Ozone in Tropospheric Chemistry: Production, Reactions, and Losses - Prof. Gunnar Schade, Study notes of Meteorology

Download Ozone in Tropospheric Chemistry: Production, Reactions, and Losses - Prof. Gunnar Schade and more Study notes Meteorology in PDF only on Docsity! Ozone central to tropospheric chemistry • Dominant producer of the ·OH radical through photolysis in the UV-B – source of atmospheric cleansing capacity • Connected to NOx through the Null-Cycle – diurnal cycle – interdependence and titration • Connected to HOx cycling – in-situ production AND loss from HO2· reactions • Connected to the direct removal of pollutants – ozonolysis – NOx oxidation More reactions relevant for tropospheric ozone • HOx sources … – Photolysis of ozone – Photolysis of formaldehyde and HONO – Ozonolysis of alkenes • … and sinks (in order of importance) NO2 + ·OH (+ M) HNO3 (+ M) HO2· + HO2· (+ M) H2O2 + O2 (+ M) HO2· + ROO· ROOH + O2 HO2· + NO2 (+ M) HO2NO2 (+ M) … and subsequent deposition of HNO , H O , and Ozone Deposition (effective ozone loss) W ar ne ck , 1 99 9 Ozone budget in the troposphere • transport from stratosphere • in-situ production • in-situ destruction • deposition to the surface W ar ne ck , 1 99 9 Homework 1. Assess the tropospheric lifetime of ozone. Consider all the processes you learned about. How, and if so why does O3 vary with geographic location and/or elevation? Does it vary in time/diurnally? 4 pts 2. What determines the amplitude of the ozone diurnal variation within the Null-Cycle? 2 pts 3. Globally, where is the production rate of ·OH maximized, and how? 1 pt 4. At a remote station in Africa, the soil emits NO at a rate of 10 µg m-2 h-1 throughout the night. Make a reasonable assumption for nighttime boundary layer depth and calculate the possible overnight reduction in ozone concentrations at this site. (3 pts)