Aik Song Chia

Detection of vegetation fires and burnt areas by remote sensing in insular Southeast Asian conditions: current status of knowledge and future challenges

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 anthropogenic origin with widely varying extent and severity. At the same time, there are several geographic, climatic, and social aspects that complicate fire monitoring in the region. In this review article, we analyse the current knowledge and limitations of active fire detection and burnt area mapping in insular Southeast Asia, highlighting the special characteristics of the region that affect all types of remote-sensing-based regional-level fire monitoring. We conclude that the monitoring methods currently employed have serious limitations that directly affect the reliability of results for fire and burnt area monitoring in this region. With the materials and methods presently available, the regional and global effects of fire activity taking place in insular Southeast Asia are in danger of being underestimated. New approaches utilizing higher spatial and temporal resolution remote-sensing data are needed for more detailed quantification of fire activity and subsequently improved estimation of the effects of fires in this region.

Modeling the reflectance spectra of tropical coastal waters

This work aims to extract optical parameters of coastal sea water with high sediment and chlorophyll content by fitting reflectance spectra to a model. Sea-truth water sampling campaigns were carried out from Dec 1996 to Dec 1999 in coastal waters around Singapore. In-situ reflectance spectra were acquired using a portable spectro radiometer. Laboratory measurements of the total suspended solid (TSS) and chlorophyll-a (Chl-a) were made from the water samples. The Chl-a concentration ranges from 1 to 90 mg/m3, with an average value of about 10 mg/m3. The three component model for sea water was used to model the reflectance spectra. The model also includes chlorophyll fluorescence and surface reflection due to skylight. Each reflectance spectrum is fitted to the model by finding a set of the fitting parameters that best fits the reflectance curve to the mode. The downhill simplex method is employed as the optimization procedure. The chlorophyll absorption coefficient at 440 nm is retrieved and is found to relate to the measured chl-A concentration by a power law relation.

Satellite observations of coastline changes in the Andaman islands after the 2004 Sumatra earthquake

Following the M9.0 Sumatra earthquake on December 26, 2004, elevation and subsidence on separate parts of the coastline of the Andaman Islands have been reported. In this study, we use satellite imagery to map the coastline changes due to land elevation or subsidence after the earthquake in the Andaman Islands. The NIR band of SPOT-5 images before and after the earthquake was used to delineate coastlines. Images with similar tide levels were chosen for comparison. Elevation or subsidence is indicated by the emergence or submersion of corals and mud flats in the preand post-earthquake images. Our results indicate a general tilt of the main Andaman Islands in a direction in agreement with seismological estimates of the thrustfaulting between the Burma and Indian plates. Changes in coastal bathymetry were estimated using a shallow water reflectance model. The vertical displacement is estimated to be about 1 m for the uplifted areas on the northwestern coast. Keywords-Andaman Islands; elevation; subsidence; earthquake; 2004 Sumatra Earthquake

Spatio-temporal variability of precipitation in southeast asia analyzed using the empirical orthogonal function (EOF) technique

The empirical orthogonal function (EOF) analysis is used to investigate the spatial and temporal variations of precipitation rate measured by the Tropical Rainfall Measuring Mission (TRMM) satellite in the Southeast Asian region. The EOF analysis decomposes the rainfall data into several modes of variations. Each mode can be associated with one or several mechanisms of variations. The most dominant mode is associated with annual seasonal monsoons while the second and third modes have moderate El-Nino influences. The precipitation rate does not seem to have significant correlation with the global warming index.

2009 earthquakes in Sumatra: The use of L-band interferometry in a SAR-hostile environment

L-band interferometry is a useful tool to help the study of earthquakes and the assessment of the resultant damage in tropical regions. It can be used at different levels: using only the coherence or fully processing the differential interferogram.

Development of a MODIS direct broadcast reception and processing system

Since the successful launching of the TERRA satellite in late 1999, CRISP has been preparing to receive MODIS data in Direct Broadcast mode. A multi-mission demodulator with SPOT, ERS, TERRA and AQUA capabilities has been purchased and integrated into CRISPs antenna system. The output of the demodulator is directly recorded on the existing direct ingest system (disk arrays). A reformatting program, with the option of performing Reed Solomon error correction, has been written to convert the recorded signal data into MODIS level-0 formatted data. This level-0 data is then fed into a level I processing program. Two versions of the level 1 processing software have been tested IMAPP by the University of Wisconsin and NASA GSFC MODIS level 1 Processing Software. One of the inputs for the NASA software is the construction record generated by a Windows-based program - Sorcerer. In order to integrate all our processing on the Unix platform, a small program that is able to generate the construction record has been written. We have found that the IMAPP software runs faster but the geolocationing is not very accurate. As for the NASA software, the geolocationing is fairly accurate, but a shortcoming is that its calibration process, MOD02, can only handle a granule size of 300 seconds. Therefore, we replace the geolocation produced by IMAPP by NASAs geolocation and further calibrate the results into level 1b using IMAPP software. A georectification code has also been developed to georectify the level 1b products onto a map.

Estimating the characteristics of sub-pixel fires using Suomi-NPP VIIRS data

The characteristics of sub-pixel fires in Suomi-NPP VIIRS data are studied using the Nightfire algorithm which attempts to fit the spectral radiance to a blackbody function. For small and/or low intensity fires, the fire temperature tends to be underestimated while the fire area are overestimated. The accuracy is improved when only the shorter wavelength bands are used in the fitting or when the whole spectrum is fitted to two blackbody functions representing the fire and the background components.

Insar monitoring of the Lusi mud volcano, East Java, from 2006 to 2010

Lusi is a mud volcano in East Java, Indonesia, which started its eruption on 29th May 2006 and never stopped. To study this volcano, we used SAR interferometry with ALOS/Palsar satellite images from 2006 to 2010. By creation of a set of interferograms, and suppression of unwanted components, such as Earth curvature and elevation, we were able to compute the motion that occurred between two dates. The obtained set of motions shows that the region of Lusi is undergoing a general subsidence of several metres. However, as this region is very wet, more precise results, on the volcano itself, can be obtained by GPS campaigns.