CCN LWC Nc T Qv Rc Rainfall LWP Vertical Velocity WRF model - - PowerPoint PPT Presentation

Yuan Wang, Yun Lin Renyi Zhang, Y angang Liu

• Marit ime st rat ocumuli

[Wang et al., under review]

• Bulk-OR:
• fixed CCN spectrum
• overestimate Nc
• underestimate Rc
• Bulk-2M:
• prognostic Na and Qa
• better agreement with

S BM

• VOCALs maritime S

c Cloud[Wang et al., under review]

• The scheme incorporating the

relative dispersion of the cloud droplet distribution [Liu and Daum, 2003] and the scheme considering the effect of turbulence on the collisions and coalescences [Franklin, 2008]

• utperform other schemes.
• Embroynic rain drop radius is

suggested to be 41 micron for S c.

[Li et al. 2008]

 Prognostic number

concentration and mass mixing ratio for cloud, rain, ice, snow graupel

 Explicitly predicted water

vapor mixing ratio and super saturation

 S

ix autoconversion

• ptions including Liu and

Daum [2003]

 Three moment aerosol

modal approach with three prognostic Qa, S a and Na

 Interacting with radiation

scheme to consider aerosol radiative properties

• Int er-comparison wit h ot her microphysics in t he F

AS TER t est bed

• Invest igat ion of aerosol effect s on t he low-level clouds
• Direct/ S

emi-direct Effect

• Indirect Effect
• Examinat ion of t he paramt erizat ions in t he microphysics
• Autoconversion
• S

aturation Adj ustment/ Predicted S aturation for Condensation

• Aerosol S

cavenging and Regeneration

• WRF v3.1.1 wit h TAMU t wo-moment

bulk microphysical scheme

• 3 int eract ive domains
• Innermost domains covers S

GP cent ral Facilit y and RACORO flight s rout es wit h 750m spat ial, 50 vert ical res.

• Nort h American Region Reanalysis
• May 26-28, cumulus and drizzling

st rat us, low CCN, low updraft

• Two different aerosol profiles used:

cont rol case (c-case) ~ 400 part icles/ cm3 and pollut ed case (p-case) ~ 2000 part icles/ cm3

• Aerosol radiat ive effect s are considered

seperat ely (prad-case)

• Obs: ARS

CL

• Model: 5x5 box
• Qtot > 10-6 kg/ kg
• Cumulus & S

t at us

• Modeled cases similar
• Timing consist ent
• Overest imat ion

close t o t he surface

Obs. Model

CCN LWC Nc

T Qv

Rc LWP Rainfall Vertical Velocity

• WRF model wit h t wo-moment cloud microphysics and t hree

moment aerosol scheme predict ed t he evolut ion of low lever cumulus, st rat us as well as CCN.

• Over-est imat ed cloud amount near t he surface is mainly

caused by biased t emperat ure simulat ion in t he WRF .

• Cloud microphysics developed at TAMU show a bet t er

agreement wit h field measurement t han some of t he ot her microphysics in t he WRF .

• Aerosol efficient ly affect t he cloud effect ive radius,

precipit at ion efficiency and t he cloud dynamics.