PNNL

Abstract

We incorporate the Model for Simulating Aerosol Interactions and Chemistry (MOSAIC) module in the Community Earth System Model version 2 (CESM2) Community Atmosphere Model Version 6 with interactive chemistry (CAM6-chem), and couple it with the MAM4 aerosol scheme and atmospheric chemistry. The MOSAIC module is used to simulate the thermodynamics of gas-aerosol mass exchange, with a special focus on simulating nitrate aerosol. By comparing against ground and satellite observations, we found that the MOSAIC/MAM4 scheme performs reasonably well in simulating spatiotemporal distributions of aerosols, including nitrate aerosols. We conducted a series of experiments and found that radiative forcing associated with nitrate aerosols substantially changes from 1975 to 2000, and further to 2010, and from region to region. Strict regulations on NOx emissions in Europe and USA slightly decreased the magnitude of radiative forcing due to aerosol-radiation interaction associated with nitrate (RFari) from 1975 to 2010, although the radiative forcing due to aerosol-cloud interaction associated with nitrate (RFaci) over Northern Atlantic Ocean adjacent to Europe and USA reaches as high as about -5 ~ -10 W m-2. As the direct consequence of rapid economic development, nitrate aerosols in China and India contribute as large as -0.28 W m-2 and -0.31 W m-2 RFari cooling locally in 2010, which are about 3.7 and 3.6 times that of the RFari in 1975, respectively. The rapid growth in nitrate RFari cooling, which is faster than that of many major aerosol types, indicates that nitrate aerosols can have greater importance in the future.