Acid rain in Big Sur – October 2010

31 10 2010

The first rains of the season have fallen here in Big Sur and the data are rather surprising . . .

Another double acid rainbow in Big Sur (photo by Lee Klinger)

Other than the one large storm that hit last week most of the rainfall events in October were light. And they were the most acidic of any set of monthly readings since the start of the record in 2006. The rain pH of 4.1 measured on Oct 18 was the lowest pH observed in more than fours years of readings in Big Sur. The readings for Oct 23 (4.3), Oct 25 (4.4), and Oct 30 (4.4) were also unusually acidic.

Rainfall amounts and pH in Big Sur - October 2010

I’m rather at a loss for explaining this. I don’t think it’s due to higher inputs of pollution. I wonder if ocean primary productivity of the California Current is still on the rise. If so, then the greater phytoplankton activity could be enhancing amounts of dimethyl sulfide (DMS), a major precursor to sulfuric acid in the air and rain over the oceans. The figure below, from a NOAA report “Climatic and Ecological Conditions in the California Current LME for July to September 2009“, indicates that, as of last year, the chlorophyll abundance, which is a fair indicator of primary productivity, has been on the rise in recent years.

Previous and current summaries of climate and ecosystem conditions in the California Current can be found at the Pacific Coast Ocean Observing System website.

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