GEOS FP upgrade January 30, 2020
01.29.20
NOTICE: 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, which are described below.
GCM
This GEOS-FP model update replaces the Relaxed Arakawa Schubert (RAS) deep convective parameterization with a combination of the Grell and Freitas scale-aware deep and congestus parameterization combined with the Park and Bretherton shallow convection scheme. The boundary layer scheme has been retuned to work well with the updated convection parameterizations. This combination of convection parameterizations enables a smooth transition from largely parameterized to partially resolved convection across resolutions and produces significantly improved forecast skill and reduces biases in moisture, temperature and winds. The change in convection parameterizations results in significantly different parameterized convective mass fluxes.
The Chou-Suarez shortwave radiation scheme has been replaced with RRTMG. Cloud liquid and ice radiative properties are updated in the single-moment microphysics, and liquid cloud radii are now informed by the transported aerosol concentrations. The single-moment microphysics has been updated to include Bergeron processes informed by aerosol concentrations to improve ice/liquid cloud ratios and the presence of super-cooled liquid. The change in the shortwave radiation scheme combined with adjustments in the single moment microphysics liquid and ice cloud radiative properties leads to further reduced tropospheric temperature biases and improved top of the atmosphere cloud-radiative balance. The change in shortwave stratospheric heating rates with RRTMG are increasing an upper-stratospheric cold bias when compared with MLS; this cold bias leads to significant cold drifts in the forecast temperatures from 30- to 1-hPa with substantially degraded forecast RMS of temperature and height in the upper stratosphere.
The GMAO Catchment land model in GEOS now includes updated hydrology features making GEOS systems consistent with operational GMAO production of SMAP Level 4 soil moisture products . This includes extensive, satellite-based updates of model boundary conditions (soil textures, vegetation phenology) and improved physical treatments of soil moisture diffusion and surface thermodynamics.
The finite-volume cubed-sphere (FV3) dynamics core is updated to the Version 1 release from the collaborative NOAA/NASA FV3 GIT repository, the general settings for FV3 in GEOS-FP are unchanged.
The frequency for incorporating analysis increments into the 4DIAU sequence has been increased from 3-hourly to 2-hourly. The higher frequency provides reduced discontinuities of the analysis increments between the 6-hour assimilation windows due to the nature of the applied digital filter. In addition, the 2-hour frequency resolves more of the higher frequencies in the observations which, in turn, results in smaller RMS errors defined by the IAU increments.
Analysis
The ensemble component of the hybrid assimilation scheme now includes stochastic perturbations of the model physics tendencies. The perturbations introduce a physically-based source of uncertainty to the ensemble members as a means of accounting for model error. This improves the forecast of winds, temperature and humidity at various levels, but especially in the stratosphere.
This upgrade introduces no changes to the data streams assimilated in the GEOS system.
More information about GEOS real-time products can be found at this link:
https://gmao.gsfc.nasa.gov/GMAO_products/
A more detailed summary of the science upgrade will be posted as a GMAO research brief in early February.
Please let us know if you have any questions or concerns.
