The extent of mixing of biomass burning (BB) aerosol into the namibian stratocumulus (SC) cloud deck remains poorly constrained, despite its importance for the magnitude and sign of the regional…

This federal contract award is for a NASA Earth Venture Suborbital campaign called Observations of Aerosols above Clouds and their Interactions (ORACLES) to study smoke-cloud interactions over the Southeast Atlantic. The $135,000 training grant was awarded to the University of Washington to address five key research questions related to the extent and impacts of biomass burning aerosol mixing into the marine boundary layer and stratocumulus cloud deck in the region. The project will leverage remote sensing and in-situ aircraft measurements from the ORACLES field seasons in 2016, 2017, and 2018, along with trajectory modeling. The research aims to improve understanding of the magnitude and sign of the effective radiative forcing from aerosol-radiation and aerosol-cloud interactions in this climatically important region. There is no set-aside designation for this prime contract award.

The extent of mixing of biomass burning (BB) aerosol into the namibian stratocumulus (SC) cloud deck remains poorly constrained, despite its importance for the magnitude and sign of the regional effective radiative forcing due to aerosol-radiation and aerosol-cloud interactions. From july to october, there is widespread biomass burning on the african continent south of the equator. Smoke produced by these fires is eventually lofted out over the southeast atlantic ocean, where IT overlays and possibly interacts with the namibian SC deck, one of the three semi-permanent subtropical SC decks that play an outsized role in setting earth s albedo. Because the 2013 physical science assessment of the international panel on climate change identified aerosol-cloud interactions and low cloud response to warming as two of the largest uncertainties in determining the anthropogenic radiative forcing, observations and modeling of this region offer the opportunity to address prime scientific objectives. Large eddy simulation studies suggest that the net impact of the smoke above clouds in the southeast atlantic is cooling, in large part due to aerosol-cloud interactions from BB aerosol mixing into the SC cloud deck. However, satellite remote sensing results offer a mixed picture of whether this BB aerosol is mixing into the clouds; lidar measurements from the calipso satellite show that the smoke and cloud layers in general are not in contact during much of the biomass burning season. Thus, constraining the temporal and spatial extents of BB aerosol mixing into the marine boundary layer (MBL) is essential for determining the magnitude and possibly even the sign of the effective radiative forcing in this region. Observations of aerosols above clouds and their interactions (oracles) is a NASA earth venture suborbital campaign to study smoke-cloud interactions over the southeast atlantic using remote sensing and in-situ aircraft measurements from field seasons in september 2016 (completed), august 2017, and october 2018. Using oracles data, i propose to address five inter-related questions: i. How often and over what geographical extent are BB aerosols mixed into the MBL and SC deck? II. What are the smoke transport pathways that lead to BB aerosol mixing into the MBL? III. What are the relative contributions to the total BB aerosol budget from entrainment at cloud top versus that from MBL advection at various locations? IV. How do questions i, II, and III vary on sub-seasonal and inter-annual timescales? V. Once in the MBL, do the BB aerosols produce noticeable changes in cloud microphysical properties? In addition to the remote sensing and in-situ observations from the oracles flights, i will use air mass trajectories from the hybrid single-particle lagrangian integrated trajectory model and lagrangian particle back trajectories from a version of the flexible particle dispersion model configured to work with the weather research and forecasting model with chemistry output from the 2016 oracles field season (and later 2017 and 2018 field seasons) to study smoke transport pathways. I will extend this analysis beyond the oracles/southeast atlantic context by comparing results with those from the variability of american monsoon systems ocean-cloud-atmosphere-land study campaign in the south pacific/peruvian SC deck. My proposal addresses the NASA science mission directorate s objective to advance knowledge of earth as a system to meet the challenges of environmental change and to improve life on our planet, specifically through the climate variability and change goal of the earth science division. In addition, i propose to integrate satellite-, aircraft-, and surface-based measurements, in conjunction with models and simulations using research focused on NASA airborne or ship-borne research campaigns, in this case oracles.