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亞熱帶溫室萵苣栽培生長模式靈敏度分析

Sensitivity Analysis of Growth mode of Lettuce in Subtropical Greenhouse

摘要


臺灣地處亞熱帶,高溫及潮濕的氣候影響作物的生長與產量。為了改善不利的環境條件,溫室常利用通風、蒸發冷卻和遮蔭等方法營造更適合作物生長的微氣候。近年來有許多國外溫室環境控制系統被引進台灣,由於這些系統所應用的地區與台灣的氣候環境有極大差異,致使在台灣無法發揮其預期的功效,因此針對本地氣候條件之環控系統的研究更顯迫切且必要。利用數學模型以各種氣候條件對溫室環境進行模擬,進而找到最佳的溫室環境控制方案已成為研究的趨勢。然而在模型參數中到底哪些參數對系統影響較大,需要更嚴謹的評估及探討,透過靈敏度分析可顯示輸入變數、初始條件和模型參數對性能指標的影響,進而深入了解模型的結構和行為。本研究利用亞熱帶氣候條件,以半結球萵苣為試驗作物,建立一個包含植株乾物重、CO_2濃度、溫度及濕度等狀態的動態模型,並對模型參數進行靈敏度分析。結果顯示萵苣栽培之溫室環境控制應著重在長期平均微氣候而非暫態響應速率的控制,太陽輻射和CO_2濃度有較大的相對靈敏度,顯示這些外部氣候因子測量的準確性對模型影響較大;外界溫度具有負值相對靈敏度,此結果揭示高溫為葉菜生產的限制條件。靈敏度分析不但能夠凸顯模型的重要參數,並能提供系統的潛在特性,對模型的分析評估不失為一項有力的工具。

並列摘要


Taiwan is located in the subtropical zone, and the high temperature as well as humid climate affect the growth and yield of crops. In order to improve adversely environmental conditions, greenhouses often use ventilation, evaporative cooling and shading to create a microclimate that is more suitable for crop growth. In recent years, many foreign greenhouse environmental control systems have been introduced to Taiwan. However, due to the different climate conditions, these systems are unable to perform their expected functions in Taiwan. Therefore, research on environmental control systems for local climatic conditions is more urgent and necessary. The use of mathematical models to simulate the greenhouse environment in various climatic conditions and to find the best greenhouse environmental control program has become a trend. However, in the model parameters, which parameters have a greater impact on the system, more rigorous evaluation and discussion are needed. Through the sensitivity analysis, the model can be understood with the influence of input variables, initial conditions and model parameters on state variables. Furthermore, the structure and behavior of the model can be well-established. Based on subtropical climate conditions, this study established a dynamic model containing the dry matter weight, CO_2 concentration, temperature and humidity. The sensitivity of the model parameters is calculated to analyze its impact on the system. The results show that greenhouse environmental control for lettuce should focus on long-term average climatic conditions rather than transient response rates, and the larger performance sensitivities and the more accurate model. Solar radiation and CO_2 concentrations have large relative sensitivities; the large performance sensitivities imply the importance of accurate measurements of these external climatic conditions for model calculations. The external temperature has a negative relative sensitivity. This result reveals that high temperature is a limiting condition for leafy vegetables production. Sensitivity analysis not only highlights the important parameters of the model, but also provides the potential characteristics of the system, which is a powerful tool for the analysis and evaluation of the model.

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