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標題: | 灌溉面積變化對陸氣交互作用之影響 Responses of Land-Atmosphere Interactions to the Change in Irrigation Area Size |
作者: | An-Chi Ho 何安琪 |
指導教授: | 羅敏輝(Min-Hui Lo) |
關鍵字: | 灌溉,面積大小,陸氣交互作用,美國大平原,當地降水, irrigation,area size,land-atmosphere interaction,the Great Plains,local precipitation, |
出版年 : | 2017 |
學位: | 碩士 |
摘要: | 農業灌溉是土地利用改變的主要行為之一,對當地和區域性氣候有著顯著的影響。在過去,已有許多研究探討灌溉對當地降水造成的改變,然而灌溉面積的大小是否對結果造成影響卻是個鮮少討論的議題。在此研究中,我們利用數值預報模式探討在美國大平原地區,灌溉後當地的水文氣候是否因灌溉面積大小〈20 × 20平方公里至600× 600平方公里〉不同而有所差異。結果顯示,灌溉造成當地的氣候改變程度會隨著灌溉面積大小而異。其中,降溫和加溼效應皆隨著灌溉面積擴大而加強;當地降水的改變量則和灌溉面積增加呈現正相關。我們分析能量和水氣收支、熱力結構、以及動力結構的改變,並提供造成此降水趨勢的可能機制。在水氣收支的分析中,水平方向的水氣輻散變化對於當地水氣隨面積變化的趨勢有重要的影響,顯示出在探討灌溉對當地氣候的影響時,不僅要考慮陸地與大氣之間的垂直交互作用,在水平方向的變異度亦是另一重要因素。在動力方面,此研究應用地轉調節的概念解釋灌溉效應在不同空間尺度下的變化情形:在較大的灌溉面積下,地轉調節由質量場主導,科氏力使得灌溉造成的低層輻散距平產生順時針旋轉,使水氣易累積在灌溉當地,進而有利於當地降水的增加。本研究顯示,灌溉面積大小對於當地氣候的改變有著一定的影響性,因此在檢視灌溉造成的陸氣交互作用變化時,應將灌溉面積列入考量的因素。 The expansion of irrigated agriculture is one of the major land use changes, which influences local and regional climate significantly. The impact of irrigation on the local precipitation has been investigated substantially, but no agreement has been reached yet. Though previous studies have examined the influence of irrigation on many aspects, few have considered the impact of irrigation area size, which might also be an influencing factor on irrigation-induced climate change. In this study, WRF model is used to explore how the local irrigation effect changes with irrigation area size from 20 × 20 km2 to 600 × 600 km2 with geometric increases in the Great Plains region. The results show that the magnitude of irrigation-induced climate change varies with the area size of irrigation. Both the cooling and moistening effects from irrigation practices are enhanced with increasing irrigation area size: the tendency of near-surface temperature difference and low-level water vapor difference with the irrigation area changes are -0.0012 ℃/km and 0.0014 mm/km, respectively. The precipitation change has an ascending tendency with area size, i.e., 0.001 mm/day/km, and such phenomenon is supported by the analyses of energy and water budget, thermodynamic structure, and circulation changes. The lateral moisture divergence, which contributes to moisture accumulation at local irrigated area, is critical to the water vapor tendency along with irrigation area size, highlighting the importance of horizontal variability to irrigation effects. The notion of geostrophic adjustment is applied to explain the dynamic changes over the irrigated area. In the larger size of irrigation simulations, geostrophic adjustment is mainly achieved by adjusting the wind field, benefiting moisture accumulation at local irrigated region. This study suggests that the irrigation area scale is necessary to be considered when examining the impact of irrigation on the local climate. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/67940 |
DOI: | 10.6342/NTU201701733 |
全文授權: | 有償授權 |
顯示於系所單位: | 大氣科學系 |
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