Balloon-Borne In Situ Measurements of Aerosol Size and Concentration in the Mid Latitudes and Tropics

University Of Wyoming, Laramie WY

Investigators

Abstract

This project will continue and extend vertical (surface to 33 km) profiles of aerosol size and concentration measurements at Laramie, Wyoming, a mid-latitude site. Extended measurements will add new size-resolved concentration measurements for aerosol between 0.03 and 0.15 micrometers in diameter, and tropical measurements from Natal, Brazil. The balloon-borne measurements will be conducted at bi-monthly intervals from Laramie and annually from Natal over five years. A collaboration with the University of Cambridge will permit exploratory measurements of OCS (carbonyl sulfide) and SO2 (sulfur dioxide) in conjunction with some aerosol profiles. An additional collaboration with the Danish Meteorological Institute will add backscattering measurements and modeling expertise to the tropical work. Continuing stratospheric aerosol measurements at Laramie is essential to help establish, unequivocally, stratospheric aerosol levels during volcanically-quiescent, "background," periods. The sulfur sources necessary to maintain background aerosol levels, and the extent of perturbations to stratospheric aerosol, are still uncertain. The Laramie record is the longest sustained record of stratospheric aerosol existent, and thus favorably positioned to address these questions. New measurements of smaller particles will address a persistent discrepancy between satellite and in situ estimates of aerosol surface area during background periods, when small particles control surface area. In the event of a large tropical volcanic eruption, the measurement focus will shift to the fresh volcanic plume. The annual tropical measurements are exploratory to address several questions, such as, how well do mid- and high latitude size distributions characterize aerosol in the tropics. The tropical measurements will also test earlier tropical stratospheric measurements of new particle formation and large particle layers, and whether models properly account for the stratospheric aerosol source gases OCS/SO2. Stratospheric aerosols have broad impacts on the atmosphere and thus on society. Modeling of global stratospheric ozone requires accurate estimates of aerosol surface area. Major volcanic eruptions produce direct impacts on ozone through heterogeneous chemistry, involving chlorine, and on radiation leading to stratospheric warming and tropospheric cooling. Tropospheric aerosols have even more far reaching impacts on radiation both directly and through their impact on clouds. This project will promote the teaching and training of graduate and postgraduate students.