Implementation of a two‐moment bulk microphysics scheme to the WRF model to investigate aerosol‐cloud interaction

Abstract

[1] A two-moment bulk microphysical scheme has been implemented into the Weather Research and Forecasting (WRF) model to investigate the aerosol-cloud interaction. The microphysical scheme calculates the mass mixing ratios and number concentrations of aerosols and five types of hydrometeors and accounts for various cloud processes including warm and mixed phase microphysics. The representation of the aerosol size distribution is evaluated, showing that the three-moment modal method produces results better in agreement with the sectional approach than the two-moment modal method for variable supersaturation conditions in clouds. The effects of aerosols on cloud processes are investigated using the two-moment bulk microphysical scheme in a convective cumulus cloud event occurring on 24 August 2000 in Houston, Texas. The modeled evolution of the distribution of radar reflectivity in the y-z section, the cell lifetime, and averaged accumulated precipitation with the aerosol concentration under the polluted urban condition are qualitatively consistent with the measurements. Sensitivity simulations are initialized using a set of aerosol profiles with the number concentrations ranging from 200 to 50,000 cm À3 and mass ranging from 1 to 10 mg m À3 at the surface level. The response of precipitation to the increase of aerosol concentrations is nonmonotonic, because of the complicated interaction between cloud microphysics and dynamics. The precipitation increases with aerosol concentrations from clean maritime to continental background conditions, but is considerably reduced and completely suppressed under highly polluted conditions, indicating that the aerosol concentration exhibits distinct effects on the precipitation efficiency under different aerosol conditions. The maximal cloud cover, core updraft, and maximal vertical velocity exhibit similar responses as precipitation. Comparison is made to evaluate the effects of different autoconversion parameterizations and bulk microphysical schemes on cloud properties. Because of its broad application in numerical weather prediction, implementation of the two-moment microphysical scheme to the WRF model will greatly facilitate assessment of aerosol-cloud interaction from individual cumulus to mesoscale convective systems.Citation: Li, G., Y. Wang, and R. , Implementation of a two-moment bulk microphysics scheme to the WRF model to investigate aerosol-cloud interaction,

Observations of aerosol‐induced convective invigoration in the tropical east Atlantic

“…studies [Andreae et al, 2004;Khain et al, 2005;van den Heever et al, 2006;van den Heever and Cotton, 2007;Lee et al, 2008a;Li et al, 2008;Rosenfeld et al, 2008;Lebo and Seinfeld, 2011;Li et al, 2011;Storer and van den Heever, 2013;Fan et al, 2013] showing evidence that increased aerosol concentrations can lead to convective invigoration. These studies are in general agreement that polluted clouds produce less warm rain through the aerosol-induced suppression of the collision and coalescence processes, as the large numbers of small droplets make the warm rain process less efficient.…”

“…This leaves higher amounts of liquid water in cloud that can be lofted to form ice, providing an additional source of latent heating which can increase the buoyancy of an updraft. These changes can lead to stronger storms with higher cloud tops, greater ice mass, and heavier surface precipitation [Andreae et al, 2004;Khain et al, 2005;Koren et al, 2005;van den Heever et al, 2006;Li et al, 2008;Rosenfeld et al, 2008;Storer et al, 2010;Tao et al, 2012;Storer and van den Heever, 2013].…”

“…Several studies [Andreae et al, 2004;Khain et al, 2005;Koren et al, 2005;van den Heever et al, 2006;van den Heever and Cotton, 2007;Lee et al, 2008a;Li et al, 2008;Rosenfeld et al, 2008;Lebo and Seinfeld, 2011;van den Heever et al, 2011;Storer and van den Heever, 2013;Fan et al, 2013] suggest that increased aerosol concentrations will lead to the invigoration of deep convective storms; however, there is still no clear consensus on this effect, as recently summarized in Tao et al [2012]. It is generally established that in a polluted environment, or one which contains higher number concentrations of aerosols that can act as cloud condensation nuclei (CCN), collision and coalescence in deep convective systems will be less effective due to the increased numbers of smaller cloud droplets, thus leading to a reduction in warm rain production.…”

Persistent sulfate formation from London Fog to Chinese haze

“…It is well established, though, that sulfate (SO 4 2− ) is ubiquitous and is a key PM constituent in the atmosphere. Moreover, hygroscopic sulfate aerosols serve as efficient cloud condensation nuclei, affecting cloud formation, precipitation, and climate (4)(5)(6)(7)(8). A major fraction of regional acid deposition is attributed to the sulfate content that exerts debilitating effects on acid-sensitive ecosystems (9).…”

Implementation of aerosol–cloud interactions in the regional atmosphere–aerosol model COSMO-MUSCAT(5.0) and evaluation using satellite data

“…Morrison et al (2009) showed that using a two-moment scheme in the WRF model produced more trailing stratiform precipitation in an idealized two-dimensional squall case, which is more consistent with observations. In another study, Li et al (2008) investigated the effect of aerosol on cloud microphysical processes with a two-moment microphysical scheme in the WRF model. Also, Lim and Hong (2010) have included a prognostic equation for cloud water and cloud condensation nuclei number concentration (C ccn ), which could reduce the uncertainty in investigating the aerosol effect on cloud properties and the precipitation process in the WRF model.…”