NEMS/GFS Overview Mark Iredell, Software Team Lead

NEMS/GFS Overview topics. GFS nomenclature GFS history GFS resolution GFS in NCEP production GFS & GDAS workflow GSM time split NEMS motivation NEMS structure NEMS/GFS Modeling Summer School2

GFS nomenclature (obsolete) MRF Medium Range Forecast Once per day late 10-day global forecast Obsolete when merged into GFS AVN Aviation forecast Twice per day early 72-hour global forecast Obsolete when merged into GFS NEMS/GFS Modeling Summer School3

GFS nomenclature (GFS) GFS Global Forecast System Applies to entire suite of jobs from observation processing to data assimilation to forecast model to product generation, including ensemble (GEFS) and aerosol (NGAC) components, but not seasonal component. GFS runs four times per day, with “early” (GFS) and a “late” (GDAS) analysis cycles. NEMS/GFS Modeling Summer School4

GFS nomenclature (GDAS) GDAS Global Data Assimilation System backbone Applies to portion of GFS which waits to run well after real-time, assimilates all available observations, cycles upon itself with 9-hour forecasts, has no customer products, but is the backbone for nearly all NCEP numerical prediction guidance. NEMS/GFS Modeling Summer School5

GFS nomenclature (apps) GSM Global Spectral Model “Only” the numerical atmospheric prediction forecast model application UPP Unified Post Processor (aka NCEP post) Downstream application creating the master file from which all GFS products are made GSM & UPP combined in NEMS/GFS NEMS/GFS Modeling Summer School6

GFS nomenclature (NEMS) NEMS NOAA Environmental Modeling System Applies to the software framework containing NCEP’s numerical models Contains both GSM and UPP components Also contains NGAC and GEFS Also contains NMM-B and FIM Soon will contain HYCOM and MOM5 Uses ESMF and NUOPC to help couple NEMS/GFS Modeling Summer School7

GFS history (timeline) NEMS/GFS Modeling Summer School8 Find full history timeline at

GFS resolution (horizontal) What the heck does “T574” mean? T is triangular, the domain shape in spectral space. Triangular is isotropic on a sphere. 574 is the maximum number of waves around a great circle in any direction, so the shortest wavelength is 40000/574=70 km. The Eulerian GSM uses 3 gridpoints per wave, so T574 is on a 1760 x 880 reduced Gaussian grid, or about 23 km. NEMS/GFS Modeling Summer School9

GFS resolution (vertical) NEMS/GFS Modeling Summer School10 Hybrid sigma-pressure vertical coordinate Pressure on interface k equals A k + B k p s (linear function of surface pressure) At bottom, A=0, B=1 (sigma) At top, A=0, B=0 (pressure) Pure pressure above 70 mb

GFS resolution (vertical function) NEMS/GFS Modeling Summer School11 pressure (Pa) thickness (Pa)

GFS resolution (vertical section) NEMS/GFS Modeling Summer School12 pressure (Pa) thickness (Pa) GFS 64 hybrid levels on a cross-section along 90 E

GFS in NCEP production NEMS/GFS Modeling Summer School13 ‘Mostly’ Satellite +Radar North American Mesoscale NMM North American Ensemble Forecast System Global Forecast System Rapid Refresh for Aviation ARW + GSI CLIMATE CFS ~3.5B Obs / Day GFS + MOM3/4 Global Data Assimilation Air Quality NMM + ARW Dispersion, Ash, Smoke & Dust ARL’s HYSPLIT Severe Weather Oceans HYCOM WaveWatch III NAM + EPA/ ARL’s CMAQ Hurricane GFDL HWRF (NMM) Regional Data Assimilation NMM + ARW + ETA + RSM GEFS + Canadian Global +… Very Short Range Ensemble Forecasts Time-Lagged RR+NAM Short-Range Ensemble Forecast

GFS & GDAS workflow (timing and dependencies) NEMS/GFS Modeling Summer School14

GFS & GDAS workflow (jobs) NEMS/GFS Modeling Summer School15 NEMSNEMS NEMSNEMS NEMSNEMS

GSM time split concept GSM does numerical prediction by integrating a series of timesteps. T574 Eulerian has a 2 minute timestep. Each timestep in the GSM is split by computing and integrating “Dynamics” processes first and then computing and integrating “Physics” processes. NEMS/GFS Modeling Summer School16

GSM time split Dynamics Ideal gas law Conservation of mass Transport (aka advection) Conservation of momenturm Pressure gradient force (including mountain torque) Coriolis force Gravity (indirectly in hydrostatic approximation) Conservation of energy (1 st law) Energy conversion term Cascade to unresolved scales (2 nd law) NEMS/GFS Modeling Summer School17

GSM time split Physics Radiation (solar and terrestrial) Surface exchange (land, sea, ice) Turbulence (surface, boundary, and free) Subscale gravity waves Tracer sources and sinks Moist processes Large-scale condensation Shallow convection Deep convection NEMS/GFS Modeling Summer School18

NEMS, what is that? NOAA Environmental Modeling System A shared, portable, high performance software superstructure and infrastructure For use in operational prediction models at NCEP NEMS/GFS Modeling Summer School19

NEMS motivation Develop a common superstructure for all NCEP models. Modularize large pieces of the models with ESMF components and interfaces, and couple using NUOPC layers and wrappers. Divide atmospheric models down into Dynamics and Physics components but no further. Take history file I/O outside the science parts and into a common Write component. Keep science code and parallelization code in the respective models the same as before. NEMS/GFS Modeling Summer School20

NEMS structure NEMS/GFS Modeling Summer School21 MAIN EARTH(1:NM) Ocean AtmIce NEMS Ensemble Coupler All boxes represent ESMF components. NEMS super- structure NEMS library Wrt nemsio, …

NEMS components NEMS/GFS Modeling Summer School22 NMM GSMFIM Solver Domains(1:ND) Dyn Phy GFS Phy Chem Physlib column physics Post libpost.a NAM mesoscale GFS global Physics parameterizations Postprocessor Other components: Model components:

NEMS/GFS Overview is over. Thanks. Questions? NEMS/GFS Modeling Summer School23