Quantification of Modern Apple Orchard Effects on Meteorological Variables

Accurate site-specific weather forecasts, observations, and decision support tools are crucial for timely tree fruit orchard management. However, these tools are often biased as orchards have different microclimates than the standard open field meteorological weather stations. The orchard effects, which are the effects of cropland on hyperlocal weather conditions, need to be corrected or adjusted for accurate site-specific weather. In this study, the orchard effects on solar radiation, air temperature, relative humidity and wind speed are quantified for three commercial apple orchards at seasonal, daily, and hourly time scales. Results suggest that the orchard microclimates have lower average daily solar radiation (28.8 W m−2 to 93.2 W m−2), air temperature (0.23 °C to 1.21 °C), and wind speed (1.1 m s−1 to 1.32 m s−1). Orchard effects have seasonal variability and depend on the phenological growth stages of the canopies. Orchard effects were stronger during the summer season and lowest during the winter season. For instance, the peak air temperature offset during the summer is 3 °C, while the same for the winter season is 1 °C. The orchard effects also differ during daytime and nighttime hours. In particular, the air temperature inside the orchard is cooler by 1 °C to 3 °C during the nighttime while, the same varies from -1.5 °C to 3 °C during daytime. Overall, all the three orchards trained in different architecture show similar pattern of the orchard effects.