Emeritus Vineyards

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June 14, 2016 |

The Importance of Fog

The Russian River Valley and Sonoma Coast are known for producing elegant Pinot Noirs. These are the cooler regions of Sonoma where the climate is heavily influenced by fog and the nearby ocean. The fog is really called the marine layer, a  phenomenon that occurs from May to November, the same time of year our Pinot grapes are growing and ripening. Both our Pinot Hill and Hallberg Ranch vineyards experience the marine layer, while our William Wesley vineyard is situated high on a mountain above the fog.

The marine layer starts as the Hawaii Pacific High, a system of high pressure winds that pushes moisture and ocean currents from the Hawaiian Islands towards California. As the winds blow over the ocean a sea mist develops.  Once the mist reaches the coast, the cold ocean air hits the warm air on the coast forming the marine layer, or fog. 

There are two main areas along the Sonoma coast where the marine layer moves inland; at the mouth of the Russian River and at Bodega Bay. The marine layer pushes inland along the breaks in the coastal mountain range, taking the path of least resistance. As the marine layer pushes inland it causes warmer air to rise creating a vacuum that brings in more fog and a cool breeze in the afternoon. Our vineyards are perfectly situated just a couple miles inland and are covered in a blanket of this cool fog from evening until late in the morning.

When planting our Pinot Noir vineyards, we look for areas that experience a large difference in daytime and nighttime temperatures, called the diurnal range. The Russian River Valley and many areas of the Sonoma Coast have a 30+ degree diurnal range making it the perfect location to plant, grow and harvest Pinot Noir.

The marine layer brings cool nighttime temperatures around 50-55 degrees. The morning sun burns off the fog and warm sunny afternoons give the vines energy to continue to ripen. Ripening stops during the cool nights allowing the grapes to retain their acids. This pattern repeats almost every day throughout our growing season. This acidity creates wines that are delicate and balanced, and the warm afternoon brings ripe flavors of fresh fruit.

Our Pinot Hill Vineyard, for example, lies in a much cooler region of Sonoma that is submerged in fog almost all day. This results in a lighter, more delicate bodied wine with  tart fruit flavors, such as cranberry. Our Hallberg Ranch, on the other hand, sees more sun exposure creating more strawberry notes and richer fruit flavors.

Fog burning off in the morning at Hallberg Ranch. The fog lingers in the distance.

Another view of Hallberg Ranch with morning fog lingering over the vines.



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