Impact assessment of COSMIC-2 bending angle in the GSI 4D-EnVar analysis scheme operational at NCMRWF

ABSTRACT

This paper highlights the quality and impact of the COSMIC-2 bending angle through an Observation System Experiment, using a hybrid Gridpoint Statistical Interpolation – 4 Dimensional Ensemble Variational analysis scheme. The data quality is assessed by comparing it with the model’s background field. Analysis and background field that fit to temperature, humidity and wind components from radiosondes are verified, and the impact over model forecasts is evaluated using various metrics. There is an overall improvement, especially over the tropical region, where consistent and statistically significant positive impact is observed over the troposphere extending up through the lower to the middle stratosphere. A case study of the Super Cyclonic Storm AMPHAN showed minor improvement in central pressure and maximum 10 m wind speed. Reduction in the direct positional error of the cyclone track showed improvement in the analysis.

Acknowledgements

The authors thank the Head, NCMRWF for providing the necessary resources to conduct this research.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data Availability statement

The COSMIC-2 GNSS-RO data used for evaluation in this study is available upon formal request and approval from the competent authority.