Radar Altimeter Database System Research Articles

Sea level rise estimation and projection from long-term multi-mission satellite altimetry and tidal data in the Southeast Asia region

ABSTRACT The Southeast Asian (SEA) region represents a complex coastal geographical location. Most countries in SEA are encircled by the ocean, with lowlands coastal areas. The advantages of long-term satellite altimetry and tide gauge measurements have enabled climate-related research, particularly sea level rise, to be examined extensively in spatial and temporal scales. In this study, sea level anomaly (SLA) derived from 26 years of multi-mission satellite altimeter data plus approximately 28 years of tidal data have been utilized. Then, the projection for every 10 years starting from 2030 until 2100 has been analysed using machine learning regression. The projections are then evaluated based on the global model of the Intergovernmental Panel on Climate Change (IPCC). The findings presented that sea level rise trends around SEA with overall means of 4.70 ± 0.37 mm yr−1 for the satellite altimeter and 3.41 ± 0.24 mm yr−1 for the coastal tide gauge. Sea level projection from coastal tide gauge and satellite altimeter are expected to rise up to 34.87 and 33.71 cm, respectively, in 2100. These outcomes prove that the altimetry data from Radar Altimeter Database System (RADS) and the redundant tidal data are capable in measuring the sea level in SEA. These results are also expected to be valuable for multidisciplinary environmental studies in SEA, such as coastal flooding, coastal erosion, and other effect of global warming. Thus, it would make a meaningful contribution towards Sustainable Development Goal (SDG) 13, climate action, by providing the sea level rate and prediction information.

Developing a near-seamless tidal datum by integrating tidal and satellite altimetry data with a Digital Elevation Model for maritime boundary delimitation

ABSTRACT The delimitation of maritime boundaries plays a significant role in preserving the country’s sovereignty and jurisdiction. The maritime baseline was established based on the combination of maritime basepoints, which represents the Lowest Astronomical Tide (LAT) along the coast. However, the current approach still relies on the limited and sparsely distributed tide gauge stations for the determination of LAT. Therefore, this study aims to develop the Peninsular Malaysia Near-Seamless Tidal Datum (PMNSTD) by integrating tide gauge, satellite altimetry, and Tide Model Driver (TMD) data. PMNSTD was further integrated with Digital Elevation Models (DEM) for the delimitation of maritime boundaries. This study methodology includes data acquisitions of 12 tide gauge stations along the coast of Peninsular Malaysia, satellite altimetry data for TOPEX, Jason-1, Jason-2, and GEOSAT Follow-On (GFO) from Radar Altimeter Database System (RADS), TMD, and TerraSAR-X add on for Digital Elevation Measurement 30 m (TanDEM-X) data. The tide gauge, satellite altimetry, and TMD data encompass 23 years of tidal observation data from 1993 to 2015. For the derivation of the tidal datum, the tide gauge and satellite altimetry data were analysed using harmonic analysis in UTide, whereas, for the TMD data, the tidal datum was determined based on tidal prediction. For compatibility in data integration, the derived Lowest and Highest Astronomical Tide (LAT and HAT) from tide gauge, satellite altimetry, and TMD data were referenced to the Mean Sea Level (MSL), denoted as and respectively. Next, the and was interpolated using Inverse Distance Weighting (IDW) to develop the PMNSTD (and ) using ArcGIS. The statistical assessment indicates that the PMNSTD ( and ) established from the integration of tide gauge, satellite altimetry, and TMD has a better agreement with the Department of Survey and Mapping Malaysia (DSMM) tide gauges with a Root Mean Square Error (RMSE) and Standard Deviation (STD) of 0.228 m and 0.175 m for , as well as 0.159 m and 0.079 m for . Next, the PMNSTD () was integrated with TanDEM-X using ArcGIS and SURFER for the delimitation of maritime boundaries. The reliability assessment illustrated a significant improvement in the continuation of 201 maritime basepoints in comparison to the 95 maritime basepoints by the DSMM. In conclusion, the proposed approach has shown a continuous, consistent, and wider establishment of the country’s maritime baseline for the Peninsular Malaysia region.

The Impact of Altimetry Corrections of Sentinel-3A Sea Surface Height in the Coastal Zone of the Northwest Atlantic

Corrections to altimeter-measured sea surface height anomalies (SSHA) have a larger proportional effect for synthetic aperture radar (SAR) altimetry than conventional, pulse-limited altimetry because of lower range noise. Here, we quantified the impact of the current generation of altimeter corrections in the coastal zone of the Northwest Atlantic, a region with significant dynamic activity. In this study, we used the sea level variance analysis to determine the change in variance for the altimeter corrections—range, geophysical, and mean surface—compared to the baseline. We also evaluated the performance of two coastal retrackers, ALES (empirical) and SAMOSA++ (fully analytical), against the SSHA from the Radar Altimeter Database System (RADS), which uses the standard SAR retracker. Tide corrections caused the largest change in sea level variance, followed by wet tropospheric corrections and sea state bias. Most non-standard altimeter corrections failed to reduce the sea level variance and performed markedly worse closer to the coast. Coastal retrackers showed a higher deviation from the standard SSHA closer to the coast, especially when the backscatter coefficient was high and the significant wave height was low. We conclude that further development of coastal corrections is needed. Contrary to our prior expectation, we found that standard altimetry corrections appear to perform as well as alternative more advanced/tailored corrections.

Analysis of Upwelling Events in the Southern South China Sea Using Multi-Mission Satellite Altimeter

Upwelling is a vital ocean behaviour, especially for the Fisheries Industry, where upwelling will help to detect fish ground at a particular ocean area. However, the study of upwelling is minimal and not well understood due to some reasons and constraints, such as limited observation. Upwelling lacks a comprehensive in-situ observation system where it relies on limited information collected from the ground-truthing execution such as ships, buoys, and current meter. This study aims to analyse the upwelling pattern in the southern region of the South China Sea by using a multi-mission satellite altimeter. In order to derive the physical oceanography that involves upwelling, such as sea surface height (SSH), Mean Dynamic Topography (MDT), and the Sea Level Anomaly (SLA), the Radar Altimeter Database System is used. Five Satellite Altimeter mission is used in this study, which is JASON-2, JASON-3, CYROSAT2, SARAL, SENTINAL3A from 2013 to 2017. Validation is made using a statistical method showing a good correlation between Altimetry data and Tidal Data at tide gauge, which is 0.84 to 0.97, respectively. Also, monthly altimetry derived Geostrophic Current was assessed by analysing the current pattern where it shows a similarity with a previous study where the current velocity is 0.5ms-1 to 2ms-1. From the result, eddies can be seen in the seasonal and monthly Absolute Geostrophic Ocean Current (AGOC) map, indicating the present presence of upwelling. In conclusion, this study will benefit other researchers in terms of both upwelling and eddy studies.

THE POTENTIAL OF OFFSHORE WIND ENERGY IN THE EAST COAST OF PENINSULAR MALAYSIA, TERENGGANU

A detailed understanding of wind characteristics is very important for offshore wind energy development. A 26 years of wind speed data (1993-2018) were retrieved using Radar Altimeter Database System (RADS) to assess the potentiality of offshore wind energy in Terengganu waters. Seasonal assessment and wind energy density derivation was carried out to choose the potential location for wind energy development. This study highlights the multi-criteria site suitability analysis using Analytical Hierarchy Process (AHP) and is supported by the geographical information system (GIS) by developing a suitability map. The site suitability analysis considered a few criteria, such as seasonal assessment, physical, environmental, and wind resources. Theoretically, the Terengganu area possessed strong wind during the Northeast monsoon with an average of 3.46m/s and experienced up to 6 m/s during this monsoon. For offshore areas, which is more than 50km from the coastline, Terengganu waters experienced a maximum of wind speed more than 5m/s and the average wind power density varied from 40W/m2 to 60W/m2. While Tenggol Island possessed a maximum wind speed between 3m/s to 5m/s and produce up to 40W/m2 of average wind energy density. From the suitability analysis, a few areas are identified as the potential location with an optimum resource of wind energy. Even though, Malaysia is located at low wind area, this research will help organisation or governments to plan suitable technology and policy for harvesting wind energy.

Seasonal and Interannual of Sea Level Variability in the Indonesian Seas using Satellite Altimetry

Sea-level rise is an extreme issue for the world that has been scientifically proven. That is why sea-level variability presents a significant role in ocean and air interactions. This study was directed to get seasonal and interannual variability in the Indonesian Seas. The research area is in the Indonesian Seas with coordinates boundaries: of 20°N - 20°S latitudes and 90°E - 150°E longitudes. The data were obtained from the Radar Altimeter Database System (RADS) for Jason Series altimetry (2008 to 2018). The analysis has been performed by taking the correlation between detrended Sea Level Anomaly (SLA) and El Nino Southern Oscillation (ENSO). The outcome showed that the seasonal and interannual sea level anomaly in Indonesian seas fluctuates. Seasonal varieties of Sea Level Anomaly in the Timor Sea, Northen Java Sea, and the Halmahera Sea were low. The high seasonal changes occurred in the Flores Sea, the Natuna Sea, and the Karimata Strait. Besides, the interannual variation of SLA fluctuated from 2009 to 2018. The impact of ENSO on the variance of SLA was strong, with a coefficient correlation of -0.66. In the most recent ten years, the SLA in the Indonesian Seas demonstrated a lowering trend.

Assessment of Coastal Altimetry Data in the South China Sea using Multiple Frequency Approaches

With a coastline length extending over 13,000 km, including the Malaysia region, the South China Sea presents a challenge to retrieve high quality data along the coastal area especially the sea level anomaly and significant wave height. Currently, coastal altimetry is still facing some issues especially when using the low frequency data such as data lacking near the coast, questionable data accuracy since the altimeter footprint contaminated with the land and less coverage of data from the installed ground truth data. This study aims to assess the coastal altimetry data of sea level and significant wave height in the South China Sea using low and high frequency approaches. This study involved deriving data from sea level anomaly (SLA) and significant wave height (SWH) through the use of Prototype for Expertise on AltiKa for Coastal, Hydrology and Ice (PEACHI) for high frequency and Radar Altimeter Database System (RADS) for low frequency of altimetry and ground truth station which is from tide gauge and Acoustic Wave and Current Profiler (AWAC). Comparison between altimetry and ground truth data has been made in order to validate the significant agreement between them. The validation of the data is to evaluate both types of frequencies with respect to the coastal distance. Consequently, the high frequency results for coastal results with a root mean square reliable ±0.14 metre level for the sea level anomaly (SLA) and ±0.18 metre level for significant wave height (SWH) are more reliable. PEACHI distance-to-coast data obtained a sufficient standard residual deviation ranging from 0 cm to 2.87 cm compared to RADS altimetry ranging from 0.08 cm to 14.20 cm. The findings of this study indicate that the coastal altimetry data benefit coastal development, coastal defence, monitoring and tourism by various related agencies.

OFFSHORE WIND ENERGY RESOURCE ASSESSMENT IN MALAYSIA WITH SATELLITE ALTIMETRY

Realistic view on the potential of offshore wind farm development in Malaysia is necessary and requires accurate and wide coverage of wind speed data. Long term global datasets of satellite altimetry of wind speed provide a potentially valuable resource to identify the potential of offshore wind energy in Malaysia. This paper presents three different assessments of offshore wind energy resources in Malaysia using satellite altimetry. The wind speed data obtained from Radar Altimeter Database System (RADS) were validated and identified to be in agreement with previous studies. The resources were then assessed at three different levels; theoretical, technical and practical offshore wind energy potential. The technical resource potential was assessed by taking into consideration the available offshore wind turbine technology. Conflicting uses and environmental constraints that define the practical offshore wind energy resources are plotted on the maps to present a practicality of offshore wind farm development in Malaysian sea. The study concluded that, in theoretical view, Malaysia does have potential of offshore wind energy resource especially in Borneo Water with average annual wind energy density above 500 kWh/m2. However, the development of offshore wind farm in Malaysia will be difficult taking into consideration the technical and practical challenge.

EXPLORING SPATIO-TEMPORAL WAVE PATTERN USING UNSUPERVISED TECHNIQUE

Abstract. The sea waves are the up and down movements of water in the sea. The various heights of sea waves are known as significant wave heights. Each type of wave has their own characteristics based on their significant wave heights. The aim of this research is to explore spatio-temporal wave patterns and their effects on Tok Jembal coastal areas. For this study, the monthly wave data were obtained from the satellite altimeters that have been processed using Radar Altimeter Database System (RADS). The Self Organizing Map (SOM) method was used to extract the spatio-temporal wave height patterns from the monthly wave height data. From the clustering results, six number of clusters were extracted and then each of these clusters was categorized into specific type of wave heights. In addition, time series of Landsat satellite images were used to observe the coastal changes at Tok Jembal areas. Finally, we analyzed the effects of spatio-temporal wave patterns towards the occurrences of coastal erosion along the coastal areas. This study has discovered that the wave heights along the coastal areas fall in slight category and showed less effects on the erosion. From the visual interpretation of time- series images (10 years gap) also proved that the erosion can be considered as moderate. Overall, this study could benefit the coastal management especially for shoreline monitoring where early action can be taken when there are signs of erosion along the coast.

Long-term quality and stability assessment of CryoSat-2 Ocean Data

Since 8 April 2010 ESA’s Earth Explorer mission CryoSat-2 has been measuring marine and land ice thickness variations with a dedicated altimeter. With the effects of a fast-changing climate becoming apparent, it is increasingly important to understand exactly how Earth’s ice fields are responding and regulate climate and sea level. It is therefore of utmost importance that the quality of the CryoSat-2 altimeter data meets the highest accuracy and precision level, not only over the ice caps and sea-ice surface but over the oceans as well. The SIRAL altimeter of CryoSat-2 is capable of measuring high-resolution geophysical parameters from the open ocean to the coast. In this paper, we validate the CryoSat-2 geophysical ocean product, Baseline-B (GOP). The analyses focus on long-term monitoring, validation, and cross-calibration of these ocean altimeter data with all the concurrent altimeter data in the Radar Altimeter Database System RADS and with independent in-situ tide gauge measurements from the Permanent Service for Mean Sea Level PSMSL. The objective is to evaluate the stability of the CryoSat-2 measurement system and the identification and explanation of biases and bias drifts. A persistent monitoring of these biases in time is important to establish the data’s usefulness for investigation of long-term sea level and ice topography/volume changes. The results constitute the final status of the GOP baseline-B product for use as essential climate variables. GOP ocean data has a - 6.3 ± 0.2 cm range bias w.r.t. to all calibrated satellites in RADS and a drift of 0.14 mm yr −1 w.r.t. Jason-2. GOP data has significant wave height and sea state biases close to that of the Jasons’, and seems to be better handling the LRM-SAR transitions than the RADS CryoSat-2 product. GOP data w.r.t. PSMSL tide gauge data has an average correlation of R = 0.83, a mean st. dev. of σ = 6.30 cm, and a drift of 0.11 mm yr −1 , equivalent to 40 Gt yr −1 ice sheet mass loss. It is concluded that GOP CryoSat-2 performs better than RADS CryoSat-2, which seems to suffer from a 480-day platform temperature cycle. GOP is also on a par with the altimeter data from the Jason reference missions, and well suited for ocean and climate studies.

Contemporary sea level rise rates around Malaysia: Altimeter data optimization for assessing coastal impact

The increase of anthropogenic activities has triggered global sea level rise to threaten many low-lying and unprotected coastal areas. Without measures, global sea levels will continue to rise at an accelerating rate in the 21st century. This paper quantifies sea level trends around the Malaysian seas using measurements from multiple altimeter missions over 1993–2015. Sea level anomalies (SLAs) are determined using data from the Radar Altimeter Database System (RADS) covering 8 altimeter missions. We use an enhanced processing strategy to optimize sea surface heights from RADS for the derivation of SLAs, including filtering, data gridding and moving average. Tidal height measurements at eight tide gauge stations around Peninsular Malaysia and East Malaysia are used to assess SLAs from altimetry. Our assessment results in similar patterns of SLAs, high correlation coefficients (>0.9) and small (few cm) root mean square differences (RMSE) between SLAs from altimetry and tide gauges over the same period. Sea level trends are determined by the robust fit regression analysis for the SLA time series. Our result shows that sea level rise trends around Malaysia range from 3.27 ± 0.12 mm yr−1 off eastern Malaysia to 4.95 ± 0.15 mm yr−1 west of Malaysia. Over 1993–2015, the mean rising rate around Malaysia is 4.22 ± 0.12 mm yr−1, and the cumulative sea level rise is 0.05 m. This paper predicts the impact of such rising sea levels on environment, urban planning and climatology in the coastal areas of Malaysia.

Significant wave height assessment using multi mission satellite altimeter over Malaysian seas

Satellite altimeter is one of the useful technique to study the variation of ocean parameters with a good temporal and spatial measurements. In situ measurements such as buoy has own disadvantages in terms of spatial observations. Thus, with the combination of satellite altimeter and buoy can improve the significant wave height measurements for both spatial and temporal over the seas. Generally, the measurement of significant wave height from altimeter using the Ku-band signal, while SARAL is borne with Ka-band altimeter (AltiKa). The aim of this research is to study the reliability of wave height data from the satellite altimeter to support marine renewable energy development. This Significant wave height (Hs) is retrieved from multi mission satellite altimeter by Radar Altimeter Database System (RADS) and evaluated using in-situ measurement over the Malaysian seas (0°N - 14°N and 95°E - 126°E). A validation with selected buoys located at Sabah Sea (5.83 N, 114.39 E) and Sarawak Sea (5.15 N, 111.82 E) is performed by statistical approach and presenting good correlation of 0.92 and 0.18 for RMSE. A climatology assessment is performed by analyzing the condition of significant wave height during monsoons. This paper highlighted, collocation between altimeter and buoy are well-correlated and reliable to use for a marine analysis for renewable energy development.

Mean dynamic topography over Peninsular Malaysian seas using multimission satellite altimetry

The development of satellite altimeters (SALTs) has brought huge benefits, among which is the ability to more adequately sense ocean-surface topography. The radar altimeter database system was used to capture and process ENVISAT, CRYOSAT-2, SARAL, JASON-1, and JASON-2 SALT data of 5 years between 2011 and 2015. The time series of monthly multimission SALT data showed an estimated sea level trend of 1.0, 2.4, 2.4, 3.6, and 12.0 mm/year at Gelang, Port Kelang, Kukup, Cendering, and Keling. The correlation analysis for the selected tide gauge stations produced satisfying results of R-squared with 0.86, 0.89, 0.91, and 0.97 for Cendering, Sedili, Gelang, and Geting, respectively. The ITG-Grace2010s geoid model was used to compute the mean dynamic topography (MDT) and plot to a grid of 0.25 deg for the Malacca Strait and South China Sea of Peninsular Malaysia, with Keling, Port Kelang, Geting, Sedili, and Johor Bahru tide gauge stations having values determined by interpolation to be 1.14, 1.19, 1.26, 1.88, and 2.91 m, respectively. MDT is computed from the SALT with respect to Port Kelang, the north–south sea slope ranges between −0.64 and 0.29 m/50 km and −0.01 and 0.52 m/50 km along the east and west coasts of Peninsular Malaysia, respectively.

Evaluation of new CryoSat-2 products over the ocean

The CryoSat-2 satellite, primarily dedicated to precise monitoring of the Cryosphere, is demonstrating its capability to provide valuable altimetric data also over the ocean. Here we present the results of a global assessment and validation of the new Geophysical Ocean Product (GOP) distributed by the European Space Agency (ESA) since April 2014, focusing on the sea surface height anomaly (SSHA), the significant wave height (SWH), and the wind speed. Our assessment involves only Low Resolution Mode (LRM) and Pseudo LRM (PLRM) data, since full SAR processing is not already operationally implemented in the GOP. The global assessment is conducted on the basis of measurement noise and along-track spectral and crossover analysis, whereas the validation is performed against a variety of in situ observations such as tide gauges, buoys and Argo floats as well as data from the WaveWatch III (WWIII) model. The performance of the GOP is compared to that of Jason-2 and CryoSat-2 data from the Radar Altimeter Database System (RADS). The mean value of the 20-Hz SSHA noise at 2m SWH is 6.3cm for LRM and 10.2cm for PLRM, and the standard deviation of the crossovers is ~5.4cm. The mean 20-HZ SWH noise over the global oceans is 49.4cm and 69.8cm, for LRM and PLRM respectively. CryoSat-2 and Jason-2 show almost identical performance when SSHAs are validated against tide gauges, with a median correlation and root mean square difference (RMSD) of 0.78 and 7.1cm for the GOP, 0.76 and 7.3cm for Jason-2, and 0.79 and 7.8cm for CryoSat-2 from RADS. The median correlation with Argo-derived steric heights is 0.68 for the GOP, 0.74 for Jason-2, and 0.67 for CryoSat-2 from RADS. However, the correlation shows a strong latitudinal dependence, with higher values at low latitudes (median value larger than 0.80 in the 10°S-10°N band). The median RMSD between the SSHAs and steric heights is 5.3cm for the GOP, 4.6cm for Jason-2, and 5.1cm for CryoSat-2 from RADS. The GOP and Jason-2 show also identical performance when SWHs are compared to buoy data, with a slope and RMS error of 0.98 and 15cm for GOP, 0.97 and 16cm for Jason-2, and 1.05 and 17cm for CryoSat-2 from RADS. On the other hand, the GOP wind speed exhibits a bias of about 2m/s relative to both Jason-2 and to buoy data. Differences between the GOP and WWIII SWH are smaller than 20% of the SWH almost everywhere. In summary the GOP products are fit for oceanographic applications.

Assessment of Altimetric Range and Geophysical Corrections and Mean Sea Surface Models—Impacts on Sea Level Variability around the Indonesian Seas

The focus of this study is the assessment of the main range and geophysical corrections needed to derive accurate sea level time series from satellite altimetry in the Indonesia seas, the ultimate aim being the determination of sea level trend for this region. Due to its island nature, this is an area of large complexity for altimetric studies, a true laboratory for coastal altimetry. For this reason, the selection of the best corrections for sea level anomaly estimation from satellite altimetry is of particular relevance in the Indonesian seas. The same happens with the mean sea surface adopted in the sea level anomaly computation due to the large gradients of the mean sea surface in this part of the ocean. This study has been performed using altimetric data from the three reference missions, TOPEX/Poseidon, Jason-1 and Jason-2, extracted from the Radar Altimeter Database System. Analyses of sea level anomaly variance differences, function of distance from the coast and at altimeter crossovers were used to assess the quality of the various corrections and mean sea surface models. The selected set of corrections and mean sea surface have been used to estimate the sea level anomaly time series. The rate of sea level rise for the Indonesian seas was found to be 4.2 ± 0.2 mm/year over the 23-year period (1993–2015).

ACCELERATION OF SEA LEVEL RISE OVER MALAYSIAN SEAS FROM SATELLITE ALTIMETER

Abstract. Sea level rise becomes our concern nowadays as a result of variously contribution of climate change that cause by the anthropogenic effects. Global sea levels have been rising through the past century and are projected to rise at an accelerated rate throughout the 21st century. Due to this change, sea level is now constantly rising and eventually will threaten many low-lying and unprotected coastal areas in many ways. This paper is proposing a significant effort to quantify the sea level trend over Malaysian seas based on the combination of multi-mission satellite altimeters over a period of 23 years. Eight altimeter missions are used to derive the absolute sea level from Radar Altimeter Database System (RADS). Data verification is then carried out to verify the satellite derived sea level rise data with tidal data. Eight selected tide gauge stations from Peninsular Malaysia, Sabah and Sarawak are chosen for this data verification. The pattern and correlation of both measurements of sea level anomalies (SLA) are evaluated over the same period in each area in order to produce comparable results. Afterwards, the time series of the sea level trend is quantified using robust fit regression analysis. The findings clearly show that the absolute sea level trend is rising and varying over the Malaysian seas with the rate of sea level varies and gradually increase from east to west of Malaysia. Highly confident and correlation level of the 23 years measurement data with an astonishing root mean square difference permits the absolute sea level trend of the Malaysian seas has raised at the rate 3.14 ± 0.12 mm yr-1 to 4.81 ± 0.15 mm yr-1 for the chosen sub-areas, with an overall mean of 4.09 ± 0.12 mm yr-1. This study hopefully offers a beneficial sea level information to be applied in a wide range of related environmental and climatology issue such as flood and global warming.

MEAN SEA SURFACE (MSS) MODEL DETERMINATION FOR MALAYSIAN SEAS USING MULTI-MISSION SATELLITE ALTIMETER

Abstract. The advancement of satellite altimeter technology has generated many evolutions to oceanographic and geophysical studies. A multi-mission satellite altimeter consists with TOPEX, Jason-1 and Jason-2, ERS-2, Envisat-1, CryoSat-2 and Saral are extracted in this study and has been processed using Radar Altimeter Database System (RADS) for the period of January 2005 to December 2015 to produce the sea surface height (hereinafter referred to SSH). The monthly climatology data from SSH is generated and averaged to understand the variation of SSH during monsoon season. Then, SSH data are required to determine the localised and new mean sea surface (MSS). The differences between Localised MSS and DTU13 MSS Global Model is plotted with root mean square error value is 2.217 metres. The localised MSS is important towards several applications for instance, as a reference for sea level variation, bathymetry prediction and derivation of mean dynamic topography.

Pre- analysis assessment of Sea Surface Temperature (SST) products in the region of Malaysian coastal water

This paper presents the pre-analysis of validation between the acquisition satellite data and in situ data. To carry out this assessment, Sea Surface Temperature (SST) data are acquired to be regressed with SST In situ. With the launch of the Moderate Resolution Imaging Spectroradiometer (MODIS) satellite with a sensor on the Terra spacecraft, data sets of the global distribution of sea surface temperature are retrieved, and need to be validated and analyzed. Radar Altimeter Database System (RADS) also has an archived data of Optimal Interpolation SST (OISST) that can be retrieved based on satellite track of altimeter. The aim of this paper is to present intercomparison study between pixel based (MODIS SST) and point based (RADS SST). The value of root mean square error (rmse) is computed to see the performance of the data product. It is an assessment and evaluation to see the performance for both data. The objective of this paper is to evaluate Malaysian coastal area through validation with in situ data. To achieve the objective, we perform pre-analysis study of the MODIS products and RADS SST to see the performance of both data in terms of spatial value during seasonal changes. However, the scope of this analysis covers only on the spatial MODIS pixel value and the OISST point value during the southwest monsoon daytime. From the result, RADS SST/RADS show higher root mean square error (rmse) at 0.731/0.677 (before calibration) and 0.6951/0.476 (after calibration). From the rmse result, we could deduce that the RADS SST has random error arising from the fact that the interpolated points are based on the track.

Satellite-based wave data and wave energy resource assessment for South China Sea

Wave energy has the potential to valuably contribute to the coastal states renewable energy mix. However, lack of data sources hinders the effort to deliberately assess this resource. This paper presents an assessment of wave energy resources in the South China Sea (Malaysian Exclusive Economic Zone) using satellite altimeter. Radar Altimeter Database System (RADS) provides data of significant wave height and wind speed from several satellite altimeters. The data were extracted for a space resolution of 0.25° × 0.25°, and within the time range from January 2001 to December 2010 and space range of 1.5°N – 10.0°N, 95.0°E − 116.0°E. For this study, fifteen 2° × 2° zones were considered around the east coast of Peninsular Malaysia and the coast of East Malaysia. The 10-year-data were validated with buoy measurements and presented as the probability distribution of wave height and wave period. The results indicate that bulk of the waves had peak period between 5s and 7s and significant wave height between 0.5 m and 1.5 m. The data were then used to calculate the theoretical available wave energy and power in the study areas. The results show that the average wave energy density of Malaysian seas facing the South China Sea is in the range of 1.41 kW/m to 7.92 kW/m, while the energy storage varies from 7.10 MW h/m to 69.41 MW h/m. This study also demonstrates the ability of satellite altimeter to provide an accurate and reliable data for more comprehensive and realistic estimate of the energy potential. The ability of satellite altimeter to provide wave data for all sea zones will enable more accurate identification of potential locations for wave energy development in Malaysia.

Derivation of Sea Level Anomaly Based on the Best Range and Geophysical Corrections for Malaysian Seas using Radar Altimeter Database System (RADS)

The utilization of satellite altimeter data sets from previous and present satellite altimeter missions is imperative to both oceanographic and geodetic applications. The important parameter that can be derived from satellite altimeter is sea level anomaly, while it is also fundamental for sea level monitoring, geoid determination and current circulations study. This paper presents an effort to determine sea level anomaly for Malaysian seas from six satellite altimeter missions; TOPEX, JASON1, JASON2, ERS1, ERS2 and ENVISAT. The best range and geophysical corrections for Malaysian seas were also investigated in this study by evaluating two state of the art corrections available for 9 years of TOPEX satellite altimeter (from January 1993 to December 2001). Sea level data retrieval and reduction were carried out using the Radar Altimeter Database System (RADS). The comparison of near-simultaneous altimeter and tide gauges observations showed good agreement with the correlations are higher than 0.87 at Tioman Island, Langkawi Island and Kota Kinabalu. This paper introduces RADS and deals with determination of sea level anomaly using the best range and geophysical corrections in Malaysian seas.