GNSS-RO Deep Refraction Signals from Moist Atmospheric Boundary Layer Dong L. Wu 1 and Jie Gong 1,2 1) NASA Goddard Space Flight Center, Greenbelt, MD 2) GESTAR, Universities Space Research Association, Columbia, MD 8th IROWG Virtual Meeting April 7-9, 12 and 13, 2021 Acknowledgments: • Support from NASA GNSS research program • UCAR/CDAAC GNSS data service
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GNSS-RO Deep Refraction Signals from Moist Atmospheric Boundary Layer
Dong L. Wu1 and Jie Gong1,2
1) NASA Goddard Space Flight Center, Greenbelt, MD2) GESTAR, Universities Space Research Association, Columbia, MD
8th IROWG Virtual Meeting April 7-9, 12 and 13, 2021
Acknowledgments: • Support from NASA GNSS research program• UCAR/CDAAC GNSS data service
Ducting/Diffraction
LEOReceiver
GPS Transmit
ter No bending
Deep SNR
Straight-Line Height (HSL
)
Atmospheric Refraction, Ducting and Diffraction
This Study
(Image Credit: Wikipedia)
Atmospheric Optics: Fata Morgana
Stra
ight
-Lin
e H
eigh
t (H
SL),
km
Normalized SNR/SNR0
Deep RefractedRO Signals
in RO
Water Vapor Bending
Grazing Reflection
Super Refraction
Melbourne [2004]
U-Shape COSMIC-1
U-S
hap
e
“Throw-Back”
• Thin phase screen model for refractive + diffractive + multi-path RO signals
• Analytical calculation for a sharp 0.5-km atmospheric layer
• U-shape and deep-refraction SNR from ‘shadow zone’ filled by ‘throw-back’ rays
Deep SNR
DiffractiveSignals
Sokolovskiy et al. [2014] • Numerical wave-optics model simulations
• Longer duct => Deeper SNR
Analysis of RO SNR Data
SNR0
• Different σ in setting and rising RO• Different σ from GPS and GLONASS ROs with same receiver (e.g., COSMIC-2)• Similar σ in the same receiver set (e.g., COSMIC-1)• Use of the data with strong signals (SNR0 > 600): still many samples
Receiver noise (σ) effect
GPS
LEO1
Tangent HeightAbove Surface (H
t)
Straight-Line Height (H
SL)
LEO2
Impact Parameter (a)
LEO Orbit Height (H
sat)
Radio Occultation
Path
Earth Radius (R
e)
LEO altitude effect
Stra
ight
-Lin
e H
eigh
t (H
SL),
km
SNR/SNR0
Red: Tropics
Jan
Correlation between Deep (HSL
=-100km) SNR/SNR0 (COSMIC 2008-2011) and ERA5 950-hPa H2O and Refractivity over Ocean