Title: Decrease in radiative forcing by organic aerosol nucleation, climate, and land use change
Authors: Jialei Zhu, Joyce E. Penner, Fangqun Yu, Sanford Sillman, Meinrat O. Andreae, Hugh Coe
Contact: Jialei Zhu, jialeiz@umich.edu

Key Points:
- A new version of the CESM/IMPACT atmospheric model that includes organic nucleation is presented.
- The aerosol concentration in present day and preindustrial period are simulated. The result is presented.

Research Overview:
We improve on previous simulations that overestimate boundary layer nucleation in the tropics and add changes to climate and land use to evaluate climate forcing. Our model includes both pure organic nucleation and heteromolecular nucleation of sulfuric acid and organics and reproduces the profile of organic aerosol number concentration measured in the Amazon. Organic nucleation decreases the sum of the total aerosol direct and indirect radiative forcing by 12.5%. The addition of climate and land use change decreases the direct radiative forcing (-0.38 W m-2) by 6.3% and the indirect radiative forcing (-1.68 W m-2) by 3.5% due to the size distribution and number concentration change of secondary organic aerosol and sulfate.  Overall, the total radiative forcing associated with anthropogenic aerosols is decreased by 16%.

Methodology:
The data are model output from climate simulations conducted with the Community Earth System Model (CESM) version 1.2.2 with the IMPACT aerosol module. The input files are default in the component set of “FC5” in CESM model for the PD and PIemi case. The component set of “F1850C5” are used for PIall case.

Files contained here:
We include three source code tar files and 36 major output netcdf files from simulations conducted in the paper. The ending of 1-12 stand for the 5-year average in each month from January to December. “PD” stands for the present day case. “PIemi” stands for the preindustrial period (around 1750) case including only anthropogenic emission change. “PIall” stands for the preindustrial period (around 1750) case including anthropogenic emission, climate and land use change. 

The files are described below:

src.cam_PD.zip
This tar file contains the source code of the IMPACT aerosol module that we implemented as additional aerosol module embedded in the CESM version1.2.2 which is publicly available from NCAR repository. This code is for the present day case applied in the related publication.

src.cam_PIall.zip
This tar file is same with src.cam_PD.zip, but for the preindustrial period case including anthropogenic emission, climate and land use change.

src.cam_PIemi.zip
This tar file is same with src.cam_PD.zip, but for the preindustrial period case including only anthropogenic emission change.

Data_PD-5a-**.nc
Netcdf output file of 5-year mean monthly meteorological and aerosol fields from the simulation PD. 

Data_PIall-5a-**.nc
Netcdf output file of 5-year mean monthly meteorological and aerosol fields from the simulation PIall.

Data_PIemi-5a-**.nc
Netcdf output file of 5-year mean monthly meteorological and aerosol fields from the simulation PIemi. 

Related publication(s):
Zhu, J. et al. Decrease in radiative forcing by organic aerosol nucleation, climate, and land use change. Nature Communications 10, 423 (24 January 2019).

Use and Access: 
This data set is made available under a Creative Commons Attribution-NonCommercial 4.0 International license(CC BY-NC 4.0).

To Cite Data: 
Zhu, J, Penner, J. E., Yu, F., Sillman, S., Andreae, M. O., Coe, H.: Decrease in radiative forcing by organic aerosol nucleation, climate, and land use change, (2018)[Data set]. University of Michigan Deep Blue Data Repository. https://doi.org/10.7302/Z20Z71JP