Recent Update on the Commercial GNSS RO Data Assimilation in NCEP GFS

In order to enhance weather forecasts and provide risk reduction, the National Oceanic and Atmospheric Administration (NOAA) has acquired commercial Global Navigation Satellite System (GNSS) Radio Occultation (RO) data to feed its operational models. In 2020, NOAA awarded the first Delivery Order (DO) under its Indefinite Delivery Indefinite Quantity (IDIQ) contract for commercial RO data. Over the period of December 2020 to July 2023, five DOs were granted to two vendors, GeoOptics and Spire Global. Among the five DOs, the fourth DO (DO-4) provided the largest dataset, consisting of approximately 5,500 profiles per day from Spire and around 500 profiles from GeoOptics for 10 months from March 2022 to January 2023. The data volume was comparable to that of COSMIC-2. At the NOAA Environmental Modeling Center (EMC), global parallel experiments were conducted to examine the quality of the commercial RO data and its impact. The result indicated a neutral impact of the commercial RO data on the short-term GFS forecasts. Furthermore, the commercial RO data began being assimilated operationally in the GFS system shortly after the start of DO-4.

In 2023, as a follow-on to the IDIQ contract, NOAA awarded the Radio Occultation Data Buy II (RODB-2) to Spire Global and PlanetiQ. RODB-2 Delivery Order 1-Test (DO-1T) purchased 500 profiles per day from each vendor for a duration of 30 days from 5 April to 4 May 2023. RODB-2 DO-2 has been granted to PlanetiQ only, currently delivering approximately 3,100 profiles per day between July 2023 and January 2024. The results from the global parallel experiments for the commercial RO data will be presented at the conference with a focus mainly on the GeoOptics and Spire data from DO-4 and PlanetiQ data from RODB-2. Data quality control for the commercial RO observations and the impact of the data on GFS forecasts will be discussed.