bruyere model setup rpsea 0310 model set-up and nesting approach cindy bruyère ncar earth system...

Bruyere Model Setup RPSEA 0310

Model Set-up and Nesting Approach

Cindy Bruyère

NCAR Earth System LaboratoryNational Center for Atmospheric Research

NCAR is Sponsored by NSF and this work is partially supported by the Willis Research Network and the Research Program to Secure Energy for

America


Two-way nested domain12 km

Over NA Basin

45S - 45N 36 km resolution

51 levels

10 mb TOA

2000 - 2005

NNRP input dataReynolds SST data

Periodic EW boundary

Phase 1: Tropical Channel


Tropical Channel: Results


WRF

12 kmWRF

36 km Imag

e by

Ste

ve D

ayo

@U

CA

R

CCSM ~ 150 km

CC

SM ~

150

km

Nested Regional Climate Model Setup


Nested Regional Climate Model Setup

• CCSM3: – One Current Climate member (1950-1999)– 3 ensemble members from 2000-2060 under two A2 and one A1B

scenarios (IPCC-AR4)

• NRCM: – 1 ensemble member from 1995-2005, 2020-2030 and 2045-2055

under A2 scenario at 36 km (complete), and 12 km grid spacing (in progress)

– No nudging

• Statistical downscaling of CCSM3 to fill in intermediate periods


Cat 3 HurricaneOctober 2046

Track density of model tropical and extratropical stormsJan-Dec 1995

Regional Model: Results


Shear in the Model (avg Aug-Oct)

Channel

NCEP/NCAR Reanalysis

NRCM


NCEP/NCAR ReanalysisCCSM

Similar Bias in CCSM


Possible Causes of High Shear

• CCSM exhibits same bias• High shear is due to strong Westerly flow at

200mb• Entire tropics has warm bias at upper-levels

in CCSM, inducing westerly wind anomaly• Also an El Niño-like SST anomaly → alters

Walker Circulation → contributes to westerly wind anomaly


Sensitivity StudiesNCEP/NCAR Reanalysis

NRCM + channel configuration NRCM + Reynolds SST

NRCM


• Describe 6-hourly CCSM data for entire simulation (1950-2060) as an average annual cycle plus a perturbation term:

CCSM = CCSM + CCSM’ (1)

- using a 20-year averaging period (1975-1994),- applied to variables: U,V,Z,T,RH,Surface T and PMSL

• Do the same for NCEP-NCAR Reanalysis data:

NNRP = NNRP + NNRP’ (2)

• Replace CCSM with NNRP:

CCSMc = NNRP + CCSM’ (3)

Base climate provided by NCEP-NCAR Reanalysis data and the weather and climate change signal provided by CCSM

Bias Correction


Shear after Adjustment NCEP/NCAR Reanalysis

Adjusted N. A. Regional Climate

NRCM


Regional Model: New Results


Conclusions

• Tropical Channel runs developed storms in the MDR, although fewer than observed

• Running NRCM directly forced with CCSM output resulted in no storms in MDR– Strong bias in shear and SST linked with this

result

• Bias corrected CCSM allowed development of storms in MDR

• Next stage is the completion of the 12km runs

bruyere model setup rpsea 0310 model set-up and nesting approach cindy bruyère ncar earth system...

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