大氣熱亂流儀量測方法建立及儀器開發與實測;Development of low-cost Instrument for Atmospheric Turbulence Measurement and Its Field Test

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Title:	大氣熱亂流儀量測方法建立及儀器開發與實測;Development of low-cost Instrument for Atmospheric Turbulence Measurement and Its Field Test
Authors:	吳崑旭;Wu, Kun-Hsu
Contributors:	大氣科學學系
Keywords:	溫度結構參數;Temperature Structure parameter
Date:	2022-06-29
Issue Date:	2022-07-13 17:21:09 (UTC+8)
Publisher:	國立中央大學
Abstract:	溫度結構參數(C_T^2)常用於量化亂流空間中不均勻性的強度，而溫度結構參數可透過量測水平空間中溫度變異量後計算得知，其意涵可代表環境不穩定度，進而剖析大氣亂流結構變化。近年來大氣現地觀測朝向高時間解析度的方向發展，但對於環境亂流的觀測依然缺乏，主要受限於儀器昂貴與維護不易。為加強了解台灣亂流的時空分布特性，本研究自主開發一套符合經濟效益的溫度結構參數量測技術，使用熱電偶(Thermocouple)配合高精度類比量測系統，並採用60Hz觀測頻率量測1.5m距離間的溫差，並透過2/3定律(Kolmogorov, 1941)標準化結構參數，解出大氣溫度結構常數，吾人稱之為大氣熱亂流儀。大氣熱亂流儀之開發經過一系列的驗證過程。在實驗室控制實驗中，我們發現儀器所得的量測值與控制溫差有良好的線性關係，並選擇以穩定條件下觀測C_T^2≅〖10〗^(-2)，取此數值做為大氣熱亂流儀穩定度基值。研究顯示，相對於高頻超音波風速計測得之C_T^2，受限於直接量測方法探頭反應時間限制，敏感度較低，受類比放大器倍率限制最低解析度較高。本研究進一步將此儀器應用於真實大氣環境條件下，共建立了兩組觀測實驗數據，第一組實驗於中央大學觀測坪32米塔上配置四組大氣熱亂流儀分別於2米、8米、16米與32米高度，透過垂直分層觀測，本實驗探討中央大學觀測坪近地表環境不穩定度於日夜轉換間及不同季節之特性。第二組實驗為參與2021年宜蘭劇烈降雨實驗 (2021 YESR) ，於宜蘭縣三星鄉與大同鄉配置三組大氣熱亂流儀，配置採用東西方向建置，西側測站海拔高330公尺，其餘皆為平原區觀測，透過空間上部署，協助解釋降雨與近地表大氣亂流發生的時空關聯性。整體來說，本研究開發的大氣熱亂流儀所求得的溫度結構參數可對應到大氣不穩定度特徵，解釋觀測位置亂流特徵變化，透過多點時序觀測，可偵測出時空變化奇異點，提供極短期降雨潛勢的預測。未來，如本研究團隊亦將利用無人機載具搭載大氣熱亂流儀，解析不同天氣系統下，大氣亂流三維分布與特徵。 ;The temperature structure parameter (C_T^2) is often used to quantify the intensity of the turbulence. Measuring the temperature variation can calculate C_T^2 in the horizontal space, and it can represent the environmental instability to analyze the structural changes of atmospheric turbulence. In recent years, in-situ atmospheric observation has been developed towards high temporal resolution, but the observation of environmental turbulence is still lacking, which is mainly limited by expensive instruments and difficult maintenance. In order to strengthen the understanding of the temporal and spatial distribution characteristics of turbulence in Taiwan. This research developed a set of temperature structure parameter measurement technology that is cost-effective, using a thermocouple with a high-precision analog measurement system. The sample rate we use 60Hz to measure 1.5m differential temperature. To solve C_T^2 function, the temperature difference between the distances are normalized by the 2/3 law (Kolmogorov, 1941). The new insturement we call the Mirco-Thermometer. The development of the Mirco-Thermometer has gone through a series of validation processes. In the laboratory control experiment, we found that the measured value obtained by the instrument has a good linear relationship with the control temperature difference. Testing the observed C_T^2 under stable conditions as the base value of the stability of the atmospheric disturbance instrument. In this study, this instrument was further applied to the real atmospheric environment, and two sets of observational experiment data were established. The first experiment is in NAHO (NCU Atmospheric and Hydrological Observatory) station. The Mirco-Thermometer was mounted at heights of 2, 8, 16 and 32 meters, through vertically layered observation, this experiment explores the characteristics of the near-surface environmental instability and dirual cycle at NAHO station. The second group of experiments is a part of field campaign in the 2021 Yilan Experiment of Servere Rainfall (2021 YESR). Three sets of atmospheric thermal turbulence measurement systems are installed in Sansing Township and Datong Township, Yilan County. In this spatial deployment at plain and mountain area, helps to explain the temporal and spatial interaction between rainfall and the occurrence of near-surface atmospheric turbulence. Overall, the C_T^2 obtained by the Mirco-Thermometer developed in this study can correspond to the characteristics of atmospheric instability and explain the changes in the turbulent flow. It can provide forecasts of very short-term rainfall precursor. For the future application, the instrument can be used onboard an unmanned aerial vehicle to measure the three-dimensional distribution and characteristics of atmospheric turbulence under different weather systems.
Appears in Collections:	[Department of Atmospheric Sciences and Graduate Institute of Atmospheric Physics ] Department of Earth Sciences

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