A non-uniform discretization GNSS water vapor tomography refined method considering water vapor distributions

doi:10.11947/j.AGCS.2024.20220534

Abstract

Abstract:

GNSS water vapor tomography technique has become a crucial tool for retrieving atmospheric water vapor distributions with high spatiotemporal resolution, owing to its high precision and all-weather availability. The existing GNSS water vapor tomography method divides the three-dimensional (3D) tomography area with a uniform discretization scheme. However, due to the spatial heterogeneity of atmospheric water vapor, this method does not follow the actual distribution of atmospheric water vapor in the vertical direction. Based on the vertical decreasing tendency of atmospheric water vapor, an improved non-uniform discretized GNSS water vapor tomography method that considers water vapor distributions is proposed. The method analyzes the vertical decreasing characteristics of water vapor content and constructs a vertically non-uniform stratification scheme based on the change rate of precipitable water vapor. Furthermore, a horizontal non-uniform discretization scheme at different altitude layers is set up, forming an uneven discretization tomography framework with the decreasing resolution voxels from the surface to the top of the tomography area. Experiments are conducted using actual GNSS measurements, radiosonde data and ERA5 reanalysis in the Hong Kong region in July 2017. Taking radiosonde water vapor profiles as reference, the root mean square errors (RMSE) of the tomography results obtained from the non-uniform discretization approach are reduced by 21.8%, 20.9%, and 20.5% against three traditional schemes, respectively. Compared with ERA5 data, the RMSE values of the proposed method's tomography results are reduced by 15.4%, 11.4%, and 12.6%, respectively. Additionally, in the near-surface tomographic region below 2 km, the accuracy of the tomographic results obtained by the proposed method is significantly superior to that of the traditional method, which highlights that the proposed method is expected to provide higher accuracy and higher resolution near-surface 3D atmospheric water vapor products for rainfall forecasting.

Key words: GNSS water vapor tomography, horizontal non-uniform discretization, vertical non-uniform stratification, radiosonde, ERA5

CLC Number:

P228

Wenyuan ZHANG, Mingxin QI, Shubi ZHANG. A non-uniform discretization GNSS water vapor tomography refined method considering water vapor distributions[J]. Acta Geodaetica et Cartographica Sinica, 2024, 53(12): 2282-2294.

Figures/Tables 12

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高度/km	PWV值/mm	占比/（%）
0.25	5.25	10
0.55	11.02	20
0.85	16.20	30
1.20	21.48	40
1.65	27.43	50
2.10	32.54	60
2.70	37.93	70
3.50	43.30	80
4.80	48.62	90
5.90	51.24	95
7.00	52.58	98
9.00	53.64	99.5
11.00	53.92	100

试验方案	探空数据		ERA5
试验方案	RMSE	MAE	RMSE	MAE
方案Ⅰ	1.40	1.19	1.32	1.09
方案Ⅱ	1.79	1.42	1.56	1.19
方案Ⅲ	1.77	1.38	1.49	1.14
方案Ⅳ	1.76	1.39	1.51	1.16