Improving Convective Sensitivity to Tropospheric Relative Humidity

Richard Neale (NCAR)and

Brian Mapes (RSMAS, University of

Miami)

AMWG Meeting, Mar 20, 2006

0 Moisture sensitivity +

FreeTroposphere

Alti

tude

PBL

0.2 X 100% +0.8 X RHclr =1.0 X 10%=> RHclr = -12.5%

dzE

EP

LNB

LFC v

vvgUCAPE

.constP v

Undilute

Pseudoadiabatic Ascent-No cloud water-No freezing-No entrainment (but implied)

DilutedzE

EP

LNB

LFC v

vgDCAPE

Entraining Plume-Cloud water (1 g/kg)-Freezing below 273K-Entrainment chosen

))(),0(( klevf Ev

PP

DiluteUndilute

Dilute

Undilute

Undilute - GPCPDilute minus GPCP

JJA FV 2x2.5 1979-1988

Dilute minus ERS

Undilute minus ERS

DiluteUndilute

Dilute

Undilute

CAPTCCCP-ARM ParametrizationTestbed

Dilute

Undilute

Variance of 5-day ave rainfall

Dilute

Undilute

ENSOWarmminusCold

DJF Prect.

Amplitude of Diurnal Cycle (mm/day) (JJA 1984)

CAM3 (T85)3B42 TRMMTMI/PR

Local Time of Daily Rainfall Max

CAM3 (T85)3B42 TRMMTMI/PR

0300 Local Rainfall

OverallJJA significant improvements (DJF some improvements Africa/Australia rainfall)-Reduction in S. Indian Ocean ITCZ-Enhanced Asian-Monsoon rainfall-Reduced twin ITCZ bias-Improved tropospheric humidity, MSE structure-Decrease in large Pacific high PSL error-Reduction in amplitude of diurnal cycle of rainfall/increased night-time rainfall-More realistic balance of convective/stratiform rainfall-CAPT tests, < half the error through day 5 forecast-ENSO wider Pacific equatorial signal (tentative)-Enhanced subseasonal variability (too much?)

Some deterioration-Indian monsoon precipitation excess-South Atlantic circulation pattern-No change or slightly earlier diurnal cycle rainfall maximum