Investigation of aerosol indirect effects using a cumulus microphysics parameterization in a regional climate model

Lim, Kyo‐Sun Sunny; Fan, Jiwen; Leung, L. Ruby; Ma, Po‐Lun; Singh, Balwinder; Zhao, Chun; Zhang, Yang; Zhang, Guang; Song, Xiaoliang

doi:10.1002/2013jd020958

Cited by 41 publications

(39 citation statements)

References 104 publications

(160 reference statements)

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“…The surface cooling effect of dust can decrease the SST, which may influence the ISM rainfall response to Middle East dust. Thirdly, the aerosol indirect effect is parameterized only in the microphysics scheme on the grid scale (i.e., stratiform rainfall) in current WRFChem (e.g., Lim et al, 2014), therefore experiments with a relatively coarse horizontal resolution of 54 km that cannot resolve convective clouds (typically 1-5 km wide) fails to consider the aerosol indirect effects on the ISM convective rainfall. In future studies, we suggest the use of a highresolution RCM with grid spacing at 1-5 km coupled with an ocean model to quantify the impacts of dust-induced SST change and aerosol indirect effects on the ISM rainfall.…”

Section: Discussionmentioning

confidence: 99%

Consistent response of Indian summer monsoon to Middle East dust in observations and simulations

Jin

Wei

et al. 2015

Atmos. Chem. Phys.

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Abstract. The response of the Indian summer monsoon (ISM) circulation and precipitation to Middle East dust aerosols on sub-seasonal timescales is studied using observations and the Weather Research and Forecasting model coupled with online chemistry (WRF-Chem). Satellite data show that the ISM rainfall in coastal southwest India, central and northern India, and Pakistan is closely associated with the Middle East dust aerosols. The physical mechanism behind this dust-ISM rainfall connection is examined through ensemble simulations with and without dust emissions. Each ensemble includes 16 members with various physical and chemical schemes to consider the model uncertainties in parameterizing short-wave radiation, the planetary boundary layer, and aerosol chemical mixing rules. Experiments show that dust aerosols increase rainfall by about 0.44 mm day −1 (∼ 10 % of the climatology) in coastal southwest India, central and northern India, and north Pakistan, a pattern consistent with the observed relationship. The ensemble mean rainfall response over India shows a much stronger spatial correlation with the observed rainfall response than any other ensemble members. The largest modeling uncertainties are from the boundary layer schemes, followed by short-wave radiation schemes. In WRF-Chem, the dust aerosol optical depth (AOD) over the Middle East shows the strongest correlation with the ISM rainfall response when dust AOD leads rainfall response by about 11 days. Further analyses show that increased ISM rainfall is related to enhanced southwesterly monsoon flow and moisture transport from the Arabian Sea to the Indian subcontinent, which are associated with the development of an anomalous low-pressure system over the Arabian Sea, the southern Arabian Peninsula, and the Iranian Plateau due to dust-induced heating in the troposphere. The dust-induced heating in the mid-upper troposphere is mainly located in the Iranian Plateau rather than the Tibetan Plateau. This study demonstrates a thermodynamic mechanism that links remote desert dust emissions in the Middle East to ISM circulation and precipitation variability on subseasonal timescales, which may have implications for ISM rainfall forecasts.

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Section: Discussionmentioning

confidence: 99%

Consistent response of Indian summer monsoon to Middle East dust in observations and simulations

Jin

Wei

et al. 2015

Atmos. Chem. Phys.

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“…For the Zhang and McFarlane (1995) deep convection, although a two-moment microphysics scheme has been developed and evaluated (Song and Zhang, 2011;Song et al, 2012;Lim et al, 2014), it is not included in the model version used in this study. Moist turbulence is represented by the parameterization of Bretherton and Park (2009).…”

Section: A Brief Overview Of Cam5mentioning

confidence: 99%

Technical Note: On the use of nudging for aerosol–climate model intercomparison studies

et al. 2014

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Abstract. Nudging as an assimilation technique has seen increased use in recent years in the development and evaluation of climate models. Constraining the simulated wind and temperature fields using global weather reanalysis facilitates more straightforward comparison between simulation and observation, and reduces uncertainties associated with natural variabilities of the large-scale circulation. On the other hand, the forcing introduced by nudging can be strong enough to change the basic characteristics of the model climate. In the paper we show that for the Community Atmosphere Model version 5 (CAM5), due to the systematic temperature bias in the standard model and the sensitivity of simulated ice formation to anthropogenic aerosol concentration, nudging towards reanalysis results in substantial reductions in the ice cloud amount and the impact of anthropogenic aerosols on long-wave cloud forcing.In order to reduce discrepancies between the nudged and unconstrained simulations, and meanwhile take the advantages of nudging, two alternative experimentation methods are evaluated. The first one constrains only the horizontal winds. The second method nudges both winds and temperature, but replaces the long-term climatology of the reanalysis by that of the model. Results show that both methods lead to substantially improved agreement with the freerunning model in terms of the top-of-atmosphere radiation budget and cloud ice amount. The wind-only nudging is more convenient to apply, and provides higher correlations of the wind fields, geopotential height and specific humidity between simulation and reanalysis. Results from both CAM5 and a second aerosol-climate model ECHAM6-HAM2 also indicate that compared to the wind-and-temperature nudging, constraining only winds leads to better agreement with the free-running model in terms of the estimated shortwave cloud forcing and the simulated convective activities. This suggests nudging the horizontal winds but not temperature is a good strategy for the investigation of aerosol indirect effects since it provides well-constrained meteorology without strongly perturbing the model's mean climate.

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“…To facilitate the use of regional models as testbed for physics parameterizations used in global models, a new online-coupled climate and chemistry model, i.e., the Weather Research and Forecasting model coupled with chemistry (WRF/Chem) ( [5]) with the physics suite of Community Atmospheric Model version 5 (referred to as WRF-CAM5) ( [6,7]) has been recently developed. WRF-CAM5 is based on WRF/Chem version 3.5 released as of April 2013 and CAM version 5.0 released as of June 2010.…”

Section: Introductionmentioning

confidence: 99%

Application of an Online-Coupled Regional Climate Model, WRF-CAM5, over East Asia for Examination of Ice Nucleation Schemes: Part I. Comprehensive Model Evaluation and Trend Analysis for 2006 and 2011

Chen

Zhang

Fan

et al. 2015

Climate

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Online-coupled climate and chemistry models are necessary to realistically represent the interactions between climate variables and chemical species and accurately simulate aerosol direct and indirect effects on cloud, precipitation, and radiation. In this Part I of a two-part paper, simulations from the Weather Research and Forecasting model coupled with the physics package of Community Atmosphere Model (WRF-CAM5) are conducted with the default heterogeneous ice nucleation parameterization over East Asia for two full years: 2006 and 2011. A comprehensive model evaluation is performed using satellite and surface observations. The model shows an overall acceptable performance for major meteorological variables at the surface and in the boundary layer, as well as column variables (e.g., precipitation, cloud fraction, precipitating water vapor, downward longwave and shortwave radiation). Moderate to large biases exist for cloud condensation nuclei over oceanic areas, cloud variables (e.g., cloud droplet number concentration, cloud liquid and ice water paths, cloud optical OPEN ACCESSClimate 2015, 3 628 depth, longwave and shortwave cloud forcing). These biases indicate a need to improve the model treatments for cloud processes, especially cloud droplets and ice nucleation, as well as to reduce uncertainty in the satellite retrievals. The model simulates well the column abundances of chemical species except for column SO2 but relatively poor for surface concentrations of several species such as CO, NO2, SO2, PM2.5, and PM10. Several reasons could contribute to the underestimation of major chemical species in East Asia including underestimations of anthropogenic emissions and natural dust emissions, uncertainties in the spatial and vertical distributions of the anthropogenic emissions, as well as biases in meteorological, radiative, and cloud predictions. Despite moderate to large biases in the chemical predictions, the model performance is generally consistent with or even better than that reported for East Asia with only a few exceptions. The model generally reproduces the observed seasonal variations and the difference between 2006 and 2011 for most variables or chemical species. Overall, these results demonstrate promising skills of WRF-CAM5 for long-term simulations at a regional scale and suggest several areas of potential improvements.

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Investigation of aerosol indirect effects using a cumulus microphysics parameterization in a regional climate model

Cited by 41 publications

References 104 publications

Consistent response of Indian summer monsoon to Middle East dust in observations and simulations

Consistent response of Indian summer monsoon to Middle East dust in observations and simulations

Technical Note: On the use of nudging for aerosol–climate model intercomparison studies

Application of an Online-Coupled Regional Climate Model, WRF-CAM5, over East Asia for Examination of Ice Nucleation Schemes: Part I. Comprehensive Model Evaluation and Trend Analysis for 2006 and 2011

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