UNCERTAINTIES ASSOCIATED WITH THE USE OF AIR TEMPERATURE AS INPUT IN DECISION SUPPORT SYSTEMS FOR VINEYARD MANAGEMENT

Thesis (Ph.D.), Biological and Agricultural Engineering, Washington State UniversityUnder the assumption that tissue temperature and canopy air temperature are similar, air temperature is a primary input in agricultural models. However, most often, the data used as input in the models are measured at weather stations, under standard conditions. The use of air temperature measured at weather stations involves assuming that air temperature measured within the canopy and in the tissues is the same that temperature recorded at the weather station. Those assumptions could be a source of uncertainty for the output of the models. When the models are used for supporting decision making, the assumption establishing that nearest weather station represents the air temperature surrounding the crops become another source of uncertainty. The objective of this dissertation was to evaluate the assumptions previously presented and to find a way to reduce the uncertainty associated with the definition of the "nearest weather station," at least under the point of view of air temperature data. The research was based on the use of air temperature data of the agricultural weather network of the state of Washington (AgWeatherNet), and the sampling of air temperature data within the canopy and tissue temperatures of grapevines cv. Chardonnay. The vineyard, in which the temperature sensors were installed, was at 410 m from the Roza weather station, both located at the Roza farm of the Irrigated Agriculture Research and Extension Center (IAREC) in Washington State University, Prosser, Washington (46.29°N, 119.73°W, 359 masl). The approaches used in the dissertation were mainly methodologies for comparing data series and for evaluating the variance of two sampling points as a function of the separation distance. The results showed that: a) there were significant differences between the air temperature, measured within the canopy of the vines and the air temperature measured at a weather station location that was immediately adjacent to the grapevines b) There were also significant differences between tissue temperatures and air temperature, and c) The concept of the nearest is subjective and depends on the region in which the weather station is installed and the season of the year.Washington State University, Biological and Agricultural Engineerin