NEMS/GFS Overview

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 School

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 School

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 School

GFS nomenclature (GDAS) • GDAS • Global Data Assimilation System • 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 School

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 School

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 School

GFS history (timeline) Find full history timeline at http://www.emc.ncep.noaa.gov/gmb/STATS/html/model_changes.html NEMS/GFS Modeling Summer School

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 School

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

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

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

Hurricane GFDL HWRF (NMM) GFS in NCEP production CLIMATE CFS Oceans HYCOM WaveWatch III GFS + MOM3/4 ~3.5B Obs / Day ‘Mostly’ Satellite +Radar North American Mesoscale NMM Dispersion, Ash, Smoke & Dust ARL’s HYSPLIT Global Forecast System Global Data Assimilation Severe Weather NMM + ARW Regional Data Assimilation Short-Range Ensemble Forecast Air Quality NMM + ARW + ETA + RSM NAM + EPA/ ARL’s CMAQ North American Ensemble Forecast System GEFS + Canadian Global +… Rapid Refresh for Aviation ARW + GSI Very Short Range Ensemble Forecasts Time-Lagged RR+NAM NEMS/GFS Modeling Summer School 13

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

GFS & GDAS workflow (jobs) NEMS NEMS NEMS NEMS/GFS Modeling Summer School

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 School

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 (1st law) • Energy conversion term • Cascade to unresolved scales (2nd law) NEMS/GFS Modeling Summer School

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 School

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 School

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 School

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

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

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

NEMS/GFS Overview