Physical and chemical properties of aerosol across northern India and the Middle East

Abstract

Atmospheric aerosol particles are ubiquitous in the atmosphere and their properties can have significant impacts on the atmospheric energy balance. Uncertainties lie in the characteristics of atmospheric aerosols, due to instrumentation limitations but also due to the complexity of aerosol emission and aging mechanisms. South Asia is one of the world’s largest aerosol emitters due to the large population density and growth, as well as complex emissions sources. During the pre-monsoon, a thick aerosol haze forms across northern India which undergoes vast changes as the monsoon season progresses. To date, there has been a lack of detailed in-situ measurements during both the pre-monsoon and monsoon seasons with high temporal and spatial resolution. Similar trends exist in the scientific understanding behind aerosol properties across the Middle East. It is therefore becoming ever more important to understand the aerosol characteristics across both of these regions, which will have consequences for issues as diverse as public health and global climate change. This project addresses this problem through two field campaigns. First, aircraft observations were made in northern India during the South West Asian Aerosol Monsoon Interactions (SWAAMI) field campaign in the pre-monsoon and monsoon seasons of 2016, to observe the broad regional-scale distribution of aerosol chemical and physical properties. Results were collected in-situ with an Aerosol Mass Spectrometer (AMS) and a Single Particle Soot Photometer (SP2), alongside other online aerosol instrumentation. Second, ship-borne observations were made across the Mediterranean and Middle East during the Air Quality and climate change in the Arabian BAsin (AQABA) campaign during the summer of 2017. Again, collecting in-situ measurements with an Aerosol Mass Spectrometer (AMS), alongside other online aerosol instrumentation. Airborne observations across northern India highlighted the organics dominated boundary layer and sulphate dominated elevated aerosol layer inside the Indo-Gangetic Plain (IGP), compared to a sulphate dominated profile outside of the IGP. It was also demonstrated that moderately-coated black carbon particles dominate the aerosol column inside the IGP, whereas small BC particles with little coating are present outside of the IGP. Ship-borne observations across the Middle East found acidic, sulphate dominated air masses throughout the Persian Gulf, whereas organic aerosol dominated air masses throughout the Mediterranean. The aerosol loading was influenced by a complex mixture of both locally and long-range transported air masses. In summary, these findings provide insight into aerosol properties in regions where such intensive in-situ observations have been lacking.

Date of Award	31 Dec 2019
Original language	English
Awarding Institution	The University of Manchester
Supervisor	James Allan (Supervisor), Paul Williams (Supervisor) & Hugh Coe (Supervisor)