Warm Season Precipitation Predictions over North America with the Eta Regional Climate Model

Model Sensitivity to Initial Land States and Choice of Domain Size

The 30th Climate Diagnostic Prediction Workshop (Oct.24 - 28, 2005) State College, PA

Rongqian Yang and Kenneth Mitchell

Environmental Modeling Center

National Centers for Environmental Prediction

This development is sponsored by the GAPP program of NOAA/OAR/OGP

Presentation Outline

Brief Introduction of the Eta RCM

Model Predictions using CFS Hcst data

• Initial starting time (10 members from CFS, Mid April to Early May

out to 6 months)

• Land States from Reanalysis II and Regional Reanalysis

• Big vs Small Domain

2004 results (NAME period, Precip, 500h, T2m etc.)

Preliminary Conclusions

Future Work

The Eta Regional Climate Model Development at NCEP

• Developed: uses very recent version of Eta Model physics

• As implemented in NCEP Regional Reanalysis

• As implemented in operational NCEP Eta on 24 Jul 01

• Virtually exact match to Eta model in Regional Reanalysis (R/R)

• R/R domain and grid (32-km, 45-levels, large R/R domain)

• R/R Eta model physics, e.g. Noah Land Model 2.3, with 4 soil layers

• Daily updates of several surface boundary fields

• Daily CFS predicted SST (or observed 1-deg weekly Reynolds/Stokes SST )

• Satellite NDVI-based 0.15-degree monthly greenness (NESDIS)

• Seasonal 1.0-deg snow-free albedo climatology (NASA)

• Initial land states of soil moisture and soil temperature

• Soil moist/temp from :

• Regional Reanslysis

• Global Reanalysis II

• Snow depth: USAF operational 47-km daily global snow depth

The Eta Regional Climate Model Development at NCEP (Cont’d)

• Tests of different initial land states (GR2 or R/R)• Test with both big and small domain size

• Predicted Lateral Boundary Conditions (CFS Hindcast)

• Predicted SSTs (CFS Hindcast)

• 10 summer members (mid-April/early May through mid-November)

• Currently 2004 (summer of NAME field campaign)

• 2000, 2001, 2002, and 2003 under way (to achieve 5yr model climo)

• Ultimate goal is to execute 10-20 yrs

Model Prediction (Experiments)

The Big Domain

The Small Domain

Focus Issues

• Model's sensitivity to initial land states

• Choice of domain size

• Full prediction mode (i.e. using CFS predicted LBC and SSTs)

• To see if the regional model shows any skill in seasonal prediction mode, if any, where (in ensemble sense)?

• Focusing on precipitation over the CONUS domain and whether the skills are better than CFS

10 Member Mean June Precipitation

RCMRCM/R2CFS Hcst

CPC AnalysisRCM/RR

All missed this heavy rainJust a HintBig Domain

CFS Hcst

CPC Analysis

RCM/R2

RCM/RR

10 Member Mean June Precipitation

All missed this heavy rain with small domain tooNothing HereSmall Domain

NAM

NAM

10 Member Mean July Precipitation

RCM/R2

RCM/RR CPC Analysis

CFS Hcst

NAM: North American Monsoon

Big Domain

NAM is weaker compared to Big Domain

CFS Hcst

CPC Analysis

RCM/R2

RCM/RR

10 Member Mean July Precipitation

Small Domain

Sustained NAM

10 Member Mean August Precipitation

RCM/R2

RCM/RR

CFS Hcst

CPC Analysis

Big Domain

CFS Hcst

CPC Analysis

RCM/R2

RCM/RR

10 Member Mean August Precipitation

Small Domain

Dry in Southern Great Plains

RCM/RR

RCM/R2CFS Hcst

CPC Analysis

10 Member Mean JJA Precipitation

Big Domain

Less dry in Southern Great Plains than the results using big domain

CFS Hcst

CPC Analysis

RCM/R2

RCM/RR

10 Member Mean JJA Precipitation

Small Domain

Eta-RCM and CFS Temperature is somewhat warmer in central US than the RR verification

RCM/R2CFS Hcst

RRRCM/RR

10 Member Mean June 2m Temperature

Orography signatures are much better revealed in RCM than in Global CFS Big Domain

Eta-RCM temperature is somewhat warmer than RR verification

CFS Hcst

RR Analysis

RCM/R2

RCM/RR

10 Member Mean June 2m Temperature

Small Domain

500mb GPH is low compared to RR, RCM/R2 Better

RCM/R2 CFS Hcst

RR Analysis

RCM/RR

10 Member Mean June 500mb GPH

GPH: Geo-potential Height

Big Domain

500mb GPH is high compared to RR verification

RCM/R2 CFS Hcst

RR Analysis

RCM/RR

10 Member Mean June 500mb GPH

Small Domain

Diffs in Initial Land States from One Member (April, 23)

Comparison of the two Initial Land States

Soil T Temp

Total Soil Moisture

0-100cm percentage of Soil Saturation

0-10 cm Soil Moisture

GR2 cooler

GR2 drier

(Difference Fields: EtaRCM with GR2 Land States minus EtaRCM with RR Land States)

Comparison of May Predicted Fields

Latent Heat 500mb

GPH

200mb GPH Precip

Comparison of Area-avgd Precipitation Timeseries (over CONUS)

Area Avgd Precip is low at the beginning of integration with big domain

Big Domain Small Domain

Green: GR2 land states Yellow: R/R land states

Other Comparisons between the two domains using GR2 and RR land states

Ensemble Mean Kinetic Energy

Big with R2 LS

CFS Hindcast

Big with R/R LS

Small with R2 LS

Small with R/R LS

Regional Reanalysis

Model Losing Kinetic Energy in May/June ?

Ensemble Mean Ratio of ACPCP/APCP

R/R

Small with R/R LS

Small with R2 LS

Big with R/R LS

CFS Hcst

Big with R2 LS

Small domain has the highest percentage of convective Precip

Preliminary Conclusions• Domain size choice is crucial to model results.

• Diffs caused by different land landstates is secondary.

• Big Domain EtaRCM yields better results than other combinations in general.

• The EtaRCM shows skills in warm season precipitation predictions (Compared to Obs and CFS hindcast, especially with features associated with NAM system), still problems?

LBC errors plus physics?

Future Work

• More tests on different years (under way, 2000-2003). To drive the Eta-RCM, CFS hindcasts need to be re-run (saved sigma files). It takes a lot CPU time (so only 2004 finished so far).

• Establishing model climatology to evaluate a relative dry/wet year with respect to model climatology.

• Further testing Land states from Regional Reanalysis and its impact on warm season precipitation.

Thanks to Suranjana Saha Wanqiu Wang Cathy Thiaw Jun Wang Kingtse Mo