CCN effects on numerically simulated mixed-phase

convective storms

with

Klaus D. Beheng, University Karlsruhe, Germany

Alexander Khain, Hebrew University Jerusalem, Israel

Axel Seifert

National Center for Atmospheric Research (ASP/MMM)

Motivation

• Explicit simulation of aerosol-cloud interactionis necessary to estimate indirect aerosol effects on climate

• Considering aerosol conditions might increasethe forecast skill of NWP models

• How can we improve the representation of clouds in weather and climate models?

(Seifert and Beheng 2001)

A two-moment 5-class cloud scheme

Nucleation? RICO!

(Seifert and Beheng 2003, submitted)

Comparison within theHebrew Univ. Cloud Model (HUCM)

Comparison within theHebrew Univ. Cloud Model (HUCM)

BIN BULK

CONT

MARI

Timeseries of maximum mass concentrations

Maximum vertical velocities

Total grid averaged precipitation

(Seifert et al. 2004, submitted)

A numerical study of CCN effects on different storm types

Weisman and Klemp (1982)sensitivity study, but nowincluding CCN as a third external parameter:

Variation of 1. CAPE 2. vertical wind shear3. CCN concentration

Effects on total precipitation?(Seifert and Beheng 2003, submitted)

Total 3h-precipitation

supercell convection

multicell conv.

Total 3h-precipitationand rel. change for cont. CCN

Coupling of microphysics and dynamics!

Continuous transition from maritime to cont. CCN

Confronting the model with real data!

Dual-wavelength radar data from CRYSTAL-FACE:

(data provided by G. Heymsfield, NASA)

Observations vs. WRF Simulation

Summary• A new two-moment microphysical scheme has been

developed and is implemented in WRF (KAMM2, LM, MM5)

• The scheme is able to resolve CCN effects explicitly

• The scheme shows a good agreement with the spectralbin microphysics in the Hebrew Univ. Cloud Model

• A sensitivity study shows an inverse aerosol effectfor multicellular convection (latent heat effect)

• Validation with dual-wavelength radar?

Autoconversion

GATE squall line – total precip.

Bulk nucleation scheme