National Aeronautics and Space Administration

GEOS-5.29.5-p6 was implemented starting with the 12:00 UTC cycle on May 22, 2024. An update was made to the assimilation system that improves the use of several microwave data-types and incorporates an additional source of ozone data. The changes include an improvement to the data-selection process for bias-correcting GMI radiances; reinitialization of the bias correction coefficients for AMSU-A and ATMS radiances; and active assimilation of OMPS-LP ozone observations (which were previously implemented as a passive data-type). Collectively, these changes provide a small but measurable improvement in the overall quality of the analysis.

GEOS-5.29.5-p5 was implemented starting with the 12:00 UTC cycle on March 7, 2024. An update was made in the assimilation system to account for erroneous reports of observed surface pressure from some ships. The change involves replacing the observed pressure with the mean sea level pressure at the report location if the two differ by more than 0.1 hPa. This discrepancy most often occurs when the ship's barometer height is not accurately accounted for in the observed pressure. The updated procedure reduces the bias in the analyzed surface pressure in the vicinity of the report locations and improves the forecast impact of these data.

GEOS-FP will be upgraded to GEOS-5.29.5 on February 7, 2023 with the 06:00 UTC assimilation cycle. There are no changes to the file formats documented in the GEOS-FP File Specification or access methods via the NCCS Data Portal with this upgrade. There may be some delay in producing and posting the 06:00 UTC assimilation data, but the 12:00 UTC forecast cycle is expected to start at the normal time.

Version 5.29.5 of the GEOS atmospheric data assimilation system includes a limited number of updates to both the analysis scheme and forecast model. In the analysis, commercially produced radio occultations from SPIRE are now assimilated, sourced from NOAA’s real-time commercial data purchase. This brings the total number of radio occultations assimilated in each 6-hr analysis cycle to approximately 450,000 on average, or an increase of roughly 45% compared with version 5.29.4 of the GEOS system. Also in the analysis, the maximum height for assimilation of (all) radio occultation data has been lowered from 60 km to 55 km, for better consistency with the vertical discretization of the model. Finally, an information data base has been introduced to control changes in the availability and usage of conventional observations (similar to the method used for satellite radiances) but this is a zero-difference change. In the forecast model, the orbital parameters used in the radiation scheme have been updated, which yields only a minor change in the model solution.

Overall, these updates provide a neutral to small positive impact on the GEOS analysis and short-term forecast performance, as revealed by traditional skill-scores and estimates of analysis errors for wind, temperature and specific humidity, with the largest impacts observed in the tropical middle troposphere. The impact is due primarily to the assimilation of the additional radio occultation data.

The GMAO will be upgrading the GEOS Forward Processing (GEOS FP) system, from GEOS-5.27.1 to GEOS-5.29.4 starting with the 06:00 UTC cycle on Tuesday, March 1, 2022. There may be a short delay in producing the 06:00 GMT forecast on that day.

This upgrade will not result in any structural changes to products documented in the GEOS FP File Specification, which is available at the link included at the bottom of this notice. Formats and access methods for GEOS FP will remain the same.

Version 5.29.4 of the GEOS atmospheric data assimilation system includes updates to both the analysis and forecast model. For the analysis, these include changes to both the algorithm and input observing system. The radiative transfer model used in the GSI has been updated to CRTM version 2.3.0, and modifications have been made to the treatment of GOES-16 satellite winds, the observation operator for radio occultation data, and the handling of buoy observations at high latitudes. Updates to the input observing system include the assimilation of IR radiances from IASI on Metop-C as well as radio occultations from KOMPSAT and Paz. The forecast model has been updated to version 1.12.3 of the code base, this includes several technical updates and a bug-fix in the Henry’s law wet deposition code within the Grell-Freitas convection scheme and updated scavenging coefficients for gaseous constituent species CO, CO2, CH4 and NH3. Finally, the MAPL software interface layer has been updated to MAPL-2.

Overall, these updates provide significant positive impact on the GEOS analysis and short-term forecast performance, as revealed by the forecast fit to observations and traditional skill-scores, including reduced root mean square errors and increased anomaly correlations. The largest improvements occur in the tropical wind field at almost all levels, but statistically significant improvements also occur in the temperature and humidity fields. The impacts in the extratropics are neutral to slightly positive. The bulk of the improved performance appears due to the revised treatment of the GOES-16 satellite winds, with smaller contributions from the remaining analysis system updates. Updates to the forecast model for this implementation are mostly technical in nature with the exception of the revised scavenging updates, which provide more realistic concentrations for some gaseous and aerosol species.

The GMAO will be upgrading the GEOS Forward Processing (GEOS FP) system, from GEOS-5.25.1-p5 to GEOS-5.27.1, starting with the 06:00 UTC cycle on Thursday February 25, 2021.

This upgrade will not result in any changes to products documented in the GEOS FP File Specification, which is available at the link included at the bottom of this notice. Formats and access methods for GEOS FP will remain the same.

Version 5.27.1 of the GEOS atmospheric data assimilation system includes significant updates to the GSI analysis code plus numerous additions to the input observing system. There are no significant changes to the GEOS model in this update.

The updated GSI code is a merged version of the latest NCEP and GMAO code bases. Active new features include variational bias correction of aircraft temperature observations, modified observation operator for GNSS RO (radio occultation) data, a reformulated atmosphere-ocean interface layer suitable for coupled model applications, and reformatted diagnostic output to facilitate development of a future (JEDI-based) version of the assimilation system.

Updates to the input observing system include the assimilation all-sky radiances from MHS (all platforms) and GCOM-W AMSR-2 (over water only). The AMSR-2 radiances are new to GEOS, while the MHS radiances were previously assimilated in clear-sky conditions only. Ozone-sensitive radiances are assimilated for all hyperspectral infrared instruments. Observations from the Metop-C satellite are assimilated, including radiances from AMSU-A and MHS, plus radio occultations from GRAS. CrIS full spectral resolution (FSR) radiances from SNPP and NOAA-20 are assimilated (over water only), with channel-correlated observation errors. Finally, radio occultations from the COSMIC-2 constellation of (six) satellites are assimilated.

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On January 30, 2020, GMAO upgraded GEOS-FP to GEOS-5.25.1-p3. The GMAO is announcing an update to this system, GEOS-5.25.1-p5, to be implemented at 06:00 UTC on April 7, 2020. This new update introduces two changes to the GEOS model that are needed to rectify deficiencies detected in the 5.25.1-p3 version of the GEOS-FP system. There are no changes to the file specification or data access methods for GEOS-FP data.

The first change is an update of the RRTMG-SW code to v4.10 from the developers at Atmospheric and Environmental Research (AER). This update addresses a cold bias of up to ~2K°/day in the heating tendency in the stratosphere, between 10-0.1mb, peaking at 1mb in the Tropics and summer hemisphere. The AER developers have provided an update to the correlated k-Distribution (CKD) for band 28 (~ 200-263 nm), in which both ozone and molecular oxygen are significant absorbers. This change significantly reduces the underestimate in solar heating rates that lead to this cold bias in the temperature analyses and forecasts.

The second change is to the Grell-Freitas deep convection code. It addresses errors in the convective mass flux diagnostics which have downstream impacts on moist processes and transport in the GEOS-FP system. These patches resolve an underestimation of cloud ice in the tropical upper troposphere and associated errors in outgoing longwave radiation comparisons with CERES-EBAF. Another patch to the Grell-Freitas code corrects an evaporation-check bug introduced in the previous GEOS-FP system: this bug fix results in improved extratropical skill scores for heights in the mid-troposphere.

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The GMAO will be upgrading the GEOS Forward Processing (GEOS FP) system, from GEOS-5.22.0 to GEOS-5.25.1, starting with the 06:00 UTC cycle this Thursday January 30, 2020. The 06:00 UTC assimilation will be delayed by a few hours. There is also a chance there will be a short delay initializing the 12 UTC 5-day forecast cycle.

This upgrade will add a new variable to the tavg3_2d_adg_Nx collection:
    NISV: nitrate tendency due to convective scavenging
Due to technical issues, the assimilation time-series of this collection will no longer be available on OpenDAP, but it will remain available for the daily forecasts. Assimilation and forecast versions can still be downloaded via HTTPS.

This upgrade will not result in any other changes to the file specification, formats, or access methods for GEOS FP data.

The new release of the GEOS atmospheric data assimilation system includes changes to both the forecast model and the analysis scheme.

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The GMAO will make an adjustment to the GEOS FP-IT production stream, that will lead to small discontinuities in some fields. This adjustment is tentatively scheduled for June 13, 2019.

The adjustment corrects a problem in the GEOS FP-IT analyses that began on September 30, 2017, and has persisted until the present day. The impact is generally quite small and was discovered only recently. The following impacts have been detected:

• A jump of approximately 0.5hPa in MSLP over the high latitudes of the southern hemisphere (30-70° S)
• A corresponding cooling of several tenths of a Kelvin in the lower troposphere at these latitudes
• Decreases of about 20-40% in cumulus mass flux and cloud liquid water in the middle tropical troposphere
• A small decrease of about 1-2% in global low-cloud fraction by about 1-2%

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The GEOS Forward Processing (GEOS FP) system upgrade from GEOS-5.21.2 to GEOS-5.22.0 was completed successfully on March 13, 2019. This upgrade does not result in any changes to the file specification, formats, or access methods for GEOS FP data.

The new release of the GEOS atmospheric data assimilation system includes changes to both the forecast model and the analysis scheme, which are described below.

GCM

The model includes a single scientific update which increases the effectiveness of the ‘sponge’ in the top nine model layers, used to control the vertical propagation of gravity waves. This change produces no discernible qualitative change in the analysis or forecast fields. There are several zero-difference structural changes including an updated capability for re-gridding to and from the Cubed-Sphere and Lat-Lon grids, and support for new grid naming conventions for HISTORY and re-gridding.

Analysis

The analysis was updated to include assimilation of radiances from CrIS and ATMS on the NOAA-20 polar orbiting satellite. The ATMS observations follow the same configuration as those on Suomi-NPP, but the CrIS observations are from the full spectral resolution (FSR) stream. Only longwave channels consistent with Suomi-NPP are implemented; water vapor channels are not utilized. Total column ozone measurements from the OMPS nadir mapper instrument on Suomi NPP have also been added, while NEXRAD velocity-azimuth display (VAD) winds have been disabled in the system. Observation errors for all polar atmospheric motion vectors from MODIS and AVHRR have been re-tuned. Finally, the analysis scheme was updated to allow for inter-channel correlations in the specification of the observation error matrix for AIRS and IASI hyper-spectral infra-red radiances. Overall, these changes result in more accurate short-range forecasts (reduced bias) of tropical middle-tropospheric temperature with respect to radiosonde observations, a similar improved fit to observed winds at high latitudes, and improved medium-range forecasts of middle-tropospheric wind and temperature in the Souther Hemisphere extratropics. There also appears to be an increased bias in tropical upper-tropospheric temperature in some locations, but this is not considered a serious deficiency at the present time.

The GEOS Forward Processing (GEOS FP) system was upgraded from GEOS-5.17.0 to GEOS-5.21.0 starting with the 06z cycle on Wednesday July 11, 2018. This upgrade did not result in any changes to existing products in the file specification, formats, or access methods for GEOS FP data. An additional 2D collection was added containing mass tendencies.

The new release of the GEOS atmospheric data assimilation system includes changes to both the forecast model and the analysis scheme.

GCM

The model physics are updated to use the RRTMG longwave radiation scheme along with improved representation of cloud ice and liquid effective radii. These updates result in an improved comparison of simulated outgoing longwave radiation with CERES-EBAF version 4. The dynamical core is updated to the NOAA Virtual Lab Version 0 public release of the Finite-Volume Cubed-Sphere (FV3) dynamical core jointly developed between NASA and NOAA. This FV3 update includes new advection schemes for thermodynamic and momentum variables, higher order divergence damping schemes and updated vertical remapping options. These FV3 updates improve the effective resolution of the simulated energy spectrum in the mesoscale regime. The combination of radiation, cloud physics and dynamics updates result in reduced vertical temperature biases in many locations between 850 to 150mb. This model update also includes software and compiler optimizations that reduce the execution time of the forecast allowing a small reduction in the latency of forecast products.

Analysis

Updates to the analysis scheme include the assimilation of Global Precipitation Mission (GPM) Microwave Imager (GMI) radiances based on an “all-sky” approach, which utilizes cloud- and precipitation-affected observations in addition to just clear-sky observations. This update improves the representation of lower tropospheric temperature, humidity and wind fields, especially in the tropics. The in-line variational bias correction procedure used for assimilating all satellite radiance observations has been updated to include an explicit term for correcting instrument scan-angle biases. This improves the selection of radiance observations for assimilation, and significantly reduces the use of lower-quality observations. An impact of this update is to reduce the bias in the mid- and upper-stratospheric temperature fields. Finally, the incremental analysis update (IAU) procedure has been updated. The updated procedure allows for (appropriately) larger analysis corrections to the model background fields, increased numerical stability of the IAU procedure, and reduced biases in the IAU product fields.

A new version of the File Specification document has been posted on the GMAO NRT products page. The only change is the addition of a new product containing mass tendencies to accompany the existing tendency products.