NEMS/GFS Overview

NEMS/GFS Overview

Mark Iredell, Software Team Lead

NEMS/GFS Overview topics.

GFS nomenclatureGFS historyGFS resolutionGFS in NCEP productionGFS & GDAS workflowGSM time splitNEMS motivationNEMS structure

NEMS/GFS Modeling Summer School 2

GFS nomenclature (obsolete)

MRFMedium Range ForecastOnce per day late 10-day global forecastObsolete when merged into GFS

AVNAviation forecastTwice per day early 72-hour global forecastObsolete when merged into GFS


GFS nomenclature (GFS)

GFSGlobal Forecast SystemApplies 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.


GFS nomenclature (GDAS)

GDASGlobal Data Assimilation SystemApplies 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.


GFS nomenclature (apps)

GSMGlobal Spectral Model “Only” the numerical atmospheric prediction

forecast model applicationUPP

Unified Post Processor (aka NCEP post)Downstream application creating the master

file from which all GFS products are madeGSM & UPP combined in NEMS/GFS


GFS nomenclature (NEMS)

NEMSNOAA Environmental Modeling SystemApplies to the software framework

containing NCEP’s numerical modelsContains both GSM and UPP componentsAlso contains NGAC and GEFSAlso contains NMM-B and FIM Soon will contain HYCOM and MOM5Uses ESMF and NUOPC to help couple


GFS history (timeline)


Find full history timeline at http://www.emc.ncep.noaa.gov/gmb/STATS/html/model_changes.html

http://www.emc.ncep.noaa.gov/gmb/STATS/html/model_changes.html

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.


GFS resolution (vertical)


Hybrid sigma-pressure vertical coordinate

Pressure on interface k equalsAk + Bk ps

(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)


pres

sure

(Pa)

thickness (Pa)

GFS resolution (vertical section)


pres

sure

(Pa)

thickness (Pa)

GFS 64 hybrid levels on a cross-section along 90 E

GFS in NCEP production


‘Mostly’Satellite+Radar

North AmericanMesoscale

NMM

North American Ensemble Forecast System

GlobalForecastSystem

Rapid Refreshfor AviationARW + GSI

CLIMATE CFS

~3.5B Obs / Day

GFS + MOM3/4

Global DataAssimilation

Air Quality

NMM + ARW

Dispersion, Ash,Smoke & DustARL’s HYSPLIT

Severe Weather

OceansHYCOM

WaveWatch III

NAM + EPA/ ARL’s CMAQ

Hurricane GFDL

HWRF (NMM)

Regional DataAssimilation

NMM + ARW +ETA + RSM

GEFS + Canadian Global +… Very Short Range Ensemble ForecastsTime-Lagged RR+NAM

Short-RangeEnsemble Forecast

GFS & GDAS workflow(timing and dependencies)


GFS & GDAS workflow (jobs)


NEMS N

EMS

NEMS

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.


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)


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, what is that?

NOAA Environmental Modeling SystemA shared, portable, high performance

software superstructure and infrastructure

For use in operational prediction models at NCEP


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 structure


MAIN

EARTH(1:NM)

Ocean Atm Ice

NEMS

Ensemble Coupler

All boxes represent ESMF components.

NEMSsuper-structure

NEMSlibraryWrt nemsio, …

NEMS components


NMM GSM FIM

Solver

Domains(1:ND)

Dyn Phy

GFS Phy

Chem

Physlibcolumn physics

Postlibpost.a

NAM mesoscale GFS global

Physics parameterizations Postprocessor

Other components:

Model components:

NEMS/GFS Overview is over.

Thanks.Questions?


NEMS/GFS Overview

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