[A-AS11] Aerosol impacts on air quality, climate system, and our society

[AAS11-P09] Regional trends of combustion aerosol and dust in recent decades: a satellite-model integrated analysis

*Hongbin Yu¹, Yang Yang², Hailong Wang¹, Qian Tan^3,4, Mian Chin¹, Robert Levy¹, Lorraine Remer⁵, Steven Smith², Tianle Yuan^1,5, Yingxi Shi^1,5, Zhibo Zhang⁵, Qianqian Song⁵, Paul Ginoux⁶ (1.NASA Goddard Space Flight Center, 2.Pacific Northwest National Laboratory, 3.Bay Area Environmental Research Institute, 4.NASA Ames Research Center, 5.University oof Maryland Baltimore County, 6.NOAA GFDL)

Keywords:pollution, dust, satellite, model, trend

Emissions and long-range transport of mineral dust and combustion-related aerosol from burning fossil fuels and biomass vary from year to year, driven by the evolution of the economy and changes in meteorological conditions and environmental regulations. This study offers both satellite and model perspectives of interannual variability and possible trends of combustion aerosol and dust in major continental outflow regions over the past 15 years (2003-2017). The decade-long record of aerosol optical depth (AOD, denoted as t), separately for combustion aerosol (t_c) and dust (t_d), is derived from the aerosol products of the Moderate Resolution Imaging Spectroradiometer (MODIS) onboard both Terra and Aqua. The MODIS datasets, complemented by aerosol source-tagged simulations using the Community Atmospheric Model Version 5 (CAM5), are then analyzed to understand the interannual variability and potential trend of t_c and t_d in the major continental outflows. Both MODIS and CAM5 consistently yield a similar decreasing trend of -0.017 to -0.020 per decade for t_c over the North Atlantic Ocean and the Mediterranean Sea that is attributable to reduced emissions from North America and Europe, respectively. On the contrary, both MODIS and CAM5 display an increasing trend of +0.017 to +0.036 per decade for t_c over the tropical Indian Ocean, the Bay of Bengal, and the Arabian Sea, which reflects the influence of increased anthropogenic emissions from South Asia and the Middle East in the last 2 decades. Over the northwestern Pacific Ocean that is often affected by East Asian emissions of pollution and dust, the MODIS retrievals show non-monotonic but overall decreasing trend of -0.021 per decade for t_c and -0.012 per decade for t_d, which is however not reproduced by the CAM5 model. In other outflow regions strongly influenced by biomass burning smoke or dust, both MODIS retrievals and CAM5 simulations show no statistically significant trends; and the MODIS observed interannual variability is usually larger than that of the CAM5 simulation. Seasonal variations of regional trends will also be discussed.