CAM3 composite cyclone comparison

Satellite Observations

• AMSR – WVP, Rainfall, SST

• Quikscat – winds

• NCEP/NCAR – mslp, T-profile

• 2003, 2004, 1500 midlatitude cyclones from NP, NA, SP, SA

Compositing

• Locate low center onto 4000x4000 km grid

• 100x100 km ‘pixels’

• Subsample composites based on mean windspeed and mean wvp

Models

• 10 yr runs, analyze last 3 years• Control: CAM3 0.9x1.25deg Finite Volume• SSAT: Modify Slingo cloud fraction curve

• 4x5 : 4 by 5 degree grid spacing

0

1

CF

RHice 1.0

Satellite Control

ssat 4x5

All show positive correlation with cyclone strength

Control ~+3% bias in high cloud fraction

Ssat ~no bias, slightly more dependence on wvp that obs

4x5 ~+10% bias

High Cloud

Satellite Control

ssat 4x5

All show positive correlation with cyclone strength

All show greater dependency of rainfall on cyclone strength than obs

Rainfall

Satellite Control

ssat 4x5

Obs shows no correlation with cyclone strength or wvp

Model runs show positive correlation with cyclone strength

Control & ssat ~ -7% bias

4x5 less bias

RHcol

Satellite Control

ssat 4x5

All show high cloud to east and se

Model runs greater means and extent

Ssat is better than control

4x5 is worse than control

High Cloud Composite

(max strength, med wvp)

Satellite Control

ssat 4x5

All show max rain to east and se

Model runs greater means and extent

Rainfall composite

(max strength, med wvp)

Satellite Control

ssat 4x5

All show positive correlation

Models show greater dependency of rainfall on cyclone strength than obs

Warm Conveyor Belt

Conclusions (so far)

• Rainfall behavior largely unaffected by differences in models (try conv off)

• High cloud is better in ssat run. Introduction of scheme that allows supersat should be improvement

• RHcol dependence on strength – is this related to the conv scheme?