發(fā)布時間：2018-04-19 09:43

  本文選題：MST雷達(dá) + 大氣參數(shù)反演��； 參考：《武漢大學(xué)》2016年博士論文

【摘要】：MST (Mesosphere-Stratosphere-Troposphere)雷達(dá)基于晴空湍流散射原理,用以觀測中間層、平流層和對流層大氣三維運(yùn)動狀態(tài),主要獲取相應(yīng)高度區(qū)間的大氣三維風(fēng)廓線和湍流特性參數(shù)。武漢MST雷達(dá)作為中國大陸首批建設(shè)MST雷達(dá),坐落于湖北省崇陽縣(地理坐標(biāo)：11408'8''E,29°31'58”N；地磁緯度約為：19.56°)。MST雷達(dá)的建成對于深入研究中高層大氣風(fēng)場的空間結(jié)構(gòu)和時間變化、辯明中高層大氣中關(guān)鍵的動力學(xué)過程、弄清中高層大氣與電離層及低層大氣的耦合機(jī)制、建立我國上空中高層大氣的風(fēng)場模式、提供空間環(huán)境監(jiān)測和預(yù)報服務(wù)等具有重要的科學(xué)意義和工程應(yīng)用價值。本文主要基于武漢MST雷達(dá)多年的觀測數(shù)據(jù),對其應(yīng)用技術(shù)開展研究。本文的主要工作和研究特色、創(chuàng)新點如下：1、利用MST雷達(dá)垂直風(fēng)速的變化計算B-V (Brunt-Vaisala)頻率,再根據(jù)B-V頻率和溫度的關(guān)系,建立了離散的溫度反演模型。然后結(jié)合地面大氣溫度和中性大氣參考模型可以反演得到大氣溫度剖面,通過與探空儀實測溫度剖面比較,二者的吻合度非常高,變化趨勢也完全一致。同時計算表明在對流層和平流層B-V頻率的平均值有很大的差異,而B-V頻率的跳變值則是對流層頂高度的位置。2、為了更加方便地判斷對流層頂高度,并且分析對流層頂結(jié)構(gòu)形態(tài)的變化,根據(jù)對武漢MST雷達(dá)和北京MST雷達(dá)兩個地區(qū)的對流層頂探測數(shù)據(jù)的統(tǒng)計分析,考慮到對流層頂可能會發(fā)生傾斜,本文建立了更加普適的雷達(dá)對流層頂模型。通過與實測溫度剖面對比分析,發(fā)現(xiàn)氣象對流層頂比雷達(dá)對流層頂約高2 km。利用本文模型計算的對流層頂相對回波的強(qiáng)弱,可以反映了對流層頂雷達(dá)回波的空間方向敏感性,對于理解對流層頂?shù)男纬珊拖?以及層結(jié)的疏密結(jié)構(gòu)非常有幫助。利用武漢和北京兩部MST雷達(dá)2012年的對流層頂觀測數(shù)進(jìn)行據(jù)統(tǒng)計分析,結(jié)果表明：1)崇陽地區(qū)對流層頂?shù)钠骄叨缺认愫拥貐^(qū)對流層頂平均高度高約1 km,這是因為香河的地理緯度比崇陽的高,體現(xiàn)了對流層頂高度隨著緯度增加而降低的特性；2)崇陽地區(qū)對流層頂?shù)南鄬夭◤?qiáng)度比香河地區(qū)對流層頂相對回波強(qiáng)約4dB,說明在緯度較高的地區(qū)對流層頂?shù)慕Y(jié)構(gòu)稀疏,對流層頂雷達(dá)回波的方向依賴性較弱；3)崇陽和北京地區(qū)對流層頂?shù)母叨群拖鄬夭◤?qiáng)度的標(biāo)準(zhǔn)差都非常接近,說明對流層頂高度變化及結(jié)構(gòu)形態(tài)相對差異在各個地區(qū)是基本一致的。通過對模型計算的相對回波數(shù)據(jù)的周期譜分析,可以發(fā)現(xiàn)雷達(dá)對流層頂相對回波同時受潮汐波和行星波的調(diào)制,即潮汐波和行星波會影響對流層頂?shù)男纬珊徒Y(jié)構(gòu)形態(tài)。3、通過折射率理論研究和模型仿真表明,對于波長為6m(武漢MST雷達(dá)波長為5.58 m)左右的電磁波而言,降雨粒子和大氣湍流具有幾乎等數(shù)量級的反射率,由此可以推斷武漢MST雷達(dá)能夠同時明顯地觀測到大氣湍流回波和降雨粒子回波。基于降雨粒子回波和大氣湍流回波的譜特征,本文建立了相應(yīng)的頻譜分離模型,分別了計算降雨環(huán)境中的雨滴運(yùn)動參數(shù)和背景大氣運(yùn)動狀態(tài)。利用武漢MST雷達(dá)分別對崇陽地區(qū)大氣層狀降雨和大氣強(qiáng)對流降雨進(jìn)行了觀測,分別研究了不同降雨類型下大氣降雨粒子回波的特性、雨滴的運(yùn)動狀態(tài)以及背景大氣三維風(fēng)場的變化。結(jié)果表明：1)降雨粒子回波譜比大氣湍流譜的譜寬更寬,可以明顯地區(qū)分大氣融解層和雨滴下墜區(qū)域；2)層狀降雨回波一般出現(xiàn)在零度等溫線以下,而強(qiáng)對流降雨回波則會出現(xiàn)在零度等溫線以上；3)強(qiáng)對流降雨的背景風(fēng)場非常紊亂,降雨持續(xù)時間較短；4)利用層狀降雨粒子回波可以分析亮帶及融解層特性,可以反演不同高度的雨滴粒徑分布。此外,局部強(qiáng)對流天氣使得雷達(dá)不同方向波束觀測到的大氣運(yùn)動狀態(tài)完全不同,因此在強(qiáng)對流天氣下很難得到雷達(dá)波束掃描空間內(nèi)的大氣平均運(yùn)動狀態(tài),這對波束掃描合成大氣三維風(fēng)場帶來了挑戰(zhàn)。本文結(jié)合強(qiáng)對流天氣武漢MST雷達(dá)波束掃描觀測實例,詳細(xì)地分析了強(qiáng)對流天氣下雷達(dá)水平風(fēng)的測量困境,并給出相關(guān)探測建議。4、基于準(zhǔn)單色重力波模型,利用武漢MST雷達(dá)觀測數(shù)據(jù)對低平流層和對流層大氣慣性重力波進(jìn)行了討論分析,并對強(qiáng)對流和對流層頂急流激發(fā)的重力波傳播特性進(jìn)行了事例分析。利用武漢MST雷達(dá)兩年多的觀測數(shù)據(jù)分別對上行和下行重力波的特征頻率,垂直波長、水平波長、譜斜率和峰值能量密度等大氣慣性重力波參數(shù)進(jìn)行了統(tǒng)計分析,可以為構(gòu)建局部大氣重力波參考模型提供技術(shù)參數(shù)。此外,利用Lomb-Scargle周期譜分析方法對2012年全年武漢MST雷達(dá)觀測的對流層和低平流層的經(jīng)向風(fēng)和緯向風(fēng)進(jìn)行了季節(jié)潮汐波和行星波檢測分析,結(jié)果表明：1)各個季節(jié)的周日潮分量都相對較強(qiáng),小周期潮汐分量非常弱,潮汐波的振幅具有明顯的周期性變化；2)潮汐波的振幅會受到比其時間尺度更長的潮汐波和行星際波的共同調(diào)制,但是比其時間尺度小的波基本不足以影響它；3)在下對流層高度區(qū)間主要是以相對較短的時間尺度行星波存在,而在上對流層和低平流層高度區(qū)間則是以相對較長的時間尺度的行星波存在。5、利用武漢MST雷達(dá)數(shù)字波束合成技術(shù),分析了不同傾角下不同波束在不同高度范圍內(nèi)的回波特性,計算了不同高度雷達(dá)回波的方向敏感性,即大氣角譜,研究不同高度雷達(dá)回波的物理機(jī)制,結(jié)果表明：1)在對流層小傾角空問內(nèi),雷達(dá)回波主要是部分反射和各向異性湍流散射為主,在相對高傾角則是各向異性和各向同性湍流共同散射作用；2)高度越高和傾角越大,雷達(dá)回波中各向同性湍流散射的貢獻(xiàn)越大,在中間層和低熱層雷達(dá)回波主要以各向同性散射為主；3)大氣穩(wěn)定層結(jié)的雷達(dá)回波方向敏感性參數(shù)相對較小,主要是因為這些穩(wěn)定層結(jié)大氣結(jié)構(gòu)相對密實,對雷達(dá)回波有很好的部分反射作用,但是通過改變傾角可以發(fā)現(xiàn),這些大氣穩(wěn)定層結(jié)隨著波束傾角增大并非一直存在,而是具有一定的水平尺度。6、雷達(dá)對稱波束的回波差異表明了大氣層的傾斜狀態(tài),當(dāng)對稱波束中有一個方向的回波明顯高于另一個方向時,則大氣層表現(xiàn)為向回波強(qiáng)的方向傾斜；傾斜的角度,則需要在同一個方向通過變化傾角連續(xù)掃描,回波最強(qiáng)的傾角對應(yīng)大氣層傾斜的角度。為了研究大氣層傾斜的影響因素,本文對不同高度的對稱波束回波差進(jìn)行了周期檢測,結(jié)果表明：1)在對流層區(qū)域,各種尺度的波動(重力波、潮汐波和行星波等)幾乎都能對大氣層結(jié)構(gòu)產(chǎn)生一定的影響；2)在低平流層,行星波的影響基本很弱,同時小尺度的重力波的影響也相對較弱,8小時潮、12小時潮和24小時潮分量相對較強(qiáng)；3)在中間層和低熱層區(qū)域,雷達(dá)對稱波束回波功率差的擾動周期分量基本全是潮汐波分量,而且24小時潮的周期譜最寬,說明24小時潮的脈動最強(qiáng),由此可見在中間層和低熱層區(qū)域潮汐波是導(dǎo)致大氣層結(jié)構(gòu)發(fā)生傾斜的主要因素。
[Abstract]:The MST ( MST ) radar is based on the principle of clear air turbulence scattering , which is used to observe the three - dimensional motion state of the middle layer , the drift layer and the counter - flow layer . The three - dimensional wind profile and the turbulence characteristic parameters of the atmospheric three - dimensional wind profile and the turbulence characteristic parameters are obtained . The Wuhan MST radar is used as the first construction MST radar in the mainland of China , and is located in Chongyang County , Hubei Province ( geographic coordinates : 11408 ' 8 ' E , 29 擄 31 ' 58 " N ;
The geomagnetic latitude is about 19.56 擄 . This paper studies the spatial structure and temporal change of the upper atmosphere wind field in the middle and high - rise atmosphere , and the key dynamic process in the middle and high - rise atmosphere is studied .
2 ) The relative echo intensity of the convective layer top in Chongyang area is about 4dB stronger than that of the convective layer in the Xianghe area , which indicates that the structure of the convective layer top is sparse in the area with higher latitude , and the directional dependence of the echo of the top radar is weaker ;
Based on the periodic analysis of the relative echo data of the model , it can be found that the relative echo of the top of the radar can be modulated by tidal wave and planetary wave .
2 ) Layered rainfall echo generally occurs below zero degree isotherm , while strong convective rainfall echo will appear above zero degree isotherm ;
3 ) the background wind field of strong convection rainfall is very disordered and the rainfall duration is short ;
Based on quasi - monochromatic gravity wave model , the atmospheric inertia gravity waves of the upper and lower layers of the radar beam are analyzed by means of the observation data of Wuhan MST radar . The results show that : 1 ) The diurnal tidal components of the upper and lower flow layers are relatively strong and the tidal component of the small period is very weak , and the amplitude of tidal wave has obvious periodic variation .
2 ) The amplitude of tidal wave will be co - modulated by tide wave and intergalactic wave longer than its time scale , but the wave whose time scale is smaller than its time scale is not enough to affect it ;
In this paper , the echo characteristics of different wave beams at different altitudes are analyzed by using the technique of digital beam synthesis in Wuhan MST radar . The physical mechanism of different altitude radar echoes is analyzed . The results show that : 1 ) In the small dip angle of the counter flow , the radar echo is mainly part reflection and anisotropic turbulent scattering , and the relative high inclination is the co - scattering of anisotropic and isotropic turbulence .
2 ) The higher the height and the greater the inclination angle , the larger the contribution of isotropic turbulence scattering in the radar echo , the larger the isotropic scattering in the middle layer and the low - heat - layer radar echo ;
3 ) The sensitivity parameters of the radar echo direction of the atmospheric stable layer junction are relatively small , mainly because of the relatively compact structure of these stable layers , which has a good partial reflection effect on the radar echo . However , by changing the inclination angle , it can be found that these atmospheric stable layers are not always present along with the increase of the beam tilt angle , but have a certain horizontal dimension .
In order to study the influence factors of the atmospheric tilt , this paper makes periodic detection of the difference of symmetric beam echo in different heights . The results show that : 1 ) In the region of the Troposphere , the fluctuation of various scales ( gravitational waves , tidal waves and planetary waves ) can exert a certain influence on the structure of the atmosphere ;
2 ) At the low level , the influence of the planetary wave is very weak , and the influence of the small scale gravity wave is relatively weak , the 8 - hour tide , the 12 - hour tide and the 24 - hour tide component are relatively strong ;
3 ) In the middle layer and the low heat layer area , the disturbance period component of the radar symmetric beam echo power difference is basically the tidal wave component , and the periodic spectrum of the 24 hours tide is the widest , which shows that the pulsation of the 24 hours tide is strongest , thus the tidal wave in the middle layer and the low heat layer region is the main factor leading to the inclination of the atmosphere structure .

【學(xué)位授予單位】：武漢大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2016
【分類號】：P412.25
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本文編號：1772574