Abstract
Abstract. The spatio-temporal distribution of atmospheric water vapour information plays a crucial role in the establishment of modern numerical weather forecast models and description of the different weather variations. A troposphere tomographic method has been proposed considering the signal rays penetrating from the side of the area of interest to solve the problem of the low utilisation rate of global navigation satellite system (GNSS) observations. Given the method above needs the establishment of a unit scale factor model using the radiosonde data at only one location in the research area, an improved approach is proposed by considering the reasonability of modelling data and the diversity of the modelling parameters for building a more accurate unit scale factor model. The new established model is established using grid point data derived from the European Centre for Medium-Range Weather Forecasts (ECMWF) and evenly distributed in the tomographic area, which can enhance the number of calculated initial water vapour density values with high accuracy. We validated the improved method with respect to the previous methods, as well as the result from a radiosonde using data from 12 stations from the Hong Kong Satellite Positioning Reference Station Network. The obtained result shows that the number of initial values estimated by the new model is increased by 6.83 %, while the internal and external accuracies are 0.08 and 0.24 g m−3, respectively. Integrated water vapour (IWV) and water vapour density profile comparisons show that the improved method is superior to previous studies in terms of RMS, MAE, and bias, which suggests higher accuracy and reliability.
Highlights
Atmospheric water vapour only accounts for a small proportion of total atmospheric volume, but it plays an important role in the formation of clouds and rainfall, as well as the evolution of weather systems (Liu et al, 2005; Wang et al, 2014)
A new unit scale factor model was proposed using the layered data provided by European Centre for Medium-Range Weather Forecasts (ECMWF), which considered the reasonability of selecting modelling data as well as the modelling parameters
We analysed the accuracy of this new unit scale factor model and validated the tomographic result of the improved method
Summary
Atmospheric water vapour only accounts for a small proportion of total atmospheric volume, but it plays an important role in the formation of clouds and rainfall, as well as the evolution of weather systems (Liu et al, 2005; Wang et al, 2014). Yao et al (2016) proposed a method which considers the signals penetrating from the side face of the research area by introducing the unit scale factor model, while the unit scale factor refers to the proportion between the value of signal SWV inside the tomographic area and the total value of this signal SWV. This method proposed above enhanced the utilisation rate of signal observations as well as the number of voxels crossed by satellite rays. The experimental results show that the tomographic result using the new unit scale factor model is superior to those methods outlined in previous studies
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