Climate sensitivity of the CCM3 to horizontal resolution and interannual variability of simulated tropical cyclones

J. Tsutsui, K. Nishizawa,H. Kitabata, Y. Yoshida

(CRIEPI, Japan)

Acknowledgement

NCAR/CRIEPI collaborative research

Support from MEXT (Japanese government)

Outline

IntroductionSensitivity to horizontal resolutionModifications of physicsPerformance of simulated TCsSummary

Background / Motivation

Preparations for IPCC AR4contribution to scenario runsemphasis on regional aspects and

extreme eventslarge natural variability and model to

model differencesComputing resourceJapanese “Earth Simulator”

Objectives

To prepare higher resolution modelsCO2 scenario runs

time-slice runs

To investigate models’ performancesensitivity to various configurationsregional aspectstropical cyclones (TCs)

Model configurations

Based on CCM3.6Optimized for vector machinesT42 to T341, L18 and L26Modifications to physicscloud diagnosticsprecipitation processessurface exchange of moisture

Migrating to CAM2

Surface height (Asia)

(m)

Surface height (Japan)

(m)

Preliminary tuning

Resolution

time step (s)

T42/L18

1200

T85/L18

600

T170/L26

180

T341/L26

120

Min.RH_low 0.90 0.90 0.90 0.87

Min.RH_high 0.90 0.70 0.65 0.50

Adj.T_hack (s) 3600 1800 540 450

Adj.T_zm (s) 7200 3600 1800 900

Global annual mean (TOA)

OLR Abs. Solar

Global annual mean (surface)SW LW

SHLH

Global annual mean (precip)Total LS

Conv. ZM

DJF 200-hPa zonal windT42

T341T170

T85

JJA precipitation rateT42

T341T170

T85

JJA precipitable waterT42

T341T170

T85

Monthly precipitation rate (T341)Dec FebJan

CMAP

Model

Changes in higher resolutionsGlobal propertiesincreased precipitationdecreased water vapordecreased cloud amountnegative energy budget

Large-scale fieldsnot much differentdeficiencies left unchanged

Regional aspectsrealistic, but large-scale dependent

Further modifications

adjustment time scalesefficiency of evaporation from LS rainsurface moisture exchangeinhibition mechanism of ZM scheme

Global precipitation rateTotal ZM scheme

RHc: RH threshold for triggering ZMDifferent from Maloney and Hartmann (2001)

Precip-CAPE relationship

RHc=85% RHc=0%

daily, 20N-20S, July, Year 0006

Time series of CAPE/Precip

at 9.4N, 138.1E

RHc=85%

RHc=0%

(Yap Island)

McBride and Frank (1999) suggest weak negative correlation.

Moist static energy profileat 9.4N, 138.1E (Yap Island)

RHc=85% RHc=0%

MODEL

RAOBS

Simulated TC frequenciesDefinition•40N-40S over ocean•SLP gradient•warm-core structure

STC distributions

JJA Precipitation rateRHc=85% RHc=0%

CMAP

Ensemble simulations

T42 model with RHc=85%Observed SST from 1979 to 20009 members

Interannual variations

Interannual variations

SummaryIncreased horizontal resolution results inmore transparent for LW (could be tuned),overestimated precipitation,detailed regional climate with similar large-scale.

Partition change in convection affectscharacteristic in the tropics,frequencies of simulated TC (not depend on resoluti

ons).

Interannual variations of simulated TCs showsuccessful simulation for some seasonal activity,model's usefulness to study TC variability.