The NCEP North American The NCEP North American Mesoscale Modeling System: Mesoscale Modeling System:

Recent Changes and Future PlansRecent Changes and Future PlansEric Rogers Geoff DiMego Thomas Black Michael Ek Brad Eric Rogers Geoff DiMego Thomas Black Michael Ek Brad Ferrier George Gayno ZaviFerrier George Gayno Zavišša Janjia Janjićć Ying Lin Matthew Pyle Ying Lin Matthew Pyle

Vince Wong Wan-Shu Wu Vince Wong Wan-Shu WuMesoscale Modeling Branch, EMC/NCEPMesoscale Modeling Branch, EMC/NCEP

Jacob CarleyJacob CarleyPerdue University Perdue University

AMS 23AMS 23stst WAF / 19 WAF / 19thth NWP Conference, Omaha, NE NWP Conference, Omaha, NE1 June 20091 June 2009

Where the Nation’s climate and weather services begin

Overview of PresentationOverview of Presentation

Summarize March 2008 and December Summarize March 2008 and December 2008 NAM implementations2008 NAM implementations

Discuss some of the specific changes in Discuss some of the specific changes in more detailmore detail

Planned NAM changes in 2010Planned NAM changes in 2010 More details can be found in extended More details can be found in extended

abstract and at underlined hyperlinksabstract and at underlined hyperlinks

PRE-2008 NAM HISTORYPRE-2008 NAM HISTORY

June 2006 June 2006 : WRF-NMM and GSI analysis : WRF-NMM and GSI analysis replace Eta model / 3DVAR analysis in the replace Eta model / 3DVAR analysis in the NAMNAM

December 2006 December 2006 Extensive tuning of convection / microphysicsExtensive tuning of convection / microphysics New divergence damping scheme with extra New divergence damping scheme with extra

damping of external mode gravity waves; 5x damping of external mode gravity waves; 5x higher damping of both internal and external higher damping of both internal and external modes during NDAS to reduce noise in modes during NDAS to reduce noise in analysis increments analysis increments

MARCH 2008 NAM CHANGESMARCH 2008 NAM CHANGES Expanded (~18%) computational domain Expanded (~18%) computational domain Model changesModel changes

Gravity wave drag / mountain blocking Gravity wave drag / mountain blocking Unified Noah Land-surface physicsUnified Noah Land-surface physics Modified advection of passive substances (q, cloud water, TKE) Modified advection of passive substances (q, cloud water, TKE) Two minor changes in radiationTwo minor changes in radiation

• Improved computation of surface longwave radiationImproved computation of surface longwave radiation• Fix bug for climatological OFix bug for climatological O33

Analysis changesAnalysis changes Retuned background error covariancesRetuned background error covariances New observations : AIRS & GOES SFOV radiances, EUMETSTAT New observations : AIRS & GOES SFOV radiances, EUMETSTAT

& MODIS satellite winds, surface mesonet winds from sites on & MODIS satellite winds, surface mesonet winds from sites on NCEP use listNCEP use list

Adjust NDAS soil moisture outside of CONUS using 00Z Adjust NDAS soil moisture outside of CONUS using 00Z 12-36 h NAM QPF12-36 h NAM QPF

Smoother model terrainSmoother model terrain

Gravity Wave Drag & Mountain Blocking Gravity Wave Drag & Mountain Blocking (GWD)(GWD)

““Mountain blocking” Mountain blocking” (Lott & Miller, 1997; Alpert 2004)(Lott & Miller, 1997; Alpert 2004) Wind flow around subgrid orographyWind flow around subgrid orography Low-level flow is blocked below a dividing streamline (air Low-level flow is blocked below a dividing streamline (air

flows around, not over barrier)flows around, not over barrier) Gravity wave drag Gravity wave drag (Alpert et al., 1988, 1996; Kim & (Alpert et al., 1988, 1996; Kim &

Arakawa,1995)Arakawa,1995) Mountain wave stress, pressure dragMountain wave stress, pressure drag Vertical distribution of the wave stress, Vertical distribution of the wave stress,

changes winds aloft (momentum deposition)changes winds aloft (momentum deposition) Parallel testing : GWD can improve NAM synoptic Parallel testing : GWD can improve NAM synoptic

forecasts, greatest impact seen on upper troposphere forecasts, greatest impact seen on upper troposphere winds/height and lower troposphere temperatures winds/height and lower troposphere temperatures

Impact of GWD: 12Z 20 Dec 2006 Runs: 72-h Impact of GWD: 12Z 20 Dec 2006 Runs: 72-h

SLP (500 hPa and QPF in extended abstract)SLP (500 hPa and QPF in extended abstract)

In GWD run:

• High pressure breaks down over Canada & New England

• Low pressure forms over western NC and SC

Control GWDControl

1024 hPa 1032 hPa1016 hPa

Much better depiction of low-levelinversion in GWD run

Example of the impact of GWD on lower tropospheric vertical profiles : valid 12z 10/28/07

Black= Omaha (OAX) raob

Red= Ops NAM 48-h fcst

Blue = Parallel NAM (with GWD) 48-h fcst

Model soundings are from grid point closest to OAX

Hurricane Dean: 24-h SLP forecast valid 12z 18 Aug 07Hurricane Dean: 24-h SLP forecast valid 12z 18 Aug 07

OPS NAM Pll NAM

TPC Best Track Position (Franklin, 2008)

OPS NAM Pll NAM

Hurricane Dean: 48-h SLP forecast valid 12z 19 Aug 07Hurricane Dean: 48-h SLP forecast valid 12z 19 Aug 07

TPC Best Track Position (Franklin, 2008)

OPS NAM Pll NAM

Hurricane Dean: 72-h SLP forecast valid 12z 20 Aug 07Hurricane Dean: 72-h SLP forecast valid 12z 20 Aug 07

TPC Best Track Position (Franklin, 2008)

TPC predicted position (issued 12z

8/17) valid 06z 8/21

OPS NAM Pll NAM

Hurricane Dean: 84-h SLP forecast valid 00z 21 Aug 07Hurricane Dean: 84-h SLP forecast valid 00z 21 Aug 07

TPC Best Track Position (Franklin, 2008)

DECEMBER 2008 CHANGESDECEMBER 2008 CHANGES NDAS “Partial Cycling” NDAS “Partial Cycling” Model ChangesModel Changes

Vertically mix/diffuse each hydrometeor speciesVertically mix/diffuse each hydrometeor species Radiation change : double absorption coefficients for Radiation change : double absorption coefficients for

water and ice in cloudswater and ice in clouds Land-sfc model changes to address problematic 2-m Land-sfc model changes to address problematic 2-m

dew point temps over snow coverdew point temps over snow cover Analysis ChangesAnalysis Changes

New observations : MetOp-a radiances and New observations : MetOp-a radiances and TAMDAR/AMDAR aircraft dataTAMDAR/AMDAR aircraft data

New version of radiative transfer model w/default New version of radiative transfer model w/default climatologyclimatology

Use hi-res (23 km) AFWA snow depth analysisUse hi-res (23 km) AFWA snow depth analysis

NDAS ConfigurationNDAS Configuration

12-h spin-up; 4 successive analyses & 3-h model 12-h spin-up; 4 successive analyses & 3-h model forecasts; last 3-h forecast is first guess for NAM forecasts; last 3-h forecast is first guess for NAM analysisanalysis

Prior to July 1998, 12-h NDAS was started from a 6-Prior to July 1998, 12-h NDAS was started from a 6-h forecast from the NCEP Global Data Assimilation h forecast from the NCEP Global Data Assimilation System (GDAS)System (GDAS)

Since July 1998, NDAS was fully cycled (3-h model Since July 1998, NDAS was fully cycled (3-h model forecast from previous cycle used to initiate NDAS)forecast from previous cycle used to initiate NDAS)

Rationale for full cyclingRationale for full cycling Eliminates adjustments/inconsistencies if a model forecast Eliminates adjustments/inconsistencies if a model forecast

with different characteristics (resolution, physics) is used with different characteristics (resolution, physics) is used as a first guess…..as a first guess…..butbut

NDAS ConfigurationNDAS Configuration GFS tends to outperform NAM GFS tends to outperform NAM WRF-NMM forecasts initialized off GFS initial WRF-NMM forecasts initialized off GFS initial

conditions sometimes produce better synoptic-scale conditions sometimes produce better synoptic-scale forecastsforecasts Issues still exist with respect to “noisy” analysis Issues still exist with respect to “noisy” analysis

increments in the NDASincrements in the NDAS Not practical to run ops NAM off global analysis Not practical to run ops NAM off global analysis

(GFS runs after NAM, NDAS is necessary to (GFS runs after NAM, NDAS is necessary to provide fully cycled soil states)provide fully cycled soil states)

Revisit use of 6-h GDAS forecast to provide Revisit use of 6-h GDAS forecast to provide atmospheric first guess states to initiate the NDAS atmospheric first guess states to initiate the NDAS while using fully cycled NDAS soil states (NDAS while using fully cycled NDAS soil states (NDAS Partial Cycling, or “NPCY”)Partial Cycling, or “NPCY”)

Impact of NDAS Partial Cycling Impact of NDAS Partial Cycling during parallel testingduring parallel testing

Tended to improve NAM forecast (sometimes Tended to improve NAM forecast (sometimes more “GFS-like”, especially at day 2-3)more “GFS-like”, especially at day 2-3)

Occasional significant improvement in QPF over Occasional significant improvement in QPF over ops NAMops NAM

Occasionally, parallel NAM would do worse than Occasionally, parallel NAM would do worse than ops NAM when GFS had a “dropout” forecast ops NAM when GFS had a “dropout” forecast (see example in extended abstract)(see example in extended abstract)

NPCY method implemented in Dec 2008 bundle, NPCY method implemented in Dec 2008 bundle, is considered temporary while more advanced is considered temporary while more advanced techniques to control noise in the NDAS mature, techniques to control noise in the NDAS mature, such as digital filter initialization (Colsuch as digital filter initialization (Colóón, paper n, paper 18A.2)18A.2)

72-h forecast – GDAS anl 72-h forecast – GDAS anl 500 hPa height difference 500 hPa height difference valid 00z 8 Oct 08valid 00z 8 Oct 08 NPCY NAM has lower NPCY NAM has lower

errors associated errors associated w/trough over central w/trough over central US and Gulf of AlaskaUS and Gulf of Alaska

Ops NAMPll NAM w/NCPY

Ops GFS

24-h QPF valid 12z 8 Oct 2008

72-h Ops NAM forecast72-h Pll NAM forecast w/NPCY

CPC 1/8 deg observed pcp analysis

Parallel NAM improves 24-h QPF across Iowa, Northern Illinois, Wisconsin and U.P. of Michigan Parallel NAM shifts heaviest precip further east into central KY/TN than ops NAM

Impact of March 2008 changes and partial cycling : Impact of March 2008 changes and partial cycling : Vertical profile of cumulative RMS errors from Vertical profile of cumulative RMS errors from

December 2007 – March 2008December 2007 – March 2008

Height

Temp

Vector Wind

RH

- Solid = Ops NAM- Dash = Pll NAMwith 3/08 changes- Dash-dot = Pll NAM with 3/08changes + NDAS Partial Cycling

Black = 24-h FcstRed = 48-h FcstBlue = 72-h Fcst

Impact of radiation changeImpact of radiation change 12 February 2008 Mid-Atlantic Freezing Rain Case; Poor 12 February 2008 Mid-Atlantic Freezing Rain Case; Poor

forecast by NAM for DC areaforecast by NAM for DC area

Significant Cold Air

Damming

RUC Analysis of 2-m T at 00z 13 Feb 2008

CTL

Control WRF-NMM 12-hr forecast of 2-m T valid 00z 13 Feb 2008

2-m Temperature (°F): Black line is 32oF isotherm

Increase cloud optical depths Increase cloud optical depths by doubling absorption by doubling absorption coefficients of water and ice in coefficients of water and ice in clouds clouds

Intended effect is to reduce Intended effect is to reduce the amount of incoming solar the amount of incoming solar radiation reaching the ground radiation reaching the ground and warming the surface, thus and warming the surface, thus keeping the surface slightly keeping the surface slightly cooler beneath cloudcooler beneath cloud

Impact of radiation changeImpact of radiation change

Experimental WRF-NMM 12-hr forecast of 2-m T valid 00z 13 Feb

2008

Result: more pronounced damming

signature

NAM 2010 PlansNAM 2010 Plans December 2008 bundle is the last major set of December 2008 bundle is the last major set of

changes to WRF-based NAMchanges to WRF-based NAM NAM changes planned in fall 2010 NAM changes planned in fall 2010

Change to ESMF-based NOAA Environmental Change to ESMF-based NOAA Environmental Modeling System (NEMS) framework (Black, paper Modeling System (NEMS) framework (Black, paper 2A.6)2A.6)

Replace E-grid NMM with B-grid NCEP Nonhydrostatic Replace E-grid NMM with B-grid NCEP Nonhydrostatic Multiscale Model (NMMB, JanjiMultiscale Model (NMMB, Janjićć, paper 5A.1), paper 5A.1)

Use physics packages developed for WRFUse physics packages developed for WRF Parent NAM domain will remain at 12km resolution and Parent NAM domain will remain at 12km resolution and

84-h forecast range84-h forecast range Add ~3-6 km runs nested in NAM over CONUS and Add ~3-6 km runs nested in NAM over CONUS and

Alaska, out to 36-48 h (try to match or better NDFD grid Alaska, out to 36-48 h (try to match or better NDFD grid resolution)resolution)

Possibly add ~3 km nests over Hawaii/Puerto RicoPossibly add ~3 km nests over Hawaii/Puerto Rico