Kostas Tsigaridis

He is currently working on a variety of topics related to aerosol research and their sources, sinks, and interactions with climate at various levels of complexity. His studies range from detailed aerosol processes such as the formation of secondary organic aerosols (SOA), to centennial time scale climate variability related to natural variability and external forcings. While his main expertise is organic aerosols, he's also experienced in working with all other aerosol types as well as tropospheric gas-phase and heterogeneous chemistry. He has extensively used both box models that he developed, and 3-dimensional global models: the TM3 chemistry/transport model, the IPSL general circulation model LMDz-INCA, and the GISS modelE Earth System Model (ESM), for which he had contributed to the IPCC AR5 model development. Currently he is working with the next generation of the NASA GISS ESM, the GISS ModelE2.1, which is part of CMIP6.  Topics that he works on or plan to work in the future include studies of:

• missing aerosol species and sources, such as the primary oceanic aerosols and their importance on the remote marine atmosphere, the in-cloud and aerosol water aqueous formation of organic aerosols that can lead to brown carbon formation, the primary terrestrial biological particles, and the organic nitrogen
• missing aerosol parameterizations, such as the effect of aerosol mixing on cloud condensation nuclei and aerosol absorption, the semi-volatility of primary organic aerosols, the importance of in-canopy processes on natural terrestrial aerosol and aerosol precursor sources, and the mineral dust iron solubility and bioavailability
• the change of aerosol burden and its spatiotemporal distribution, especially with regard to its role and importance on gas-phase chemistry via photolysis rates changes and heterogeneous reactions in the atmosphere, as well as their effect on key gas-phase species like ozone
• the physical and optical properties of aerosols, which affect aerosol transport, lifetime, and light scattering and absorption, with the latter being very sensitive to the vertical distribution of absorbing aerosols
• aerosol-cloud interactions, which include cloud activation, the aerosol indirect effect and the impact of clouds on aerosol removal
• changes on climate and feedbacks related with all these topics

In order to understand the climate system as a whole, improve the aerosol representation in the GISS ModelE2.1 and contribute to future IPCC climate change assessments and CMIP activities, he's also interested in understanding the importance of natural and anthropogenic aerosol changes in the atmosphere on the terrestrial biosphere, the ocean and climate. The climate feedbacks involved with these changes, which are key in understanding the climate system as a whole, include:

• the importance of aerosol absorption on climate
• the impact of aerosol deposition which affects biology and, hence, emissions of aerosols and aerosol precursors via organic nitrogen, organic phosphorus and iron fertilization
• the importance of land use and land use changes on natural and anthropogenic aerosol sources
• the SOA sources and impact on climate, with special attention on the impact human activities have on natural SOA formation

In order to quantitatively answer such questions he performs simulations of the past, present and future atmospheres, and make comparisons with measurements and remote sensing data, all of which help understand, evaluate and improve the model’s parameterizations and performance, and our understanding of the Earth system.