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Aerosols, Clouds & Radiation

Aerosols, Clouds & Radiation


Radiative forcing due to aerosols and clouds are a large source of climate uncertainty, in part due to the difficulty of obtaining accurate observations. It is especially difficult to observe aerosols above clouds, a situation that occurs frequently in some parts of the world, with poorly understood impacts.

The NASA ORACLES (ObseRvations of Aerosols above CLouds and their intEractionS) field campaign was devoted to reducing this uncertainty, by deploying instrumented aircraft to the South East Atlantic Ocean in the Austral spring of 2016, 2017 and 2018. Dr. Segal-Rozenhaimer has participated in ORACLES as a science-team-member, the AERONET (ground based aerosol) measurements and the airborne AFS (Aerosol Filter System) Instruments PI, as well as the deputy-PI for 4STAR (NASA Ames Airborne sunphotometer). During ORACLES, we took extensive measurements of clouds, aerosol and radiation on the airborne platform and we are involved in multiple studies and data analysis efforts understanding the radiative budget and forcing in this part of the world.

The NASA P-3 is getting ready for take off, at Sao-Tome, Africa



Understanding how aerosol mixing state, chemical composition, morphology and microstructure affect bulk optical properties such as the single-scattering albedo (SSA), and how they affect the sign of the net top-of-atmosphere radiative forcing. In this DOE-ASR funded project we investigate how aging time in the atmosphere and cloud processing time and extent might affect the mixing state of the biomass-burning aerosol particles that were sampled in ORACLES ( as well as other campaigns including the UK-Met Office CLARIFY and LASIC, and how these affect their ability to absorb visible light.

ORACLES Research Flight 010 (Oct-17-2018) trajectory (top right), including time in cloud, with analyzed TEM imagery of some BC (black carbon) mixed particles, and their calculated MACs for various optical mixing models.



Studying how aerosols affect marine stratocumulus cloud (MSC) type and dynamics in the South-East Atlantic (SEA). In this NASA funded project, we are working on developing a new tool to detect cloud types (see our machine learning applications page), and to utilize it to track diurnal changes in the frequency of open versus closed marine cellular convection cells under various aerosol conditions.

Diurnal cycle of total cloud fraction in SE Atlantic region during biomass burning season (Aug.-Oct.) based on 3 years from the Meteosat SEVIRI geostationary satellite observations. We see that the within and between seasonal variability is high and we investigate how aerosol amount might affect this and how cloud fraction depends on the MCC (closed/open) cloud types.
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