The Acidity of Clouds and Fogs Around the World
Abstract
The initial acidity of a fog or cloud drop is determined by the balance between inputs of acids and bases that enter the drop through particle scavenging and uptake of soluble gases, with subsequent changes from aqueous chemical reactions that release or consume H+ ions. While inputs of sulfuric and nitric acids and ammonia are often the principal determinants of fog or cloud pH, other compounds can also be important contributors to droplet acidity or alkalinity. Among important pH-altering constituents are carbon dioxide, carboxylic and dicarboxylic acids, and soil dust. Because individual droplets in a fog or cloud form on different cloud condensation nuclei and because gas uptake efficiency can vary with drop size, one expects some degree of variability among individual droplet pH values within a single cloud or fog.
This presentation will review measurements of cloud and fog pH from around the world from the 1930s until present. Measurements are included from approximately 240 locations in North and South America, Europe, Asia, Australia, Antarctica, and over the oceans. Observed pH values range from approximately 1.7 to 7.8. Early measurements tended to focus on Europe and North America while Asia has received increased attention in recent years. We will examine regional patterns in observed acidity and highlight temporal changes in pH over recent decades. Reductions in emissions of sulfur and nitrogen oxides have produced clear increases in fog/cloud pH in North America and Europe while trends in Asia are more complex.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.A33N2906C
- Keywords:
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- 3311 Clouds and aerosols;
- ATMOSPHERIC PROCESSES;
- 3322 Land/atmosphere interactions;
- ATMOSPHERIC PROCESSES;
- 1813 Eco-hydrology;
- HYDROLOGY;
- 4548 Ocean fog;
- OCEANOGRAPHY: PHYSICAL