1. A brief introduction to NEMS
NMMB Tutorial
March 2, 2016
Mark Iredell

2. What is NEMS? NEMS stands for: NOAA Environmental Modeling System
A shared, portable, high performance software superstructure and infrastructure
For use in operational prediction models at the National Centers for Environmental Prediction (NCEP)
Support to community through the Developmental Test Center (DTC)

3. Model Components in NEMS (at least in progress)
Atmosphere
NMM-B
GSM
FIM
Chemistry
GOCART
CMAQ
Ocean
MOM
HYCOM
POM
Sea Ice
CICE
KISS
Wave
WaveWatch3
Land/Hydro
LIS
WRF-Hydro
Ionosphere
IPE
Coupling mediators
Ensemble mediator
Atmosphere-Ocean-Ice mediator
Physics-Chemistry mediator
Space Weather mediator

4. Newer NEMS Coupling standard
Newer NEMS Coupling standard* NUOPC (National Unified Operational Prediction Capability)
NEMS
ESMF
Field brokering.
Initialize sequence.
Run sequence.
Compatibility testing.
Compliance checker. ** ** **
Driver  - Provides a harness for Models, Mediators, and Connectors, coordinating their initialization and driving them during the application time loop.
Model  - Typically implements a specific physical domain, e.g. atmosphere, ocean.
Mediator  - Used for custom coupling code (flux calculations, averaging, etc.) between multiple Models.
Connector  - Connects pairs of components, e.g. Model to/from Model, or Model to/from Mediator, and executes simple transforms (Regrid or Redist).
* Sources of the materials on the slide is a courtesy of NUOPC group
** Will be revised according to dynamic core selection and NGGPS budget
2/2/2016

5. Another View of NEMS: NGGPS Schematic
Image courtesy of the Developmental Testbed Center

6. NEMS Architecture NUOPC Driver NUOPC Mediator NUOPC Models NUOPC
Main Program
ESMF Component
NUOPC
Driver
NUOPC
Mediator
NUOPC
Models
NUOPC
Connector

7. NEMS Structure (with respect to NMMB)
MAIN
NEMS
All boxes represent
ESMF components.
EARTH(1:NM)
NMMB
Overall NEMS superstructure. The atmosphere-ocean mediator is recently included.
Solver
Write

8. Could have multiple instantiations for different forecast hours.
NEMS Write component
Could have multiple instantiations for different forecast hours.
Each instantiation runs on the union of model processors and its own quilt processors.
Import state is forecast data on forecast processors and forecast decomposition.
No export state.
Overall NEMS superstructure. The atmosphere-ocean mediator is recently included.

9. NEMS Write component steps
Send model data to quilt processors, independently decomposed on latitude.
Return from model processors so model can resume running.
Run full UPP post-processor and write GRIB master files (if requested).
Write model history files using NEMSIO.
Overall NEMS superstructure. The atmosphere-ocean mediator is recently included.

10. NUOPC Physics Driver Schematic
Key
Model Standard
Model Specific
Dynamics
Dynamical equations, advection, horizontal mixing, diffusion.
Δt, u, v, w, T, θ, p, z, qx, cx, ax
staggered
Tendencies
and Updates
Vertical flipping
Destaggering
(direction check)
Vertical flipping
Restaggering
(direction check)
Pre-Physics
Interface
qx (microphysics species)
cx (chemistry species)
ax (aerosol species)
Post-Physics
Interface
Δt, u, v, w, T, θ, p, z, qx, cx, ax
destaggered
Tendencies
and Updates
Atmospheric Physics Driver
(init, run, finalize modes)
Initialize
Physics Tables and Databases
Output
Diagnostics
fields
rates
budgets
others
Modified Kalnay Rules Layer
Init
Mode
Finalize
Mode.
Radiation
Deep and
Shallow
Cumulus
Surface Layer
PBL and Vertical Mixing
Micro-physics
Sat. adjust
fluxes, precipitation
radiation, stability, exchange coefficients
fluxes, SST,
coefficients, etc.
NUOPC Layer
Wave Prep/Post
LSM Prep/Post
Ocean Prep/Post
LSM, Ocean, Wave, Chemistry, Aerosol, Ice Drivers

11. Summary ●
The NOAA Environmental Modeling System is being built to unify
operational systems under a single framework in order to more easily
share common structures/components and to expedite interoperability. ●
The first two systems under NEMS have been implemented into NCEP
operations with others to follow in the next few years. ●
The NUOPC layer will be used to make collaboration with other groups
less difficult when building/coupling modeling systems. ●
Incorporation of a NUOPC physics driver can help standardize the
often complex connections to physics packages thereby enhancing
their portability. ●
There are now atmosphere, ocean, sea ice, wave, land, hydro, chemistry, ionosphere,
and mediator components within the NEMS framework.