A Refined Tomographic Window for GNSS-Derived Water Vapor Tomography

Abstract

Global navigation satellite system (GNSS) tomography can effectively sense the three-dimensional structure of tropospheric water vapor (WV) using the GNSS observations. Numerous studies have utilized a tomographic window to include more epochs of observations, which significantly increases the number of valid signals. However, considering the tomography grid limits, a massive number of valid signals inevitably exhibits linear dependence. This dependence makes it impossible to improve the rank score of the tomography coefficient matrix by blindly introducing a large number of valid rays. Furthermore, excessive valid signals may lead to a high condition number in the coefficient matrix (ill-condition problem), which causes unstable results using the GNSS-WV tomography. Considering these problems, we proposed an improved tomographic approach, which applies a refined tomographic window. It differs from the general tomographic window in that the window is refined to traverse the valid signals available 15 min before and after the target epoch while retaining only the linearly independent parts (characteristic signal). Compared to the conventional method, the proposed method can filter the characteristic signal, which increases the rank score of the coefficient matrix and improves the stability of the tomography model. In this paper, we used GNSS observations from the Hong Kong Satellite Positioning Reference Station Network (SatRef) to validate the performance of the proposed method over the day-of-year (DOY) periods of 130–132, 2019 and 146–148, 2019. The numerical results showed that, by using a refined tomographic window, the proposed method obtained superior WV products in comparison with that of the conventional method.

Variation characteristics of precipitable water vapor retrieved by CORS in China Southern Power Grid during heavy rainfall

“…The GNSS ZTD solved by GAMIT features mm-level accuracy, which is usually used as a reference value for the tropospheric delay model or ground-based GNSS water vapor tomography experiment [8] . Taking BJFS station as an example, this paper verifies its reliability by treating ZTD products provided by IGS as reference values.…”

A method for constructing the weighted mean temperature grid model considering the hourly near-surface temperature lapse rate in GNSS PWV

“…Traditional techniques for detecting PWV mainly include water vapor radiometers, radiosondes and remote sensing. These methods are unable to meet the increasing demands of modern meteorological development, primarily due to the expensive devices, heavy workload and low spatiotemporal resolution [7][8][9] .…”

Augmentation Method for Weighted Mean Temperature and Precipitable Water Vapor Based on the Refined Air Temperature at 2 m above the Surface of Land from ERA5

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