2025-03-07 北海道大学
＜関連情報＞
- https://www.hokudai.ac.jp/news/pdf/250307_pr.pdf
- https://www.sciencedirect.com/science/article/abs/pii/S0168192324000261
- https://www.jstage.jst.go.jp/article/agrmet/advpub/0/advpub_D-22-00016/_pdf
1層エネルギーバランスモデルに基づく植物キャノピーにおける露形成に関する理論的研究 Theoretical study on dew formation in plant canopies based on a one-layer energy-balance model
Tsuneo Kuwagata, Atsushi Maruyama, Junsei Kondo, Tsutomu Watanabe
Agricultural and Forest Meteorology Available online: 29 May 2024
DOI:https://doi.org/10.1016/j.agrformet.2024.109911
Graphical abstract
Highlights
- The physical basis of dew formation in canopies is theoretically summarized.
- The critical relative humidity for dew formation depends on effective radiation.
- Condensation rate largely varies with relative humidity and effective radiation.
- Condensation rate also depends on air temperature and exchange velocity of canopy.
- Two physical indices for assessing leaf wetness duration and amount are proposed.
Abstract
Dew formation on leaves plays an important role in plant growth and water use, but it also contributes to the development of a variety of plant diseases. However, the quantitative relationship between dew formation in plant canopies and meteorological conditions has not been fully elucidated. In the present study, a one-layer energy-balance model (1L-model) of a plant canopy was developed to systematically investigate this relationship, obtaining the following results: (1) Dew formation (condensation rate) on leaves is highly dependent on four parameters: effective radiation, relative humidity, air temperature, and exchange velocity (kL) of the plant canopy. (2) Dew formation occurs when relative humidity (rh) exceeds the critical value (rhcr), wherein rhcr decreases with a decrease in effective radiation and is lower at lower air temperatures. (3) Under conditions where rh > rhcr, the condensation rate reaches a maximum at a specific exchange velocity; however, condensation does not occur when kL is greater than the critical value. (4) The maximum condensation rate increases with decreasing effective radiation, but rapidly decreases with decreasing relative humidity, and increases with increasing air temperature under humid conditions.
Given these theoretical considerations, we proposed two physical indices (reference dew amount, W0, and potential dew amount, Wp) calculated from meteorological conditions using the 1L-model. Here, Wp is the maximum dew amount for given meteorological conditions, excluding wind speed. The efficacy of W0 and Wp in assessing leaf wetness duration (LWD) and dew amount in plant canopies was confirmed through actual measurements in a rice paddy and numerical simulations using a more comprehensive multilayer energy-balance model.
This study contributes to a better understanding of the nature of dew formation on plants and improves the accuracy of LWD and dew amount estimation in plant canopies for the prevention of various plant diseases.
多層微気候モデルを用いた稲キャノピーにおける露形成の観測とそのシミュレーション Observations on dew formation in the rice canopy and its simulation using a multilayer microclimate model
Atsushi Maruyama, Tsuneo Kuwagata, Tsutomu Watanabe
Journal of Agricultural meteorology Accepted: July 22, 2022
DOI: 10.2480/agrmet.D‑22‑00016
Abstract
Dew formation in the rice canopy was directly observed to assess its actual nature and was simulated using a multilayer microclimate model to understand the relationship between the dew amount and atmospheric conditions. Observations were made on four nights during August and October in a paddy field in Kumamoto, Japan under warm temperate climate. The vertical profile of the dew amount in the canopy was measured every 2 h at 0.2 m intervals. The maximum dew amount was recorded in the early morning on all observation days. The total dew amount for the whole canopy at 6:00 on August 19, 21, and 24, and on October 1 was 0.10, 0.07, 0.15, and 0.23 mm, respectively. The dew amount determined from the simulation showed a good agreement with the actual observations. The dew amount per unit leaf area was larger in the upper layers than in the lower layers of the canopy on all days. This vertical difference in the dew amount was explained by the difference in effective radiation (net longwave radiation). The vertical gradient of the dew amount was steep on August 19 and October 1, whereas it was gentle on August 21 and 24. This difference in gradient was explained by the difference in paddy water temperature. When the water temperature was higher than the air temperature, the vertical gradient of the effective radiation and dew amount became steeper. The total amount and source of dew also varied with water temperature. The dominant source of dew was dewfall (water flux from the atmosphere) at lower water temperature, whereas it was distillation (water flux from the ground surface) at higher water temperature. From these results, we conclude that water temperature plays an important role in dew formation in the rice canopy.
