Abstract
AbstractMicrowave signals traveling through the troposphere are subject to delays. These delays are mainly described by spatial and temporal variations in pressure, temperature, and relative humidity in the lower part of the troposphere, resulting in a spatially varying tropospheric signal in interferometric synthetic aperture radar (InSAR). Tropospheric correction techniques rely either on external data, often limited by spatial and temporal accuracy or can be estimated from the high‐resolution interferometric phase itself. However, current phase‐estimated correction techniques do not account for the spatial variability of the tropospheric properties and fail to capture tropospheric signals over larger regions. Here we propose and test a novel power law correction method that accounts for spatial variability in atmospheric properties and can be applied to interferograms containing topographically correlated deformation. The power law model has its reference fixed at the relative top of the troposphere and describes, through a power law relationship, how the phase delay varies with altitude. We find the power law model reduces tropospheric signals both locally (on average by ∼0.45 cm for each kilometer of elevation in Mexico) and the long‐wavelength components, leading to an improved fit to independent Global Navigation Satellite Systems data. The power law model can be applied in presence of deformation, over a range of different time periods and in different atmospheric conditions, and thus permits the detection of smaller‐magnitude crustal deformation signals with InSAR.
Highlights
Radar signals propagating through the atmosphere are affected by the medium in which they travel, which can result in a phase delay or advance
The power law model has its reference fixed at the relative top of the troposphere and describes, through a power law relationship, how the phase delay varies with altitude
In this paper we present a new tropospheric correction technique that can be applied to deforming regions and which allows for a spatially varying relationship between phase and topography
Summary
Radar signals propagating through the atmosphere are affected by the medium in which they travel, which can result in a phase delay or advance. Variations of temperature, pressure, and relative humidity lead to a spatially varying tropospheric phase delay, which partly correlates with topography. Hooper et al, 2012] The former method assumes a linear relation between the interferometric tropospheric delay and the topography (Δφtropo = KΔφh + Δφ0), estimated from data in the non-deforming region. At h0 the relative tropospheric delays between different acquisitions converge to zero, while the delay itself continues to decrease with increasing height This can be observed empirically from the tropospheric delays computed from balloon sounding measurements as shown in Figures 1a and 1b. In this paper we present a new tropospheric correction technique that can be applied to deforming regions and which allows for a spatially varying relationship between phase and topography. The tectonic implications of the results are presented in a companion paper [Bekaert et al, 2015]
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