Near-Real-Time GPS Sensing of Atmospheric Water Vapour

Bai, Zhengdong (2005) Near-Real-Time GPS Sensing of Atmospheric Water Vapour. PhD thesis, Queensland University of Technology.


An important goal in modern weather prediction is to improve short-term weather

forecasts, especially of severe weather and precipitation. However, the ability to

achieve this goal is hindered by the lack of timely and accurate observations of

atmospheric water vapour, which is one of the most poorly measured and least

understood constituents of the Earth's atmosphere due to its high temporal and spatial

variability. This situation is being addressed by the Global Positioning System (GPS)

technology. GPS radio signals are slowed and bent by changes in temperature,

pressure and water vapour in the atmosphere. Traditionally, the GPS signal

propagation delay is considered a nuisance parameter that is an impediment to

obtaining precise coordinates using GPS. Recent development in GPS precise

positioning and orbit determination has enabled the atmospheric parameters to be

determined to a high degree of accuracy on a routine basis, using continuous tracking

data from ground-based GPS receivers.

The aim of this research is to address several critical scientific challenges in

estimating the atmospheric water vapour content in near-real-time (NRT) in

Australia. Contributions are made to the field of GPS meteorology in the following

five areas:

First of all, research efforts were made to develop a technical platform for the

ground-based GPS meteorology studies and demonstration of GPS Precipitable

Water Vapour (PWV) estimation using observations from Australian Regional GPS

Networks (ARGN). Methods of estimation of water vapour from GPS and

radiosonde data have been developed and tested. GAMIT-based GPS data processing

strategies and compare analysis with radiosonde water vapour solutions from the

Australia Upper Air Network (AUAN) were undertaken, providing an effective

technical basis for further studies.

Secondly, the research has developed techniques to allow estimation of atmospheric

water vapour from GPS data and surface meteorological observations collected

around the GPS sites. Ideally a dedicated meteorological sensor is installed adjacent

to the GPS antenna. However, meteorological sensors are normally not installed at

most Australian GPS stations. Installing a new meteorological sensor at each GPS

station would involve additional cost at the level of one-third or half of the geodetic

GPS receiver cost. We have experimentally developed and demonstrated

interpolation methods for making use of hourly collected surface meteorological data

from the Australian Automatic Weather Station (AWS) network operated by the

Bureau of Meteorology (BOM) to estimate atmospheric water vapour.

Thirdly, the research has studied ocean tidal loading and its effects on GPS derived

precipitable water vapour estimates. The periodic motion of the Earth's surface due

to ocean loading is one of the largest periodic motions. However, very little work has

been done to quantify their effects on GPS-derived solutions at the GPS sites in the

Australian region surrounded by ocean waters. The research presents the theoretical

analysis and experimental results from the ARGN network, focusing on ocean

loading and its effects on GPS derived precipitable water vapour estimates.

The fourth important effort was the development of techniques for estimating highrate

Slant Water Vapour (SWV) values for future operational meteorological

applications in Australia, including addressing such issues as slant-path delay

recovery from post-fit double-difference residuals, and overcoming site multipath

effects. The experimental results have demonstrated the efficiency of the proposed


Finally, in order to address the meteorological applications with the existing and

anticipated GPS reference stations in the Australian region, and measure the

atmospheric water vapour content in near-real-time, the technical issues to

implement NRT GPS water vapour estimation were identified and discussed,

including the data requirements for meteorological and climate applications, NRT

data processing and quality control procedures for GPS orbits. The experimental

GPS PWV results from NRT and post data processing are compared and presented.

Impact and interest:

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ID Code: 16059
Item Type: QUT Thesis (PhD)
Supervisor: Feng, Yanming & Moody, Miles
Keywords: GPS, Global positioning system, NRT, near-real-time, PWV, Precipitable Water Vapour, ARGN, Australian Regional GPS Networks, GAMIT-based, AUAN, Australia Upper Air Network
Divisions: Past > QUT Faculties & Divisions > Faculty of Built Environment and Engineering
Department: Faculty of Built Environment and Engineering
Institution: Queensland University of Technology
Copyright Owner: Copyright Zhengdong Bai
Deposited On: 03 Dec 2008 03:55
Last Modified: 28 Oct 2011 19:42

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