Evaluation of Organic aerosols over the Amazon rainforest using WRF-chem with MOSAIC aerosol model

Abstract:

Organic aerosol (OA) accounts for a large fraction of 70 to 80% in particulate matter over the amazon rainforest. We find that the default WRF-chem model underestimates OA by 57% in Amazon rainforest compared with observations from GoAmazon2014/5 field campaign during March. Simulation is largely improved when aging of secondary organic aerosol (SOA) and formation of isoprene-epoxydiol-derived secondary organic aerosol (IEPOX-SOA) are considered in the model. With the improved model, we show that the OA budget PM_2.5 is 0.13±0.03 Tg in Amazon, which is about 40% to 75% of total PM_2.5. We then evaluate the convective influence on the vertical profiles of OA over the Amazon rainforest. We find that low tropospheric OA are removed by the secondary activation of OA above cloud base. Simulations suggest that when Amazon rainforest is replaced by grassland and barren (representing one extreme scenario in climate change), OA burden is decreased by 25% to 80% in the Amazon rainforest. The corresponding change in radiation budget and precipition are evaluated in the study.