Soo Chin Liew

National University of Singapore | NUS · Centre for Remote Imaging, Sensing and Processing (CRISP)

Shelf seas provide valuable ecosystem services, but their productivity and ecological functioning depend critically on sunlight transmitted through the water column. Anthropogenic reductions in underwater light availability are thus a serious threat to coastal habitats. The flux of light-absorbing coloured dissolved organic matter (CDOM) from land...

Purpose: To investigate the influence of radiographic contrast agent on the accuracy of the photon counts arising from the emission of gamma rays of radionuclides in single-photon emission computed tomography (SPECT), when dual-energy x-ray CT (DXCT) is employed for providing object/energy-specific attenuation coefficient correction in SPECT. Appro...

Shelf seas provide valuable ecosystem services, but their productivity and ecological functioning depend critically on sunlight transmitted through the water column. Anthropogenic reductions in underwater light availability are thus recognized as a serious threat to coastal habitats. The flux of strongly light-absorbing coloured dissolved organic m...

The ECO-BB (Sea Bird Scientific) is a popular instrument used by water optics researchers to measure the backscattering coefficient of waters in the visible to near-infrared wavelengths. The ECO-BB is calibrated by default for oceanic waters where the backscattering coefficient is typically low. In inland and coastal waters however, there is a tend...

In coastal waters, colored dissolved organic matter (CDOM) is often present in moderate to high concentrations due to input from nearby landmasses and rivers. CDOM absorbs light sharply in the UV-blue region, causing waters to appear yellow or brown. This has a significant effect on optical and biogeochemical processes in coastal waters, as it inhi...

In coastal waters, colored dissolved organic matter (CDOM) is often present in moderate to high concentrations due to input from nearby landmasses and rivers. CDOM absorbs light sharply in the UV-blue region, causing waters to appear yellow or brown. This has a significant effect on optical and biogeochemical processes in coastal waters, as it inhi...

p>Colorectal cancer (CRC) is the third most frequent cancer and the second leading cause of cancer mortality in the developed world including Singapore. Despite an aging populace which is now more compliant to having a baseline colonoscopy at age 50 or earlier, interval cancer (cancer that develops in between colonoscopies) is an unmet critical pro...

An extreme biomass burning event occurred in Indonesia from September through October 2015 due to severe drought conditions, partially caused by a major El Niño event, thereby allowing for significant burning of peatland that had been previously drained. This event had the highest sustained aerosol optical depths (AODs) ever monitored by the global...

In ocean-color remote sensing, subsurface remote-sensing reflectance (rrs) of optically deep waters can be linked to its absorption (a) and backscattering coefficients (bb) by various models. The use of such models allows for quick calculations rrs from such coefficients, eliminating the need to solve the radiative transfer equation. In that common...

Studies on the role of urban green spaces (UGS) in mitigating the urban heat island (UHI) effect demonstrate the influence of two related, but distinct attributes of UGS: the composition (amount), and configuration (spatial attributes and distribution) of UGS patches. While the positive role of UGS amount in providing cooling effect seems unequivoc...

In this work, algorithms were developed for retrieving water quality parameters related to Singapore's reservoirs. The main constituents that affect the water reflectance (WR) – i.e. proportion of incident light reflected from the surface of water bodies after removing the surface glint component – are the suspended particles, phytoplankton and col...

Singapore, branded as a “City in a Garden”, has a long standing commitment to green the nation, one which has resulted in trees becoming an integral component of the urban environment. Similarly for its digital twin, Virtual Singapore, we undertake the research to automate the population of this virtual city with semantically and biologically repre...

3D tree database provides essential information of tree species abundance, spatial distribution and tree height for forest mapping, sustainable urban planning and 3D city modelling. Fusion of passive optical satellite imagery and active Lidar data can potentially be exploited for operational forest inventory. However, such fusion requires very high...

Accurate simulations of surface meteorological variables are important for the transport and dispersion of air pollutants and air quality in the lower atmosphere. In the present study, the surface meteorological variables over Singapore are simulated using WRF-ARW mesoscale model. The sensitivity tests are conducted with six different planetary bou...

Around 16 Mha of land is estimated to be under oil palm agriculture in insular Southeast Asia. There is a growing need to verify that palm oil is produced without causing negative environmental effects. Monitoring changes in the extent and condition of oil palm plantations by remote sensing is the first necessary step. The changing appearance of oi...

In this paper, we describe the development of algorithms for retrieving water quality parameters of Singapore reservoirs. The main constituents that affect the water leaving reflectance (WLR) are the suspended particles, phytoplankton and coloured dissolved organic matter (CDOM). We found that the existing model for the absorption spectrum of phyto...

The role of stem cells in the development of solid tumors remains controversial. In colorectal cancers (CRC), this is complicated by the conflicting "top-down" or "bottom-up" hypotheses of cancer initiation. We profiled the expressions of genes from the top (T) and bottom (B) crypt fractions of normal-appearing human colonic mucosa (M) at least 20...

In this study we create and critically analyse an automated decision tree classification approach for regional level land cover mapping in insular Southeast Asian conditions, using a combination of 10-30 m resolution optical and radar data. The resulting map contains 11 land cover classes and reveals a great deal of contextual information due to hi...

In this paper, we analyze the spatio-temporal distribution of vegetation fires in Peninsular Malaysia, Sumatra, and Borneo in the severe El Niño year of 2015, concentrating on the distribution of fires between mineral soils and peatland areas, and between land cover types in peatland areas. The results reveal that 53% of all Moderate Resolution Ima...

In the present study, the surface meteorological parameters over Singapore are simulated using WRFARW mesoscale model by varying the planetary boundary layer (PBL) parameterization schemes, horizontal resolutions and two land cover data sets (USGS and MODIS). Simulations are conducted with four nested domains having horizontal resolution of 27, 9,...

The first International Peat Congress (IPC) held in the tropics - in Kuching (Malaysia) - brought together over 1000 international peatland scientists and industrial partners from across the world (“International Peat Congress with over 1000 participants!,” 2016). The congress covered all aspects of peatland ecosystems and their management, with a...

Daytime top-of-the-atmosphere (TOA) cirrus cloud radiative forcing (CRF) is estimated for cirrus clouds observed in ground-based lidar observations at Singapore in 2010 and 2011. Estimates are derived both over land and water to simulate conditions over the broader Maritime Continent archipelago of Southeast Asia. Based on bookend constraints of th...

Tropical peatlands of the western part of insular Southeast Asia have experienced extensive land cover changes since 1990. Typically involving drainage, these land cover changes have resulted in increased peat oxidation in the upper peat profile. In this paper we provide current (2015) and cumulative carbon emissions estimates since 1990 from peat...

As part of the Seven Southeast Asian Studies (7SEAS) program, an Aerosol Robotic Network (AERONET) sun photometer and a Micro-Pulse Lidar Network (MPLNET) instrument have been deployed at Singapore to study the regional aerosol environment of the Maritime Continent (MC). In addition, the Navy Aerosol Analysis and Prediction System (NAAPS) is used t...

The first International Peat Congress (IPC) held in the tropics - in Kuching (Malaysia) - brought together over 1000 international peatland scientists and industrial partners from across the world ("International Peat Congress with over 1000 participants!," 2016). The congress covered all aspects of peatland ecosystems and their management, with a...

In this letter, we present the methodology and accuracy assessment results of a new 250 m spatial resolution land cover map of Southeast Asia (covering Brunei, Cambodia, Indonesia, Laos, Malaysia, Myanmar, Philippines, Singapore, Thailand, Timor-Leste and Vietnam). The map is based on semi-automated classification of Moderate Resolution Imaging Spe...

This study examined urban expansion of selected cities (Suzhou, Wuxi, and Changzhou) in Yangtze River Delta, China using time-series satellite remote sensing data from 1986 to 2014. A total of 16 cloud-free Landsat satellite images for the study area were downloaded and three-class (impervious cover, vegetated area, and water) land cover map produc...

Insular Southeast Asian peatlands have experienced rapid land cover changes over the past decades inducing a variety of environmental effects ranging from regional consequences on peatland ecology, biodiversity and hydrology to globally significant carbon emissions. In this paper we present the land cover and industrial plantation distribution in t...

The paper illustrates application of satellite images for studying the anatomy of a long-duration, extensive, and slow flood on the Chao Phraya River in 2011 that inundated Bangkok in its lower reach. The spread of floods in the valley was mapped with MODIS, month by month, from July 2011 to February 2012. A subsampled WorldView-2 mosaic was used t...

AbstractThis work describes among the most extensive ground-based observations of the aerosol profile collected in Southeast Asia to date, highlighting the challenges in simulating these observations with a mesoscale perspective. An 84-hr WRF-Chem mesoscale simulation of smoke particle transport at Kuching, Malaysia, in the southern Maritime Contin...

The 26 October-23 November 2010, eruption is Merapi's largest event (VEI 4) over the past 140 years. We tracked and identified the 2010 Merapi's PDC deposits in the most impacted catchment (South) using high-resolution optical (from GeoEye and SPOT-5 satellites as well as low altitude photograph) imagery. We show that high-resolution imagery enable...

We compare identification, delineation and recording of freshly erupted deposits around active volcanoes from very high resolution optical images with that done by traditional geologic mapping. Object-oriented classification (OOC) and normalized difference spectral indices of vegetation, moisture and soil redness (NDVI, NDWI and NDRSI) have been ap...

We applied Persistent Scatterer Interferometric Synthetic Aperture Radar (PS-InSAR) onto the Advanced Land Observing Satellite (ALOS) Phased Array L-band SAR (PALSAR) dataset from December 2006 to February 2011 to monitor the inter-eruption (2006 and 2010) period and the post 2010 eruption of Mount Merapi. L-band is chosen for the long wavelength t...

The 26 October–23 November 2010 eruption is Merapi’s largest event (VEI 4) over the past 140 years. We used high-spatial-resolution (HSR) imagery from GeoEye, Pléiades, IKONOS, and SPOT5 satellites to assess the extent and effects of the pyroclastic density currents (PDCs) and subsequent lahars. We have tracked the geomorphic and structural (fractu...

Persistent Scatterer InSAR (PS-InSAR) technique provides ground deformation monitoring in an accuracy of millimeter, due to its capability of overcoming the atmospheric disturbance, geometrical and temporal decorrelation. The Phased Array L-band Synthetic Aperture Radar (PALSAR) of ALOS (Advanced Land Observation Satellite) provides better capabili...

In this paper, the extreme precipitation events in the Southeast Asia region were studied using the TRMM 3B42v7 gridded daily precipitation product. The daily rain rate data were used to construct intensity-probability distribution curves for daily rainfall. Our results indicate that extreme precipitation events seem to occur more frequently than p...

The semi-aquatic, aquatic and green spaces of emerging Southeast Asian mega-cities act as ecological infrastructure, providing diverse ecosystem services to rapidly, growing, urban populations.. The cultural and natural biodiversity integrated within urban ecological infrastructure is a key to metropolitan sustainability. However, rapid urban devel...

The new high-spatial resolution (HSR) optical images allow for the identification of fresh volcanic deposits and analysis of structural changes on active volcanoes with an unprecedented accuracy. We used HSR imagery from PLEIADES, GeoEye, IKONOS and SPOT5 satellites to track the geomorphic and structural changes of Merapi's summit prior to, and aft...

The present work explores the object-oriented classification (OOC) of high-spatial resolution (HSR) satellite panchromatic imagery for mapping the geology of the persistently active Semeru volcano and its ring plain, east Java, Indonesia. A panchromatic SPOT5 image and a digital elevation model (DEM) have been used to identify geologic units, struc...

An object oriented approach was developed to derive land use/land cover classification maps over the island of Sumatra, Indonesia. The approach was developed to be used for Landsat 8 data over Sumatra. The accuracy assessment of the classified image used for development is about 90% while the test data yielded 80 %. The method will be applied to th...

In the past decades, the turbidity in Singapore's coastal waters has been increasing. This has led to reduced visibility and increased siltation rates, detrimental for the coral reefs and other sensitive ecosystems around Singapore. The reasons for this increased turbidity are poorly known because little quantitative information exists on sediment...

We report our first measurements, over the 2011 dry season period, of aerosol optical depth, Angstrom exponent number and its fine mode counterpart obtained from photometric measurements at AERONET's newest site located at the city of Kuching, Sarawak, East Malaysia. This site was set up as part of the collaborative efforts of the Seven South East...

The 26 October-23 November 2010, eruption is Merapi's largest event (VEI 4) over the past 140 years. We assessed the extent and effects of the deposits from pyroclastic density currents (PDCs) and lahars from this eruption, using high-spatial-resolution (HSR) imagery (from GeoEye and SPOT-5 satellites). We have mapped PDC deposits in particular the...

The ongoing conversion and degradation of insular Southeast Asian peat swamp forests causes globally important carbon emissions and leads to loss of unique biodiversity. Little quantitative information is available on the dynamics of peat swamp forest conversion. In this case study, we present a time-series of peatland conversion and degradation in...

We report our first photometric measurements of aerosol optical depth from AERONET's mini-DRAGON sites at Singapore performed over the months of August and September 2012. Multi-spectral measurements of aerosol optical depth provide essential spectral information to obtain and/or retrieve the so-called Angstrom exponent number which is an essential...

The Straits of Malacca has rich biodiversity, but it experienced a dramatic decline due to the anthropogenic activities for economical development and natural disasters. The objective of this study was to generate the coastal and marine habitat map for the Straits of Malacca using the SPOT and Landsat data acquired at low tide in 2010 ~ 2012. Image...

In this paper, we use the MODIS thermal anomaly product (hotspots data) to study the temporal and spatial patterns of vegetation fires in the western part of Insular Southeast Asia for a decade from 2001 to 2010. Fire occurrence exhibits a negative correlation with rainfall, and is more severe overall during the El-Nino periods. However, not all re...

The concentration of total suspended sediments (TSS) has often been empirically related to the above-surface remote-sensing reflectance, Rrs(λ). However, since a wide range of particle types exists in natural waters, a given TSS can often be the result of different particle size distributions (PSD). Directly relating TSS to Rrs(λ) disregards the ef...

Classification of Very high-resolution optical sensors imagery into Land Cover/Land use map is an important and challenging task. The detailed visual information of land targets makes the classification task difficult and methods difficult to standardize. In this work, we use an objected orientated approach to classify worldview-2 images into Land...

The humid tropical insular Southeast Asian region is one of the most biologically diverse areas in the world. It contains around 70 Gt of carbon stored in peat deposits susceptible to burning when drained and it has significantly higher population density than any other humid tropical region. This region experiences yearly fire activity of anthropo...