Abstract
The Yangtze River region is the main production area for famous, high-quality tea in China. Radiation frost frequently occurs in this region, especially in the early spring during calm and clear nights, and it causes substantial damage to crops, which leads to huge economic losses for tea growers. The formation of frost is difficult to experimentally control due to the complexity and variability of the agro-micrometeorological environment. The objective of this study was to evaluate an artificial radiation frost chamber based on the temperature difference between leaf and air dew point, which was designed for advanced frost-related research. Micro-meteorological data and the frost formation process were monitored in an experimental tea field during typical radiation frost nights to mimic declining temperatures that are consistent with nature. The radiation frost chamber model and main parameters were determined by theoretical calculations and computational fluid dynamics (CFD) simulation. A frost-forming experiment was conducted to evaluate the performance of the frost chamber. The observation results showed that the greatest temperature difference between leaf and air dew point (Tdiffer) was −2.3 °C. The simulation results showed that the desublimation cooling rate of the air vapor was greater than sublimation, and the Tdiffer should be greater than −3.2 °C, which could cause frost to easily form on the leaf. The performance testing results showed that leaf temperature slowly declined after a rapid decrease, which is similar to the natural condition, which results in noticeable frost formation on the leaf.
Highlights
Frost refers to the formation of ice crystals on surfaces, either by freezing of dew or a phase change from vapor to ice, which causes injurious frost formation on crops and plants [1,2]
In a typical radiation frost night, the desublimation rate of the water vapor in the air must be greater than the sublimation rate of frost, which could cause frost formations on the leaf
Observation results showed that greatest Tdiffer was −2.3 ◦ C in the natural frost night
Summary
Frost refers to the formation of ice crystals on surfaces, either by freezing of dew or a phase change from vapor to ice, which causes injurious frost formation on crops and plants [1,2]. It occurs at temperatures of less than or equal to 0 ◦ C, as measured in a “Stevenson-screen” shelter at a height between 1.25 and 2.0 m [3]. Advection frosts are associated with large-scale incursions of cold air with a well-mixed, windy atmosphere and a temperature that is often subzero, even during the daytime. A combination of both advection and radiation conditions will occur
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