Tropospheric water vaporTropospheric water vapor• water vapor delay of radar propagation
nondispersive, affects all wavelengths equally
• large variation in time (random and seasonal) and space (power law)
• stratified water vapor vertical gradient change and dry atmospheric pressure changes cause delays correlated with topography
• independent and InSAR-derived estimates of delays possible for correcting ground deformation measurements
• water vapor delay of radar propagation nondispersive, affects all wavelengths equally
• large variation in time (random and seasonal) and space (power law)
• stratified water vapor vertical gradient change and dry atmospheric pressure changes cause delays correlated with topography
• independent and InSAR-derived estimates of delays possible for correcting ground deformation measurements
InSAR tropospheric water vapor corrections
InSAR tropospheric water vapor corrections
• time series filtering• correlation of phase with topography• CGPS zenith wet delay interpolated spatially (and
temporally)• water vapor measurements from absorption of
reflected near IR—MODIS and MERIS• water vapor measurements from thermal IR and
microwave radiometers—AIRS, MODIS (IR)• water vapor estimates from numerical weather
models—could even assimilate InSAR back into weather
• time series filtering• correlation of phase with topography• CGPS zenith wet delay interpolated spatially (and
temporally)• water vapor measurements from absorption of
reflected near IR—MODIS and MERIS• water vapor measurements from thermal IR and
microwave radiometers—AIRS, MODIS (IR)• water vapor estimates from numerical weather
models—could even assimilate InSAR back into weather
InSARInSARderivedderived}}
InSARtime series
InSARtime series
•Water vapor largest source of error
•Dec. 2003 Bam, Iran EQ
•postseismic 30 dates:Jan. 2004–June 2007
•descending track, 10 AM local time
•plane fit removed from each epoch
•referenced to epoch 1 (Jan. 2004—not shown) with substantial atmospheric effects
•Water vapor largest source of error
•Dec. 2003 Bam, Iran EQ
•postseismic 30 dates:Jan. 2004–June 2007
•descending track, 10 AM local time
•plane fit removed from each epoch
•referenced to epoch 1 (Jan. 2004—not shown) with substantial atmospheric effects
Fielding, E.J., Lundgren, P.R., Bürgmann, R., and Funning, G.J., 2009, Shallow fault-zone dilatancy recovery after the 2003 Bam earthquake in Iran: Nature, v. 458, p. 64-68.
OSCAR: Online Services for Correcting Atmosphere in Radar
OSCAR: Online Services for Correcting Atmosphere in Radar
• NASA Advanced Information Systems Technology project started May 2009
• Paul von Allmen, PI (JPL)
• Eric Fielding, Evan Fishbein, Zhangfan Xing, Lei Pan (JPL), Zhenhong Li (U. Glasgow), Co-Is
• Online server to collect and process atmospheric data (tropospheric water vapor) to make corrections for InSAR
• NASA Advanced Information Systems Technology project started May 2009
• Paul von Allmen, PI (JPL)
• Eric Fielding, Evan Fishbein, Zhangfan Xing, Lei Pan (JPL), Zhenhong Li (U. Glasgow), Co-Is
• Online server to collect and process atmospheric data (tropospheric water vapor) to make corrections for InSAR
OSCAR: Online Services for Correcting Atmosphere in Radar
OSCAR: Online Services for Correcting Atmosphere in Radar
• Sources in first stage: MODIS, MERIS, AIRS, NCEP or ECMWF forecast models
• May add GPS or other GNSS data and mesoscale models
• Highest resolution data used when available
• Global weather forecasts provide background coverage every place and time
• Optimal combination of sources
• Single-date or interferogram two-date corrections
• Sources in first stage: MODIS, MERIS, AIRS, NCEP or ECMWF forecast models
• May add GPS or other GNSS data and mesoscale models
• Highest resolution data used when available
• Global weather forecasts provide background coverage every place and time
• Optimal combination of sources
• Single-date or interferogram two-date corrections
Water vapor mappingWater vapor mapping•MERIS on Envisat so simultaneous with ASAR
•high-resolution column WV, 1.2 or 0.3 km
•day only, affected by clouds
•AIRS works everywhere, lower resolution (45 km) but has profile
•need good interpolation
•MERIS on Envisat so simultaneous with ASAR
•high-resolution column WV, 1.2 or 0.3 km
•day only, affected by clouds
•AIRS works everywhere, lower resolution (45 km) but has profile
•need good interpolation
• GPS Topography-dependent Turbulence Model (GTTM)
• MODIS water vapour correction model
• MERIS water vapour correction model
• MERIS/MODIS combination correction model (MMCC)
• MERIS/MODIS stacked correction model (MMSC)
• GPS Topography-dependent Turbulence Model (GTTM)
• MODIS water vapour correction model
• MERIS water vapour correction model
• MERIS/MODIS combination correction model (MMCC)
• MERIS/MODIS stacked correction model (MMSC)
InSAR water vapor correction modelsInSAR water vapor correction models
PWV retrievals rely on channel ratio techniquesPWV retrievals rely on channel ratio techniques
MODIS: MODIS: 2 non2 non--absorbing absorbing
3 absorbing3 absorbing
MERIS:MERIS:1 non1 non--absorbing absorbing
1 absorbing1 absorbing
(Figure adapted from (Figure adapted from Gao Gao and Kaufman and Kaufman [1998])[1998])
MODIS/MERIS Channel Positions Related to PWVMODIS/MERIS Channel Positions Related to PWV
GPS, MODIS and MERIS PWV products are complementary!GPS, MODIS and MERIS PWV products are complementary!
Comparisons of GPS, MODIS and MERIS PWVComparisons of GPS, MODIS and MERIS PWV
References:References:Li, Z., E.J. Fielding, P. Cross, and J.Li, Z., E.J. Fielding, P. Cross, and J.--P. Muller, Interferometric synthetic aperture radar atmospheric P. Muller, Interferometric synthetic aperture radar atmospheric
correction: MEdium Resolution Imaging Spectrometer and Advanced correction: MEdium Resolution Imaging Spectrometer and Advanced Synthetic Aperture Radar integration, Synthetic Aperture Radar integration, Geophysical Research LettersGeophysical Research Letters, , 3333, L06816, 2006., L06816, 2006.
Li, Z., J.Li, Z., J.--P. Muller, P. Cross, P. Albert, J. Fischer, and R. Bennartz, AssP. Muller, P. Cross, P. Albert, J. Fischer, and R. Bennartz, Assessment of the potential of MERIS nearessment of the potential of MERIS near--infrared water vapour products to correct ASAR interferometric minfrared water vapour products to correct ASAR interferometric measurements, International Journal of easurements, International Journal of
• MERIS data can be acquired at the same time as ASAR data because both on Envisat (time differences between MODIS and SAR data: ~1 hour)
• MERIS has better spatial resolution, up to 300 m against 1km for MODIS
• MERIS near IR water vapour product agrees more closely with GPS than MODIS
• MERIS vs MODIS
• MERIS data can be acquired at the same time as ASAR data because both on Envisat (time differences between MODIS and SAR data: ~1 hour)
• MERIS has better spatial resolution, up to 300 m against 1km for MODIS
• MERIS near IR water vapour product agrees more closely with GPS than MODIS
MERIS water vapour correction modelMERIS water vapour correction model
InSAR Time Series with water vapor correctionInSAR Time Series with water vapor correction
&&
Postseismic motion after the 2003 Bam (Iran) earthquake Postseismic motion after the 2003 Bam (Iran) earthquake
References:References:
Li, Z., Fielding, E. J., and Cross, P.: Integration of InSAR timLi, Z., Fielding, E. J., and Cross, P.: Integration of InSAR time series analysis and water vapour correction for e series analysis and water vapour correction for mapping postseismic deformation after the 2003 Bam, Iran Earthqumapping postseismic deformation after the 2003 Bam, Iran Earthquake, IEEE Transactions on Geoscience and ake, IEEE Transactions on Geoscience and
Remote Sensing, 2009. Remote Sensing, 2009.
Bam Bam postseismicpostseismic time seriestime series
Without PWV correction With PWV correction Without PWV correction With PWV correction
InSARInSAR Time Series (TS) ResultsTime Series (TS) Results
Interpolating Atmospheric Data at High Spatial Resolution for InSARInterpolating Atmospheric Data at High Spatial Resolution for InSAR•How to resolve mismatch between atmospheric data sets having 8-100 km spatial resolution, and InSAR data having 10 –100 m resolution?
•Proposed solutions:
–High-resolution atmospheric data assimilation models
–Interpolated gridded atmospheric data
–High-resolution atmospheric water vapor fields from satellite-based imagers and sounders
•How to resolve mismatch between atmospheric data sets having 8-100 km spatial resolution, and InSAR data having 10 –100 m resolution?
•Proposed solutions:
–High-resolution atmospheric data assimilation models
–Interpolated gridded atmospheric data
–High-resolution atmospheric water vapor fields from satellite-based imagers and sounders
Local Atmospheric Correction AlgorithmsLocal Atmospheric Correction Algorithms
• On scales at which approximation is applied:• No local sources of water vapor• No adiabatic heating or cooling• Surface water vapor mixing ratio and
temperature along surface is conserved• Flow is along slope, not around obstacle• Free troposphere structure unperturbed by
topography
• Stretch water vapor and temperature profiles across the boundary layer, holding values at top and bottom fixed
• Recalculate total precipitable water vapor, surface pressure and wet and dry delays
• On scales at which approximation is applied:• No local sources of water vapor• No adiabatic heating or cooling• Surface water vapor mixing ratio and
temperature along surface is conserved• Flow is along slope, not around obstacle• Free troposphere structure unperturbed by
topography
• Stretch water vapor and temperature profiles across the boundary layer, holding values at top and bottom fixed
• Recalculate total precipitable water vapor, surface pressure and wet and dry delays
11 Green Green –– the original profile from the the original profile from the forecastforecast
22 Magenta Magenta –– the extrapolated curvethe extrapolated curve•• Black Black –– the stretched boundary layer the stretched boundary layer
curve.curve.
Comparison of Techniques
Comparison of Techniques
• Envisat ASAR interferogram 2006/06/03–2006/09/16
• MODIS NIR destriped
• MODIS corrected interf.
• ECMWF stretched boundary layer model
• AIRS simple interp.
• GPS Topo-dependent turbulence model interp.
• Envisat ASAR interferogram 2006/06/03–2006/09/16
