# Presentation: 441463

## Mesoscale weather prediction with the RUC hybrid isentropic-sigma coordinate model and data assimilation system

- Stan Benjamin
- NOAA Forecast System Lab
- Boulder, Colorado
- Stan.Benjamin@noaa.gov
- http://ruc.fsl.noaa.gov

- Rainer Bleck	- Los Alamos
- John M. Brown	- NOAA/FSL
- Kevin Brundage	 	“
- Dezso Devenyi	 	“
- Georg Grell	 	“
- Dongsoo Kim	 	“
- Geoff Manikin	- NCEP/EMC
- Barry Schwartz	- NOAA/FSL
- Tanya Smirnova		“
- Tracy Lorraine Smith	“
- Steve Weygandt	“

- Symposium - 50th Anniversary - Operational NWP
- 15 June 2004

## 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)

## ~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

## Choices for vertical coordinate for

- 	atmospheric 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 stream
- 	function - inaccurate integration of hydrostatic 	equation

##  Eliassen and Raustein – 1968

-  Eliassen and Raustein – 1968
*But 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
- . . . . .

## 1990 FSL/Bleck model

- using Uccellini-type
- hybrid - model

- Bleck and Benjamin – 1993- MWR
- Benj, Grell, Brown, Smirnova,
-    Bleck, 2004 – MWR
- Bleck and Boudra – 1981
-    - hybrid-isopycnic model
- Generalized vertical coordinate
-  - Used in all oper RUC versions

## Hybrid (isopycnic-sigma) Ocean Community Model – HYCOM 

- 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

## 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)

## Quasi-horizontal / Cartesian 

- 	vs.
- functional spatial definitions

- Isobaric    		 Isentropic

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

-   each of  RUC levels.

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

- Cross section A

- Vertical coordinate
-       definition
-     - examples:
- _Sigma-pressure_
- p(k), ptop 	         (fixed)
-         (+psfc)        (adaptive)
-      	 p(i,j,k)
- _Generalized ____-___
- pmin(k), v- ref(k)  (fixed)
-  (+psfc , v)        (adaptive)
- 	  p(i,j,k)

## Continuity equation

- 	(inviscid, adiabatic conditions
- 	 in generalized coordinate s)

- Pressure		~0				 0
- Isentropic		  0				~ 0

- Mass conv/div

## RUC 20km model forecast 

- 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

## 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

## e conservation tests

- ___e__ conservation tests_
- Histogram of
-  e  - e (proxy)
- RUC model with
-   a)   coord
- 	(control)
-   b)   coord
-         (fixed)
-   much better moist reversibility w/  model
- 24h forecast
- Init 00z 8 Feb 2001
- (test concept  - Johnson -1997)

-  e  - e (proxy) (K)

-  PDF – grid pts at lev 40

- MWR article – Feb 2004
- Mesoscale wx pred
- W/ RUC hybrid  model
- Benj, Grell, Brown,
-    Smirnova, Bleck

## Advantages of  Coordinates for Data Assimilation

- 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 Assimilation**

- OI, 3dvar techniques
-   in  coordinate
-   developed for RUC analysis

## ~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

## The 1-h Version of the Rapid Update Cycle at NCEP

- The 1-h Version of the Rapid Update Cycle at NCEP

## Model/     Horizontal	No. 	Assimilation	Implement at

- Assim	     resolution		vert	frequency	NMC/NCEP
- _system__	__	__	__levels__	__	__	__	__	_
- _RUC1__	__	__60 km__	__	__25__	__3 h__	__	__1994_
- _RUC2__	__	__40 km__	__	__40__	__1 h__	__	__1998_
- 	Added
-  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 h__	__	__2002_
- 	Added assimilation of GOES cloud-top data

- RUC development – ongoing interaction with NCEP and NCAR

## Obs Data for RUC 

- Rawinsonde 				    80		/12h
- NOAA 405 MHz profilers  		    31		/  1h
- VAD winds (WSR-88D radars)      110-130	/  1h
- Aircraft (ACARS) (V,temp)    	1800-5500	/  1h
- Surface/METAR (T,Td,V,p) 		1500-1700	/  1h
- Buoy/ship			 	 100-150	/  1h
- GOES precipitable water		1500-3000	/  1h
- GOES cloud drift winds 		1000-2500	/  1h
- GOES cloud-top pressure/temp	~10km res    /  1h
- SSM/I precipitable water		1000-4000	/  6h
**     **_**In testing at FSL – early 2004**_
- GPS precipitable water		~250		/  1h
- Radar reflectivity / lightning	4 km
- Mesonet				3000-5000	/  1h
- METAR cloud/vis/wx obs				/  1h

**Obs Data for RUC **

## RUC20

- Wind forecast
- Accuracy
- Sept-Dec
- 2002

- Verification against rawinsonde data over RUC domain
- RMS 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

- 9

- 12

- Analysis
- ~ ‘truth’

## Quasi-isentropic option for non-hydrostatic model 

- Quasi-isentropic option for non-hydrostatic model
- Breaking mountain wave simulation - 2 km horizontal resolution
*Sigma-z version**	**	**Quasi-isentropic version*

- Thick - 
- Thin -
-    coordinate
-    surfaces

- Zuwen He,
- 2002 Ph.D.
- U. Miami

## 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

## RUC changes

-  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**