Abstract

High resolution numerical weather models (NWM) are being to play a role of increasing importance foratmospheric phase screen (APS) mitigation. Here we present preliminary investigations concerning the estimationof the atmospheric contribution to X-band InSAR phase fields through numerical weather modeling. We selectedtandem-like pairs of Stripmap COSMO/SkyMED images acquired over Parkfield (California, USA) with shortnormal baselines, thus ensuring low sensitivity to elevation. By using a 30m SRTM DEM available for the area ofinterest, we generated differential phase fields, mainly related to the difference between atmospheric conditions atthe times of the two acquisitions.The interferometric artifacts have been hence compared to independent estimates of the atmospheric phase delayintroduced by both wet and dry the components of the troposphere, obtained through Regional AtmosphericModeling System (RAMS), a finite-difference, primitive equation, three-dimensional mesoscale NWM originallydeveloped at Colorado State University. RAMS is a prognostic model capable of simulating a wide range ofatmospheric motions due to the use of a nested grid system. Incorporation of topographic features occurs throughthe use of a terrain-following vertical coordinate system, while turbulence is parameterized using Mellor andYamada's level 2.5 scheme, as modified by Helfand and Labraga for growing turbulence.In order to assess the impact of the boundary conditions, numerical simulations have been repeated by usingGFS, ECMWF and NAM data (resolution: 0.5 deg, 0.25 deg and 12km respectively). A spin-up time exceeding24h was necessary for ensuring a realistic computation of the atmospheric boundary layer depth. Finally, the 3Dcomputation of the scaled-up refractive index and its integration along the Line-Of-Sight (LOS) of the SAR sensorwas performed in order to estimate the two-way radar phase delay.The preliminary results confirm the indications coming from recent similar studies: weather models are good forthe long wavelengths (>20 km) and for vertical stratification which depends on the hydrostatic component of thetroposphere, while they cannot actually ensure a sub-centimetric accuracy in the estimation of the wet component,as instead required in X-band interferometry.Finally, we used the GPS daily RINEX available on the Parkfield area to infer the atmospheric Zenith Total Delay(ZTD) and validate the outcomes of the NWM. GPS data were processed at ASI/CGS by using the NASA/JPLGIPSY-OASIS II for data reduction. The Precise Point Positioning approach was applied fixing JPL fiducial-freesatellite orbits, clocks and earth orientation parameters, IGS absolute phase center variations and estimating, witha cut-off angle of 7deg, site coordinates, station clock, phase ambiguities, ZTD and tropospheric gradients. ZTDand tropospheric gradients are modeled as random walk processes and estimated with a sampling rate of 5

Autore Pugliese

• Bovenga Fabio

Tutti gli autori

• D.O. Nitti; R. Nutricato;; F. Intini; F. Bovenga; M. T. Chiaradia; R. Pacione; F. Vespe

Titolo volume/Rivista

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Anno di pubblicazione

2012

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Numero di citazioni Wos

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Settori ERC

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