Wine, Weather, and Smoke

Remember the extensive wildfires east of the Cascade crest last summer? Will you be tasting a bit of it when you enjoy your favorite Washington or Oregon wine with a 2012 vintage?

At the Northwest Weather Workshop last weekend, there was a nice poster by Dr. Tes Ghidey of the AgWeatherNet group headquartered at Washington State University (WSU) and it stimulated my interest in this important question.

At the tail end of the historic August-September 2012 drought a number of significant wildfires were initiated by lightning and human causes, the most famous being the huge Taylor Bridge fire near Ellensburg. The following MODIS satellite image is for September 24th. The red dots indicate fire locations. The smoke is pretty obvious.

According to Dr. Ghidey, September 2012 was central Washington's smokiest since at least 2000. Large number of small particles were injected into the lower atmosphere, including dangerous small particles smaller than 2.5 microns (millionths of a meter) and a brew of fire-produced chemicals. I have a joint effort with Dr. Brian Lamb's group at WSU for forecasting air quality around the Northwest, with my group's WRF model forcing the CMAQ air quality model run by Dr. Lamb and Dr. Joseph Vaughn. Here is the 24-h small particle concentration for September 25th. A lot of places had concentrations of 35-60 micrograms per cubic meter. That is a whole lot, since reaching 35 represents a serious air quality incident. And such poor air quality lasted for days and weeks.

So what about the wine? As documented in a report by WSU, smoke contains high concentrations of volatile chemicals (phenols), such as guaiacol and eugenol, which provide the smoky aroma. As noted in this report, these chemicals can:

"accumulate in the skin and pulp of the berry. These compounds are released during ... fermentation, causing the wine to become unpleasantly ‘pharmaceutical’, ‘dirty’, ‘ash tray’, ‘medicinal’, ‘camp fire’, or ‘burnt’, and reduces the perception of varietal fruit aroma." The term given to this condition is "smoke taint" and grapes are most vulnerable during the week after the onset of véraison (beginning of ripening of the grape). Unfortunately, the smoke was at its peak during this time.

Smoke residues generally concentrate in and can cause discoloration of the grape skins. Thus, the problem is less severe for white wines than for red wines, in which the juice is in contact with the skins for an extended period. The WSU report talks about a number of approaches to minimize smoke taint.

At this point I can not find any definitive information about the seriousness of the 2012 smoke taint--perhaps someone in the industry who reads this blog can fill us in. Smoke levels were highest between Ellensburg (Taylor Bridge Fire) and Wenatchee (Wenatchee Complex Fire), so perhaps wineries in that area will be most affected. Here is a plot of the concentrations of the 2.5 micron particles during August and September at various eastern Washington locations. Clearly, Wenatchee and Ellensburg got hit hardest.

Another issue I have heard is that the reduction in solar radiation associated with the smoke might have lessened photosynthesis and thus reduced the amount of sugar in the grapes.

There was a recent online article by KIRO/MyNorthwest on this subject of smoke tainting of wine, found here.

I very much enjoy Washington State wines so I am hoping for the best.