# Presentation: 015746

## Winter Weather Workshop October 2002What’s new in NWP 

- Bill Bua, ***COMET*** NWP resource at NCEP
- Bill.Bua@noaa.gov
- Many thanks to Stephen Jascourt and Geoff DiMego for contributing slides. Some Global Forecast System slides have images taken from the T254 Technical Procedures Bulletin

## OUTLINE

- 1. Global Forecast System changes
- 2. Eta model changes
- 3. Nonhydrostatic Mesoscale Model (NMM)
- 4. RUC-20
- 5. Short range ensembles (SREF)
- 6. *COMET*

## Global 
Forecast 
System

**Forecast **
**System**

## GFS

**GFS**
**00, 06, 12, 18 UTC**
- “MRF” with late data cutoff is gone, fields labeled “MRF” are same as fields labeled “AVN”

**Ensembles**

**2002 until Oct 29           Starting Oct 29, 2002**

-           84h       180h             384h
-        3 1⁄2 d      7 1⁄2 d              16 d

-           84h       180h             384h
-        3 1⁄2 d      7 1⁄2 d              16 d

-           84h       180h             384h
-        3 1⁄2 d      7 1⁄2 d              16 d

-           84h       180h             384h
-        3 1⁄2 d      7 1⁄2 d              16 d

- T170
- L42

- T62  L28

- T254
- L64

- T170
- L42

- T126
- L28

- T126
- L28

- T62  L28

- T126
- L28

- T62  L28

- 11 members (1 control, 10 perturbations)    11 members (1 cont., 10 pert)
-             00 UTC, 12 UTC                             00 UTC, 06 UTC, 12 UTC, 18 UTC

** ****2002 (all year)                  Starting sometime 2003**

## Slide 5

## Slide 6

## Slide 7

## Slide 8

## Improved assimilation of satellite radiances

- Better-resolved
- PBL, low level moisture

**64L  ****E****ta  ****42L**
**         ****60L**

## Concentration of new points in stratosphere and model top raised, to help better use...

**MORE SATELLITE RADIANCES**
-  NOAA 15 and NOAA 16 AMSU-A channels 12 and 13
-  HIRS from NOAA-16 (NOAA-14, 15 HIRS already was used)
- Contrast with Eta stratospheric levels... Eta has been having problems with radiance assimilation because even channels peaking lower in troposphere have contributions from stratosphere

## Reminder from last year May 2001 Implementation

- Related to winter weather forecasts:
- Prognostic cloud water (similar to old Eta before Nov 2001)
- Direct tie-in of cloud water to radiation scheme through use in cloud fraction diagnostics
- Better QC on AMSU radiances going into data assimilation scheme (affects oceanic regions with high low-level winds)

## T170      T254

**T170      ****T254**

-    **OCT ’01                                             JAN ’02                                      APR ’02**
** ****T170 and T254 track together, very slight improvement**

## Slide 13

## No bias

**Eta better light amounts**

**T254 improves over T170 heavy amounts**

- .01        .10       .25       .5         .75     1.00     1.50       2.00     3.00

**T254 higher bias for heavy precip**

**No bias**

## Fits to raobs nearly same for T170, T254 tests

- MOS tested using T254 parallel MRF vs. T170 operational MRF 12/15/01 to 3/15/02
-  nearly identical but cold bias slightly worse
- MOS tested using 00 UTC AVN vs. 00 UTC MRF 3/7/02 to 3/27/02
- (only difference is data cutoff time – MRF runs later)
-  results essentially indistinguishable, extremely close

## Slide 16

## Slide 17

## Slide 18

## Eta 
Model

**Model**

## Coming in early 2003

**NEXRAD WINDS**
**Superobs (combining individual data points) to 1 km radial x 6******** **
**azimuth**
**Not used where VAD quality flag says bad data (including birds) or where radar beam runs into model topography**
**32 km test shows no forecast impact**
**10 km test but without assimilation cycling shows improved fits to raob initially but no overall forecast impact**
**2) Radiance processing**
**Upgrade to global model processing methods, including new emissivity model over land**
**Allows channels used over water to be used over land. GOES PW no longer used over land because redundant with radiance data**
**Hardly any overall forecast impact (32 km test)**

## Coming in early 2003 (continued)

**3) Output and Radiation made consistent with the new (Nov 2001) cloud microphysics**
**Microphysics fields cycled**
**Long wave effects of clouds updated hourly instead of every 2 hours**
**Convective cloud fraction increased; shallow convection assumes 10% cloud cover**
**Formulation for cloud fraction from Xu and Randall (1996), instead of Randall (1994)**
**RH for cloud fraction calculated consistently with Nov 2001 microphysics**
**Cloud optical properties changed**
**FORECAST IMPACT in 32 km test:**
**<0.5” precip improved, >0.5” even drier**
**Improved slightly all forecast hours fit to raobs and 2-meter temperatures**

## Coming early 2003 (continued)

**4)  GOES cloud-top assimilation **
**Remove moisture above observed cloud tops**
**Add moisture at observed cloud levels**
**Use as top anchor point for precip assimilation if have to add precipitating cloud**
**5)  Output/postprocessing changes (related to clouds and precipitation)**
**  ****Cloud water/ice, rain, snow, total condensate output separately **
**  ****Cloud-base, cloud-top pressures from shallow non-precipitating and deep convection, and grid-scale clouds output separately**
**  ****Visibility calculations changed to use new cloud fields, responding to mixing ratios of cloud water, cloud ice, rain, and snow**
**  ****Low-level clouds in the lowest 100 mb and upper-level clouds above the tropopause no longer ignored**

## Changes last year affecting winter wx:  what new have we learned?

**Precip assimilation**
**EDAS adds water vapor and condensate where needed to make model precip during assimilation match radar and METAR reports**
**Improved cloud and precipitable water analyses**
**NOT performed where model temperatures cold enough for snow, because obs of precip rates unreliable for snow**
**2) Land surface model changes**
**Many improvements affecting performance with snowcovered ground**
**3) Grid-scale microphysics**
**Mixed-phase microphysics**
**Precip falls at realistic speeds, not instantly reaching ground**
**Precip advects while falling – snow can drift over peaks on way down**
**Deep isothermal 0****o****C layers form, Baldwin precip type algorithm troubles**
**4) 12-km resolution and corresponding topography**

## Land Surface Model 2001 upgrade

- Cold season processes (Koren et al 1999)
- Patchy snow cover
- Frozen soil (new state variable)
- Variable snow pack density (new state variable)
- Soil heat flux under snowpack (Lunardini 1981)
- New maximum snow albedo database (Robinson & Kukla 1985)
- Takes into account ***observed*** effect of vegetation on the albedo of grid box

## Too warm

- Too cold

## 6

**6**

**12**

**18**

**24**

**Model dries out during forecast, summer (winter too?)**
**6/12/18/24 h forecast 900 mb RH vs. analysis RH**
**Blue shades start at 10% too dry, color interval is 10%**

**This picture from Steve Silberberg’s AWC model verification page:**** ****http://www.awc-kc.noaa.gov/metdata/verify/models.html ****Problem is under investigation, cause not found yet**

**Notes:**
Don’t know exactly what the cause is.  May not apply to cold season, but certainly worth mentioning!

## WHY NO PRECIP ASSIM FOR SNOWCoop Daily versus Sum of Hourly Analyses Using Gage&Radar Estimates 29December

**WHY NO PRECIP ASSIM FOR SNOW**Coop Daily versus Sum of Hourly Analyses Using Gage&Radar Estimates 29December

- COOP

- SUM

- Generally poor agreement due to underestimation of snow.

## North Platt, Neb.

**18Z**

**0 C**

**SKIN TEMP**

**2 m AIR TEMP**

**Model ******** 0 C**

**OBS**

**OLD: **snowcover     ground=freezing

**NEW:** snowcover - ground > freezing

- _previous model formulation_ (until snow completely melts):=> all incoming energy melts/sublimates snow => skin temp held at freezing
- => 2-m air temp held near freezing
- _Current formulation_:=> patchy snow cover for snow depth less than threshold depth (veg-type dependent) => reduces surface albedo => accelerates melting => more available energy at sfc
- => skin temp can exceed 0 C => 2-m air temp rises further above freezing.

## Snow drifting downwind while falling

**Snow drifting downwind while falling**

## Slide 30

**Notes:**
Along-lake (large single band) lake effect snow band development and maintenance improved...good forecast up to about 18-24 hrs even on position of snowband in strongly forced events.

## Slide 31

## -4C isotherm

***-4************C isotherm***

## Precip type grids are not from model microphysics

_**Precip type grids are not from model microphysics**_

## Problems with precip type from Baldwin-Schictel:

-  New grid-scale scheme has 98% RH threshold versus 75% over land for old scheme algorithm set up to work with
-  Deep isothermal 0C layers with new scheme
- Model microphysics precip type = fraction of frozen precip not available in AWIPS
- If interested in getting this, contact Ashley.Kells@noaa.gov, explain the operational need for this field. While you’re at it, may as well ask for the 3-d microphysics fields (rain, snow, cloud water, cloud ice)

## 14z 2/7/02 Lexington KY Eta BUFR sounding, Baldwin prec type, model fraction of rain to snow

## 16z 2/7/02 Lexington KY BUFR sounding, same information as previous graphic. 

- 16z 2/7/02 Lexington KY BUFR sounding, same information as previous graphic.
- NOTE: Changeover from rain to snow via model precipitation microphysics (cooling of layer through latent heat of fusion taken into account)!

## Slide 37

## Slide 38

## Slide 39

## Miscellaneous:

- FREEZING LEVEL
- Will be extended below model topography using standard atmosphere lapse rate
- 12-km grids getting into AWIPS:
- Testing began for a few fields distributing over SBN starting July 23
- Next AWIPS build will have some fields on 12-km grid

## New hybrid vertical coordinate
Replaced the Eta model for high-resolution windows runs
Similar physics to Eta
No assimilation cycling yet, starts with Eta-12 analysis
BEGINS THE TRANSITION TOWARD Weather Research and Forecasting (WRF) Model
Modular design: different model options “plug in”
WRF will allow collaborators outside NCEP to run the same model and to supply parameterizations that will more readily work in the NCEP operational environment (a great difficulty now)

**Replaced the Eta model for high-resolution windows runs**
**Similar physics to Eta**
**No assimilation cycling yet, starts with Eta-12 analysis**
**BEGINS THE TRANSITION TOWARD Weather Research and Forecasting (WRF) Model**
**Modular design: different model options “plug in”**
**WRF will allow collaborators outside NCEP to run the same model and to supply parameterizations that will more readily work in the NCEP operational environment (a great difficulty now)**

**N****ONHYDROSTATIC**** ****M****ESOSCALE**** ****M****ODEL**** ****(NMM)**

## 8 km Nested Meso

- Lateral boundary conditions (out to 48 hours)
- Generated by 12 km Eta run
- On model vertical levels
- Every hour of forecast
- Initial conditions
- Interpolated from 12 km Eta run
- High resolution terrain incorporated
- Lynch digital filter speeds adjustment

## Large Fixed-Domain Nests

## Nonhydrostatic Mesoscale Model

- See Janjic, Gerrity,and Nickovic, 2001 for model equations, solution techniques & other test results [MWR,Vol. 29, No. 5, 1164-1178]
- Highly refined version of nonhydrostatic option released in May 2000 upgrade to NCEP’s workstation Eta
- NMM retains full hydrostatic capability
- Incorporate nonhydrostatic effects through ****** where ******=(1/g) dw/dt
- Then split prognostic equations into:
- hydrostatic parts plus
- corrections due to vertical acceleration
- Set ****** to zero to run in hydrostatic mode

## Nonhydrostatic Mesoscale ModelFeature Comparison With Meso Eta

| Feature | Meso Eta Model | Nonhydrostatic Meso Model |
| --- | --- | --- |
| Horizontal grid | 12 km E-grid  | 8 km E-grid (readily downscales when more computer power available) |
| Vertical coordinate | 60 step-mountain eta levels | 60 hybrid sigma-pressure levels |
| Terrain | Unsmoothed silhouette with lateral boundary set to sea-level | Unsmoothed grid-cell mean everywhere |

## Hybrid and Eta Coordinates

**MSL**

*Pressure domain*

*Sigma domain*

********* ******= 0***

********* ******= 1***

********* ******= 1***

**Ptop**

**Ptop**

********* ******= 0***

## 12 km Terrain                                       4 km Terrain 

- 12 km Terrain                                       4 km Terrain
- 					(not running at 4 km yet)

- Dots represent water points  Domain is San Francisco Bay

## Dots represent water points  Domain is Chesapeake Bay

- 12 km Terrain                                       4 km Terrain
- 					(not running at 4 km yet)

## 12 km Terrain                                       4 km Terrain

- 				(not running at 4 km yet)

- Dots represent water points  Domain is Puget Sound

## NMM improvements over Eta

- Keep structures and their amplitudes more intact (NMM numerical calculations for advection are less damping than in Eta)
- Various advection and PBL changes should allow for better moisture transport and evapotranspiration from surface moisture sources
- Tweaks to B-M-J allow for more buildup of PBL moist static energy in NMM
- No changes to radiation scheme, ***yet***

## Nonhydrostatic Mesoscale ModelFeature Comparison With Meso Eta

| Feature | Meso Eta Model | Nonhydrostatic Meso Model |
| --- | --- | --- |
| Dynamics | Hydrostatic | Hydrostatic plus nonhydrostatic corrections |
| HorizontalAdvection spatial scheme | Janjic conservative
T, u, v, TKE; shape preserving for q and condensate | Janjic conservative
T, u, v; 
shape preserving for TKE, q, and condensate |

## Nonhydrostatic Mesoscale ModelFeature Comparison With Meso Eta

| Feature | Meso Eta Model | Nonhydrostatic Meso Model |
| --- | --- | --- |
| Vertical
Advection | Euler backward
T, u, v, TKE; conservative q and condensate | Shape preserving T, u, v, TKE, q and condensate |
| Pressure gradient force  | Forward backward  | Forward backward with adjustment for sigma |
| Advective time scheme | Euler backward | Adams - Bashforth |

## Nonhydrostatic Mesoscale ModelDamping Feature Comparison With Meso Eta

| Damping Features | Meso Eta Model | Nonhydrostatic Meso Model |
| --- | --- | --- |
| Vertical
advection | Euler backward
is damping | Shape-preserving scheme is not damping |
| Advective time-step | Euler backward is damping | Adams - Bashforth is not damping |
| Divergence damping | Coeff = 6.5
Grid-coupling=1. | Coeff = 15
Grid-coupling < 0.5 |
| Lateral diffusion | Coeff = .25 with no limit on deformation | Coeff = .50 with limit on deformation |

## Nonhydrostatic Mesoscale ModelPhysics Features Comparison With Meso Eta

| Physics Feature | Meso Eta Model | Nonhydrostatic Meso Model |
| --- | --- | --- |
| Turbulent mixing | Mellor-Yamada Level 2.5 dry | Mellor-Yamada Level 2.5 including moist processes |
| Surface exchange | ...+ Paulson functions | ...+ Holtslag and de Bruin functions |
| Land-sfc | NOAH LSM | NOAH LSM |
| Gridscale  | Ferrier | Ferrier |
| Convective  | B-M-J | B-M-J’ |
| Radiation | GFDL | GFDL |

## Dissemination

- GRIB and BUFR data available for ftp
- Fields do not go out over SBN
- Model will not run if hurricane model needs to run (they share same time slot on computer)
- _How do I get it? __(times in filename will change when schedule is implemented)_
- The model grib files are accessed the same as for the 10-km regional
- nested runs, on ftp://ftpprd.ncep.noaa.gov/pub/emc/mmb/mmbpll/
- (note new directories are all lower case letters)
- new directory        old directory
- -----------------        ----------------
- alaska10.t00z         Alaska12.t00z
- central08.t12z       Central10.t12z
- east08.t18z             East10.t18z
- hi08.t00z                 hi10.t00z
- hi08.t12z                 hi10.t12z
- pr08.t06z                 pr10.t06z
- pr08.t18z                 pr10.t18z
- west08.t06z             West10.t06z

## RUC-20

-  Still uses Optimum Interpolation; the 3D-VAR analysis
-    is coming in early 2003 (yes it finally really is coming)
-  Complete model overhaul in April
-  See info on COMET NWP matrix page at
-    http://meted.ucar.edu/nwp/pcu2/index.htm and the
-    RUC page at http://maps.fsl.noaa.gov/
-  Large improvement in error stats (precip, raobs, METARS, sensible weather, visibility, cloud patterns, everything!)
-  2-level snow model
-  GOES cloud top assimilation, boundary layer profilers
-  many many model changes. Still uses theta-sigma hybrid coordinate.

## Short-Range Ensemble Forecasts (SREF)

- _What?_
-  5 Eta 48 km (control + 2 perturbation pairs)
-  5 Regional Spectral Model 48 km (control + 2 perturbation pairs)
-    [RSM has old AVN/MRF physics, not upgraded version]
-  5 Eta members using Kain-Fritsch convective parameterization
-  “Soon” 5 RUC members will be added
-  “Soon”? 5 ARPS (CAPS at Oklahoma) members may be added
- _When?_
-  21, 09 UTC in time for your use with 00, 12 UTC Eta
- _Status?_
-  To become officially operational NWS-wide fall 2002
-  Output might get into AWIPS sometime in 2003
-  New user-friendly web interface linked from SREF home page,
-   which is http://wwwt.emc.ncep.noaa.gov/mmb/SREF/SREF.html

## http://wwwt.emc.ncep.noaa.gov/mmb/SREF/SREF.html

**http://wwwt.emc.ncep.noaa.gov/mmb/SREF/SREF.html**

## COMET

**Keeps you informed through the Eta and AVN newsgroups. **
** ****Read it like email, but it doesn’t get mixed up with your regular email**
** ****Post questions, get answers**
** ****Start at ****http://meted.ucar.edu/nwp/newsgroups/index.htm**

## Http://meted.ucar.edu/nwp/pcu3/cases/

**More cases being added monthly, many under development now**

**Http://meted.ucar.edu/nwp/pcu3/cases/**