GEOS Forward Processing (GEOS FP) Upgraded to GEOS-5.21.0
07.11.18
The GMAO is pleased to announce an upgrade to the GEOS Forward Processing (GEOS FP) system from GEOS-5.17.0 to GEOS-5.21.2 starting with the 06z cycle on Wednesday July 11, 2018. This upgrade will not result in any changes to existing products in the file specification, formats, or access methods for GEOS FP data. An additional 2D collection will be 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 will be posted soon on the GMAO NRT products page:
https://gmao.gsfc.nasa.gov/GMAO_products/NRT_products.php
The only change will be the addition of a new product containing mass tendencies to accompany the exiting tendency products. More information about GEOS operational products can be found on the GMAO website:
