## Refinement of the Algorithmic Parameters for Сalculating the Tropospheric Delay Using Local Radio Sounding Data of the Atmosphere

Transactions of IAA RAS, issue 63, 8–16 (2022)

**DOI**: 10.32876/ApplAstron.63.8-16

**Keywords**:
water vapor radiometer, propagation of radio signals in the atmosphere, tropospheric delay, radio sounding, tropospheric delay calculation algorithm

### Abstract

The calculation of the tropospheric wet delay (TWD) from the data of remote radio sounding of the atmosphere is based on measurements of the brightness temperature of the atmospheric radiation (BT) obtained using a water vapor radiometer (WVR). The accuracy of the TWD calculation is determined by two main factors: the accuracy of measuring the radio brightness temperature of the atmosphere and the accuracy of the models for a parameter number using the algorithm for converting BT into the corresponding values of the TWD. Such parameters, for example, include the effective temperature of the atmosphere, weighted by the absorption coefficient of the radio signal in the atmosphere, the component of the atmosphere optical thickness associated with absorption in molecular oxygen, the value reflecting the ratio of absorption in water vapor at WVR frequencies, and others. Details of the TWD calculation algorithm are given in the literature references. The model for calculating the parameters of the algorithm is based on the data of radiosonde measurements of vertical profiles of meteorological parameters. In order to refine the algorithm parameters, it seems quite logical to use the data of radio sounding stations located near the place where WVR is installed. The modern spectral theory of the radio signal absorption in atmospheric gases, used in the processing of a long-term series of radiosonde profiles with meteorological parameters, makes it possible to obtain the most accurate values of the radio signal absorption in oxygen and water vapor and other quantities necessary for calculating the TWD. Based on radio sounding data, it is possible to build a regression model that takes into account seasonal fluctuations in calculated values depending on surface temperature and pressure. Thus, the parameters of the algorithm are tied to the WVR certain geographical location and the climatic conditions corresponding to this place. The calculation of the algorithm parameters was carried out on the basis of data from atmosphere sounding stations located near the Quasar VLBI Network observatories. The estimation of the algorithm parameters was carried out based on the analysis of measurement data from atmosphere sounding stations for the period from 2019 to 2021. As a result, refined coefficients of the algorithm for calculating the tropospheric delay were obtained, taking into account the climatic features of the observatories location. Comparison of the TWD values calculated according to the proposed scheme with similar values of the international IGS service in the of the Quasar VLBI network stations showed the coincidence of the absolute values of the TWD with an accuracy of 10 mm in the absence of precipitation.

### Citation

`G. N. Ilin, V. Yu. Bykov. Refinement of the Algorithmic Parameters for Сalculating the Tropospheric Delay Using Local Radio Sounding Data of the Atmosphere // Transactions of IAA RAS. — 2022. — Issue 63. — P. 8–16.`

```
@article{ilin2022,
abstract = {The calculation of the tropospheric wet delay (TWD) from the data of remote radio sounding of the atmosphere is based on measurements of the brightness temperature of the atmospheric radiation (BT) obtained using a water vapor radiometer (WVR). The accuracy of the TWD calculation is determined by two main factors: the accuracy of measuring the radio brightness temperature of the atmosphere and the accuracy of the models for a parameter number using the algorithm for converting BT into the corresponding values of the TWD. Such parameters, for example, include the effective temperature of the atmosphere, weighted by the absorption coefficient of the radio signal in the atmosphere, the component of the atmosphere optical thickness associated with absorption in molecular oxygen, the value reflecting the ratio of absorption in water vapor at WVR frequencies, and others. Details of the TWD calculation algorithm are given in the literature references. The model for calculating the parameters of the algorithm is based on the data of radiosonde measurements of vertical profiles of meteorological parameters.
In order to refine the algorithm parameters, it seems quite logical to use the data of radio sounding stations located near the place where WVR is installed. The modern spectral theory of the radio signal absorption in atmospheric gases, used in the processing of a long-term series of radiosonde profiles with meteorological parameters, makes it possible to obtain the most accurate values of the radio signal absorption in oxygen and water vapor and other quantities necessary for calculating the TWD. Based on radio sounding data, it is possible to build a regression model that takes into account seasonal fluctuations in calculated values depending on surface temperature and pressure. Thus, the parameters of the algorithm are tied to the WVR certain geographical location and the climatic conditions corresponding to this place.
The calculation of the algorithm parameters was carried out on the basis of data from atmosphere sounding stations located near the Quasar VLBI Network observatories. The estimation of the algorithm parameters was carried out based on the analysis of measurement data from atmosphere sounding stations for the period from 2019 to 2021. As a result, refined coefficients of the algorithm for calculating the tropospheric delay were obtained, taking into account the climatic features of the observatories location. Comparison of the TWD values calculated according to the proposed scheme with similar values of the international IGS service in the of the Quasar VLBI network stations showed the coincidence of the absolute values of the TWD with an accuracy of 10 mm in the absence of precipitation.},
author = {G.~N. Ilin and V.~Yu. Bykov},
doi = {10.32876/ApplAstron.63.8-16},
issue = {63},
journal = {Transactions of IAA RAS},
keyword = {water vapor radiometer, propagation of radio signals in the atmosphere, tropospheric delay, radio sounding, tropospheric delay calculation algorithm},
note = {russian},
pages = {8--16},
title = {Refinement of the Algorithmic Parameters for Сalculating the Tropospheric Delay Using Local Radio Sounding Data of the Atmosphere},
url = {http://iaaras.ru/en/library/paper/2136/},
year = {2022}
}
```

```
TY - JOUR
TI - Refinement of the Algorithmic Parameters for Сalculating the Tropospheric Delay Using Local Radio Sounding Data of the Atmosphere
AU - Ilin, G. N.
AU - Bykov, V. Yu.
PY - 2022
T2 - Transactions of IAA RAS
IS - 63
SP - 8
AB - The calculation of the tropospheric wet delay (TWD) from the data of
remote radio sounding of the atmosphere is based on measurements of
the brightness temperature of the atmospheric radiation (BT) obtained
using a water vapor radiometer (WVR). The accuracy of the TWD
calculation is determined by two main factors: the accuracy of
measuring the radio brightness temperature of the atmosphere and the
accuracy of the models for a parameter number using the algorithm for
converting BT into the corresponding values of the TWD. Such
parameters, for example, include the effective temperature of the
atmosphere, weighted by the absorption coefficient of the radio
signal in the atmosphere, the component of the atmosphere optical
thickness associated with absorption in molecular oxygen, the value
reflecting the ratio of absorption in water vapor at WVR frequencies,
and others. Details of the TWD calculation algorithm are given in the
literature references. The model for calculating the parameters of
the algorithm is based on the data of radiosonde measurements of
vertical profiles of meteorological parameters. In order to refine
the algorithm parameters, it seems quite logical to use the data of
radio sounding stations located near the place where WVR is
installed. The modern spectral theory of the radio signal absorption
in atmospheric gases, used in the processing of a long-term series of
radiosonde profiles with meteorological parameters, makes it possible
to obtain the most accurate values of the radio signal absorption in
oxygen and water vapor and other quantities necessary for calculating
the TWD. Based on radio sounding data, it is possible to build a
regression model that takes into account seasonal fluctuations in
calculated values depending on surface temperature and pressure.
Thus, the parameters of the algorithm are tied to the WVR certain
geographical location and the climatic conditions corresponding to
this place. The calculation of the algorithm parameters was carried
out on the basis of data from atmosphere sounding stations located
near the Quasar VLBI Network observatories. The estimation of the
algorithm parameters was carried out based on the analysis of
measurement data from atmosphere sounding stations for the period
from 2019 to 2021. As a result, refined coefficients of the algorithm
for calculating the tropospheric delay were obtained, taking into
account the climatic features of the observatories location.
Comparison of the TWD values calculated according to the proposed
scheme with similar values of the international IGS service in the of
the Quasar VLBI network stations showed the coincidence of the
absolute values of the TWD with an accuracy of 10 mm in the absence
of precipitation.
DO - 10.32876/ApplAstron.63.8-16
UR - http://iaaras.ru/en/library/paper/2136/
ER -
```