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SCHARROO, J. LUIS, AND F. WOBBE inquire about default parameters, and carry out other common tasks. All modules are called dynamically and loaded on demand from shared libraries. ...doi:10.1002/2013eo450001 fatcat:k3ta7d7ozffzppghcgc6loj3me
R A D A R A lT i M e T e R S on-board the Jason-1, TOPEX, Envisat, and GFO satellites obtained profiles of sea surface height on transects across the Indian Ocean between two and nine hours after the December 26 Sumatra earthquake. The data are received hours to days after "real time," too late to be used in detection and warning of tsunamis. We compared the sea level anomaly profiles of December 26 measured along the satellite tracks (Figure 1D-G) with the measurements on previous passes ofdoi:10.5670/oceanog.2005.62 fatcat:bshuvkaazvh7decsniiqplonyu
more »... same satellites 10 days, 35 days, and 17 days earlier. This allowed us to remove the majority of permanent and slowly varying features of sea level, revealing transient signals. The altimeters also provide wind speed and wave height data, and these allowed us to interpret a sea-level anomaly at 16°S in the Jason-1 profile (Figure 1D) as being due to a severe storm. The remaining sea-level anomaly signal appears to be associated with the tsunami. The signal of the leading edge two hours after the earthquake is particularly prominent, with an amplitude of 60 cm and two narrow peaks where the NOAA tsunami model forecast shows two overlapping peaks coalescing into one broad (250 km) crest. Increased sea-surface roughness at spatial scales from 150 to 15 km wavelengths also appears inside the portion of the ocean excited by the tsunami. The first model simulation results of the Indian Ocean tsunami (Figure 1A-C) were obtained from the "MOST" (Method of Splitting Tsunamis) model (Titov and Synolakis, 1998) and were posted by V.V. Titov on the Internet Tsunami Bulletin Board less than 12 hours after the earthquake. MOST is part of the tsunami forecasting and warning system under development for the Pacific Ocean (Titov et al., 2005) that will provide fast realtime estimates of tsunami amplitudes using preset models, real-time seismic data, and, most importantly, deep-ocean tsunami amplitude data from a network of deep-ocean pressure sensors. Other researchers also ran models and posted results. Results of MOST and other model runs have been widely used worldwide by the media for early planning of relief efforts and for post-tsunami field surveys. Unlike the Pacific, the Indian Ocean does not yet have a network of deepocean pressure sensors, and so coastal tide gauges provide the only direct measurement of Indian Ocean tsunami amplitudes. The satellite altimeter data we present here are the only measurements of the amplitude of the December 26 tsunami in the deep, open ocean. At the time of the first MOST model simulation, earthquake source mechanism models described a rupture confined to only the southernmost portion of the broad region mapped out by the aftershock pattern. However, it seemed clear that the tsunami should have been generated by displacements distributed along the entire aftershock zone. The initial conditions for the MOST model were set assuming this more spatially distributed source, with initial amplitude guesses based on preliminary estimates of the earthquake magnitude and one coastal tide-gauge measurement from Cocos Island. Because of the lack of in situ deep-ocean data, the tsunami simulation accuracy was uncertain until the satellite altimeter data arrived. The first value of the altimeter data is in basic confirmation of the general pattern of the deep-water features of the model. However, detailed inspection shows that there are some discrepancies between altimeter observations and e A R lY M O D e l e S T i M AT e S C O N F i R M e D Unlike the Pacific, the indian Ocean does not yet have a network of deep-ocean pressure sensors, and so coastal tide gauges provide the only direct measurement of indian Ocean tsunami amplitudes. The satellite altimeter data we present here are the only measurements of the amplitude of the December 26 tsunami in the deep, open ocean.
Originally designed for applications over the ocean, satellite altimetry has been proven to be a useful tool for hydrologic studies. Altimeter products, mainly conceived for oceanographic studies, often fail to provide atmospheric corrections suitable for inland water studies. The focus of this paper is the analysis of the main issues related with the atmospheric corrections that need to be applied to the altimeter range to get precise water level heights. Using the corrections provided on thedoi:10.3390/rs6064952 fatcat:qs3f52x5u5gklaefu77q4eopdu
more »... adar Altimeter Database System, the main errors present in the dry and wet tropospheric corrections and in the ionospheric correction of the various satellites are reported. It has been shown that the model-based tropospheric corrections are not modeled properly and in a consistent way in the various altimetric products. While over the ocean, the dry tropospheric correction (DTC) is one of the most precise range corrections, in some of the present altimeter products, it is the correction with the largest errors over continental water regions, causing large biases of several decimeters, and along-track interpolation errors up to several centimeters, both with small temporal variations. The wet tropospheric correction (WTC) from the on-board microwave radiometers is hampered by the contamination on the radiometer measurements of the surrounding lands, making it usable only in the central parts of large lakes. In addition, the WTC from atmospheric models may also have large errors when it is OPEN ACCESS Remote Sens. 2014, 6 4953 provided at sea level instead of surface height. These errors cannot be corrected by the user, since no accurate expression exists for the height variation of the WTC. Alternative and accurate corrections can be computed from in situ data, e.g., DTC from surface pressure at barometric stations and WTC from Global Navigation Satellite System permanent stations. The latter approach is particularly favorable for small lakes and reservoirs, where GNSS-derived WTC at a single location can be representative of the whole lake. For non-timely critical studies, for consistency and stability, model-derived tropospheric corrections from European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis ERA Interim, properly computed at surface height, are recommended. The instrument-based dual-frequency ionospheric correction may have errors related with the land contamination in the Ku and C/S bands, making it more suitable to use a model-based correction. The most suitable model-based ionospheric correction is the Jet Propulsion Laboratory (JPL) global ionosphere map (GIM) model, available after 1998, properly scaled to the altimeter height. Most altimeter products provide the GIM correction unreduced for the total electron content extending above the altitude of these satellites, thus overestimating the ionospheric correction by about 8%. Prior to 1998, the NIC09 (NOAA Ionosphere Climatology 2009) climatology provides the best accuracy.
Satellite radar altimetry has been providing estimates of global mean sea level (GMSL) since 1992. The early TOPEX record originates from two identical instruments, which requires the estimation of an intermission bias and careful handling of the problematic first part of the record. Calibration of TOPEX is crucial to obtain a continuous and consistent record, which is needed to quantify any recent acceleration. We propose a novel approach to calibrate TOPEX altimeter data using sea surfacedoi:10.1038/s41598-019-47340-z pmid:31358809 pmcid:PMC6662663 fatcat:by4vctjeobbnlho2q6vdjqxfb4
more »... ht differences at crossovers of TOPEX and ERS. Tide gauges are only used to determine a drift in one of the two datasets. We provide a new and more accurate estimate of the intra-mission bias, which leads to a much reduced GMSL acceleration over the whole record. Hence, the conundrum of an uncertain GMSL acceleration from altimetry is still unsolved, in spite of recent opposite claims, and in contrast to the expected effect of ocean warming and continental freshwater fluxes.
This method is similar to the construction of hybrid sea-state bias models with wind speed, rather than sea surface height, as the dependent variable (Vandemark et al. 2002; Scharroo and Lillibridge 2005 ...doi:10.1175/jtech-d-13-00167.1 fatcat:aco5kx5q4rb4pox3qssrtgejry
Ocean Science (OS)
Scharroo et al.: Jason continuity of services forms. ... Scharroo et al.: Jason continuity of services www.ocean-sci.net/12/471/2016/ Ocean Sci., 12, 471-479, 2016 ...doi:10.5194/os-12-471-2016 fatcat:iic27gky4rhazjabv63ybrlgti
A conceptually simple formulation is proposed for a new empirical sea state bias (SSB) model using information retrieved entirely from altimetric data. Nonparametric regression techniques are used, based on penalized smoothing splines adjusted to each predictor and then combined by a Generalized Additive Model. In addition to the significant wave height (SWH) and wind speed (U10), a mediator parameter designed by the mean wave period derived from radar altimetry, has proven to improve the modeldoi:10.3390/rs8070576 fatcat:cawbikdp3zauzc5sqyktisflym
more »... performance in explaining some of the SSB variability, especially in swell ocean regions with medium-high SWH and low U10. A collinear analysis of scaled sea level anomalies (SLA) variance differences shows conformity between the proposed model and the established SSB models. The new formulation aims to be a fast, reliable and flexible SSB model, in line with the well-settled SSB corrections, depending exclusively on altimetric information. The suggested method is computationally efficient and capable of generating a stable model with a small training dataset, a useful feature for forthcoming missions.
Ocean Science (OS)
Finally, the Sentinel-6 or Jason-CS satellites provide high-precision radar altimetry data, complementing those of Sentinel-3 as a follow-on to the Jason series of altimetry satellites (see Scharroo et ...doi:10.5194/os-12-787-2016 fatcat:vf6akkyvfvf77ccd4aos7rrfk4
Scharroo, and Pieter Visser changes in data processing (bug-fixes/upgrades). ... Microwave Radiometer Data David Brockley, Steven Baker, Pierre Féménias, Bernat Martinez, Franz-Heinrich Massmann, Michiel Otten, Frederic Paul, Bruno Picard, Pierre Prandi, Mònica Roca, Sergei Rudenko, Remko ...doi:10.1109/tgrs.2017.2709343 fatcat:4pfajjftebhwzbiajqjzhbprq4
Remote Sensing of the Ocean, Sea Ice, Coastal Waters, and Large Water Regions 2017
Sentinel-3A, launched in February 2016, is part of ESA's long-term commitment to climate monitoring from space. Its suite of instruments for measuring surface topography includes a Microwave Radiometer (MWR) and SRAL, the first delay-Doppler instrument to provide global coverage. SRAL promises fine spatial resolution and reduced noise levels that should together lead to improved performance over all Earth surfaces. The Sentinel-3 Mission Performance Centre (S3MPC) has been developing thedoi:10.1117/12.2277593 fatcat:mwdyslsa4vgj7ezbkodr4r5tqm
more »... logy to evaluate the accuracy of retrievals, monitor any changes and develop solutions to known problems. The S3MPC monitors internal temperatures, path delays and the shape of the generated pulses to assess the instruments health. The MWR records over known reference surfaces are compared with those from other spaceborne instruments. Over the ocean the SRAL's return pulses are analysed to give range to the sea surface, wave height and signal strength (which can be interpreted as wind speed). The metocean data are regularly contrasted with records from in situ measurements and the output from meteorological models, which rapidly highlights the effects of any changes in processing. Range information is used to give surface elevation, which is assessed in three ways. First, flights over a dedicated radar transponder provide an estimate of path delay to within ~10 mm (r.m.s.). Second, measurements are compared to GPSlevelled surfaces near Corsica and over Lake Issyk-kul. Third, there are consistency checks between ascending and descending passes and with other missions. Further waveform analysis techniques are being developed to improve the retrieval of information over sea-ice, land-ice and inland waters.
PLRM/RDSAR are derived from the Full Bit Rate (FBR) data by processing the pulse-limited echoes incoherently, like in the conventional LRM concept (Smith and Scharroo, 2015) . ...doi:10.3389/fmars.2019.00348 fatcat:bfcvgljvpfeenjsqw2ztjfsl3i
See Scharroo et al. (2016) for a complete review. ... Scharroo et al., 2004 , Ablain et al., 2010 , external measurements from in-situ measurements (e.g. ...doi:10.1016/j.rse.2021.112395 fatcat:de4tps7yevf3lgmktqtmvusezu
Scharroo et al ... On behalf of the Project Scientists (Josh Willis, NASA; Pascal Bonnefond, CNES; Eric Leuliette, NOAA; Remko Scharroo, EUMETSAT; Craig Donlon, ESA), Pascal Bonnefond presented the agenda and explained logistics ...fatcat:d2l6rsxezzg3nfctvl4hkkkj2a
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