類別:http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/612026-03-09T18:39:34Z2026-03-09T18:39:34Z高雄都會區氣膠吸濕特性之探討Chia-Hung Hsu徐嘉鴻http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/552342021-06-16T03:52:34Z2015-01-01T00:00:00Z標題: 高雄都會區氣膠吸濕特性之探討; A study of hygroscopicity for urban aerosols in Kaohsiung
作者: Chia-Hung Hsu; 徐嘉鴻
摘要: 氣膠的吸溼能力在大氣中扮演重要的角色，它會影響氣膠成雲，進而影響整個生活環境及氣候系統。本研究在2013年的1月和7月利用雲凝結核計數器(CCNc)，凝結核計數器(CPC)以及掃描式電移動度微粒分徑器(SMPS)在高雄都會區量測氣膠的活化率(NCCN/NCN)和粒徑分布，並根據活化粒徑(DA)和過飽和度(SS)，進而推算吸溼參數(κ)。除了探討當地氣膠吸溼能力的特性外，也和其他台灣地區的量測結果做一比較及討論。
高雄冬季和夏季的平均觀測結果可以看到氣膠老化的特徵，也就是隨著粒徑增加(60-200nm)，氣膠的吸溼參數有跟著增加(冬天：0.15-0.21，夏天：0.08-0.23)。冬季的觀測可以由氣象條件和氣團來源分成4個時期。1/18前後由台灣北部移入的氣團可以量測到最高的吸溼參數為0.27-0.54。同樣由台中外海移入的氣團，也會因為當地的風速大小使氣膠有不同的吸溼性，1/23-24的平均風速為1.73m/s，吸溼參數為0.10-0.15；1/25-26的平均風速為2.05m/s，吸溼參數為0.15-0.34。夏季的觀測可以分成平日時期和颱風時期，颱風時期的吸溼參數較高且並無規律變化。平日時期的氣膠吸溼參數有明顯的日變化，推測氣膠吸溼性的減少可能和汽機車排放有關，氣膠的吸溼性增加則和大氣化學反應以及當地的風速增加有關。
台灣郊區的氣膠吸溼性平均而言都比都會區還來得佳，可能和汽機車排放以及郊區的氣膠特性有關。在都會區之中以夏季的高雄都會區有最佳的吸溼性，台北(κ=0.02-0.12)和台中(κ=0.04-0.14)都會區則較低。在高雄都會區又以冬季的氣膠的吸溼性優於夏季。; Hygroscopicity of aerosol played an important role in the atmosphere. It would influent human life and climate system by acting as cloud condensation nuclei to affect cloud formation. In this study, we measured the activation ratios (NCCN/NCN) and the aerosol number size distribution using a cloud condensation nuclei counter (CCNc), condensation particle counter (CPC) and a scanning mobility particle sizer system (SMPS). The critical diameter (Dc) for a given supersaturation (SS) was estimated. The (SS, Dc) datasets were applied to derive the single hygroscopic parameter (κ). We discussed κ of aerosol, when measured in January and July 2013 in Kaohsiung city. And we focused on hygroscopicity variation for other sites.
Both Kaohsiung city winter and summer κ increased from 0.15 to 0.21 and from 0.08 to 0.23 meanly, exhibited a string size dependence in the ranging of 60 nm to 200 nm. Based on the weather condition and back trajectory analysis, winter observation was divided into 4 periods. 1/18 measured highest κ (0.27-0.54) where air parcel from north of Taiwan. Local wind speed would change κ, although the air parcel from same place. Both air parcels from sea beside Taichung, 1/23-24 measured lower mean wind speed (1.73m/s) and lower κ (0.10-0.15), and 1/25-26 measured higher mean wind speed (2.05m/s) and higher κ (0.15-0.34). Summer observation was divided into 2 periods, normal and typhoon. Latter period measured higher κ and irregular trend. Normal period showed a significant diurnal variation. It was likely that soot from vehicle coagulated and decreased κ, and then atmospheric chemical reaction and local wind speed increased κ.
Hygroscopicity of country aerosol was higher than urban in Taiwan. It was likely that soot from vehicle coagulated and decreased κ in cities, and then environment of countries increased κ. Hygroscopicity in Kaohsiung city was greater than Taipei city (κ=0.02-0.12) and Taichung city (κ=0.04-0.14) in summer. For seasonal variation, κ of winter was better than summer in Kaohsiung city.2015-01-01T00:00:00Z高層槽對颱風強度影響的機制探討Kun-Huang Kuo郭崑皇http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/306832021-06-13T02:12:14Z2007-01-01T00:00:00Z標題: 高層槽對颱風強度影響的機制探討; The Effect of Upper-Layer Trough on the Intensity Change of Tropical Cyclones
作者: Kun-Huang Kuo; 郭崑皇
摘要: 本研究利用TCM4 (Wang 1999, 2001) 針對高層槽對颱風強度的影響進行一系列理想數值實驗及機制與敏感性探討，當颱風在達到不同強度時加入不同大小範圍和不同強度的高層槽，分析各組實驗颱風強度和結構對高層槽的反應，結果發現範圍越小、強度越弱的高層槽對颱風強度的發展越有利。而相對較弱的颱風而言，在颱風強度較強時與高層槽作用初期大部份均會呈現減弱的現象而比較沒有快速增強的情形出現。
當颱風與高層槽產生交互作用時，在颱風高層均有明顯外流噴流的產生，而隨著高層槽往颱風接近，也會帶來垂直風切的增強，但於颱風外流和槽之間的交互作用下，高層槽在較高層的部份尺度會變小，強度會減弱，而在其下的部分甚至會與颱風有合併的現象，因而使垂直風切強度減小進而減弱其對颱風的破壞力。而高層槽所伴隨的垂直風切也會使颱風出現明顯波數一不對稱的結構，並在部份實驗中導致較強的中、低層增溫。且當颱風在與高層槽作用後，檢視其暴風半徑和強度(strength)的發展可發現其均比在沒有高層槽影響下的颱風來得大，這些結果與過去文獻的結論一致。
本研究中在部分實驗雖有較大垂直風切的存在，但颱風強度仍能夠繼續增強，主要可能是由於高層槽其氣旋式環流的結構會額外帶來渦流角動量的傳送而抵消較大垂直風切對颱風發展的負面影響。在各項實驗中渦流角動量通量輻合增強的區域，外流也會變大，當高層外流被增強，則有利於低層內流的增加，因此有助於颱風強度的增強。但值得注意的是並非每次渦流角動量通量輻合增加都能使颱風增強，在一些實驗中有大範圍渦流角動量通量輻合為正值的情況下，颱風強度並未增強，這可能是與渦流角動量通量輻合所增強的外流位置有關。而對照高海表面溫度的實驗結果可發現若要使颱風產生快速增強的現象，除了高層要有適宜高層槽的存在之外，海表面溫度的高低也是影響此一現象產生的重要關鍵。而對平穩狀態的颱風而言，似乎沒有適宜的高層槽可使颱風強度增強，高層槽的加入均會使已達平穩狀態的颱風產生減弱。; This research utilizes Tropical Cyclone Model Version 4(TCM4, Wang 1999, 2001) to conduct a series of ideal numerical experiments and investigate the mechanism and sensitiveness of the effect of upper-layer trough on the intensity of tropical cyclones (TCs). In these experiments, the TC with different intensity encounters the upper-layer trough of varied size and magnitude. The analyzed results of this research shows that weak upper-layer trough with small scale is favorable to TC development. Contrary to weaker TCs(category 1), interacting with upper-layer trough makes almost all stronger TCs(category 3) weaken initially and no rapid intensification occurs. The vertical wind shear increases as the upper layer trough approaches. After interacting with the upper layer trough, it tends to decrease, and this is favorable for TC development. Upper layer PV meandering decays while approaching the TC, and then outflow-jet aloft forms at north and northwest of the TC center. After the TC-trough interaction, mid- and high-troposphere cools while low troposphere warms and both the vertical velocity and rainfall rate reveal wave-number one structure, and thus affects the TC intensity. In all numerical experiments, the outflow in intense eddy flux convergence of relative momentum (EFC) region often increases, but it does not guarantee TC’s intensification due to the position of the outflow. The result of high SST’s experiment reveals that although the SST is an important factor, the upper-layer trough also plays an important role in the TC intensification. In the cases of TCs of the steady state, there is not favorable upper-layer trough that can induce TC intensification. The intensity of the TC that reaches steady state often weakens when it interacts with upper-layer trough.2007-01-01T00:00:00Z高層冷心低壓對颱風強度及結構影響之機制探討Yu-An Chen陳禹安http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/799192022-11-23T09:16:43Z2021-01-01T00:00:00Z標題: 高層冷心低壓對颱風強度及結構影響之機制探討; Environmental Forcing of Upper-tropospheric Cold Low on Tropical Cyclone Intensity and Structural Change
作者: Yu-An Chen; 陳禹安
摘要: 颱風與槽線交互作用對颱風強度可同時造成有利和不利影響，因此在研究與預報上仍具挑戰。其中在西北太平洋，高層冷心低壓則是另一種常見可與颱風交互作用的高層環境系統。本研究目的在於了解高層冷心低壓對颱風強度及結構的影響，以及區分有利和不利颱風發展的高層冷心低壓配置。研究的第一部分進行真實個案模擬，控制組實驗(CTRL)模擬2016年的尼伯特颱風，另外還透過片段位渦反演的方法進行移除高層冷心低壓的實驗(noCL)，目的是能夠量化高層冷心低壓對颱風的影響程度。第二部分則在準理想(quasi-idealized)的架構下進行高層冷心低壓與颱風間配置的敏感性實驗測試。 真實個案模擬的結果顯示，控制組實驗在颱風與冷心低壓交互作用期間，冷心低壓將伴隨慣性穩定度較低、對稱不穩定度較高、渦流角動量通量輻合較高等環境條件，使得颱風外流形成不對稱結構且有利於其擴張。此外，控制組實驗的快速增強時間明顯較早，伴隨眼牆附近較強的對流活動以及較快的軸對稱化過程。本研究接著提出三個冷心低壓影響颱風內核結構的可能機制。首先，冷心低壓環流相對於颱風將伴隨較低的絕對角動量，這將使颱風外流擴展所需的能量耗散下降，因此颱風可保留較多的淨能量來源進行其他方面的作功，也使的颱風增強速率提高。另外，由於冷心低壓始終與颱風保持一定的距離，且交互作用過程中不斷被颱風本身的外流反氣旋場削弱，這可使冷心低壓引發的垂直風切有效降低。因此在控制組實驗中，風切引發的下沉運動所伴隨的邊界層頂低熵空氣明顯較低，颱風的淨能量來源也能有效保留不被抵銷。最後，我們透過Sawyer-Eliassen平衡診斷方程發現冷心低壓的環境渦流強迫可直接造成颱風次環流的增強，有利於颱風發展。整體來說，尼伯特颱風與冷心低壓的交互作用有利颱風發展。冷心低壓除了額外提供有利條件，也降低風切造成的不利因素，使得颱風淨能量來源得以保留、軸對稱化過程較快且快速增強肇始時間提早。 敏感性實驗結果顯示颱風增強速度主要由垂直風切量值所決定。當冷心低壓位於颱風北側或西北側且維持大約一倍羅士培變形半徑的適當距離(約600到1000公里)，交互作用將最有利颱風發展。若冷心低壓始終位在颱風近距離東側且保持一定強度，交互作用將不利颱風發展。另外，只要冷心低壓伴隨的風切保持不高，即使距離很近也可發生有利的交互作用。2021-01-01T00:00:00Z飛機積冰模擬與診斷Hsuan-Wei Wang王璿瑋http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/466682021-06-15T05:22:08Z2010-01-01T00:00:00Z標題: 飛機積冰模擬與診斷; The Simulation and Diagnosis of Aircraft Icing
作者: Hsuan-Wei Wang; 王璿瑋
摘要: 積冰對於飛航安全影響重大，也是雲物理觀測與模擬的一項科學議題。過去發生的航空器積冰事件的統計結果發現，積冰發生的有效環境溫度介於-3~-15°C，而且很少低於-25°C以下。從環境溼度的統計發現，相對溼度必須超過70%以上才有較高的機率產生積冰。研究文獻指出，積冰預測以及民用航空器的積冰警告系統，大多直接從溫度與相對溼度兩參數(T-RH algorithm)加以推測，因此航空氣象作業單位直接利用中尺度天氣數值模式之輸出參數來估算積冰(Thompson et al. 1997; Schultz and Politovich 1992; Knapp 1992)。綜合言之，綜觀大氣背景環境以及液態水含量(LWC)的掌握是判斷積冰潛勢(Icing Potential)的必要條件。
本文透過美國航空Eagle-4184航班個案(1994年10月31日15:57UTC)以及復興航空GE-791航班個案(2002年12月20日17:52UTC)，嘗試使用WRF中尺度模式和WISCDYMM雲物理動力模式，來模擬診斷這兩次嚴重的ATR-72飛機積冰的大氣環境和數值模式預報能力。在Eagle-4184個案模擬中，WRF在綜觀環境場的模擬結果跟美國天氣服務(NWS)所發布的地面天氣圖是相當一致，飛行高度10,000呎的環境溫度-2℃，西南風，風速約為20ms-1。從WISCDYMM雲模式所提供的高時空解析參數中，進行液態水含量的計算，得知飛行空層LWC都超過0.24(g kg-1)，而且有局部的區域超過0.36(g kg-1)，屬於輕度到中度強度的積冰。在GE-791個案中，利用WRF輸出參數進行LWC計算，模擬出飛行路徑上LWC大約介於0.05 ~ 0.15 (g kg-1)，積冰訊號並不明顯，但是使用WISCDYMM診斷空難發生空域的LWC，由模式模擬出17:49UTC的LWC高達0.2(k/kg)，相對於WRF的模擬結果更為顯著。另外，在17:34UTC以及17:49UTC兩時段的雷達回波有出現峰值，這兩筆回波峰值訊號出現的時間點跟WISCDYMM所模擬出的LWC高值的時間點相符。
WRF模式模擬結果顯示，綜觀與中尺度天氣條件大致掌握這兩個案飛機的盤旋與巡航高度之LWC大於氣候平均值的特徵，WISCDYMM模式則進一步提供了更高時間與空間解析度的環境場，可以用檢視飛機失事前數十分鐘期間的大氣溫度場以及LWC空間分布，進而估算飛行航路上的積冰程度。; Icing plays a significant role in the issue of fight safety, and it’s also an important issue of microphysical observation and model simulation in meteorology. In the literatures, the current icing forecasting and warning system only use temperature and relative humidity parameters. But the over-prediction of the spatial extent of aircraft icing has reduced the reference for flight path planning. Some research found Icing intensity can deduce from estimation of liquid water content (LWC), and the U.S. NOAA/NWS icing forecasting production for United States Route is referential. Before 2006, the icing forecasting from Taipei Flight Information Region (Taipei FIR) stayed the icing prediction by temperature and relative humidity, and then used the NCAR product directly until now. It is necessary that we should explore more on the microphysical simulation and application of Taiwan.
American Airline Flight Eagle-4184 encountered icing when it was holding at 10,000 ft, then the flight lost control and crashed at 15:57 UTC, October 31 of 1994 near Roselawn, Indiana. It was the first loss of an ATR 72 aircraft in the world. In Taiwan, TransAsia Airways cargo flight GE-791 encountered serve icing and crashed off the coast of southwest Makung at 15:52UTC, October 21 of 2002. It led to weather forecaster litigation. In this study, we focus on the small and mesoscale weather diagnosis and icing potential forecast. First, WRF (Weather Research and Forecasting Model V3.1) is used to analyze the environmental field. Then we implant WRF output into WISCDYMM (Wisconsin Dynamic-Microphysical Model), and diagnose these two cases with WISCDYMM high spatial and temporal resolution (1.0 km horizontally, 0.2 km vertically, 2 sec time step). The 1 km thickness of LWC parameter in Flight Air Layer (18000 feet) is computed and compared with weather radar and Infrared satellite image date.
The results showed that the LWC simulated from WRF is 0.1~0.2 (g/kg) in two cases, it only arrived at a weak icing level. From WISCDYMM simulation in lasted 10 minutes of Eagle-4184 , the atmospheric environment was cold and rainy. This might be the reason why the plane cannot de-ice clearly. Comparison of radar data and LWC simulation in GE-791 case, LWC has an increasing trend before the radar reflection increased. It shows that WISCDYMM cloud model under WRF mesoscale simulation has good performance for diagnosing the small scale feature for aviation weather watch.2010-01-01T00:00:00Z