Comparison of Envisat radar and airborne laser altimeter measurements over Arctic sea ice

Connor, L. N.; Laxon, Seymour W.; Ridout, A.; Krabill, William B.; McAdoo, D. C.

doi:10.1016/j.rse.2008.10.015

Cited by 106 publications

(83 citation statements)

References 20 publications

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“…The radar altimeter on board Envisat has a much coarser resolution and lower data coverage than the one on board CS-2. Due to the delay/Doppler processing, the CS-2 footprint corresponds to the size of a Doppler cell, which is approximately 300 × 1600 m (Wingham et al, 2006), while Envisat has a footprint of 2-10 km (Connor et al, 2009). Envisat waveforms from mixed surfaces are often discarded since they do not match the classification scheme.…”

Section: Discussionmentioning

confidence: 99%

About the consistency between Envisat and CryoSat-2 radar freeboard retrieval over Antarctic sea ice

et al. 2016

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Abstract. Knowledge about Antarctic sea-ice volume and its changes over the past decades has been sparse due to the lack of systematic sea-ice thickness measurements in this remote area. Recently, first attempts have been made to develop a sea-ice thickness product over the Southern Ocean from space-borne radar altimetry and results look promising. Today, more than 20 years of radar altimeter data are potentially available for such products. However, the characteristics of individual radar types differ for the available altimeter missions. Hence, it is important and our goal to study the consistency between single sensors in order to develop long and consistent time series. Here, the consistency between freeboard measurements of the Radar Altimeter 2 on board Envisat and freeboard measurements from the SyntheticAperture Interferometric Radar Altimeter on board CryoSat-2 is tested for their overlap period in 2011. Results indicate that mean and modal values are in reasonable agreement over the sea-ice growth season (May-October) and partly also beyond. In general, Envisat data show higher freeboards in the first-year ice zone while CryoSat-2 freeboards are higher in the multiyear ice zone and near the coasts. This has consequences for the agreement in individual sectors of the Southern Ocean, where one or the other ice class may dominate. Nevertheless, over the growth season, mean freeboard for the entire (regionally separated) Southern Ocean differs generally by not more than 3 cm (8 cm, with few exceptions) between Envisat and CryoSat-2, and the differences between modal freeboards lie generally within ±10 cm and often even below.

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Section: Discussionmentioning

confidence: 99%

About the consistency between Envisat and CryoSat-2 radar freeboard retrieval over Antarctic sea ice

et al. 2016

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“…Various methods for the retrieval of freeboard from the ATM airborne laser altimetry data have been described in the literature (e.g., Kurtz et al, 2008;Connor et al, 2009Connor et al, , 2012Kwok et al, 2012). Here, we describe a new approach utilizing geolocated aerial photography and a lead discrimination algorithm to maximize the quality and number of laser altimeter data points used to determine the sea surface height.…”

Section: Sea Ice Freeboard Retrievalsmentioning

confidence: 99%

“…Data on sea ice properties from satellite altimetry missions have been used to study the behavior of sea ice at regional to global scales (e.g., Laxon et al, 2003;Giles et al, 2008a;Kwok et al, 2009;Farrell et al, 2009;Zwally et al, 2008;Kurtz and Markus, 2012), while data from airborne remote sensing missions have been used to validate satellite data (e.g., Kurtz et al, 2008;Connor et al, 2009;Laxon et al, 2013) and identify new ways to extend the range of sea ice properties that can be studied using satellite remote sensing data (e.g., . The sea ice properties that remote sensing data sets can retrieve depend on the type of instruments used.…”

Section: Introductionmentioning

confidence: 99%

Sea ice thickness, freeboard, and snow depth products from Operation IceBridge airborne data

et al. 2013

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Abstract. The study of sea ice using airborne remote sensing platforms provides unique capabilities to measure a wide variety of sea ice properties. These measurements are useful for a variety of topics including model evaluation and improvement, assessment of satellite retrievals, and incorporation into climate data records for analysis of interannual variability and long-term trends in sea ice properties. In this paper we describe methods for the retrieval of sea ice thickness, freeboard, and snow depth using data from a multisensor suite of instruments on NASA's Operation IceBridge airborne campaign. We assess the consistency of the results through comparison with independent data sets that demonstrate that the IceBridge products are capable of providing a reliable record of snow depth and sea ice thickness. We explore the impact of inter-campaign instrument changes and associated algorithm adaptations as well as the applicability of the adapted algorithms to the ongoing IceBridge mission. The uncertainties associated with the retrieval methods are determined and placed in the context of their impact on the retrieved sea ice thickness. Lastly, we present results for the 2009 and 2010 IceBridge campaigns, which are currently available in product form via the National Snow and Ice Data Center.

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“…Over sea ice, conventional pulse-limited altimeters such as Envisat have a typical footprint of 2-10 km (Connor et al, 2009). Unlike pulse-limited altimetry, the SAR technology and the Doppler post-processing allow the along-track position of each scatterer to be identified and offer SIRAL an along-track footprint of ∼ 300 m (the across-track being unchanged).…”

Section: K Guerreiro Et Al: Comparison Of Cryosat-2 and Envisat Radmentioning

confidence: 99%

Comparison of CryoSat-2 and ENVISAT radar freeboard over Arctic sea ice: toward an improved Envisat freeboard retrieval

et al. 2017

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Abstract. Over the past decade, sea-ice freeboard has been monitored with various satellite altimetric missions with the aim of producing long-term time series of ice thickness. While recent studies have demonstrated the capacity of the CryoSat-2 mission (2010-present) to provide accurate freeboard measurements, the current estimates obtained with the Envisat mission (2002)(2003)(2004)(2005)(2006)(2007)(2008)(2009)(2010)(2011)(2012) still require some large improvements.In this study, we first estimate Envisat and CryoSat-2 radar freeboard by using the exact same processing algorithms. We then analyse the freeboard difference between the two estimates over the common winter periods (November 2010-April 2011 and November 2011-March 2012. The analysis of along-track data and gridded radar freeboard in conjunction with Envisat pulse-peakiness (PP) maps suggests that the discrepancy between the two sensors is related to the surface properties of sea-ice floes and to the use of a threshold retracker.Based on the relation between the Envisat pulse peakiness and the radar freeboard difference between Envisat and CryoSat-2, we produce a monthly CryoSat-2-like version of Envisat freeboard. The improved Envisat data set freeboard displays a similar spatial distribution to CryoSat-2 (RMSD = 1.5 cm) during the two ice growth seasons and for all months of the period of study.The comparison of the altimetric data sets with in situ ice draught measurements during the common flight period shows that the improved Envisat data set (RMSE = 12-28 cm) is as accurate as CryoSat-2 (RMSE = 15-21 cm) and much more accurate than the uncorrected Envisat data set (RMSE = 178-179 cm).The comparison of the improved Envisat radar freeboard data set is then extended to the rest of the Envisat mission to demonstrate the validity of PP correction from the calibration period. The good agreement between the improved Envisat data set and the in situ ice draught data set (RMSE = 13-32 cm) demonstrates the potential of the PP correction to produce accurate freeboard estimates over the entire Envisat mission lifetime.

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Comparison of Envisat radar and airborne laser altimeter measurements over Arctic sea ice

Cited by 106 publications

References 20 publications

About the consistency between Envisat and CryoSat-2 radar freeboard retrieval over Antarctic sea ice

About the consistency between Envisat and CryoSat-2 radar freeboard retrieval over Antarctic sea ice

Sea ice thickness, freeboard, and snow depth products from Operation IceBridge airborne data

Comparison of CryoSat-2 and ENVISAT radar freeboard over Arctic sea ice: toward an improved Envisat freeboard retrieval

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