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VERSION:2.0
PRODID:icalendar-ruby
CALSCALE:GREGORIAN
X-WR-CALNAME:The secrets of tropospheric ozone: lifetime\, timescales\, sou
 rces\, sinks
X-WR-TIMEZONE:Eastern Time (US & Canada)
BEGIN:VEVENT
DTSTAMP:20260817T045206Z
UID:tag:localist.com\,2008:EventInstance_48711822335649
DTSTART:20250418T160000Z
DTEND:20250418T170000Z
DESCRIPTION:Michael J. Prather (Professor of Earth System Science at UC Irv
 ine)\n\n \n\nThe lifetime of tropospheric O3 is difficult to quantify beca
 use we model O3 as a secondary pollutant\, without direct emissions. For o
 ther reactive greenhouse gases like CH4 and N2O\, we readily model lifetim
 es and timescales that include chemical feedbacks based on direct emission
 s. Here\, we devise a set of artificial experiments with a chemistry-trans
 port model where O3 is directly emitted into the atmosphere at a quantifie
 d rate. We create 3 primary emission patterns for O3\, mimicking secondary
  production by surface industrial pollution\, that by aviation\, and prima
 ry injection through stratosphere–troposphere exchange (STE). The pertur
 bation lifetimes for these O3 sources includes chemical feedbacks and vari
 es from 6 to 27 days depending on source location and season. Previous stu
 dies derived lifetimes around 24 days estimated from the mean odd-oxygen l
 oss frequency. The timescales for decay of excess O3 varies from 10 to 20 
 days in northern hemisphere summer to 30 to 40 days in northern hemisphere
  winter. For each season\, we identify a single O3 chemical mode applying 
 to all experiments. Understanding how O3 sources accumulate (the lifetime)
  and disperse (decay timescale) provides some insight into how changes in 
 pollution emissions\, climate\, and stratospheric O3 depletion over this c
 entury will alter tropospheric O3. This work incidentally found 2 distinct
  mistakes in how we diagnose tropospheric O3\, but not how we model it. Fi
 rst\, the chemical pattern of an O3 perturbation or decay mode does not re
 semble our traditional view of the odd oxygen family of species that inclu
 des NO2. Instead\, a positive O3 perturbation is accompanied by a decrease
  in NO2. Second\, heretofore we diagnosed the importance of STE flux to tr
 opospheric O3 with a synthetic “tagged” tracer O3S\, which had full st
 ratospheric chemistry and linear tropospheric loss based on odd-oxygen los
 s rates. These O3S studies predicted that about 40% of tropospheric O3 was
  of stratospheric origin\, but our lifetime and decay experiments show cle
 arly that STE fluxes add about 8% to tropospheric O3\, providing further e
 vidence that tagged tracers do not work when the tracer is a major species
  with chemical feedbacks on its loss rates\, as shown previously for CH4.M
 ichael J. Prather\, Professor of Earth System Science at UC Irvine (1992-)
 \, held post-doctoral research appointments at Harvard (1975-1985) and NAS
 A GISS (1985-1992).  He was also Jefferson Science Fellow at the U.S. Stat
 e Department (2005-2006) and a program manager at NASA HQ (1987-1992).  Pr
 ather received undergraduate degrees in mathematics and physics from Yale 
 and Merton Colleges and a doctoral degree in astronomy and astrophysics fr
 om Yale University.  His studies of the chemistry and composition of the a
 tmosphere have focused on ozone depletion and climate change\, including a
 uthoring WMO/UNEP and IPCC reports. Prather’s core research addresses th
 e mathematical underpinnings of atmospheric chemistry and global biogeoche
 mical cycles. \n\n \n\nMichael J. Prather\, Professor of Earth System Scie
 nce at UC Irvine (1992-)\, held post-doctoral research appointments at Har
 vard (1975-1985) and NASA GISS (1985-1992).  He was also Jefferson Science
  Fellow at the U.S. State Department (2005-2006) and a program manager at 
 NASA HQ (1987-1992).  Prather received undergraduate degrees in mathematic
 s and physics from Yale and Merton Colleges and a doctoral degree in astro
 nomy and astrophysics from Yale University.  His studies of the chemistry 
 and composition of the atmosphere have focused on ozone depletion and clim
 ate change\, including authoring WMO/UNEP and IPCC reports. Prather’s co
 re research addresses the mathematical underpinnings of atmospheric chemis
 try and global biogeochemical cycles.
GEO:42.3783;-71.117081
LOCATION:Pierce Hall\, 100F
SUMMARY:The secrets of tropospheric ozone: lifetime\, timescales\, sources\
 , sinks
URL;VALUE=URI:https://events.seas.harvard.edu/event/the-secrets-of-troposph
 eric-ozone-lifetime-timescales-sources-sinks
CATEGORIES:Colloquia / Seminar / Lecture
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