ALTICORE – India
Transcription
ALTICORE – India
Preliminary Studies on Coastal Altimetry of the Indian Seas (ALTICORE – India) Y.K. Somayajulu1, M. Ravichandran2, Rakesh V. Patil1 and Prakash Mehra1 1 National 2 Indian Institute of Oceanography, Dona Paula, Goa, India. National Centre for Ocean Information Services, Hyderabad, India. (e-mail of the corresponding author: [email protected] Objectives ALTICORE-India: A Collaborative Program: Present study aims at analyzing the RADS reprocessed, along-track coastal altimeter data near the Indian coasts, to recover maximum information and thereby improve quality of derived products. We investigate the limitations of 1 Hz data stream before assessing the advantages and feasibility of using along track higher data stream rates (typically 10 Hz or 20 Hz) and multi-satellite data scenarios. Further, we propose to evaluate how improved averages over satellite footprints and in-situ point measurements collected at different time scales could be compared with suitable assumptions on local scales of variability of the altimeter-derived products. Corrections to SLA Science Issues: • Study of the monsoon related coastal circulation, seasonal and interannual surface variability of the Arabian Sea and Bay of Bengal, based on multi-misson altimetry data. • Study of the requirements for developing an innovative set of Satellite Altimeter derived products for the EEZ, with improved accuracy and spatial sampling in the coastal regions, with emphasis on the operational applications. • Implementation of software for computing sea level anomalies (SLA) grids from merged sets of SA data. The existing altimetry in the coastal zone is not still at sufficient resolution to simulate the appropriate dynamics, but the use of improved altimeter-derived observations jointly with models and in situ data, will enable better representation and prediction of the structure and evolution of the coastal ocean environment. A coastal ocean operational system in India would be useful in assessing environmental impact of existing and future developments, sediment load, oil-spills and contaminants dispersion, etc. Hence, the objective of the ALTICORE-India program would be to strengthen the scientific cooperation between India and Europe in the area of ocean observing systems (in situ, satellite, modelling), exchanging views and experiences and ultimately explore potential mechanisms of synergy. Preliminary results: Analysis of atmospheric and tide related correction terms along selected ground tracks off the west coast of India which cross the coast near Kochi and Goa) of various satellites has been taken up. Plots of along track correction terms showed influence of annual cycle of variations on sea level change. Contributions of wet tropospheric and ocean tide corrections seem to be large compared to the ionospheric, dry tropospheric, load and pole tide corrections. Further, wet tropospheric correction depicted a steep gradient in the vicinity of the coast, probably, due to a sudden decrease in the water vapour content towards land. Comparison between one year TG observations, coastal tidal model results and SL from altimetry near Mormugao (Goa) showed good match between each other, indicating necessity of the models and in-situ observations, to establish use of satellite altimetry derived coastal measurements. Evaluation of AVISO and Alticore regional products for the Indian coastal and Island regions reveals that the methodology needs improvement with filtering/ reconstruction, similar to the one done for Corsica Channel involving additional interpolation steps. Summary and conclusions 1. Altimeter sea level data is extremely important for resolving complex dynamics of the coastal ocean. Though, altimetry was not originally conceived with coastal ocean in mind, future missions (such as, AltiKa and Cryosat-2) promise much improved near shore capabilities. 2. There are difficulties in processing and interpretation of data eg., proximity of land, control by seabed and rapid variations due to tides and atmospheric effects. There are also difficulties of accessing and manipulating data from multiple sources, which undergo revision/ enhancement. Better processing would permit to recover more data otherwise flagged as bad and that a coastal altimetry product is really a welcome step in this direction. 3. The aim of NIO-INCOIS joint project, is to build up capacity in collaboration with EU, as part of (ALTICORE-India), for providing altimeter-based information in support of coastal ocean studies, off the Indian coast, and enhance networking in the area of satellite altimetry. 2nd Coastal Altimetry Workshop, 6-7 Nov 2008, Pisa, Italy
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