A Novel Tool for the Determination of Tropopause Heights by Using GNSS Radio Occultation Data

Vespe, F.; Pacione, R.; Rosciano, Elisa

doi:10.4236/acs.2017.73022

Cited by 7 publications

(4 citation statements)

References 30 publications

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“…Second, in the tropics, the coldest point of the temperature (CPT) is well marked, and more meaningful than the temperature lapse rate to identify the tropopause. Other possible tropopause definitions concern ozone or other gas concentrations [62,69], potential vorticity [70], and definitions based on the bending angle profile in an RO, corresponding to an irregular pattern [6] or to a deviation from bending angle models with a constant temperature lapse rate hypothesis, as that of Hopfield [71]. In this study, temperature being the only quantity available for both the datasets, we opted for a temperature-based definition for the tropopause.…”

Section: Water Vapor In the Stratospherementioning

confidence: 99%

Comparisons of Different Methods to Determine Starting Altitudes for Dry Air Atmosphere by GNSS-RO Data

Andrisani

Vespe

2021

Atmosphere

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Boundary profile evaluation (BPV) is an approach proposed in order to estimate water vapor content in the atmosphere. It exploits radio occultation (RO) observations of the signals emitted by the satellites of global navigation systems (GNSS) which are eclipsing (rising) as viewed by a low earth orbit satellite (LEO). BPV requires, as a preliminary step, the estimation of the dry background atmosphere model of refractivity (i.e., obtained from bending angle profiles) to be subtracted from the real observations in order to extract water vapor profiles. The determination of the lowest layer of the atmosphere over which the concentration of water vapor can be deemed negligible is particularly crucial for a correct application of the BPV method. In this study, we have applied three methods to set the starting altitudes for the dry air layers of the atmosphere: (1) by air temperature below some threshold values (for example, 250 K); (2) by “smooth” bending angle profiles in ROs; (3) by saturated water vapor pressure. These methods were tested with thermodynamic and bending angle profiles from 912 radiosonde excursions colocated with RO observations. For every dry air starting altitude we determined the best estimator from each of the three methods. In particular, by comparing those estimators with the quantiles and momenta of the dry air starting altitude distributions, we achieved improvements of up to 50% of the humidity profiles.

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Section: Water Vapor In the Stratospherementioning

confidence: 99%

Comparisons of Different Methods to Determine Starting Altitudes for Dry Air Atmosphere by GNSS-RO Data

Andrisani

Vespe

2021

Atmosphere

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“…Additionally, the tropopause serves as the upper limit for the integration of tropospheric parameters in physics and chemistry, including tropospheric temperature [11] and tropospheric column ozone [12]. The TPH can be determined from the use of radiosonde data [7,[13][14][15] or from Global Navigation Satellite System (GNSS) radio occultation (RO) data from different satellites [5,[16][17][18][19][20][21][22][23][24][25].…”

Section: Introductionmentioning

confidence: 99%

“…be determined from the use of radiosonde data [7,[13][14][15] or from Global Navigation Satellite System (GNSS) radio occultation (RO) data from different satellites [5,[16][17][18][19][20][21][22][23][24][25].…”

Section: Introductionmentioning

confidence: 99%

Evaluation of Tropopause Height from Sentinel-6 GNSS Radio Occultation Using Different Methods

Zhran,

Mousa,

Alshehri

et al. 2023

Remote Sensing

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The tropopause is described as the distinction between the troposphere and the stratosphere, and the tropopause height (TPH) is an indicator of climate change. GNSS Radio Occultation (RO) can monitor the atmosphere globally under all weather conditions with a high vertical resolution. In this study, four different techniques for identifying the TPH were investigated. The lapse rate tropopause (LRT) and cold point tropopause (CPT) methods are the traditional methods for determining the TPH based on temperature profiles according to the World Meteorological Organization (WMO) definition. Two advanced methods based on the covariance transform (CT) method are used to estimate the TPH from the refractivity (TPHN) and the TPH from the bending angle (TPHα). Data from the Sentinel-6 satellite were used to evaluate the different algorithms for the identification of the TPH. The analysis shows that the CPT height is greater than the LRT height and that the CPT is only valid in tropical regions. The CPT height, TPHN, and TPHα were compared with the LRT height. In general, the TPHα had the largest value, followed by the TPHN, and the LRT had the lowest value of TPH at and near the equator. In the equatorial region, the maximum TPH results from the TPHα (approximately 17.5 km), and at the poles, the minimum TPH results from the LRT (approximately 9 km). The results were also compared with the European Center for Medium-Range Weather Forecasts (ECMWF), and there was a strong correlation of 0.999 between the different approaches for identifying the TPH from RO and the ECMWF model. The identification of the TPH is critical for the transfer of mass, water, and trace gases between the troposphere and stratosphere.

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“…In the last decade, some studies used a large dataset of bending angles (BAs) derived from the Global Navigation Satellite System Radio Occultation (GNSS-RO) to determine the tropopause. However, to derive physical atmospheric profiles, parametric dry atmospheric refractivity models are required [9][10][11]. In addition, the GNSS-RO vertical resolution is lower than the radiosondes resolution, which leads to lower accuracy.…”

Section: Introductionmentioning

confidence: 99%

Global Empirical Models for Tropopause Height Determination

2022

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The calculation of the tropopause height is crucial to the investigation of fundamental interactions between the troposphere and stratosphere, playing an essential role in areas such as climatology, geodesy, geophysics, ecology, and aeronautics. Since the troposphere and stratosphere have many distinct features, it is possible to define the boundary between them using different variables, such as temperature lapse rate, potential vorticity and chemical concentrations. However, according to the chosen variable, different tropopause definitions are created, each one with some limitations. Using 41 years of European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis (ERA5) data, we examined the variability of the tropopause for the north and south hemispheres and developed two models, both based on blending the potential vorticity and thermal tropopauses. One model (based on a sigmoid function, named STH) depends only on latitude and day of the year, while the other model (based on bilinear interpolation, named BTH) requires an additional look-up table. In order to account for the different behaviors of the tropopauses in the north and south hemispheres, we estimated two sets of model coefficients (one for each hemisphere). When compared against a benchmark of estimated tropopause heights during three years of radiosonde data, we obtained an average RMSE for the differences of 0.88 km for the STH model and 0.67 km for the BTH model. A similar comparison for alternative models available in the literature shows that the new models have superior performance and represent a significant improvement in tropopause height determination.

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A Novel Tool for the Determination of Tropopause Heights by Using GNSS Radio Occultation Data

Cited by 7 publications

References 30 publications

Comparisons of Different Methods to Determine Starting Altitudes for Dry Air Atmosphere by GNSS-RO Data

Comparisons of Different Methods to Determine Starting Altitudes for Dry Air Atmosphere by GNSS-RO Data

Evaluation of Tropopause Height from Sentinel-6 GNSS Radio Occultation Using Different Methods

Global Empirical Models for Tropopause Height Determination

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