EARTH SYSTEM PHYSICS - GUEST SEMINAR Wednesday, 7 October 11:00 am

[Earth System Physics Section]

EARTH SYSTEM PHYSICS SEMINAR
Wednesday, 7 October - 11:00 am
Central area, 2nd floor, ex-SISSA bldg.

Guest speaker:      Nicholas Meskhidze
     North Carolina State University
             Raleigh, NC, USA

*New instrument for measuring size-resolved submicron sea spray particle 
production from ocean*

Marine aerosols play an important role in controlling the Earth’s 
radiation balance, cloud formation and microphysical properties, and the 
chemistry of the marine atmosphere.Since observations only constrain the 
net forcing of aerosols (anthropogenic + natural) and the global 
model-predicted radiative effects are shown to be sensitive to 
prescribed/diagnosed number-size distribution of background aerosols, an 
accurate knowledge of size‐and composition‐dependent production flux of 
sea spray particles is important for correct assessment of the role of 
anthropogenic aerosols in climate change.One particular knowledge gap in 
sea spray particle emissions resides in yet uncharacterized 
contributions of sea spray to the cloud condensation nuclei (CCN) budget 
over the marine boundary layer.The chemical composition of 50 to 200 nm 
sized sea spray particles, most critical to modeling CCN concentration 
from size distribution data is often simplified as purely organic, 
purely sea-salt or mixture of both.The lack of accurate information of 
the size‐dependent production flux of sub-micron sea spray particles 
prevents the modeling community from resolving discrepancies between 
model-predicted and measured CCN number concentration in the marine 
boundary layer.

This presentation will show the first results from a new method that can 
be used to constrain the source strength of the sea salt bearing 
particles that are injected into the atmosphere from the bubble 
bursting.We designed a sea-salt specific relaxed eddy accumulation flux 
system that is composed of a 3D sonic anemometer, two thermodenuders, 
three differential mobility analyzers, two condensation particle 
counters, and a CCN counter. The system is based on the 
volatility/humidified tandem differential mobility analyzer technique 
and is therefore designed to measure the size-resolved turbulent fluxes 
of sub-micron sized sea-salt particles for a wide range of 
meteorological, hydrological and ocean chemical/biological conditions. 
The system is designed to operate in both Eddy Covariance (EC) and 
Relaxed Eddy Accumulation (REA) modes. The first field-testing of the 
instrument was done at North Carolina State University’s Center for 
Marine Science Technology (CMAST) in Moorehead City, NC. The 
measurements were conducted from November 22 to 30, 2014. The instrument 
was field deployed at the US Army Corps of Engineers Field Research 
Facility in Duck, NC from April 25 to May 9th, 2015. The method and the 
setup will be presented along with some results from both studies. The 
presentation will also show some laboratory results for the anemometer 
wind corrections using a custom built “ship-simulator” and a motion 
correction package.

*Nicholas Meskhidze* is an associate professor at North Carolina State 
University.

Meskhidze’s research interests include laboratory and ambient 
measurements of sea spray aerosol hygroscopicity and cloud condensation 
nuclei (CCN) properties and application of remotely sensed data (MODIS, 
MISR, CALIPSO) for exploring potential interactions between marine 
aerosols, ocean productivity, clouds, and climate.His research group is 
also working on the development of parameterizations of organic aerosol 
and trace gas emissions from the oceans required for regional and global 
climate models.

Born in Tbilisi, Georgia, Meskhidze received his Diploma in Physics from 
Tbilisi State University. He received his PhD from Georgia Institute of 
Technology, Atlanta, GA, where for two years he worked as a postdoctoral 
fellow with Thanos Nenes. Meskhidze also worked as a visiting fellow at 
NASA Goddard Space Flight Center (GSFC). In 2006 Meskhidze became an 
Assistant Professor at NC State University Department of Marine Earth 
and Atmospheric Sciences.

Meskhidze has authored or co-authored over 35 articles in peer-reviewed 
scientific journals. Organized several international workshops and is an 
editorial board member for Advances in Meteorology, Atmospheric and 
Climate Sciences, and Journal of Marine Science: Research & Development.