Implementation of an aerosol–cloud‐microphysics–radiation coupling into the NASA unified WRF: Simulation results for the 6–7 August 2006 AMMA special observing period

Abstract

Aerosols affect the Earth's radiation balance directly and cloud microphysical processes indirectly via the activation of cloud condensation and ice nuclei. These two effects have often been considered separately and independently, hence the need to assess their combined impact given the differing nature of their effects on convective clouds. To study both effects, an aerosol-microphysics-radiation coupling, including Goddard microphysics and radiation schemes, was implemented into the NASA Unified Weather Research and Forecasting model (NU-WRF). Fully coupled NU-WRF simulations were conducted for a mesoscale convective system (MCS) that passed through the Niamey, Niger area on 6-7 August 2006 during an AMMA special observing period. The results suggest that rainfall is reduced when aerosol indirect effects are included, regardless of the aerosol direct effect. Daily mean radiation heating profiles in the area traversed by the MCS showed the aerosol (mainly mineral dust) direct effect had the largest impact near cloud tops just above 200 hPa where short-wave heating increased by about 0.8 K day −1 ; the weakest long-wave cooling was at around 250 hPa. It was also found that more condensation and ice nuclei as a result of higher aerosol/dust concentrations led to increased amounts of all cloud hydrometeors because of the microphysical indirect effect, and the radiation direct effect acts to reduce precipitating cloud particles (rain, snow and graupel) in the middle and lower cloud layers while increasing the non-precipitating particles (ice) in the cirrus anvil. However, when the aerosol direct effect was activated, regardless of the indirect effect, the onset of MCS precipitation was delayed about 2 h, in conjunction with the delay in the activation of cloud condensation and ice nuclei. Overall, for this particular environment, model set-up and physics configuration, the effect of aerosol radiative heating due to mineral dust overwhelmed the effect of the aerosols on microphysics.

The Role of Aerosol-Cloud-Radiation Interactions in Regional Air Quality—A NU-WRF Study over the United States

“…The cloud-to-rain auto-conversion is then calculated as a function of water content using a threshold approach, and the IN is used for calculation of the cloud ice mass. Aerosol mass concentrations for black carbon, organic carbon, sulfate, sea-salt, and dust are employed to calculate aerosol optical depth (AOD), single-scattering albedo, and asymmetry factor, which serve as inputs to a radiative transfer model to simulate aerosol interactions with radiation [28].…”

“…The higher ozone (>45 ppbv) was modeled over the scatter areas in California, Arizona, Utah, Virginia, and North Carolina. Previous studies have shown that NU-WRF has sufficient skills in simulating land-atmosphere exchange, aerosol-cloud-radiation interactions, atmospheric photochemical processes, and air quality [21][22][23]28]. In this study, we compared the daily precipitation from the control experiment to the rain gauge data analyzed by the Climate Prediction Center of the National Oceanic and Atmospheric Administration under its unified precipitation project [45,46].…”

Introducing multisensor satellite radiance-based evaluation for regional Earth System modeling

“…This manuscript utilizes the NU-WRF simulation from Shi et al [2013] that features a specific Mesoscale Convective System (MCS) interacting with land and aerosols (mineral dust) processes over West Africa coincide with the African Monsoon Multidisciplinary Analyses (AMMA) experiments. As a demonstration of the radiance-based evaluation method, we primarily focus on the simulation results at 01 Z 6 August 2006, because of the maturity of the simulated MCS surrounded by mineral dust and the coinciding of these features with various satellite observations.…”

Overview of the development of the Aerosol Loading Interface for Cloud microphysics In Simulation (ALICIS)

“…The third approach is used in most global or coarseresolution regional models for studies of aerosol-cloud interactions, even on a climatic scale (e.g., Storelvmo et al 2006Storelvmo et al , 2008Lohmann et al 2007;Morrison and Gettelman 2008;Suzuki et al 2008;Takemura et al 2009;Wang et al 2011;Wang et al 2013;Park et al 2014;Shi et al 2014). Supersaturation and the vertical wind velocity cannot be resolved well on model grid points with coarse intervals.…”

“…Cloud-ice nucleation and heterogeneous freezing of supercooled droplets were calculated using the parametrizations of Bigg (1953), Koop et al (2000), Phillips et al (2008), andDeMott et al (2010). Shi et al (2014) used aerosol and chemical-transport model simulations as a tool to provide a realistically diagnosed aerosol field for their cloud microphysics calculation in the main model framework with the same domain configuration. They incorporated the following two individual models off-line: the GOCART solomodule version of the WRF coupled with chemistry (WRF-Chem; Grell et al 2005), and the National Aeronautics and Space Administration (NASA) Unified WRF (NU-WRF; Peters-Lidard et al 2015).…”