Fast and accurate ray‐tracing algorithms for real‐time space geodetic applications using numerical weather models

Hobiger, Thomas; Ichikawa, Ryuichi; Koyama, Yasuhiro; Kondo, Tetsuro

doi:10.1029/2008jd010503

Cited by 109 publications

(100 citation statements)

References 23 publications

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“…Thus, it prevents us from knowing the exact trajectory in advance, in contrast to straight-line models, and must be solved iteratively based on the preceding ray refractive index. Similar examples are given by Böhm and Schuh (2003) and Hobiger et al (2008). We assume the ray path does not leave the plane of constant azimuth for a given elevation angle to a satellite.…”

Section: Description Of Aladin-cz Solution From Wuels (Ala/wuels)mentioning

confidence: 99%

Inter-technique validation of tropospheric slant total delays

et al. 2017

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Abstract. An extensive validation of line-of-sight tropospheric slant total delays (STD) from Global Navigation Satellite Systems (GNSS), ray tracing in numerical weather prediction model (NWM) fields and microwave water vapour radiometer (WVR) is presented. Ten GNSS reference stations, including collocated sites, and almost 2 months of data from 2013, including severe weather events were used for comparison. Seven institutions delivered their STDs based on GNSS observations processed using 5 software programs and 11 strategies enabling to compare rather different solutions and to assess the impact of several aspects of the processing strategy. STDs from NWM ray tracing came from three institutions using three different NWMs and ray-tracing software. Inter-techniques evaluations demonstrated a good mutual agreement of various GNSS STD solutions compared to NWM and WVR STDs. The mean bias among GNSS solutions not considering post-fit residuals in STDs was −0.6 mm for STDs scaled in the zenith direction and the mean standard deviation was 3.7 mm. Standard deviations of comparisons between GNSS and NWM ray-tracing solutions were typically 10 mm ± 2 mm (scaled in the zenith direction), depending on the NWM model and the GNSS station. Comparing GNSS versus WVR STDs reached standard deviations of 12 mm ± 2 mm also scaled in the zenith direction. Impacts of raw GNSS post-fit residuals and cleaned residuals on optimal reconstructing of GNSS STDs were evaluated at intertechnique comparison and for GNSS at collocated sites. The use of raw post-fit residuals is not generally recommended as they might contain strong systematic effects, as demonstrated in the case of station LDB0. Simplified STDs reconstructed only from estimated GNSS tropospheric parameters, i.e. without applying post-fit residuals, performed the best in all the comparisons; however, it obviously missed part of tropospheric signals due to non-linear temporal and spatial variations in the troposphere. Although the post-fit residuals cleaned of visible systematic errors generally showed a slightly worse performance, they contained significant tropospheric signal on top of the simplified model. They are thus recommended for the reconstruction of STDs, particularly during high variability in the troposphere. Cleaned residuals also showed a stable performance during ordinary days while containing promising information about the troposphere at low-elevation angles.

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Section: Description Of Aladin-cz Solution From Wuels (Ala/wuels)mentioning

confidence: 99%

Inter-technique validation of tropospheric slant total delays

et al. 2017

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“…In Eq. (2), the first term in the right hand side represents the electromagnetic delay due to the change in the phase velocity and the second term represents the raybending effect (Hobiger et al 2008). It is noted that the propagation delay effect derived from InSAR is the relative difference between the master and slave observations.…”

Section: Tropospheric Delaymentioning

confidence: 99%

“…(1) and (2) with the ray-tracing method (Hobiger et al 2008), which enables to directly compare model results with the derived interferogram. The modeled delay comparable with the InSAR image was derived by the difference of simulated delays on two epochs (in this case one is at 01:15 UTC on 25 August 2010 and the other is at 01:15 UTC on 25 May 2010).…”

Section: Numerical Weather Modelmentioning

confidence: 99%

Localized Delay Signals Detected by Synthetic Aperture Radar Interferometry and Their Simulation by WRF 4DVAR

Kinoshita

Furuya

2017

SOLA

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Localized propagation delay signals associated with linealigned convective cells were detected by the Synthetic Aperture Radar Interferometry (InSAR) technique on 25 August 2010 in Niigata prefecture. The maximum amplitude of the signal reached up to 22.5 cm, which was approximately equivalent to 29 mm anomaly in precipitable water vapor (PWV). The nationwide radar rainfall intensity captured the spatial distribution of hydrometeors on both land and sea, which was similar to that of the InSARderived water vapor field, suggesting that the convective cells were initiated on the Japan Sea to the west-southwest of the observation area. A numerical weather model (NWM) simulation with the grid spacing of 2.5 km reproduced line-aligned convective cells with 3 cm smaller maximum amplitude to that in InSAR. A NWM simulation that assimilates Global Navigation Satellite System (GNSS)-derived PWV data for four-dimensional variational assimilation enhanced the water vapor flux convergence at the surface, which improved the amplitude of the localized delay signals. The advantage of the unique water vapor observation by InSAR enabled us to assess the meso-gamma scale NWM reproducibility in terms of water vapor, which is one of the fundamental prognostic parameter for NWMs.(Citation: Kinoshita, Y., and M. Furuya, 2017: Localized delay signals detected by synthetic aperture radar interferometry and their simulation by WRF 4DVAR. SOLA, 13, 79−84,

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“…In Eq. (2), the first term in the right-hand side represents the electromagnetic delay due to the change in the phase velocity and the second term represents the ray bending effect (Hobiger et al 2008).…”

Section: Propagation Delay Theory and Modelingmentioning

confidence: 99%

Detections and simulations of tropospheric water vapor fluctuations due to trapped lee waves by ALOS-2/PALSAR-2 ScanSAR interferometry

Kinoshita

Morishita

Hirabayashi

2017

Earth Planets Space

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Detailed wave-like spatial patterns of atmospheric propagation delay signals associated with mountain lee waves were detected in Hokkaido and Tohoku by synthetic aperture radar (SAR) interferometry (InSAR) with the ScanSAR mode observation data of a Phased Array-type L-band Synthetic Aperture Radar 2 on board the Advanced Land Observing Satellite 2. Both cases occurred under stable atmosphere conditions. The InSAR-observed peak-to-trough line of sight changes in the mountain wave signals was 4 and 5 cm with the horizontal wavelengths of 9 and 15 km in Hokkaido and Tohoku, respectively. Locations of positive phase maxima in the mountain wave signals coincides with locations of cloud streets observed by visible satellite imagery, indicating that crests of mountain waves contain relatively much water vapor compared with wave troughs. Numerical weather simulations with the horizontal grid spacing of 1 km were performed to reproduce InSAR phase variations, and as a result those simulations could reasonably reproduce observed wave amplitudes and wavelengths in both cases. On the other hand, numerical simulations tended to overestimate wave attenuation rates: simulated mountain waves decreased as the wave propagated faster than those of observed signals. Because the simulated wave attenuation rate is sensitive to physics in the planetary boundary layer (PBL), we investigated the reproducibility of five PBL schemes implemented in the WRF model. As a result, all the PBL schemes showed little attenuation except for the Yonsei University scheme (YSU), while the wavelength in the YSU was most close to the observation. Our study demonstrated the uniqueness and usefulness of InSAR for meteorological application as the ability to map the detailed water vapor distribution regardless of cloud cover. In addition, the reasonable reproducibility of the water vapor delay signal due to lee waves by the numerical weather model encourages researchers who tackle the correction of the tropospheric propagation delay, increasing the accuracy in detecting surface deformations.

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Fast and accurate ray‐tracing algorithms for real‐time space geodetic applications using numerical weather models

Cited by 109 publications

References 23 publications

Inter-technique validation of tropospheric slant total delays

Inter-technique validation of tropospheric slant total delays

Localized Delay Signals Detected by Synthetic Aperture Radar Interferometry and Their Simulation by WRF 4DVAR

Detections and simulations of tropospheric water vapor fluctuations due to trapped lee waves by ALOS-2/PALSAR-2 ScanSAR interferometry

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