Assimilation Impact of Early FORMOSAT-7/COSMIC-2 GNSS Radio Occultation Data with Taiwan’s CWB Global Forecast System

Lien, Guo-Yuan; Lin, C.; Huang, Zih Mao; Teng, Wen Hsin; Chen, Jen Her; Lin, Ching‐Yu; Ho, H. H.; Huang, Jyun Ying; Hong, Jiman; Cheng, Chia Ping; Huang, Ching Yuang

doi:10.1175/mwr-d-20-0267.1

Cited by 16 publications

(16 citation statements)

References 59 publications

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“…The Constellation Observing System for Meteorology, Ionosphere, and Climate mission II (COSMIC‐2; also known as the Formosa Satellite mission 7) that launched in June 2019 is the latest GNSS RO satellite system (Schreiner et al., 2020). The early results showed that COSMIC‐2 data benefited the global and regional forecasts and research (Cucurull & Casey, 2021; Lien et al., 2021; Singh et al., 2021). In this study, we test the hypothesis that assimilating GNSS RO data significantly improves the overall performance of TC formation forecasts, including false alarms, and explore the physical reasons behind such improvement.…”

Section: Introductionmentioning

confidence: 99%

Potential Impacts of Radio Occultation Data Assimilation on Forecast Skill of Tropical Cyclone Formation in the Western North Pacific

Teng

Kuo

Done

2023

Geophysical Research Letters

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Section: Introductionmentioning

confidence: 99%

Potential Impacts of Radio Occultation Data Assimilation on Forecast Skill of Tropical Cyclone Formation in the Western North Pacific

Teng

Kuo

Done

2023

Geophysical Research Letters

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“…Chen, Liu, et al ., 2021). A positive impact of assimilating the FS7‐C2 data on weather forecasts has been obtained in the Tropics in some preliminary studies (Lien et al ., 2021; S.‐Y. Chen, Nguyen, and Huang, 2021).…”

Section: Introductionmentioning

confidence: 99%

“…Nevertheless, Lien et al . (2021) also reported that the RO data under a few kilometers tend to be rejected due to the issues of larger data uncertainty and negative bias. Schreiner et al .…”

Section: Introductionmentioning

confidence: 99%

Understanding the impact of assimilating FORMOSAT‐7/COSMIC‐2 radio occultation refractivity on tropical cyclone genesis: Observing system simulation experiments using Hurricane Gordon (2006) as a case study

Yang

Chen

Chang

2023

Quart J Royal Meteoro Soc

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Studies have shown that assimilating the radio occultation (RO) observations, including those from the FORMOSAT-3/COSMIC (constellation observing systems for meteorology, ionosphere, and climate) (FS3-C), provides positive impacts on tropical cyclone (TC) forecasts. The FS3-C's successor, the FORMOSAT-7/COSMIC-2 (FS7-C2), provides denser spatial data coverage over the Tropics and Subtropics, where severe weather systems often occur. This study investigates the impact of FS7-C2 refractivity profiles on the prediction of TC genesis. A quick observing system simulation experiment is conducted for the period when Hurricanes Helene and Gordon (2006) occurred over the North Atlantic Ocean using a regional ensemble data assimilation system. Though assimilating FS3-C or FS7-C2 ROs successfully reproduces Helene's development, assimilating FS7-C2 ROs better captures the genesis and development of Gordon with abundant moisture and vorticity in Gordon's core region, providing conditions favorable for the development of deep convection. A minimum area-mean total precipitable water vapor of 54 mm, as well as the existence of mid-level cyclonic vorticity (e.g., 500 hPa), at the storm core region in the initial condition is required for forecasting Gordon's genesis. Also, the assimilation of FS7-C2 ROs in our experiments reduces the 500 hPa geopotential error by 22% and improves probabilistic quantitative precipitation forecast compared with assimilating FS3-C ROs. Two sensitivity tests are conducted to evaluate the impact of low-level negatively biased FS7-C2 RO profiles and the removal of FS7-C2 data below 3 km on Gordon's genesis. The former test does not degrade Gordon's genesis forecast skills due to a dipole error correlation between the background ROs and the moisture field over an observed RO profile near Gordon. The latter test does degrade Gordon's forecast skills but is still better than the assimilation of FS3-C ROs since the features of low-level moisture and mid-level vorticity are preserved to some extent.

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“…Each receiver was integrated with four antennas, two for determining precise satellite orbit and other two to provide principal measurements of radio occultation. As a mainline task for numerical weather prediction and climatology, UCAR had processed the raw RO measurement data to retrieve neutral atmosphere parameter since October 1st, 2019, for which improved the reliability of global climate monitoring by unique RO properties (Healy S. 2020;Benjamin R et al 2021;Guo Y et al 2021).…”

Section: Introductionmentioning

confidence: 99%

Un-differential processing of COSMIC-2 radio occultation measurements with 1-Hz LEO clock corrections

Guo

Zhang

Meng

et al. 2023

Preprint

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Precise isolating atmospheric excess phase (AEP) is the fundamental work of Global Navigation Satellite System (GNSS) radio occultation technique towards reconstructing on the refractivity and other meteorological profiles. Currently, the COSMIC-2 satellites AEP products from University Corporation for Atmospheric Research (UCAR) were calculated by conventional single-differential approach at cost of complicating the processing and also amplified the excess phase noise. This study provided a strengthened un-differential method for COSMIC-2 AEP calculation such that the interpretation of raw occulting phase data could be enriched. The vital bias, receiver clock offset, was modeled and calibrated at 1s sampling via pre-processing of LEO precise orbit determination, which took both two antennas’ observations into estimator for intensifying orbit and clock precision. After combining the un-differential method with 1s LEO receiver clock corrections, COSMIC-2 AEP was calculated and collected to retrieve the refractivity profiles for statistical validation. Analyzation of 2579 RO profiles indicates that the mean bias of our results against COSMIC-2 official refractivity profiles were below 0.2% at height above 10km. Furthermore, external reference of European Centre for Medium-Range Weather Forecasts (ECMWF) analysis data was adopted for revealing the characteristics of bias and investigating the advantage of un-differential approach. Validation indicates that the standard deviation (STD) of un-difference derived refractivity against co-located referred profiles were around 1.17% and 1.28% for GPS and GLONASS occultations at altitude below 35km, appearing bias less than 0.04% against single difference method derived. The un-difference processing also shows higher accuracy than single difference in the lower troposphere. Hence, the proposed UD processing for COSMIC-2 radio occultation retrieval is feasible when the 1s LEO clock offsets were estimated for correction.

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Assimilation Impact of Early FORMOSAT-7/COSMIC-2 GNSS Radio Occultation Data with Taiwan’s CWB Global Forecast System

Cited by 16 publications

References 59 publications

Potential Impacts of Radio Occultation Data Assimilation on Forecast Skill of Tropical Cyclone Formation in the Western North Pacific

Potential Impacts of Radio Occultation Data Assimilation on Forecast Skill of Tropical Cyclone Formation in the Western North Pacific

Understanding the impact of assimilating FORMOSAT‐7/COSMIC‐2 radio occultation refractivity on tropical cyclone genesis: Observing system simulation experiments using Hurricane Gordon (2006) as a case study

Un-differential processing of COSMIC-2 radio occultation measurements with 1-Hz LEO clock corrections

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