Task 258

The impacts of aerosol on convective system with WRF

Principal Investigator(s):

Tzuchin Tsai

Sponsor(s):

W. Tao

Last Updated:

October 26, 2012 15:26:19

Description of Problem

To evaluate the impacts of aerosol on convective system with WRF double-moment microphysical scheme

Scientific Objectives and Approach

Aerosol can serve as cloud condensation nuclei (CCN) to initial cloud drops and regulate drop number and size, thus affecting precipitation development. But so far most microphysical schemes in the Weather Research and Forecasting (WRF) model crudely set cloud drop number as a constant. The CLR double-moment microphysical scheme based on Chen and Liu (2004), Reisner et al. (1998), and Cheng et al. (2010) keeps track of the mixing ratios and number concentrations with respect to five hydrometeors (cloud, rain, ice, snow, and graupel), 3 groups of CCN (dry or interstitial CCN, rain CCN, and cloud CCN), as well as a specified number of ice nuclei (IN) species. The information in rain and cloud CCN allows aerosol recycling from drop evaporations. In CLR scheme, condensation nuclei (CN) are assumed to compose of ammonium sulfate with a tri-modal lognormal size distribution. Cutoffsize CN to be activated into cloud drops depending on supersaturation according to Köhler equation.

Accomplishments

Now, CLR scheme has been implemented into the newly released WRF model version 3.3.1 to evaluate aerosol impact on cloud and precipitation. The Tropical Warm Pool—International Cloud Experiment (TWP-ICE) that took place over Australia (May et al., 2008) is selected for simulation. Comparison of the simulation results with observation and other double-moment schemes like Morrison scheme is analyzing.

Other Publications and Conferences

Tsai, T.-C., J.-P. Chen, and Wei-Kuo Tao, Evaluating Aerosol Impact on Precipitation with CLR Double-Moment Microphysical Scheme in WRF Model, submitted to ICCP 2012.