| DC 欄位 |
值 |
語言 |
| DC.contributor | 大氣物理研究所 | zh_TW |
| DC.creator | 張偉裕 | zh_TW |
| DC.creator | Wei-Yu Chang | en_US |
| dc.date.accessioned | 2010-6-23T07:39:07Z | |
| dc.date.available | 2010-6-23T07:39:07Z | |
| dc.date.issued | 2010 | |
| dc.identifier.uri | http://ir.lib.ncu.edu.tw:444/thesis/view_etd.asp?URN=946401001 | |
| dc.contributor.department | 大氣物理研究所 | zh_TW |
| DC.description | 國立中央大學 | zh_TW |
| DC.description | National Central University | en_US |
| dc.description.abstract | 本研究利用二維雨滴譜儀(2D-Video Disdrometer)地面觀測及C 波段雙偏極化雷達(C-band dual-polarimetric radar)的反演資料，分析登陸北台灣地區之颱風的雨滴粒徑分佈(Rainrop Size Distribution)及其雨滴軸比關係(Drop Shape Relation)。由兩個颱風雨帶之雨滴粒徑分佈的時間演變，及其對應之降水系統的垂直結構分析，發現颱風雨帶內有三種不同的降水型態：(1) 弱層狀水、(2)層狀降水、(3)對流降水。此三種不同型態的降水系統，其質量權重雨滴直徑(mass-weighted diameter - Dm)、最大雨滴直徑(maximum diameter)及回波垂直結構等，均有不同的特徵。從雷達回波15 dBZ
等值線的距海平面高度高度(代表系統發展高度H)及雷達地面回波值(代表系統強度ZHH)的分析發現，質量權重雨滴直徑(mass-weighted diameter - Dm)隨H 及ZHH 值的增加而有增大的趨勢。從海面上雷達雨滴粒徑分佈反演發現，颱風降水系統的雨滴粒徑分佈可被歸類為海洋型對流降水系統(maritime convective type)。然而，地面雨滴譜儀觀測資料顯示，登陸後的颱風降水系統之雨滴粒徑分佈，其特徵介於海洋及大陸型對流降水系統(continental convective type)之間。在雨滴軸比關係(Drop Shape Relation)研究中發現，颱風系統內大於1.5mm 的雨滴，其「有效」雨滴軸比關係(effective DSR)隨著環境水平風速的增加，而傾向於較接近圓形(較不橢圓)。
本研究並利用觀測模擬實驗(Observing System Simulation Experiment: OSSE)在理想的環境下， 對兩種回波衰減修正(attenuation correction) 方法： 變分法(variational-based)及差異相位差法(ΦDP-based)進行詳細的評估。分析結果顯示，變分法(variational-based)能提供較為準確的回波衰減修。另外，研究利用變分法修正X 波段偏極化雷達受回波衰減影響的實驗(SoWMEX/TiMREX)資料，與同步觀測的NCARS-波段偏極化雷達(NCAR SPOL)觀測值，以及雨滴譜儀觀測之散射模擬比較，其結果均顯示變分法(variational-based) 能提供正確的衰減修正。然而， 差異反射率(ZDR:differential reflectivity)、差異相位差(ΦDP：differential phase shift)的觀測值，在降水系統強梯度區的觀測偏差，將會限制變分法(variational-based)的應用。
| zh_TW |
| dc.description.abstract | The drop size distribution (DSD) and drop shape relation (DSR) characteristics observed by a ground based 2D-Video disdrometer and retrieved from the C-band polarimetric radar in the typhoon systems during landfall and on the ocean near the northern Taiwan in the Western
Pacific regions were analyzed. The DSDs evolution and its relation with the vertical development of the reflectivity of two rain band cases were investigated. Three different types of precipitation system were studied: 1) weak stratiform type 2) stratiform type and 3) convective type according to characteristics of the mass-weighted diameter (Dm), the maximum diameter and the vertical structure of reflectivity. Further study of the relationship between the 15 dBZ contour height (H) of the vertical reflectivity profile, surface reflectivity (ZHH) and the mass-weighted diameter (Dm) showed that Dm increased with corresponding
increase in the system depth (H) and reflectivity (ZHH). The analysis of DSDs retrieved from NCU C-band polarimetric radar measurements and disdrometer in typhoon concluded that the DSDs from the typhoon systems on the ocean were mainly maritime convective type. However, the DSDs collected over land tended to uniquely locate in between of the continental and maritime clusters. The ”effective DSR” of typhoon systems tends to be more spherical with drops greater than 1.5 mm when higher horizontal winds (maximum wind speed was less than 8 m sec-1).
A detailed observing system simulation experiment (OSSE) was used for evaluating performance of the variational-based attenuation correction method and the ΦDP-based method. The variational-based method always estimates more accurate attenuation than the ΦDP-based method. The accuracy of attenuation-corrected X-band measurements in actual field measurements was evaluated by comparing the measurements with collocated NCAR S-band radar measurements. It was shown that the variational-based method is less sensitive
to measurement noise in radar observations. Attenuation-corrected X-band radar measurements are also compared with disdrometer-based simulated ZHH and ZDR observations.
There were instances, where large artifacts in ZDR (differential reflectivity) and ΦDP (differential phase shift) due to steep gradients in storm intensity, limited the usefulness of the variational-based method.
| en_US |
| DC.subject | 颱風 | zh_TW |
| DC.subject | 偏極化雷達 | zh_TW |
| DC.subject | 雨滴粒徑分布 | zh_TW |
| DC.subject | raindrop size distribution | en_US |
| DC.subject | polarimetric radar | en_US |
| DC.subject | typhoon | en_US |
| DC.title | 利用雙偏極化雷達及二維雨滴譜儀分析颱風降水系統特性 | zh_TW |
| dc.language.iso | zh-TW | zh-TW |
| DC.title | Characterization of Typhoon Rain Events UsingPolarimetric Radar and 2D-Video Disdrometer measurements | en_US |
| DC.type | 博碩士論文 | zh_TW |
| DC.type | thesis | en_US |
| DC.publisher | National Central University | en_US |