GNSS-RO Data Quality Assurance for Operational Weather Forecast Using the Integrated Calibration, Verification, and Validation System

With an increasing number of GNSS Radio Occultation (RO) missions coming in the next few years, there is a great need to ensure the data quality across missions and atmospheric profile measurements from various sources. An Integrated Calibration, Verification, and Validation System is being developed at NOAA to ensure the data quality and consistency of the satellite observations for data assimilation in numerical weather prediction (NWP). GNSS-RO data have distinct advantages due to its measurement traceability to the SI unit of time. As a result, the RO data can potentially be used as anchor and to vicariously calibrate other observations. The various GNSS-RO missions require independent verification of the data processing algorithms to ensure consistency in the algorithms, data and metadata. The GNSS-RO retrievals of atmospheric profiles can be used to compare with other satellite as well as in-situ measurements to diagnose biases and monitor data quality for NWP.

In this paper, we present an comprehensive and Integrated System for the Calibration, Verification, and Validation (ICVVS) of GNSS-RO data for NWP. The system consists of several components including independent algorithm and software verification of data processing; monitoring of GNSS-RO receiver and antenna parameters for instrument performance; independent validation between GNSS-RO retrieved atmospheric profiles and other observations such as those from microwave and reference radiosonde, as well as comparison with radiative transfer models. Examples are provided to diagnose the GNSS-RO data quality including atmospheric penetration depth due to changing signal to noise ratio, and comparisons with radiosonde data. It is expected that the integrated system will be used operationally for the longterm monitoring of GNSS-RO data for operational weather forecasts.