/ Infiltration; (4) Assessment of hydrological and mechanical effects of the land cover changes on the surface water; and (5) evaluation the impact of land cover changes on the ecosystem of the study area. Assessment of land cover impact on the environmental hydrology was computed with the improved transient rainfall infiltration and grid based regional model (Improved-TRIGRS) based on the transient infiltration, and subsequently changes in the surface water, due to precipitation events. The results showed the direct increased in surface water from development area, agricultural area, and grassland regions compared with surface water from other land covered areas in the study area. The urban areas or lower planting density areas tend to increase for surface water during the monsoon seasons, whereas the inter flow from forested and secondary jungle areas contributes to the normal surface water.