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標題: | 幹根流對陸地與大氣交互作用的影響 Stem-root flow effect on land-atmosphere interaction |
作者: | Tzu-Hsien Kuo 郭子仙 |
指導教授: | 陳正平(Jen-Ping Chen) |
關鍵字: | 幹流,根流,幹根流,土壤溼度,蒸發散,陸地與大氣交互作用, stemflow,root flow,stem-root flow,soil moisture,evapotranspiration,land-atmosphere interaction, |
出版年 : | 2016 |
學位: | 博士 |
摘要: | 降水經由植物冠層重新分配的過程中,沿著樹葉、樹枝以及樹幹流動的部分稱為幹流 (stemflow)。幹流向土壤層流動過程中,會附著在根表面繼續流動,稱為幹根流 (stem-root flow)。透過幹根流的作用,能使降水較有效地流動到較為深層的土壤層,此一作用具有重新分配土壤溼度的效果。本研究將幹根流以參數化型式與既有的地表模式結合,測試幹根流在陸地與大氣交互作用過程中所扮演的角色。使用的模式為Simplified Simple Biosphere model (SSiB 1.0) 之一維離線地表模式以及Community Land Model (CLM v4.0) 與Community Earth System Model (CESM1.0.3) 耦合之全球模式。
使用SSiB model模擬台灣蓮華池測站以及位於法國地區之密集觀測計劃HAPEX-Mobilhy (HAPEX)之資料,結果顯示幹根流會使得表層土壤溼度降低,並使得中深層土壤溼度增加,土壤溼度再分配的現象會使得地表與大氣間交換之熱通量改變。較為溼熱氣候區的蓮華池測站之土壤溼度及環境溼度較高,因而在植物蒸散作用上反應較小,主要透過土壤表層蒸發作用降低所引起的土溫上升作用增加向大氣傳輸的可感熱通量。位於地中海氣候區的HAPEX測試中,則因位於乾溼區間的過渡區,蒸散作用對土壤溼度變化敏感。透過表層與中深層土壤溼度的改變,會導致蒸散作用有較劇烈的變化。此一改變也會進一步影響冠層之內以及土壤表層的溫度,因而對土壤表層蒸發產生作用。本研究第二部分使用CLM/CESM離線以及大氣陸地耦合模式探討在氣候尺度下幹根流與大氣之間的反饋作用。在耦合模式中,地表作用可反饋到大氣,包含透過熱力作用的局地效應以及透過動力過程改變環流的區域效應。結果顯示幹根流對於不同氣候、植物與土壤的作用相異。幹根流透過降低土壤蒸發量的過程可在較為潮溼的地區造成降雨的減少。較乾的土壤表面與減少的雨量之間可能具有正回饋作用。而在過渡區的變化性則較大,透過幹根流所形成的土壤溼度垂直交換可能具有更重要的效果。 Rainfall that reaches the soil surface can rapidly move into deeper layers in the form of bulk flow through the stem-root flow mechanism, which leads to the vertical redistribution of soil moisture. In this study, the stem-root-flow (SRF) mechanism is formulated and coupled into two types of models to analyze its effects on land-atmospheric interactions. One is the Simplified Simple Biosphere model (SSiB 1.0); the other is the Community Land Model (CLM v4.0) couple with the Community Earth System Model (CESM1.0.3). The SSiB model running in single column mode was applied to simulate the Lien Hua Chih (LHC) measurements in Taiwan and HAPEX-Mobilhy (HAPEX) measurements conducted in France. The results show that SRF generally caused a decrease in soil moisture at the top soil layer and moistened the deeper soil layers. Such soil moisture redistribution results in substantial changes in heat flux exchange between land and atmosphere. In the humid environment at LHC, the effect of SRF on transpiration was minimal, and the main influence on energy flux was through reduced soil evaporation that led to higher soil temperature and greater sensible heat flux. In the Mediterranean environment of HAPEX, the SRF substantially affected plant transpiration and soil evaporation, as well as associated changes in canopy and soil temperatures. However, the effect on transpiration could either be positive or negative depending on the relative changes in the soil moisture of the top soil versus deeper soil layers due to SRF and soil moisture diffusion processes. The CLM/CESM model running in uncoupled and coupled atmosphere-land mode was applied to focus on long-term climate. The results indicated that, when the atmospheric feedback processes are included, the response to SRF effect could be nonlinear and more distinct. Changes in heat flux can alter precipitation which in return controls the capacity of evapotranspiration in the coupled run. The net outcome includes on-site effects via thermodynamic processes and dynamic effects via circulation changes. These effects vary with climate conditions, vegetation cover, and soil type. SRF can alter the heat flux, generally causing increased sensible heat and reduced soil evaporation thus the latent heat. The global model results indicated the drier surface and less precipitation may have positive feedback in some humid regions. While in transition regions, the soil vertical exchange may be more important. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/19514 |
DOI: | 10.6342/NTU201600207 |
全文授權: | 未授權 |
顯示於系所單位: | 大氣科學系 |
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