Abstract
Ozone within deep convective clouds is controlled by several factors involving photochemical reactions and transport. Gas-phase photochemical reactions and heterogeneous surface chemical reactions involving ice, water particles, and aerosols inside the clouds all contribute to the distribution and net production and loss of ozone. Ozone in clouds is also dependent on convective transport that carries low troposphere/boundary layer ozone and ozone precursors upward into the clouds. Characterizing ozone in thick clouds is an important step for quantifying relationships of ozone with tropospheric H2O, OH production, and cloud microphysics/transport properties. Although measuring ozone in deep convective clouds from either aircraft or balloon ozonesondes is largely impossible due to extreme meteorological conditions associated with these clouds, it is possible to estimate ozone in thick clouds using backscattered solar UV radiation measured by satellite instruments. Our study combines Aura Ozone Monitoring Instrument (OMI) and Microwave Limb Sounder (MLS) satellite measurements to generate a new research product of monthly-mean ozone concentrations in deep convective clouds between 30°S to 30°N for October 2004 - April 2016. These measurements represent mean ozone concentration primarily in the upper levels of thick clouds and reveal key features of cloud ozone including: persistent low ozone concentrations in the tropical Pacific of ~10 ppbv or less; concentrations of up to 60 pphv or greater over landmass regions of South America, southern Africa, Australia, and India/east Asia; connections with tropical ENSO events; and intra-seasonal/Madden-Julian Oscillation variability. Analysis of OMI aerosol measurements suggests a cause and effect relation between boundary layer pollution and elevated ozone inside thick clouds over land-mass regions including southern Africa and India/east Asia.
Highlights
Measuring tropospheric ozone in deep convective clouds including convective outflow regions in the mid-to-upper troposphere is important for several reasons
Microwave Limb Sounder (MLS) stratospheric column ozone (SCO) is used in conjunction with Ozone Monitoring Instrument (OMI) above-cloud column ozone each day to derive mean column amounts and mean concentrations of ozone measured over deep convective clouds
Liu et al (2017) combined GEOS-5 assimilated OMI/MLS ozone and Goddard Modeling Initiative (GMI) chemical transport model (CTM) simulations to quantify the causes of the interannual variability (IAV) of tropospheric ozone over four subregions of the southern hemispheric tropospheric ozone maximum
Summary
Measuring tropospheric ozone in deep convective clouds including convective outflow regions in the mid-to-upper troposphere is important for several reasons. The ozonesonde measurement record includes occurrences of very low to even “near-zero” ozone concentrations in the tropical upper troposphere associated with the passing of deep convective cloud systems (e.g., Kley et al, 1996; Folkins et al, 2002; Solomon et al, 2005). The very low ozone measurements in the tropical upper troposphere in past studies were obtained from a limited number of aircraft flights and ozonesondes at a few isolated sites in the vicinity of, but not inside, deep convective cloud systems. OMI provided the tropospheric cloud-ozone measurements after subtracting co-located MLS stratospheric column ozone (SCO). As with Ziemke et al (2009), we derive ozone mixing ratios inside tropical deep convective clouds by combining Aura OMI measurements of total column ozone and cloud pressure with Aura MLS SCO.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
