the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
All-sky AMSU-A radiance data assimilation using the gain-form of Local Ensemble Transform Kalman filter within MPAS-JEDI-2.1.0: implementation, tuning, and evaluation
Abstract. The Gain-form of Local Ensemble Transform Kalman Filter (LGETKF) has been implemented in the Joint Effort for Data assimilation Integration (JEDI) with the Model for Prediction Across Scales – Atmosphere (MPAS-A) (i.e., MPAS-JEDI). LGETKF applies vertical localization in model space and is particularly convenient for assimilating satellite radiances that do not have an explicit vertical height assigned to each channel. Additional efforts are made to optimize the ensemble analysis procedure and improve the computational efficiency of MPAS-JEDI's LGETKF. This is the first application of JEDI-based LGETKF for assimilating radiance data in all-weather situations with a global MPAS configuration. The system is firstly tuned for covariance inflation and horizontal localization settings. It is found that using a combination of relaxation to prior perturbation (RTPP) and relaxation to prior spread (RTPS) outperforms using RTPP or RTPS alone, and using a smaller horizontal localization scale for all-sky radiances is preferable. With the optimized inflation and localization settings, assimilating all-sky radiances of the Advanced Microwave Sounding Unit – A (AMSU-A) window channels with an 80-member LGETKF improved the forecasts of moisture, wind, clouds, and precipitation fields, when compared to the benchmark experiment without assimilation of all-sky AMSU-A radiances. The positive forecast impact of all-sky AMSU-A radiances is the largest over the tropical regions up to 7-day. Some degradation on the temperature forecasts is seen over certain regions, where the model forecast is likely biased, causing deficiencies for assimilating all-sky data. The LGETKF capability is available in the recent public release of MPAS-JEDI and ready for research and operational explorations.
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Status: open (until 10 Jul 2025)
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RC1: 'Comment on egusphere-2025-2079', Anonymous Referee #1, 10 Jun 2025
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This paper evaluates the impacts of assimilating all-sky radiance observations using the LGETKF implementation within the MPAS-JEDI framework. The LGETKF solver is particularly suitable for this observation type, as it performs model-space localization that does not require an explicit vertical coordinate for the observations. The authors discuss improvements to the computational efficiency of the LGETKF and explore tuning strategies for covariance inflation and localization. Following these developments, the assimilation of all-sky radiance observations in a global MPAS simulation yields improvements in many atmospheric fields, with the exception of temperature.
Overall, the manuscript is clearly written and well structured. While much of the scientific content aligns closely with findings from earlier studies (and therefore may not be especially novel), the paper’s main contribution lies in its application of the new JEDI system, particularly the global implementation of LGETKF within MPAS-JEDI. Given the emerging importance of JEDI for both operational and research-oriented data assimilation systems, this study provides timely and valuable insight into the system’s performance, optimal configuration, and computational behavior. In this context, I find the manuscript suitable for publication, provided that a few minor issues are addressed (see attached PDF). A slightly stronger focus on the novelty and implications of using the JEDI system would also enhance the paper’s contribution.
Data sets
Global Forecast System analyses National Centers For Environmental Prediction/National Weather Service/NOAA/U.S. Department Of Commerce https://rda.ucar.edu/datasets/ds084.1/
Global Ensemble Forecast System ensemble analyses NOAA https://www.ncei.noaa.gov/products/weather-climate-models/global-ensemble-forecast
Conventional and satellite observations National Centers For Environmental Prediction/National Weather Service/NOAA/U.S. Department of Commerce https://rda.ucar.edu/datasets/d337000
Conventional and satellite observations National Centers For Environmental Prediction/National Weather Service/NOAA/U.S. Department Of Commerce https://rda.ucar.edu/datasets/d735000/
ATMS radiance data NOAA https://sounder.gesdisc.eosdis.nasa.gov/opendap
Model code and software
MPAS-JEDI 2.1.0 Joint Center for Satellite Data Assimilation & National Center for Atmospheric Research https://doi.org/10.5281/zenodo.15201032
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