Stan Benjamin NOAA Forecast System Lab Boulder, Colorado Stan.Benjamin@noaa

Mesoscale weather prediction with the RUC hybrid isentropic-sigma

coordinate model and data assimilation system

Stan BenjaminNOAA Forecast System LabBoulder, Colorado

[email protected] http://ruc.fsl.noaa.gov

Rainer Bleck - Los AlamosJohn M. Brown- NOAA/FSLKevin Brundage “Dezso Devenyi “Georg Grell “Dongsoo Kim “Geoff Manikin - NCEP/EMCBarry Schwartz - NOAA/FSLTanya Smirnova “Tracy Lorraine Smith “Steve Weygandt “

Symposium - 50th Anniversary - Operational NWP

15 June 2004

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Rapid Update Cycle - An unusual branch of the operational NWP

family genealogy

- Use of a quasi-isentropic vertical coordinate for model prediction and data assimilation - Numerical weather prediction and data assimilation on a sub-12h cycle (currently 1 h)

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~1985• FAA-sponsored Aviation Weather Forecasting Task Force

• Recommendations:• Promote additional automated aircraft reports from commercial aircraft• Develop high-frequency NWP system

• NMC (now NCEP) / PROFS (now NOAA-FSL) agreement on development of ‘high-frequency’ NWP system

(Ron McPherson, Tom Schlatter, Sandy MacDonald)

• Assimilation of anticipated increase of hourly 3-d observations

• wind profilers, commercial aircraft, satellite, radar, surface

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Choices for vertical coordinate foratmospheric prediction models

• Height• Pressure• Entropy

Potential temperature - = T (1000/p)R/Cp

Isentropic weather maps- commonly used in US in late 1930s

Rossby et al. 1937- plagued by reported Montgomery

streamfunction - inaccurate integration of

hydrostatic equation

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• Eliassen and Raustein – 1968But what to do about that lower boundary condition …

• Bleck – 1974, 1977 (carrying sfc as prognostic variable)Now how to resolve the planetary boundary layer …

Modeling efforts with pure isentropic vertical coordinates

Hybrid isentropic-sigma models

• Bleck – 1978• Deaven – 1976• Gall – 1972• Uccellini et al. – 1979• Johnson et al. - 1993• Konor and Arakawa – 1997. . . . .

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1990 FSL/Bleck modelusing Uccellini-typehybrid - model

Bleck and Benjamin – 1993- MWRBenj, Grell, Brown, Smirnova, Bleck, 2004 – MWRBleck and Boudra – 1981 - hybrid-isopycnic modelGeneralized vertical coordinate - Used in all oper RUC versions

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Montevideo south

Vertical section through HYCOM solution. Heavy black lines: coordinate surfaces. Shaded contours: potential density

Hybrid (isopycnic-sigma) Ocean Community Model – HYCOM - U. Miami, Los Alamos Natl. Lab - from Rainer Bleck

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Why even try to use a quasi-Lagrangian vertical coordinate?

• Adaptive higher vertical resolution - vertical gradient of wind, moisture, chemical species …• Less cross-coordinate vertical transport

3-d fluid motion resolved largely by 2-d transport - Less non-physical diffusion, less aphysical source of entropy in numerical model

(Bleck…, Johnson 1997)

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Quasi-horizontal / Cartesian vs.

functional spatial definitions

Isobaric Isentropic

Reference v values (220-500K) pre-assigned to each of RUC levels.

RUC generalized vertical coordinate- configured as a hybrid isentropic-sigma

coordinate

Cross section A Vertical coordinate definition - examples: Sigma-pressurep(k), ptop (fixed) (+psfc) (adaptive) p(i,j,k)

Generalized -pmin(k), v- ref(k) (fixed) (+psfc , v) (adaptive)

p(i,j,k)

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0sp p ps

t s s s s

V

Continuity equation(inviscid, adiabatic conditions in generalized coordinate s)

Pressure ~0 0

Isentropic 0 ~ 0

Mass conv/div

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RUC 20km model forecast - initial conditions – 12z

4 February 2001

Tropopause level (hPa) - defined as potential vorticity (PV) unit = 2

12h forecast 24h forecast

36h forecast

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Vertical cross-sections from RUC 36-h forecasts- valid 00z 6 Feb 2001

Potential vorticity

Vertical velocity(x 10 b/s)

Relative humidity

N S

N S

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e conservation testsHistogram of e - e (proxy)

RUC model with a) coord

(control) b) coord (fixed) much better moist reversibility w/ model

24h forecastInit 00z 8 Feb 2001

(test concept - Johnson -1997)

e - e (proxy) (K)

PDF

– grid

pts

at l

ev 4

0

MWR article – Feb 2004-Mesoscale wx predW/ RUC hybrid model -Benj, Grell, Brown, Smirnova, Bleck

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Analysis

- adaptive 3-d correlation structures and analysis increments, esp. near baroclinic zones, vertical spreading = f()- improved coherence of observations near fronts for QC

Forecast Model

- reduced vertical flux through coordinate surfaces, leading to reduced vertical dispersion -- much of vertical motion implicit in 2-d horiz. advection- conservation of potential vorticity- reduced spin-up problems (Johnson et al. 93 MWR)

Advantages of Coordinates for Data

AssimilationOI, 3dvar techniques in coordinate developed for RUC analysis

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~1985• FAA-sponsored Aviation Weather Forecasting Task Force

• Recommendations:• Promote additional automated aircraft reports from commercial aircraft• Develop high-frequency NWP system

• NMC (now NCEP) / PROFS (now NOAA-FSL) agreement on development of ‘high-frequency’ NWP system

(Ron McPherson, Tom Schlatter, Sandy MacDonald)

• Assimilation of anticipated increase of hourly 3-d observations

• wind profilers, commercial aircraft, satellite, radar, surface

NCEP model hierarchy – RUC (1h frequency) Eta (6h) Global (6h)

The 1-h Version of the Rapid Update Cycle at

NCEP

Figure 1. Data ingest, analysis, and forecast cycle for the Rapid Update Cycle (RUC) NWP Model.

12 hr. fcst

3 hr. fcst

00 01 02 03 04 05 06 07 08 09 10 11 12 (UTC)

Analysis times

3 hr. fcst

12 hr. fcst To 15Z

3 hr. fcst3 hr. fcst

12 hr. fcst To 18Z


12 hr. fcst


To 21Z

1 hr. 1 hr. 1 hr. 1 hr. 1 hr. 1 hr. 1 hr. 1 hr. 1 hr. 1 hr. 1 hr. 1 hr.

DATA DATA DATA DATA DATA DATA DATA DATA DATA DATA DATA DATA DATA

fcst fcst fcst fcst fcst fcst fcst fcst fcst fcst fcst fcst

To 12Z12 hr. fcst

3 hr. fcst

00 01 02 03 04 05 06 07 08 09 10 11 12 (UTC)

Analysis times

3 hr. fcst

12 hr. fcst To 15Z


12 hr. fcst To 18Z


12 hr. fcst


To 21Z




To 12Z12 hr. fcst

3 hr. fcst

00 01 02 03 04 05 06 07 08 09 10 11 12 (UTC)

Analysis times

3 hr. fcst

12 hr. fcst To 15Z


12 hr. fcst To 18Z


12 hr. fcst


To 21Z


3 hr. fcst

12 hr. fcst To 15Z


12 hr. fcst To 18Z


12 hr. fcst


To 21Z




To 12Z12 hr. fcst

3 hr. fcst

00 01 02 03 04 05 06 07 08 09 10 11 12 (UTC)

Analysis times

3 hr. fcst

12 hr. fcst To 15Z


12 hr. fcst To 18Z


12 hr. fcst


To 21Z


3 hr. fcst

12 hr. fcst To 15Z


12 hr. fcst To 18Z


12 hr. fcst


To 21Z




To 12Z

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Model/ Horizontal No. AssimilationImplement atAssim resolution vert frequencyNMC/NCEPsystem levels

RUC1 60 km 25 3 h 1994

RUC2 40 km 40 1 h 1998Added

• state-of-art model physics – convection, mixed-phase cloud, land-sfc• assimilation of surface obs • hourly cycling of

• 5-type hydrometeor cloud variables, • land-surface variables (6 levels, snow variables)

RUC20 20 km 50 1 h2002

Added assimilation of GOES cloud-top data

RUC development – ongoing interaction with NCEP and NCAR

Data Type ~Number Freq.Rawinsonde 80/12hNOAA 405 MHz profilers 31 / 1hVAD winds (WSR-88D radars) 110-130 / 1h Aircraft (ACARS) (V,temp) 1800-5500 / 1hSurface/METAR (T,Td,V,p) 1500-1700 / 1hBuoy/ship 100-150 / 1hGOES precipitable water 1500-3000 / 1hGOES cloud drift winds 1000-2500 / 1hGOES cloud-top pressure/temp ~10km res / 1hSSM/I precipitable water 1000-4000 / 6h In testing at FSL – early 2004GPS precipitable water ~250 / 1hRadar reflectivity / lightning 4 kmMesonet 3000-5000 / 1hMETAR cloud/vis/wx obs / 1h

Obs Data for RUC

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RUC20Wind forecastAccuracy

-Sept-Dec2002

Verification against rawinsonde data over RUC domainRMS vector difference (forecast vs. obs)

RUC is able to use recent obs to improve forecast skill down to 1-h projection for winds

1 3 6 912

Analysis~ ‘truth’

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Quasi-isentropic option for non-hydrostatic model

Breaking mountain wave simulation - 2 km horizontal resolutionSigma-z version Quasi-isentropic version

Thick -

Thin - coordinate surfaces

Zuwen He,2002 Ph.D.U. Miami

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1985

Anticipated use for RUC

- Aviation community

2004

Current users of RUC data

- Aviation community air traffic mgmt

- NCEP Storm Prediction Center- NWS Forecast Offices- Private forecasting- Air quality- Energy industry. . .

Changes in • Number of NWP users• Frequency of access to NWP data• Ability to use shorter- and longer-duration NWP data• User requrements for forecast accuracy, incl. short-range

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2004-2007• Assimilation of surface cloud obs/ current weather/vis, radar reflectivity, GPS …• 13km RUC (in testing at FSL) • WRF-based “Rapid Refresh”, replacing current RUC model• More common software (model, data assimilation) for replacements to RUC, Eta, Hurricane models.

• NCEP, NCAR, NOAA labs, AFWA…

Beyond (IMHO)• 15-30 min continuous update cycle• Global update cycle• Ensemble update cycles• Use of quasi-Lagrangian vertical coordinate models – ocean, atmosphere

RUC changes

Stan Benjamin NOAA Forecast System Lab Boulder, Colorado Stan.Benjamin@noaa

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