Vernon Morris

Characterizing the chemical evolution of mineral dust and the atmospheric implications during long-range transport

I have served as the Principal Investigator and lead scientist for the trans-Atlantic AERosol and Ocean Science Expeditions (AEROSE).  AEROSE is a project based on a series of intensive field experiments conducted primarily aboard the NOAA Class 1 research vessel Ronald H. Brown  since 2006.  The inaugural cruise was a 27-day mission in 2004.  AEROSE is a comprehensive maritime observational campaign designed to investigate critical aspects of the microphysical and microchemical evolution of air mass outflows from Africa and their downstream impacts on atmospheric chemistry, climate, and environmental health.  Since 2006, the AEROSE team has collaborated in joint efforts with the NOAA Atlantic Oceanographic and Meteorological Laboratory (AOML) -sponsored PIRATA Northern Extension (PNE) project.  PNE combines a physical oceanography team focused on climate measurements in the tropical Atlantic with a chemical oceanography team that profiles the ocean column along the transect of array of moored oceanographic buoys.  Our PNE/AEROSE cruises retain the interdisciplinary spirit of the initial AEROSE mission with atmospheric scientists and oceanographers working in concert to develop a greater understanding of the earth’s climate system in remote areas that are impacted by both anthropogenic and natural phenomena.  I would seek to continue these cruises and scientific studies associated with the data sets after coming to ASU.  The experience of conducting high-power research aboard a research ship in the remote ocean can be a life-changing one for most students.  I have committed to using this field campaign as a recruiting tool and over 40 undergraduate students have participated in the cruises since 2004.  This would be a unique experience for SMNS students and faculty.

AEROSE seeks to address three central scientific questions: (1) What is the nature of the chemical, physical, and microbial changes on the mineral dust and smoke aerosol distributions as they evolve during trans-Atlantic transport? (2) How do Saharan and sub-Saharan outflows affect the regional atmosphere and ocean during trans-Atlantic transport? and (3) What is the capability of satellite remote sensing and numerical models for resolving and studying the above processes?  Along the way, we have taken advantage of the unique setting to perform a variety of satellite calibration/validation experiments, model verification, and testing of prototype instrumentation.

During each AEROSE cruise, a comprehensive suite of critical measurements are collected that enable the characterization of the chemical and microphysical evolution of aerosols from the African continent as they transit the Atlantic Ocean to the eastern seaboard of the United States and the Caribbean. (See CV publications; Morris et al., 2006; Nalli et al., 2011).  The tropical Atlantic Ocean is unique laboratory because it allows for sampling of background, Saharan dust, urban biomass burning, African industrial emission, and aerosol mixtures without significant land-surface interactions or emissions.  (Sea salt aerosol is largely separable in size and chemistry from mineral dust and biomass aerosols.) A brief description of the cruise measurements and operations are provided below. 

Profile measurements of the atmosphere, rawinsonde launches, are conducted to investigate the linkages between the vertical distributions of tropospheric ozone with dust and biomass burning outflows. Historical data shows a seasonal variation in tropospheric ozone that peaks during June-August - the summer peak in dust outflows. The origins of this peak remain uncertain and may are postulated to be due to a combination of anthropogenic sources (e.g., transport from biomass burning in the Congo Basin) and natural sources (e.g., lightning over West Africa, stratospheric injections).  The AEROSE team observed several stratospheric injections during cruises in 2017 and 2019.  The data sets from these cruises are ripe for investigation of this phenomenon and how coupling of the African easterly jet may enhance the transport.  One of my current PhD students is working on some of the case studies  and the influence on the ozone budget in the tropics.

Current atmospheric chemistry models are challenged by the need to account for a variety of chemical processes in dense aerosol outflows. Very few in situ measurements have been reported for tropical air masses that are rich in mineral dust aerosols, biomass burning aerosols, West African mega city urban aerosols, and/or mixtures of these aerosol types that characterize the trade wind and SAL outflow regimes.  The AEROSE campaigns contribute a rich record of measurements of trace gase concentrations in these regions that can be used to validate and evaluate model performance under these conditions.  The trace gas measurements include ozone, carbon monoxide, sulfur dioxide, NOx (nitric oxide and nitrogen dioxide), methane, and aggregate non-methane volatile organic carbon species (VOC).  

A comprehensive suite of aerosol measurements and in situ sampling is performed during each cruise with specific focus on quantification of the microphysical and chemical evolution of the Saharan dust during trans-Atlantic transport.  I plan to enhance the aerosol measurements with a mixed -method approach to sampling in order to characterize aerosol mixing, identify total microbial distributions and microbial load on the aerosols.   Currently, offline microbiological and chemical composition analysis are performed as a function of size and source region. The filter samples collected during the cruises are be frozen following sample collection and processing. Number distributions are measured continuously for Aitken, accumulation mode, and fine aerosols using mobility analyzers and optical particle counters. Mass density and gravimetric aerosol analyses are performed using a suite of tandem quartz crystal cascade impactors, cyclone impactors, and high volume gravimetric sequential samplers.  I will seek to continue the analysis of samples collected during the AEROSE campaigns and to use these analysis in combination with atmospheric models to test and refine our understanding of aerosol chemistry in the maritime tropics.  

As in past cruises, infrared, microwave, visible, and in situ measurements will be collected to support the calibration/validation (cal/val) and improvement of advanced satellite retrievals and data products.  Previous results have been published  (See CV publications: Nalli et al., 2006, 2011), namely the NOAA-20 and SNPP Cross-track Infrared Sounder (CrIS) and Advanced Technology Microwave Sounder (ATMS) (Nalli et al., 2013, 2018a,b), Visible Infrared Imaging Radiometer Suite (VIIRS), as well as the NOAA Geostationary Operational Environmental Satellite (GOES-16 or GOES-East).  In 2019, the AEROSE team began testing and evaluation of decision support materials from the NOAA Unique Combined Atmospheric Processing System (NUCAPS) suite for scientific field campaigns.  In particular, these satellite data products were used to strategically inform rawinsonde and ozonesonde deployments during the AEROSE 2019 campaign.  I will seek to extend these types of service evaluations for NOAA and potentially the Naval Research Lab (NRL) studies in future campaigns.  

Intersections between atmospheric chemistry and the urban atmospheric microbiome.

This research is designed with the aim of developing a large-scale microbial collection, sequencing and data analysis study of the microbial populations in the atmosphere from selected urban and rural locations.  For the proposed study, both culture dependent techniques that include the characterization of growth, substrate utilization and antibiotic resistance of these species and omic methods will be used to explore the full microbial diversity will be utilized.  I would seek to engage collaborations with the J. Craig Venter Institute, where I spent a semester while on a leave of absence from Howard University.  I have been conducting preliminary studies in Washington, DC but could modify the study to focus on metropolitan and rural regions in the Southwest or focused in Arizona.  

There are four Specific Aims for the proposed research:

• To develop a baseline of the microbial inhabitants in the atmosphere, and to correlate specific pathogens to aerosol loading using 8 locations distributed across the U.S., Puerto Rico, and West Africa.  This will be accomplished through the establishment of collection sites at the different locations, collection of air filter samples, culturing and sequencing of 16S rDNA sequences from these filters.
• To screen any potential pathogenic species for characteristics associated with pathogenicity.  This will be accomplished through an initial 16S rDNA screening of all 8,000 isolates, as well as screening for substrate utilization patterns and possible pathogenicity factors.  
• A detailed and systematic characterization of meteorological and aerosol conditions associated with various infectious diseases and acute respiratory agents that includes back-trajectory analysis.
• To develop a public database for microbial diversity of airborne aerosols.

This study presents the unique opportunity to generate a baseline of the normal microbial inhabitants in the atmosphere of major urban centers and to compare the species characteristics determined in major cities and non-urban locations that are either linked by air mass flows, similarities in climate, or similarities in aerosol sources.  This will result in the construction of a community database with significant content relating microbial populations in the atmosphere to their potential implications for human health.  The major implications for the study include developing a baseline of normal microbial populations based on both culture-dependent and non-culture based methods.  The bacterial populations that are identified will allow for a better preparation for bio-defense, and may give insight into the relative increase in certain disease conditions inclusive of asthma.