The retrieval of wet refractivity index by tomography using spherical cap harmonics

نوع مقاله: مقالة‌ تحقیقی‌ (پژوهشی‌)

نویسندگان

1 School of Surveying and Geomatics Engineering, Faculty of Engineering, University of Tehran, Iran

2 دانشگاه تهران - مهندسی نقشه برداری

3 دانشگاه تهران

چکیده

In this research, three-dimensional and four-dimensional tomography is used to demonstrate the distribution of wet refractivity index of the troposphere. In this model, spherical cap harmonics are used for the horizontal distribution of the wet refractivity index, and empirical orthogonal functions are used for the vertical distribution of the index. The region of study is in the west California State, and the wet refractivity index is retrieved from the wet tropospheric delay measurements. to validate the results, radiosonde profiles were compared to the tomographically retrieved profiles. The result shows that wet refractivity indices can be retrieved using functional models with RMSE about 2.4 ppm till 3.9 in four-dimension method. The comparisons show that the four-dimensional retrieved profiles shows improvement up to 34 and 42 percentage in mid-day tomography epochs compare to three-dimensional tomography results. Also it can be seen that in mid-night epochs three-dimensional tomography has higher accuracy compare to four-dimension method because of low variation of wet refractivity indices

کلیدواژه‌ها


عنوان مقاله [English]

The retrieval of wet refractivity index by tomography using spherical cap harmonics

نویسندگان [English]

  • Masood Dehvari 1
  • سعید فرزانه 2
  • Mohammad Ali Sharifi 3
1 School of Surveying and Geomatics Engineering, Faculty of Engineering, University of Tehran, Iran
3 School of Surveying and Geomatics Engineering, Faculty of Engineering, University of Tehran, Iran
چکیده [English]

In this research, three-dimensional and four-dimensional tomography is used to demonstrate the distribution of wet refractivity index of the troposphere. In this model, spherical cap harmonics are used for the horizontal distribution of the wet refractivity index, and empirical orthogonal functions are used for the vertical distribution of the index. The region of study is in the west California State, and the wet refractivity index is retrieved from the wet tropospheric delay measurements. to validate the results, radiosonde profiles were compared to the tomographically retrieved profiles. The result shows that wet refractivity indices can be retrieved using functional models with RMSE about 2.4 ppm till 3.9 in four-dimension method. The comparisons show that the four-dimensional retrieved profiles shows improvement up to 34 and 42 percentage in mid-day tomography epochs compare to three-dimensional tomography results. Also it can be seen that in mid-night epochs three-dimensional tomography has higher accuracy compare to four-dimension method because of low variation of wet refractivity indices

کلیدواژه‌ها [English]

  • Empirical Orthogonal Functions
  • Legendre function
  • Radiosonde
  • numerical weather model
  • tropospheric wet delay