COSMIC‐2 Radio Occultation Constellation: First Results

Schreiner, William S.; Weiss, Jie W; Anthes, Richard A.; Braun, John; Chu, Vicky; Fong, Jolene; Hunt, Doug; Kuo, Ying Hwa; Meehan, T. K.; Serafino, W.; Sjoberg, Jeremiah P.; Sokolovskiy, Sergey; Talaat, E. R.; Wee, Tae-Kwon; Zeng, Zhen

doi:10.1029/2019gl086841

Cited by 189 publications

(148 citation statements)

References 27 publications

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“…Besides the different data coverage, the FS7 satellites are capable of receiving signals from both the Global Positioning System (GPS) and Globalnaya Navigatsionnaya Sputnikovaya Sistema (GLONASS) [6]. FS7 satellites carry an antenna with a higher signal-to-noise ratio (SNR), which thus allows a deeper penetration of the ray into the lower troposphere and better detection of the atmospheric boundary layer (ABL) top and super-refraction (SR) on top of the ABL [7]. The six satellites of the FS7 constellation were successfully launched on 25 June 2019, and the FS7 neutral atmosphere data were officially released on 10 December 2019.…”

Section: Introductionmentioning

confidence: 99%

“…Applications of FS3 RO data to many aspects of weather prediction and analysis can be found in a number of literatures and have been documented in detail by [1]. The authors of [7] compared the FS7 RO data with different datasets and showed that the FS7 data possess high accuracy and precision. For example, they compared the FS7 RO dry products (bending angle and refractivity) with the European Centre for Medium-Range Weather Forecasts (ECMWF) short-term forecasts and showed that the RO data are quite consistent, with very small biases between 6 and 40 km.…”

Section: Introductionmentioning

confidence: 99%

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An Analysis Study of FORMOSAT-7/COSMIC-2 Radio Occultation Data in the Troposphere

et al. 2021

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This study investigates the Global Navigation Satellite System (GNSS) radio occultation (RO) data from FORMOSAT-7/COSMIC-2 (FS7/C2), which provides considerably more and deeper profiles at lower latitudes than those from the former FORMOSAT-3/COSMIC (FS3/C). The statistical analysis of six-month RO data shows that the rate of penetration depth below 1 km height within ±45° latitudes can reach 80% for FS7/C2, significantly higher than 40% for FS3/C. For verification, FS7/C2 RO data are compared with the observations from chartered missions that provided aircraft dropsondes and on-board radiosondes, with closer observation times and distances from the oceanic RO occultation over the South China Sea and near a typhoon circulation region. The collocated comparisons indicate that FS7/C2 RO data are reliable, with small deviations from the ground-truth observations. The RO profiles are compared with collocated radiosondes, RO data from other missions, global analyses of ERA5 and National Centers for Environmental Prediction (NCEP) final (FNL), and satellite retrievals of NOAA Unique Combined Atmospheric Processing System (NCAPS). The comparisons exhibit consistent vertical variations, showing absolute mean differences and standard deviations of temperature profiles less than 0.5 °C and 1.5 °C, respectively, and deviations of water vapor pressure within 2 hPa in the lower troposphere. From the latitudinal distributions of mean difference and standard deviation (STD), the intertropical convergence zone (ITCZ) is evidentially shown in the comparisons, especially for the NUCAPS, which shows a larger deviation in moisture when compared to FS7/C2 RO data. The sensitivity of data collocation in time departure and spatial distance among different datasets are presented in this study as well.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

An Analysis Study of FORMOSAT-7/COSMIC-2 Radio Occultation Data in the Troposphere

et al. 2021

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“…4 | EVALUATION OF COSMIC-2 IMPACTS ON NWP Schreiner et al (2020) have already demonstrated the quality of the COSMIC-2 bending angle profiles by comparing with NWP analyses and reanalyzes. We obtain similar results in these kind of comparisons, but they will not be reproduced here.…”

Section: Assumed Bending Angle Uncertaintymentioning

confidence: 99%

“…COSMIC-2 provides measurements made with GPS and GLONASS signals for the first time. Schreiner et al (2020) have presented the first estimates for the precision and accuracy of the GPS and GLONASS COSMIC-2 data, by computing differences of nearby COSMIC-2 profiles, and comparing them with both NWP short-range forecasts and reanalyzes. They emphasize that an important aim of this mission is to improve the GNSS-RO measurement quality in the troposphere, with the use of an advanced Tri-GNSS Radio Occultation System (TGRS) instrument.…”

Section: Introductionmentioning

confidence: 99%

Forecast Impact of FORMOSAT‐7/COSMIC‐2 GNSS Radio Occultation Measurements

Ruston¹,

Healy

2020

Atmospheric Science Letters

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The FORMOSAT-7/COSMIC-2 GNSS-RO mission was launched on June 25, 2019, and it has provided a large increase in the number of GNSS-RO observations available for operational numerical weather prediction (NWP) in the latitude band between ±40. A key aim of this mission has been to improve the GNSS-RO measurement quality in the lower and middle troposphere. In this study, we summarize the impact of the FORMOSAT-7/COSMIC-2 measurements in two independent NWP systems, which are now assimilating these measurements operationally. These are the United States Navy Global Environmental Model (NAVGEM) and the European Center for Medium-Range Weather Forecasts (ECMWF) Integrated Forecasting System (IFS). Both systems employ a 4-dimensional variational system (4D-Var), and assimilate GNSS-RO bending angles. The experiments cover the period January to March 2020. The impact of the FORMOSAT-7/COSMIC-2 measurements is assessed using improvements in short-range forecast departures to other observations such as radiosonde and radiances, forecast error statistics against a verifying analysis, and adjoint based Forecast Sensitivity to Observation Impact (FSOI) estimates. The FORMOSAT-7/COSMIC-2 measurement has a clear impact on stratospheric temperatures and winds in the tropics. A novel finding is that the measurements also improve the tropical tropospheric humidity fit to radiosondes, and the fit to tropospheric radiances sensitive to humidity. To date, the impact of GNSS-RO on humidity has been difficult to demonstrate in well constrained, operational NWP systems assimilating the full suite of observations. The results are achieved with a conservative assimilation approach which extended the quality control and observation error assignments used for the previous COSMIC receivers; further, possible improvements to the assimilation strategy are noted.

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“…RS stations are distributed more densely in East Asia, Europe, and North America than elsewhere. Satellite missions, such as the Constellation Observing System for Meteorology, Ionosphere, and Climate-1, -2 [5][6][7], provide nearly evenly and densely distributed RO profiles over the world, making up for the lack of conventional observations over the ocean.…”

Section: Introductionmentioning

confidence: 99%

Global 3D Features of Error Variances of GPS Radio Occultation and Radiosonde Observations

Zou

2020

Remote Sensing

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Global Positioning System (GPS) radio occultation (RO) and radiosonde (RS) observations are two major types of observations assimilated in numerical weather prediction (NWP) systems. Observation error variances are required input that determines the weightings given to observations in data assimilation. This study estimates the error variances of global GPS RO refractivity and bending angle and RS temperature and humidity observations at 521 selected RS stations using the three-cornered hat method with additional ERA-Interim reanalysis and Global Forecast System forecast data available from 1 January 2016 to 31 August 2019. The global distributions, of both RO and RS observation error variances, are analyzed in terms of vertical and latitudinal variations. Error variances of RO refractivity and bending angle and RS specific humidity in the lower troposphere, such as at 850 hPa (3.5 km impact height for the bending angle), all increase with decreasing latitude. The error variances of RO refractivity and bending angle and RS specific humidity can reach about 30 N-unit2, 3 × 10−6 rad2, and 2 (g kg−1)2, respectively. There is also a good symmetry of the error variances of both RO refractivity and bending angle with respect to the equator between the Northern and Southern Hemispheres at all vertical levels. In this study, we provide the mean error variances of refractivity and bending angle in every 5°-latitude band between the equator and 60°N, as well as every interval of 10 hPa pressure or 0.2 km impact height. The RS temperature error variance distribution differs from those of refractivity, bending angle, and humidity, which, at low latitudes, are smaller (less than 1 K2) than those in the midlatitudes (more than 3 K2). In the midlatitudes, the RS temperature error variances in North America are larger than those in East Asia and Europe, which may arise from different radiosonde types among the above three regions.

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COSMIC‐2 Radio Occultation Constellation: First Results

Cited by 189 publications

References 27 publications

An Analysis Study of FORMOSAT-7/COSMIC-2 Radio Occultation Data in the Troposphere

An Analysis Study of FORMOSAT-7/COSMIC-2 Radio Occultation Data in the Troposphere

Forecast Impact of FORMOSAT‐7/COSMIC‐2 GNSS Radio Occultation Measurements

Global 3D Features of Error Variances of GPS Radio Occultation and Radiosonde Observations

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