Mark Battany,* Rhonda Smith, and Glenn McGourty 
*University of California, 2156 Sierra Way, Suite C, San Luis Obispo, CA 93401 (mcbattany@ucanr.edu)

In grapegrowing regions that need alternatives to sprinkler frost protection, wind machines may be a viable option, provided that adequate meteorological conditions exist for their successful use. The occurrence and magnitude of temperature inversions after the onset of shoot growth are a key determinant of the potential warming effect that may be achieved by operating wind machines on frost nights. However, little information on temperature inversion conditions is available in California or elsewhere, due to the cost and difficulty of operating sufficiently tall temperature measurement towers. A previous effort by the authors used temporary 10.7 m towers to collect temperature data, but that off-line method could not provide the real-time information that would have been most beneficial to vineyard managers. In late 2013, an incipient temperature inversion-monitoring network with eight live-reporting meteorological towers was installed in vineyard areas in the Russian River watershed in Sonoma and Mendocino Counties of California. The network was gradually expanded to include 17 stations, each with temperature sensors at 1.5 m and 10.7 m to assess temperature inversion conditions at sites representative of frost-prone vineyards in the region. Sensors for wind speed, humidity, and black globe temperature were subsequently added to the stations to provide additional information on frost conditions. The black globe mimics the radiation temperature experienced by vine foliage at night, providing improved information on frost risk. The current data from these stations are reported on both NOAA and UC websites for public access. This effort has demonstrated the value of providing detailed temperature inversion and other spring frost-related information to vineyard managers who must make critical decisions regarding their frost protection strategies.

Funding Support: NOAA Russian River Habitat Blueprint