4 research outputs found
以垂直剖面氣象場及輻射資料計算地表粗糙度之研究
No full text本研究的目的在以垂直剖面氣象場及輻射資料來計算於大氣中
性、穩定及不穩定狀態下之地表粗糙度。研究地點分別在南投縣敦
和國小、新莊國小、彰化縣芬園鄉茄荖國小、台中市中興大學及台中縣梧棲鎮梧棲國小等地區進行，以繫留探空氣球及自設地面氣象站收取大氣垂直剖面氣象場及輻射資料，並假設在大氣中性狀態下，以風速、位溫及Monin-Obukhov Length(L)公式配合Bowen ratio method計算地表粗糙度。
結果分析於南投縣敦和國小的地表粗糙度為0.77公尺，標準偏差為0.21公尺，Zero-plane displacement(d0)約為10.6公尺，標準偏差為1.342公尺；於新莊國小的地表粗糙度為0.43公尺，標準偏差為0.48公尺，Zero-plane displacement(d0)約為8.85公尺，標準偏差為0.66公尺；於茄荖國小的地表粗糙度為0.33公尺，標準偏差為0.22公尺，Zero-plane displacement(d0)約為11.71公尺，標準偏差為1.49公尺；於中興大學的地表粗糙度為0.94公尺，標準偏差為0.58公尺，Zero-plane displacement(d0)約為29.22公尺，標準偏差為2.68公尺；於梧棲國小的地表粗糙度為0.78公尺，標準偏差為0.37公尺，Zero-plane displacement(d0)約為11.73公尺，標準偏差為0.67公尺。
將結果與國外學者所建議之結果相比較發現以本研究理論所計算的地表粗糙度皆在合理範圍內，但是仍需要更多高品質的垂直剖面氣象場及輻射資料來進行驗證。中文摘要Ⅰ
目錄Ⅱ
表目錄Ⅳ
圖目錄Ⅴ
第一章 前言1-1
1.1研究緣起1-1
1.2研究目的1-2
第二章 文獻回顧2-1
2.1 風之垂直變化結構2-1
2.2地表粗糙度之量測方法2-2
2.3風場資料的篩選標準2-8
第三章 研究理論與實驗方法3-1
3.1 相似理論3-1
3.2地表熱通量平衡式3-3
3.3 能量收支理論3-6
3.3.1 Bowen Ratio之量測3-7
3.4 真實潛熱通量之推估3-8
3.4.1 由探空觀測資料推估3-8
3.4.2 由Bowen Ratio觀測推估3-9
3.5繫留氣球方法3-9
3.6計算地表粗糙度3-9
3.7 實驗方法3-13
3.8實驗設備3-15
第四章 案例研究4-1
4.1草屯地區4-1
4.1.1地理環境4-1
4.1.2適應距離(fetch)4-2
4.1.3方法驗證4-2
4.1.3.1大氣中性狀態4-2
4.1.3.2 大氣不穩定狀態4-4
4.1.3.3 大氣穩定狀態4-4
4.1.4 敦和國小鄰近區域之地表粗糙度4-6
4.1.5 新莊國小鄰近區域之地表粗糙度4-8
4.1.6 茄荖國小鄰近區域之地表粗糙度4-10
4.2 台中地區4-11
4.2.1地理環境4-11
4.2.2 適應距離(fetch)4-12
4.2.3 台中地區之地表粗糙度4-12
4.3 梧棲地區4-14
4.3.1地理環境4-14
4.3.2適應距離(fetch)4-15
4.3.3梧棲地區之地表粗糙度4-15
第五章 討論5-1
5.1 風向5-1
5.1.1 草屯鎮敦和國小5-2
5.1.2 草屯鎮新莊國小5-3
5.1.3芬園鄉茄荖國小5-4
5.1.4台中市中興大學5-6
5.1.5 梧棲鎮梧棲國小5-8
5.2 大氣穩定度5-11
5.3計算發散的原因5-14
5.3.1 風速5-14
5.3.2 風向5-15
5.4 地表粗糙度之合理性5-16
第六章 結論與建議6-
Measurements of aerodynamic roughness and Bowen ratio using tethersonde and the eddy covariance system in urban, rice paddy and mixed areas
No full text本研究利用相似理論搭配地表能量平衡式於台灣中部地區觀測地表粗糙度，計有兩個都會區及三個農地混合住建築物區。在每一個實驗中以繫留探空氣球及地面氣象站觀測長短波輻射、土壤熱通量、及風速、溫度和濕度的垂直剖面。在台中都會區，地表粗糙度為2.1公尺，zero-plane displacement height為35 m；在草屯鎮市區地表粗糙度為1.2 公尺，zero-plane displacement height為11 m；在農地及建物混合區地表粗糙度為0.2-0.5公尺，而在水稻田區為地表粗糙度為0.032公尺。
本研究建立地表粗糙度與建築物分率、農地分率及建築物高(或人口密度)等土地利用型態的初步關係式，此外，日間大氣地表層的平均範圍為30<(z-d0)/z0<106, 且實驗地點的footprint約為上風處1.5公里。
本研究亦利用渦流協變性系統(Eddy covariance system)觀測地表及大氣之間的各通量，於日間能量平衡率約為94%，並於平衡式中考慮光合作用及平流向對能量的影響。利用渦流協變性系統觀測資料推估日間Bowen ratio約為0.16，利用輻射計推估地表反照率約為0.1。日間的二氧化碳通量約為1.2 mg m-2 s-1而夜晚約為0.12 mg m-2 s-1，同時建立二氧化碳通量與太陽淨輻射、氣溫及葉面積指數的關係式 。植物阻抗在日間呈現”U”型，極大值在中午約為42 s m-1，利用回歸方法建立植物阻抗與太陽淨輻射及葉面積指數的關係式，其模擬值與觀測值得相關係數為0.78。The similarity theory of the ASL in conjunction with the energy budget equation of land surface under unstable atmospheric conditions was used to determine the aerodynamic roughness lengths for two urban areas and three rice paddies mixed with buildings over a complex terrain in central Taiwan. At each of the sites, surface net radiation, ground heat flux and vertical profiles of wind speed, temperature and humidity within the atmospheric surface layer (ASL) were measured.
Over the Taichung urban area, the roughness was determined to be 2.1 m with a zero-plane displacement height of 35 m. Over the Caotun urban area, the roughness was determined to be 1.2 m with a zero-plane displacement height of 11 m. Over the two mixed farmlands, the roughness values were determined to be 0.2 - 0.5 m and over the homogeneous rice paddy in Wufeng, the roughness values were determined to be 0.032 m that close to the values (0.008 - 0.02 m) for homogeneous rice paddies reported in the literature.
A preliminary relationship for estimating roughness value as a function of residential fraction, farmland fraction and building height (or population density) is derived. The observations show that during the daytime, the mean height range of the ASL was 30<(z-d0)/z0<106 and the fingerprint areas extended 1.5 km upwind from the three profile sites.
During the day, the energy balance ratio measured by an Eddy Covariance (EC) system is found to be 94% after considering the photosynthetic and local advected heat fluxes. The observations by the EC system suggest that the Bowen ratio was about 0.16 during the daytime. Albedo is estimated as 0.1 according to the solar radiation and the reflected show-wave radiation. The EC system also measured the daytime absorbed CO2 flux at 1.2 mg m-2 s-1 and nighttime respiration rate at 0.12 mg m-2 s-1. Relationships of CO2 flux as functions of net solar radiation, air temperature and leaf area index are derived. The diurnal pattern of the canopy resistance for evapotranspiration is found to be a U shape with the minimum value at 42 s m-1 around noon of the rice paddy. A relationship of canopy resistance related to net solar radiation and leaf area index is derived with a correlation coefficient of 0.78.摘要 1
1. Introduction 5
1.1. Motivation 5
1.2. Background 6
1.2.1 Flux-profile relationships 6
1.2.2 Bowen ratio 7
1.2.3 Aerodynamic roughness length 8
1.2.3 Rice paddy and surface energy closure 9
1.3 Purpose 10
2. Basic Theory 13
2.1 Profile method 13
2.2 Bowen ratio method 19
2.3 Single-level method 21
2.4 Footprint 23
2.5 Surface energy balance components 23
2.6 Examination of energy balance closure 25
2.7 Evaluation of canopy resistance 26
3. Instruments 29
3.1 Tethersonde system 29
3.2 Eddy covariance system 29
3.3 Surface micrometeorological station 29
4. Determining aerodynamic roughness using tethersonde and heat flux measurements in an urban area over a complex terrain 33
4.1 Study site 33
4.2 Identification of Surface Sublayer 35
4.3 Zero-plane displacement and Roughness 38
4.4 Discussion 42
5. Aerodynamic roughness over an urban area and over two farmlands in a populated area as determined by wind profiles and surface energy flux measurements 45
5.1 Study site 45
5.1.1 Urban Canopy site (UC) 48
5.1.2 Farmland Canopy sites (FC) 49
5.1.3 Field measurements 49
5.2 Results 50
5.2.1 Height range of the atmospheric surface layer 50
5.2.2 Zero-plane displacement height and aerodynamic roughness 59
5.3 Discussion 62
5.3.1 Comparison with other studies 62
5.3.2 Proposed roughness function for a heterogeneous terrain 64
6. Comparison of the turbulence characteristics of a rice paddy as observed by a tethersonde system and by an eddy-covariance system 69
6.1 Study site 69
6.2 Results 70
6.2.1. Calculations of profile method and single-level method 70
6.2.2 Aerodynamic roughness length for momentum (z0m) and for heat (z0T) 76
6.2.3 Friction velocity 77
6.2.4 Bowen ratio 78
6.3 Discussions 82
6.3.1 Footprint analysis 82
6.3.2 Surface layer range 83
7. Surface energy components, CO2 flux and evapotranspiration from a rice paddy in Taiwan 87
7.1 Characteristics of rice paddy and site description 87
7.2 Surface energy components 91
7.2.1 Coordinate rotation correction 99
7.2.2 Webb correction 99
7.2.3 Canopy heat storage (C) correction 99
7.2.4 Advected heat flux (A) correction 100
7.2.5 Photosynthesis correction 100
7.3 CO2 flux 101
7.4 Land surface parameters for rice paddy 105
7.4.1 Albedo 106
7.4.2 Aerodynamic resistance 107
7.4.3 Canopy resistance for evapotranspiration 108
8. Conclusion 111
Reference 115
Appendix: C++ program for the calculation of aerodynamic roughnes
Measurements of aerodynamic roughness and Bowen ratio using tethersonde and the eddy covariance system in urban, rice paddy and mixed areas
No full text本研究利用相似理論搭配地表能量平衡式於台灣中部地區觀測地表粗糙度，計有兩個都會區及三個農地混合住建築物區。在每一個實驗中以繫留探空氣球及地面氣象站觀測長短波輻射、土壤熱通量、及風速、溫度和濕度的垂直剖面。在台中都會區，地表粗糙度為2.1公尺，zero-plane displacement height為35 m；在草屯鎮市區地表粗糙度為1.2 公尺，zero-plane displacement height為11 m；在農地及建物混合區地表粗糙度為0.2-0.5公尺，而在水稻田區為地表粗糙度為0.032公尺。
本研究建立地表粗糙度與建築物分率、農地分率及建築物高(或人口密度)等土地利用型態的初步關係式，此外，日間大氣地表層的平均範圍為30<(z-d0)/z0<106, 且實驗地點的footprint約為上風處1.5公里。
本研究亦利用渦流協變性系統(Eddy covariance system)觀測地表及大氣之間的各通量，於日間能量平衡率約為94%，並於平衡式中考慮光合作用及平流向對能量的影響。利用渦流協變性系統觀測資料推估日間Bowen ratio約為0.16，利用輻射計推估地表反照率約為0.1。日間的二氧化碳通量約為1.2 mg m-2 s-1而夜晚約為0.12 mg m-2 s-1，同時建立二氧化碳通量與太陽淨輻射、氣溫及葉面積指數的關係式 。植物阻抗在日間呈現”U”型，極大值在中午約為42 s m-1，利用回歸方法建立植物阻抗與太陽淨輻射及葉面積指數的關係式，其模擬值與觀測值得相關係數為0.78。The similarity theory of the ASL in conjunction with the energy budget equation of land surface under unstable atmospheric conditions was used to determine the aerodynamic roughness lengths for two urban areas and three rice paddies mixed with buildings over a complex terrain in central Taiwan. At each of the sites, surface net radiation, ground heat flux and vertical profiles of wind speed, temperature and humidity within the atmospheric surface layer (ASL) were measured.
Over the Taichung urban area, the roughness was determined to be 2.1 m with a zero-plane displacement height of 35 m. Over the Caotun urban area, the roughness was determined to be 1.2 m with a zero-plane displacement height of 11 m. Over the two mixed farmlands, the roughness values were determined to be 0.2 - 0.5 m and over the homogeneous rice paddy in Wufeng, the roughness values were determined to be 0.032 m that close to the values (0.008 - 0.02 m) for homogeneous rice paddies reported in the literature.
A preliminary relationship for estimating roughness value as a function of residential fraction, farmland fraction and building height (or population density) is derived. The observations show that during the daytime, the mean height range of the ASL was 30<(z-d0)/z0<106 and the fingerprint areas extended 1.5 km upwind from the three profile sites.
During the day, the energy balance ratio measured by an Eddy Covariance (EC) system is found to be 94% after considering the photosynthetic and local advected heat fluxes. The observations by the EC system suggest that the Bowen ratio was about 0.16 during the daytime. Albedo is estimated as 0.1 according to the solar radiation and the reflected show-wave radiation. The EC system also measured the daytime absorbed CO2 flux at 1.2 mg m-2 s-1 and nighttime respiration rate at 0.12 mg m-2 s-1. Relationships of CO2 flux as functions of net solar radiation, air temperature and leaf area index are derived. The diurnal pattern of the canopy resistance for evapotranspiration is found to be a U shape with the minimum value at 42 s m-1 around noon of the rice paddy. A relationship of canopy resistance related to net solar radiation and leaf area index is derived with a correlation coefficient of 0.78.摘要 1
1. Introduction 5
1.1. Motivation 5
1.2. Background 6
1.2.1 Flux-profile relationships 6
1.2.2 Bowen ratio 7
1.2.3 Aerodynamic roughness length 8
1.2.3 Rice paddy and surface energy closure 9
1.3 Purpose 10
2. Basic Theory 13
2.1 Profile method 13
2.2 Bowen ratio method 19
2.3 Single-level method 21
2.4 Footprint 23
2.5 Surface energy balance components 23
2.6 Examination of energy balance closure 25
2.7 Evaluation of canopy resistance 26
3. Instruments 29
3.1 Tethersonde system 29
3.2 Eddy covariance system 29
3.3 Surface micrometeorological station 29
4. Determining aerodynamic roughness using tethersonde and heat flux measurements in an urban area over a complex terrain 33
4.1 Study site 33
4.2 Identification of Surface Sublayer 35
4.3 Zero-plane displacement and Roughness 38
4.4 Discussion 42
5. Aerodynamic roughness over an urban area and over two farmlands in a populated area as determined by wind profiles and surface energy flux measurements 45
5.1 Study site 45
5.1.1 Urban Canopy site (UC) 48
5.1.2 Farmland Canopy sites (FC) 49
5.1.3 Field measurements 49
5.2 Results 50
5.2.1 Height range of the atmospheric surface layer 50
5.2.2 Zero-plane displacement height and aerodynamic roughness 59
5.3 Discussion 62
5.3.1 Comparison with other studies 62
5.3.2 Proposed roughness function for a heterogeneous terrain 64
6. Comparison of the turbulence characteristics of a rice paddy as observed by a tethersonde system and by an eddy-covariance system 69
6.1 Study site 69
6.2 Results 70
6.2.1. Calculations of profile method and single-level method 70
6.2.2 Aerodynamic roughness length for momentum (z0m) and for heat (z0T) 76
6.2.3 Friction velocity 77
6.2.4 Bowen ratio 78
6.3 Discussions 82
6.3.1 Footprint analysis 82
6.3.2 Surface layer range 83
7. Surface energy components, CO2 flux and evapotranspiration from a rice paddy in Taiwan 87
7.1 Characteristics of rice paddy and site description 87
7.2 Surface energy components 91
7.2.1 Coordinate rotation correction 99
7.2.2 Webb correction 99
7.2.3 Canopy heat storage (C) correction 99
7.2.4 Advected heat flux (A) correction 100
7.2.5 Photosynthesis correction 100
7.3 CO2 flux 101
7.4 Land surface parameters for rice paddy 105
7.4.1 Albedo 106
7.4.2 Aerodynamic resistance 107
7.4.3 Canopy resistance for evapotranspiration 108
8. Conclusion 111
Reference 115
Appendix: C++ program for the calculation of aerodynamic roughnes
Productions of Initial and Boundary Condition for Mesoscale Model - Construction of Taiwan Surface Roughness Dateset and the Soil Moisture from Remote Sensing Data
No full textLand is the major component of the climate system, but it inclusion in climate models isstill relatively simplistic. More realistic treatments of land processes and a fuller appropriatedataset are current research objectives. Some Land surface scheme (LSS) parameters, such asalbedo, fraction of vegetated cover, leaf area index, etc., can be measured (estimated) at boththe patch scale and the large scale (via remote sensing), and the relationship between theirarea-averaged values at patch and large scales is linear. However, other parameters such assoil hydraulic conductivity, stomatal resistance, aerodynamic resistance, etc., are not easilymeasured at the relevant scales, and their relationship at different scales is less simple.The main work in this project will be divided into five items and completed within threeyears: 1) Construction of NCHU flux tower over urban areas to observe the fluxes betweenthe atmosphere and the underlying surface and the meteorological data , 2) Derivation of landcharacteristics, including roughness length for heat, albedo, surface emissivity, area heatcapacity, canopy resistance and Bowen ratio using the observed data of N. Tongyen Mt.,NHCU and TFRI, 3) Development of a 1-km resolution dataset of roughness length formomentum and heat based on observations and its relationship to landuse types, andImplementation the roughness dataset for use in WRF under the cooperation with CWB, 4)Construction of long-term observation sites for soil moisture and development of hydrologicalrunoff model applied to the complex terrain in Taiwan, and 5) Development of a localizedland surface scheme (LSS) for use in WRF based on observation in Taiwan.地表真實值的觀測(例如各能量通量與土壤函水率等)及地表參數的表現在氣候及氣象模式中極為重要。在國外所提供之氣動粗糙度一般過小，造成風速模擬過快(Tsuang etal., 2003; Tsai and Tsuang, 2005)。計畫申請人過去5 年，已發表了相關研究期刊論文達3篇，利用繫留氣球、渦流協變性系統等觀測資料，或反演等方法求取中部地區等參數(Tsaiand Tsuang 2005; Tsai et al., 2007; Tsuang et al., 2008; Tsuang et al., 2009; Tsai et al.,2010a)。本計畫主要目的是希望能建立全台灣之動量粗糙度及熱粗糙度資料庫和台灣地區地表阻抗及土壤含水率在時間、空間上的分布，進而整合入WRF 區域氣象模式。此研究計畫將有以下四個工作方向。第一、收集地面觀測氣象資料並推導不同地貌的動量粗糙度(z0m)，並搭配過去成果(Tsuang et al., 2003; Tsai and Tsuang, 2005; Tsai etal., 2010a)及本計畫資料建立台灣地區動量粗糙度資料庫。第二、利用水稻田及森林地觀測資料推導熱粗糙度。第三、利用遙測資料推導台灣地區地表阻抗及土壤含水率時間、空間上的分布，以提供初始及邊界場予中尺度氣象模式使用。第四、將所得之初始及邊界資料應用於WRF 模式比較其是否改善地面風場及各能量通量模擬的模式表現。本計畫預定主要工作人力為計畫申請人本人，並搭配共同主持人所提供之地面觀測資料及衛星遙測資料來進行研究。希望三年內可以完整建立台灣地區重要大氣陸地下邊界之參數化過程包含觀測，並整合入WRF 之模式中，方便台灣之研究團隊及氣象單位使用
