Validation of Jason-2 Altimeter Data by Waveform Retracking over California Coastal Ocean

Lee, Hyongki; Shum, C. K.; Emery, William J.; Calmant, Stéphane; Deng, Xiaoli; Kuo, Chung Yen; Roesler, Carolyn; Yi, Yuchan

doi:10.1080/01490419.2010.488982

Cited by 43 publications

(38 citation statements)

References 18 publications

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“…For the SGDR products, ICE provides more accurate measurements than OCEAN and MLE3 in coastal areas, which is consistent with previous studies [33,43]. It is reasonable since in some degree, the ICE retracker moderates the influence of excessive energy in the trailing edge by combining threshold and OCOG retrackers.…”

Section: Conclusion and Recommendationssupporting

confidence: 78%

“…For instance, Hwang et al [32] presented an improved threshold retracker (ITR) and verified better performance than the OCEAN and TR methods using Geosat geodetic mission (GM) altimeter data around Taiwan. Another modified threshold retracker (MTR) was applied to Jason-2 data over California coastal ocean, which could filter the pre-leading edge bumps [33]. This kind of retracker extracts subwaveform in order to avoid superimposed signals from non-marine surfaces by detecting the apparent leading edge.…”

Section: Introductionmentioning

confidence: 99%

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Improving Jason-2 Sea Surface Heights within 10 km Offshore by Retracking Decontaminated Waveforms

et al. 2017

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Abstract:It is widely believed that altimetry-derived sea surface heights (SSHs) in coastal zones are seriously degraded due to land contamination in altimeter waveforms from non-marine surfaces or due to inhomogeneous sea state conditions. Spurious peaks superimposed in radar waveforms adversely impact waveform retracking and hence require tailored algorithms to mitigate this problem. Here, we present an improved method to decontaminate coastal waveforms based on the waveform modification concept. SSHs within 10 km offshore are calculated from Jason-2 data by a 20% threshold retracker using decontaminated waveforms (DW-TR) and compared with those using original waveforms and modified waveforms in four study regions. We then compare our results with retracked SSHs in the sensor geophysical data record (SGDR) and with the state-of-the-art PISTACH (Prototype Innovant de Système de Traitement pour les Applications Côtières et l'Hydrologie) and ALES (Adaptive Leading Edge Subwaveform) products. Our result indicates that the DW-TR is the most robust retracker in the 0-10 km coastal band and provides consistent accuracy up to 1 km away from the coastline. In the four test regions, the DW-TR retracker outperforms other retrackers, with the smallest averaged standard deviations at 15 cm and 20 cm, as compared against the EGM08 (Earth Gravitational Model 2008) geoid model and tide gauge data, respectively. For the SGDR products, only the ICE retracker provides competitive SSHs for coastal applications. Subwaveform retrackers such as ICE3, RED3 and ALES perform well beyond 8 km offshore, but seriously degrade in the 0-8 km strip along the coast.

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Section: Conclusion and Recommendationssupporting

confidence: 78%

Section: Introductionmentioning

confidence: 99%

Improving Jason-2 Sea Surface Heights within 10 km Offshore by Retracking Decontaminated Waveforms

et al. 2017

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“…Waveform dari satelit altimeter dapat memberikan informasi tentang jarak antara satelit altimeter dengan permukaan bumi pada posisi nadir dari waktu yang dibutuhkan oleh sinyal pada saat ditransmisikan hingga diterima kembali setelah pemantulan oleh permukaan laut oleh satelit (Lee et al, 2010). Lintasan (pass) yang digunakan pada penelitian ini antara lain 051, 064, 127, 140, 203, dan 229.…”

Section: Identifikasi Waveformsunclassified

Waveform Identification of Altimetry Satellite Data of Shallow and Deep Waters in Southern Java Waters

Nababan¹,

Hakim²,

Adrian³

et al. 2015

J. Ilmu dan Teknologi Kelautan Tropis

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ABSTRAKPola waveform data satelit altimeter mempengaruhi tingkat akurasi hasil estimasi ketinggian paras laut dari satelit altimeter. Pola waveform yang ditemui di perairan pesisir umumnya tidak mengikuti pola waveform yang ideal (Brown-waveform) sehingga menghasilkan estimasi ketinggian paras laut yang tidak akurat. Penelitian ini bertujuan untuk mengidentifikasi pola waveform dari satelit altimeter dan menentukan variabilitasnya. Data yang digunakan adalah data satelit altimeter Jason-2 SGDR (Sensor Geophysical Data Record) tipe D pada perairan selatan pulau Jawa selama tahun 2013 yang diperoleh dari situs jaringan data "NOAA's Comprehensive Large Array-data Stewardship System" (www.class.ncdc.noaa.gov). Identifikasi waveform dilakukan sepanjang lintasan Satelit Altimetry Jason-2 yang dibagi menjadi tiga kategori jarak yaitu, 0 -10 km (wilayah pesisir), 10 -50 km (transisi wilayah pesisir-laut lepas), dan 50 -100 km (laut lepas atau laut dalam). Hasil penelitian menunjukkan, secara umum, ditemukan empat bentuk non-Brown-waveform pada daerah study. Jumlah non-Brownwaveform terbanyak (69%) ditemui pada daerah pesisir pada jarak 0-10 km dari garis pantai. Sedangkan pada jarak 10-50 km (wilayah transisi pesisir-laut lepas) dan 50-100 km (laut lepas) dari garis pantai, jumlah non-Brown-waveform masing-masing 5% dan 3%. Pola Brownwaveform umumnya sudah dapat ditemui mulai pada jarak 7,58 km dari garis pantai, namun di laut lepas terkadang masih ditemui non-Brown-waveform. Faktor daratan dekat perairan pesisir, kedalaman dan bentuk permukaan perairan, aerosol di atmosfer, bangunan (contoh: mercusuar atau kapal) yang ditemui di daerah pesisir diduga menjadi penyebab noise pada waveforms.

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“…Satellite altimetry has long been a promising tool for studies over the deep ocean (Shum et al 1995;Fu and Cazenave 2001), coastal ocean (Vignudelli et al 2009;Lee et al 2010), inland hydrology (Birkett 1995;Koster et al 1999;Shum et al 2003;Berry et al 2005;Calmant and Seyler 2006;Zhang et al 2010;Hwang et al 2011;Kuo and Kao 2011), vertical crustal motion (Lee et al 2008), ice sheet and sea ice freeboard elevation changes (Zwally et al 1989;Bamber 1994;Wingham et al 1998;Kwok et al 2009;Lee et al 2012). These extended applications have been possible due in part to the advances in radar waveform retracking methodologies (Frappart et al 2006).…”

Section: Introductionmentioning

confidence: 99%

Envisat Altimetry Radar Waveform Retracking of Quasi-Specular Echoes over the Ice-Covered Qinghai Lake

Tseng¹,

Shum²,

Yi³

et al. 2013

Terr. Atmos. Ocean. Sci.

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The use of satellite radar altimetry has long been extended to areas other than the deep-ocean primarily because of the advances in radar waveform retracking methodologies. However, the retracking algorithms are limited to a handful shapes of return echoes over assumed known surfaces, while numerous unknown waveforms exist due to the complexity of real-world land cover and other surfaces. Measurements over a surface with seasonal or ephemeral patterns could thus degrade in accuracy due to varying characteristics from the corresponding radar backscatters. In this study, we demonstrate that the Qinghai Lake, an alpine water body with distinct seasonal variation between water and ice causes inaccurate surface-height estimates when using Envisat radar altimetry and conventional retracking techniques. Following the characterization of the lake surface using EO-1 and Landsat multispectral analysis, we hypothesize that the overestimation of the lake level during winter and early spring is not from the snow accumulation; rather it is due to an error of the onboard retracker (ICE-1) which is unable to properly model the quasi-specular waveforms. Hence, we first build a classification algorithm to identify the anomalous waveforms, and then use an empirical retracking gate correction to mitigate the ice contamination. The accuracy of the 20% threshold retracker (TR) after applying suggested gate correction has a significant improvement with a root-mean-square error (RMSE) of 6 ± 7 cm and a correlation of 0.98 compared with the in situ gauge data. The improvement in accuracy is 54% better than the ICE-1 and 85% than the OCEAN retrackers, respectively.

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Validation of Jason-2 Altimeter Data by Waveform Retracking over California Coastal Ocean

Cited by 43 publications

References 18 publications

Improving Jason-2 Sea Surface Heights within 10 km Offshore by Retracking Decontaminated Waveforms

Improving Jason-2 Sea Surface Heights within 10 km Offshore by Retracking Decontaminated Waveforms

Waveform Identification of Altimetry Satellite Data of Shallow and Deep Waters in Southern Java Waters

Envisat Altimetry Radar Waveform Retracking of Quasi-Specular Echoes over the Ice-Covered Qinghai Lake

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