Asymmetric tropospheric delays from numerical weather models for UT1 determination from VLBI Intensive sessions on the baseline Wettzell–Tsukuba

2010 ◽  
Vol 84 (5) ◽  
pp. 319-325 ◽  
Author(s):  
Johannes Böhm ◽  
T. Hobiger ◽  
R. Ichikawa ◽  
T. Kondo ◽  
Y. Koyama ◽  
...  
Keyword(s):  
Numerical Weather ◽  
Numerical Weather Models ◽  
Tropospheric Delays ◽  
Weather Models

scholarly journals Validation of a New Model for the Estimation of Residual Tropospheric Delay Error Under Extreme Weather Conditions

2018 ◽  
Author(s):  
Ildikó Juni ◽  
Szabolcs Rózsa
Keyword(s):  
Systematic Error ◽  
Solution Space ◽  
Global Navigation Satellite Systems ◽  
Performance Standard ◽  
Tropospheric Delay ◽  
Electron Content ◽  
Numerical Weather ◽  
Numerical Weather Models ◽  
Tropospheric Delays ◽  
Weather Models

The electromagnetic signals of the Global Navigation Satellite Systems (GNSS) satellites suffer delays while propagating through the troposphere. The tropospheric delay is a significant systematic error of GNSS positioning. For safety-of-life applications of positioning many systematic error effects are either mitigated or eliminated in the positioning solution. Space based augmentation systems provide corrections for the orbital and satellite clock error, the ionospheric effects, etc. Moreover advanced GNSS provide dual frequency code observations for civilian users to eliminate the ionospheric delays caused by the electron content of the upper atmosphere. Nevertheless tropospheric delays are still taken into account using empirical models.For safety-of-life applications besides the accuracy of the positioning, the integrity of the positioning service is an important factor, too. The integrity information includes the maximal positioning error at an extremely rare probability level, called protection level to ensure highly reliable position solution in the aviation. The Radio Technical Commission for Aeronautics Minimum Operational Performance Standard (RTCA MOPS) recommends 0.12 m as the maximum zenith tropospheric error in terms of standard deviation. Previous studies show that this recommendation seems to be too conservative leading to a lower service availability. Therefore a more realistic integrity model has to be derived for the estimation of maximal residual tropospheric delay error.In the recent years many advanced empirical tropospheric delay models have been formulated compared to the one recommended by the RTCA. Recently new integrity models have been derived for estimating the maximum residual tropospheric delay error using numerical weather models under real extreme weather.The aim of this paper is to study the reliability of these models conditions. In order to achieve this, high-resolution numerical weather models were ray-traced using an improved ray-tracing algorithm to evaluate the slant and zenith tropospheric delays with the geographical resolution of 0.1° × 0.1°.

scholarly journals Benchmark campaign and case study episode in Central Europe for development and assessment of advanced GNSS tropospheric models and products

2016 ◽  
Author(s):  
J. Douša ◽  
G. Dick ◽  
M. Kačmařík ◽  
R. Brožková ◽  
F. Zus ◽  
...  
Keyword(s):  
Central Europe ◽  
Functional Model ◽  
Heavy Precipitation ◽  
Severe Weather ◽  
Path Delay ◽  
Numerical Weather ◽  
Horizontal Gradients ◽  
Numerical Weather Models ◽  
Zenith Path Delay ◽  
Weather Models

Abstract. Initial objectives and design of the Benchmark campaign organized within the European COST Action ES1206 (2013-2017) are described in the paper. This campaign has aimed at supporting the development and validation of advanced GNSS tropospheric products, in particular high-resolution and ultra-fast zenith total delays (ZTD) and tropospheric gradients derived from a dense permanent network. A complex dataset was collected for the 8-week period when several extreme heavy precipitation episodes occurred in central Europe which caused severe river floods in this area. An initial processing of data sets from Global Navigation Satellite System (GNSS) and numerical weather models (NWM) provided independently estimated reference parameters – zenith tropospheric delays and tropospheric horizontal gradients. Their provision gave an overview about the product similarities and complementarities and thus a potential for improving a synergy in their optimal exploitations in future. Reference GNSS and NWM results were inter-compared and visually analysed using animated maps. ZTDs from two reference GNSS solutions compared to global ERA-Interim re-analysis resulted in the accuracy at the 10-millimeter level in terms of RMS (with a negligible overall bias), comparisons to global GFS forecast showed accuracy at the 12-millimeter level with the overall bias of -5 mm and, finally, comparisons to mesoscale ALADIN-CZ forecast resulted in the accuracy at the 8-milllimetre level with a negligible total bias. The comparison of horizontal tropospheric gradients from GNSS and NWM data demonstrated a very good agreement among independent solutions with negligible biases and the accuracy of about 0.5 mm. Visual comparisons of maps of zenith wet delays and tropospheric horizontal gradients showed very promising results for future exploitations of advanced GNSS tropospheric products in meteorological applications such as severe weather event monitoring and weather nowcasting. The GNSS products revealed a capability of providing more detailed structures in atmosphere than the state-of-the-art numerical weather models are able to capture. Initial study on contribution of hydrometeors (e.g. cloud water, ice or snow) to GNSS signal delays during severe weather reached up to 17 mm in zenith path delay and suggested to carefully account them within the functional model. The reference products will be further exploited in various specific studies using the Benchmark dataset. It is thus going to play a key role in these highly inter-disciplinary developments towards better mutual benefits from advanced GNSS and meteorological products.

Impact of Numerical Weather Models on Gravity Field Analysis

2015 ◽  
pp. 355-365
Author(s):  
Maria Karbon ◽  
Johannes Böhm ◽  
Elisa Fagiolini ◽  
Frank Flechtner ◽  
Harald Schuh
Keyword(s):  
Gravity Field ◽  
Field Analysis ◽  
Numerical Weather ◽  
Numerical Weather Models ◽  
Weather Models
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