Determining the time response in GNSS tomographic modeling of troposphere

GNSS tomography is a method for the three-dimensional reconstruction of wet refractivity ( N_w ) in a set of voxels, each covering a specific part of the troposphere. The substantial assumption is the homogeneity of atmosphere in each voxel in given time intervals, known as the time response of model. Determining the optimal time resolution is one of the existing challenges in the tomography of the Earth’s atmosphere. We apply Empirical Orthogonal Functions (EOFs) to find an optimal time response for our tomographic model. To investigate our method, we compute the EOFs using the numerical atmospheric model that is available in our test area as the reference field on an already designed tomographic model. Using time resolutions of 30, 45, 60, 75, 90, 105 and 120 min, our EOF based method suggests the time periods of 60 to 75 and 75 to 90 min as the time response in the two days (a dry and a wet day) of our experiments, respectively According to our analysis, because of the quality of our reference field, it is not possible to expect similarities better than 85