55 research outputs found
Sea state monitoring using coastal GNSS-R
We report on a coastal experiment to study GPS L1 reflections. The campaign
was carried out at the Barcelona Port breaker and dedicated to the development
of sea-state retrieval algorithms. An experimental system built for this
purpose collected and processed GPS data to automatically generate a times
series of the interferometric complex field (ICF). The ICF was analyzed off
line and compared to a simple developed model that relates ICF coherence time
to the ratio of significant wave height (SWH) and mean wave period (MWP). The
analysis using this model showed good consistency between the ICF coherence
time and nearby oceanographic buoy data. Based on this result, preliminary
conclusions are drawn on the potential of coastal GNSS-R for sea state
monitoring using semi-empirical modeling to relate GNSS-R ICF coherence time to
SWH.Comment: All Starlab authors have contributed significantly; the Starlab
author list has been ordered randomly. Submitted to GR
The Eddy Experiment: accurate GNSS-R ocean altimetry from low altitude aircraft
During the Eddy Experiment, two synchronous GPS receivers were flown at 1 km
altitude to collect L1 signals and their reflections from the sea surface for
assessment of altimetric precision and accuracy. Wind speed (U10) was around 10
m/s, and SWH up to 2 m. A geophysical parametric waveform model was used for
retracking and estimation of the lapse between the direct and reflected signals
with a 1-second precision of 3 m. The lapse was used to estimate the SSH along
the track using a differential model. The RMS error of the 20 km averaged
GNSS-R absolute altimetric solution with respect to Jason-1 SSH and a GPS buoy
measurement was of 10 cm, with a 2 cm mean difference. Multipath and retracking
parameter sensitivity due to the low altitude are suspected to have degraded
accuracy. This result provides an important milestone on the road to a GNSS-R
mesoscale altimetry space mission.Comment: All Starlab authors have contributed significantly; the Starlab
Author list has been ordered randoml
Potential synergetic use of GNSS-R signals to improve the sea-state correction in the sea surface salinity estimation: Application to the SMOS mission
It is accepted that the best way to monitor sea surface
salinity (SSS) on a global basis is by means of L-band radiometry.
However, the measured sea surface brightness temperature
(TB) depends not only on the SSS but also on the sea surface
temperature (SST) and, more importantly, on the sea state, which
is usually parameterized in terms of the 10-m-height wind speed
(U10) or the significant wave height. It has been recently proposed
that the mean-square slope (mss) derived from global navigation
satellite system (GNSS) signals reflected by the sea surface could
be a potentially appropriate sea-state descriptor and could be used
to make the necessary sea state TB corrections to improve the
SSS estimates. This paper presents a preliminary error analysis of
the use of reflected GNSS signals for the sea roughness correction
and was performed to support the European Space Agency’s
Soil Moisture and Ocean Salinity (SMOS) mission; the orbit and
parameters for the SMOS instrument were assumed. The accuracy
requirement for the retrieved SSS is 0.1 practical salinity units
after monthly averaging over 2â—¦ Ă— 2â—¦ boxes. In this paper, potential
improvements in salinity estimation are hampered mainly
by the coarse sampling and by the requirements of the retrieval
algorithm, particularly the need for a semiempirical model that
relates TB and mss.Postprint (published version
The GNSS-R Eddy Experiment II: L-band and Optical Speculometry for Directional Sea-Roughness Retrieval from Low Altitude Aircraft
We report on the retrieval of directional sea-roughness (the full directional
mean square slope, including MSS, direction and isotropy) through inversion of
Global Navigation Satellite System Reflections (GNSS-R) and SOlar REflectance
Speculometry (SORES)data collected during an experimental flight at 1000 m. The
emphasis is on the utilization of the entire Delay-Doppler Map (for GNSS-R) or
Tilt Azimuth Map (for SORES) in order to infer these directional parameters.
Obtained estimations are analyzed and compared to Jason-1 measurements and the
ECMWF numerical weather model.Comment: Proceedings from the 2003 Workshop on Oceanography with GNSS
Reflections, Barcelona, Spain, 200
Rainfall Field Reconstruction by Opportunistic Use of the Rain-Induced Attenuation on Microwave Satellite Signals: The July 2021 Extreme Rain Event in Germany as a Case Study
This paper presents a practical application of an
opportunistic technique for the estimation of rainfall intensity
and accumulated precipitation. The proposed technique is based
upon signal strength measurements made by commercial-grade
interactive satellite terminals. By applying some processing, the
rain-induced attenuation on the microwave downlink from the
satellite is first evaluated; then the rain attenuation is eventually
mapped into a rainfall rate estimate via a tropospheric model.
This methodology has been applied to a test area of 30Ă—30 km2
around the city of Dortmund (North Rhine-Westphalia, upper
basin of Ermscher river), for the heavy rain event that devastated
western Germany in July, 2021. A rainfall map on this area is
obtained from the measurements collected by a set of satellite
terminals deployed in the region, and successfully compared with
a map obtained with a conventional weather radar
Tsunami detection using the PARIS concept
Abstract On 26 December 2004 a tsunami generated by an earthquake with its epicentre in the Indian Ocean West of Indonesia caused a real human and material catastrophe in the region. After the event some proposals to establish a network of sensors for tsunami detection were put forward. This paper presents an alternative concept that can be applied from satellite, aircraft or from the coast, and which can complement such a network of sensors for fast tsunami detection. The concept makes use of GNSS signals reflected from the ocean's surface to perform mesoscale ocean altimetry. The technique, designated PARIS (Passive Reflectometry and Interferometry System), aims at capturing fast topographic events happening on the ocean surface such as eddies and fronts. The paper includes details of some aircraft experiments whereby a PARIS altimeter was used to map a topographic signature with amplitude and wavelength similar to a tsunami in open ocean
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