Improving Model physics in
NCEP GFS towards Next-
Generation Global Prediction
System (NGGPS)
Yu-Tai Hou
NOAA/NWS/NCEP/EMC
TWPGFS Planning Workshop, June 2015
Acknowledgement: presentation materials come from the works by staffs of EMC Global and Climate Modeling Branch, special working groups, such as the DA team, Land model team, and on-going CPT project collaborations.
The 2015 Operational GFS Overview
Commence Date: January 14, 2015
Major upgrade areas:
Dynamic core and model resolution,
Physics,
Data-assimilation system,
Fixed data inputs,
Model outputs, etc.
(http://www.emc.ncep.noaa.gov/?branch=GFS&tab=imp)
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Dynamics:
from Eulerian Dyn Semi-Lagrangian Dyn
1st-seg: from 0-192 hr (8 days) 0-240 hr (10 days)
T574 (27km) L64 T1534 (13km) L64
2nd-seg:from 192-240 fcst hrs 240-384 fcst hrs
T192 (84km) L64 T574 (35km) L64
Divergence damping in stratosphere
X-numbers for spectral transform base functions
The 2015 Operational GFS Overview
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Physics: Monte-Carlo Independent Column Approximation
(McICA) in RRTM Radiation
Hybrid Eddy-Diffusivity Mass-Flux (EDMF) PBL,
Turbulent Kinetic Energy (TKE), and Sh-Cu
schemes
Stationary convective gravity wave drag
Upgrades in cloud Microphysics, ozone column
mess, land model, orographic gravity-wave
forcing/mountain block, …
The 2015 Operational GFS Overview
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The 2015 Operational GFS Overview
DA: Hybrid 3D-EnVAR (Ensemble KalmanFilter)
Inc horiz res: from T254 (62km) to T574 (27km)
Assimilate hourly GOES and EUMETSAT motion vectors
Updated SSM/IS UPP LAS and Metop-B IASI radiances assimilation
Enhanced radiance bias correction
Updated CRTM (v2.1.3)
Stochastic phys in EnkF for ensemble fcsts
6-hr window expansion for GOES wind data
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Fixed/input data: Replace the 1⁰ 7-day SST with new 5-min daily real-
time global (RTG) SST
4-km IMS anal to init small inland lakes, and 5-min
NCEP/MMAB ice analysis for large water body
Replace the 1⁰ bucket soil moisture clim with
CFS/GLDAS clim at T574 (27km)
Replace momentum roughness length clim with
veg-type based look-up table
AFWA snow depth data blended with model first
guess
The 2015 Operational GFS Overview
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Improved ETS score and reduced forecast BIAS for all intensity and forecast lead time
Usefulness of GFS synoptic forecast improved by 3h in NH and 4.4h in the SH
24-h half-inch per-day precipitation threat forecast improved ~4% over CONUS
2015 Model Improvements Over Previous Version
Mark Iredell, GFS FY15Q1 review, 2015 7
ISCCP
Old Shallow
New Shallow
Improved PBL clouds from
hybrid EDMF with TKE
dissipation and upgraded
Sh-Cu convection
Jongil Han, NGGPS Workshop, Jan. 2015
2015 Model Improvements Over Previous Version
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2015 Model Deficits and Upcoming Changes
Winter night time T-2m cold bias in east
CONUS, low-level strong wind over the
CONUS
-- modifications: prevent decoupling
turbulent transport by limit the
stability parameter and modify surface
roughness length
Weizhong Zheng, phys meeting Mar. 2015 9
Lack of medium rainfall, but
too much convective and
light rain
-- modifications: improve
non-precipitating shallow-
convective scheme to
suppress light rains, reduce
the convective rain ratio
over total rain amount
2015 Model Deficits and Upcoming Changes
Jongil Han, Physics Update, Apr. 2015 10
Activities for the Next GFS Implementation
(Q1 2016)
DA: Hybrid 4D-EnVAR to replace Hybrid 3D-EnVAR (hourly
update)
Additional obs data (aircraft, satellite winds, cloudy radiances)
Upgraded GSI and CRTM
GFS: Semi-implicit modification to improve numerical stability
PBL Cu-convection upgrade to improve clouds and rainfall (cld base MF, rain/snow conv rate, conv inhib trigger, …)
Land model (roughness, canopy height…) to improve T-2m bias and low level winds
NSST model to improve SST and near surface T profile
Glenn White, EMC MEG, March 2015 11
Coupled Model
Ensemble Forecast
NEMS
OC
EA
N
SE
A-I
CE
WA
VE
LA
ND
AE
RO
AT
MO
S
Ensemble Analysis
(N Members)
OUTPUT
Coupled Ensemble
Forecast (N
members)
INPUT
Coupled Model
Ensemble Forecast
NEMS
OC
EA
N
SE
A-IC
E
WA
VE
LA
ND
AE
RO
AT
MO
S
NCEP Coupled Hybrid-EnKF Data Assimilation System
Suranjana Saha (EMC) 12
NGGPS: A joint project of NOAA/NWS and Office of OAR
Program Manager: Fred Toepfer
ESMF/NEMS based, Community, Coupled sys, 5-yr effort
Atms, Ocean, Land, Ice, Wave, Aerosol
AM Dynamic Core Selection
Non-hydrostatic, Multi-way nests, High scalability
Define eval criteria for selection from a targeted pool (currently 6)
Prototype by fall 2015, recommendation by spring 2016
Model physics upgrade objective
Develop or R2O-transition, state-of-science representations of
AM physical processes
Spatial scales from km (cloud resolve) to 100km (climate)
DA, Ocean/Land, TS, Ensm, Nest-subsys, …
NCEP Next-Generation Global
Prediction System (NGGPS)
Fred Toepfer, NGGPS workshop , Jan. 2015 13
R2O CPT projects funded by the
MAPP Program:
Improving model moist physics processes: developing coherent PBL, deep/shallow convection and cloud parameterizations:
1. CLUBB (Cloud Layers Unified By Bi-normals) scheme and EDMF PBL-convection scheme led by Bretherton of U Wash and Han of EMC, also Golaz of GFDL and Teixeira of JPL…
2. SHOC (Simplified High Order Closure) PBL and C-S (Chikiraand Sugiyama) Cu schemes led by Krueger of U Utah and Moorthi of EMC, also Randall of Co StU and Pincus of U Co…
3. MG (Morrison and Gettleman) double moments cloud microphysics interact with prognostic aerosols, led by Lu of SUNYA and Hou of EMC, also Silva of GSFC…
Improving other model components:
Lake module led by Jin of Utah St U and Ek of EMC …
Land module led by Chen of NCAR and Ek of EMC …
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PBL-Convection-Cloud Physics CPT-1
Team PIs: Kruger (U Utah) …, Moorthi (EMC)
Goals: Improve GFS PBL, Sc-Cu convection
Status: In progress, duration: 2015-2017
Method: Assumed PDF for better representing SGS clouds and
turbulence• Prognosis high order (HO) moments (mean and various)
• Select PDF member from assumed function form
• Use selected PDFs to close other HO terms (buoyancy flux, cloud fraction sub-grid condensation…)
Simplified High Order Closure (SHOC) approach method• Diagnose second moments (Bechtold et al. 1995)
• Diagnose third moment of w (Canuto et al. 2001)
• Those diagnosed moments are function of prognostic SGS TKE
• Turbulence length related to SGS TKE and eddy length scales
Unified Convection Parameterization (Randall)• Use C-S deep convection scheme (Chikira and Sugiyama , 2010)
• Plus A-W extension for unified representation (Wu and Arakawa, 2014)
15Kruger, randall, NGGPS Workshop, Jan. 2015
Team Pis: Bretherton (U Wash) …, Han (EMC)
Goals: Improve GFS PBL, Sc-Cu conv, and cloud microphysics
Status: In progress, duration: 2010-2013, 2015-2017
Method: Upgraded to ‘Hybrid EDMF scheme (Han et al. 2015)
(done)
Added TKE dissipation heating (Han et al. 2015)(done)
‘Hybrid’ ‘Moist’ EDMF schemeNeed to transport moist variables, Su-top entrainment and merging with MF Cu parameterization
• Modified cloud base MF calculation
• Increase convective inhibition constraint in trigger function
Improve microphysics process in cu-convection• Modify rain/snow conversion rate and evaporation
• Improve global cloud/radiation in GFS
Develop stochastic shallow convection scheme
PBL-Convection-Cloud Physics CPT-2
Jongil Han, NGGPS Workshop, Jan. 2015 16
Cloud-Aerosols Physics CPT-3
Team Pis: Lu (SUNYA) …, Hou (EMC)
Goals: Improve GFS cld micro-phy and interaction with
aerosols
Status: In progress, duration: 2015-2017
Method: Adapt MG (Morrison and Gettleman, 2008) two-moment cloud
microphysics (Barahona et al. 2013)
Adapt Modal Aerosol Module (MAM-7, Liu et al. 2012)
Improve Interactions among Cloud, Aerosol, Radiation, Large-
scale Circulation
• Cloud microphysics driven by aerosol size and
composition provided by aerosol module (MAM-7 or
updated GOCART)
• Cloud microphysics consistently link with the PDF based
cloud macrophysics processes
17Lu, NGGPS Workshop, Jan. 2015
Radiation Upgrades
Updating RRTM-McICA radiation (clouds and aerosols
representations and interactions, bug fixes, improve
efficiency, …)
Using cloud de-correlation length scheme to determine sub-
column cloud overlapping distribution (more realistic than
max-random overlap method, suitable for McICA scheme)
Introducing non-homogeneous cloud condensates by pdf
distributions (more consistent with microphysics)
Using flux and heating rate derivatives w.r.t. to surface
temperature changes to approximate diurnal variation in LW
radiation
Spectral distributed surface albedo to address the
shortcomings in the 2-band albedo scheme
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Summary
NGGPS requires wide scale ranges ( from ~kms to ~100kms, from hours to
decadal) to meet future NWCP needs. Not only in weather predictions, modern
climate models also require good presentations of micro-scaled physical
processes.
Moisture processes are involved in a wide range of scales (from micro-scaled
eddy turbulences to synoptic-scaled parcel movement). Compounded with the
complexity of phase changes, energy transformations, and strong interactions with
other processes, research in better understanding of the science fundamentals is
one of the top priorities for the next-gen NWCP development.
Traditional ways applied in parameterizations are largely incoherent, segmented,
and imbalanced, due to the constrains of limited understanding of many basics of
science.
It is a great challenge for modeling physics in a more coherent and high-scalable
fashion, especially in the “grey zone” that clouds and convection are neither
explicitly resolved nor easily parameterized by traditional assumptions.
Need a new generation of physical parameterizations (shallow and deep
convections, PBL, microphysics, cloud-aerosol physics, land/ocean/ice models,
and their interactions with turbulence and radiation…)
NCEP/EMC is working towards NGGPS through collaborations with science
community and pushes to accelerate the model development through R2O
transition programs (MAPP/NGGPS, CTB, CPT …).
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