Thesis supervisor: Szabolcs Rózsa
Location of studies (in Hungarian): BME Depatment of Geodesy and Surveying Abbreviation of location of studies: BMEAF
Description of the research topic:
In the recent years the continuously operating GNSS (global navigation satellite systems) stations play a substantial role in modern national, regional and global geodetic infrastructure.
Although these stations were primarily established for the maintenance of global/continental/national geodetic reference systems, furthermore, they also play an important role in the global geodetic observing system (GGOS). One of the aim of GGOS is to monitor and observe the Earth's atmosphere using geodetic techniques. GNSS observations are successfully used for the monitoring of the total electron content of the ionosphere, and to the monitoring of the neutral atmosphere, too. Analysing the tropospheric delay, the atmospheric water vapour content can be estimated, providing valuable information for weather forecasts and climatic studies.
The doctoral project focuses on two topics. Firstly, the candidate will develop a mathematical algorithm for the optimal tomographic reconstruction of atmospheric water vapour using the slant tropospheric delays in the satellite-receiver direction. The candidate will study various versions of algebraic reconstruction techniques (ART, MART, etc.) in order to derive four-dimensional (3D space + time) water vapour fields. The developed algorithms will be tested and validated with simulated data derived from numerical weather models. Furthermore the Hungarian and the Egyptian continuously operating GNSS networks will be used for the field tests of the approach. The candidate investigates the feasibility of the monitoring of the movements of weather fronts in near realtime based on the derived 4D water vapour fields using the developed tomographic approach. The to-be-developed water vapour models can fill a gap in meteorological observations technology, since currently 4D water vapour fields could be derived using a network of costly water vapour radiometers, of which Hungary operates only a single unit in the observatory of the Hungarian Meteorological Service in Szeged.
The second topic of the PhD project is to analyse the GNSS based precipitable water vapour estimates from the perspective of climate change. Since GNSS networks have been operating for more than 10-15 years, in the current days these data sets can be used for climatic studies as well. However, the data sets must be processed in a consistent way in order to provide consistent results over a longer time span. The candidate will set up and operate an automatic GNSS processing system based on the Bernese Processing Engine and process the GNSS observations obtained from the Hungarian and Egyptian GNSS stations at least from the past decade and estimate the integrated water vapour from the derived wet tropospheric delays in the zenith direction. Analysing the time series of the obtained integrated water vapour content, the candidate will pursue to study the effect of climate change on the integrated water vapour content in the natural laboratories of Hungary and Egypt located in continental and dry sub-tropical climate.
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